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publish/documentation/0.10.0/ publish/documentation/0.10.0/build-system/
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Added: aurora/site/publish/documentation/0.12.0/configuration-tutorial/index.html
URL: http://svn.apache.org/viewvc/aurora/site/publish/documentation/0.12.0/configuration-tutorial/index.html?rev=1733548&view=auto
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--- aurora/site/publish/documentation/0.12.0/configuration-tutorial/index.html (added)
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@@ -0,0 +1,1098 @@
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+ <title>Apache Aurora</title>
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+ <ul class="nav navbar-nav navbar-right">
+ <li><a href="/documentation/latest/">Documentation</a></li>
+ <li><a href="/community/">Community</a></li>
+ <li><a href="/downloads/">Downloads</a></li>
+ <li><a href="/blog/">Blog</a></li>
+ </ul>
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+ </div>
+</div>
+
+ <div class="container-fluid">
+ <div class="container content">
+ <div class="col-md-12 documentation">
+<h5 class="page-header text-uppercase">Documentation
+<select onChange="window.location.href='/documentation/' + this.value + '/configuration-tutorial/'"
+ value="0.12.0">
+ <option value="0.12.0"
+ selected="selected">
+ 0.12.0
+ (latest)
+ </option>
+ <option value="0.11.0"
+ >
+ 0.11.0
+ </option>
+ <option value="0.10.0"
+ >
+ 0.10.0
+ </option>
+ <option value="0.9.0"
+ >
+ 0.9.0
+ </option>
+ <option value="0.8.0"
+ >
+ 0.8.0
+ </option>
+ <option value="0.7.0-incubating"
+ >
+ 0.7.0-incubating
+ </option>
+ <option value="0.6.0-incubating"
+ >
+ 0.6.0-incubating
+ </option>
+ <option value="0.5.0-incubating"
+ >
+ 0.5.0-incubating
+ </option>
+</select>
+</h5>
+<h1 id="aurora-configuration-tutorial">Aurora Configuration Tutorial</h1>
+
+<p>How to write Aurora configuration files, including feature descriptions
+and best practices. When writing a configuration file, make use of
+<code>aurora job inspect</code>. It takes the same job key and configuration file
+arguments as <code>aurora job create</code> or <code>aurora update start</code>. It first ensures the
+configuration parses, then outputs it in human-readable form.</p>
+
+<p>You should read this after going through the general <a href="/documentation/0.12.0/tutorial/">Aurora Tutorial</a>.</p>
+
+<ul>
+<li><a href="#aurora-configuration-tutorial">Aurora Configuration Tutorial</a>
+
+<ul>
+<li><a href="#the-basics">The Basics</a>
+
+<ul>
+<li><a href="#use-bottom-to-top-object-ordering">Use Bottom-To-Top Object Ordering</a></li>
+</ul></li>
+<li><a href="#an-example-configuration-file">An Example Configuration File</a></li>
+<li><a href="#defining-process-objects">Defining Process Objects</a></li>
+<li><a href="#getting-your-code-into-the-sandbox">Getting Your Code Into The Sandbox</a></li>
+<li><a href="#defining-task-objects">Defining Task Objects</a>
+
+<ul>
+<li><a href="#sequentialtask-running-processes-in-parallel-or-sequentially">SequentialTask: Running Processes in Parallel or Sequentially</a></li>
+<li><a href="#simpletask">SimpleTask</a></li>
+<li><a href="#combining-tasks">Combining tasks</a></li>
+</ul></li>
+<li><a href="#defining-job-objects">Defining Job Objects</a></li>
+<li><a href="#the-jobs-list">The jobs List</a></li>
+<li><a href="#templating">Templating</a>
+
+<ul>
+<li><a href="#templating-1-binding-in-pystachio">Templating 1: Binding in Pystachio</a></li>
+<li><a href="#structurals-in-pystachio--aurora">Structurals in Pystachio / Aurora</a>
+
+<ul>
+<li><a href="#mustaches-within-structurals">Mustaches Within Structurals</a></li>
+</ul></li>
+<li><a href="#templating-2-structurals-are-factories">Templating 2: Structurals Are Factories</a>
+
+<ul>
+<li><a href="#a-second-way-of-templating">A Second Way of Templating</a></li>
+</ul></li>
+<li><a href="#advanced-binding">Advanced Binding</a>
+
+<ul>
+<li><a href="#bind-syntax">Bind Syntax</a></li>
+<li><a href="#binding-complex-objects">Binding Complex Objects</a>
+
+<ul>
+<li><a href="#lists"></a></li>
+<li><a href="#maps"></a></li>
+<li><a href="#structurals"></a></li>
+</ul></li>
+</ul></li>
+<li><a href="#structural-binding">Structural Binding</a></li>
+</ul></li>
+<li><a href="#configuration-file-writing-tips-and-best-practices">Configuration File Writing Tips And Best Practices</a>
+
+<ul>
+<li><a href="#use-as-few-aurora-files-as-possible">Use As Few .aurora Files As Possible</a></li>
+<li><a href="#avoid-boilerplate">Avoid Boilerplate</a></li>
+<li><a href="#thermos-uses-bash-but-thermos-is-not-bash">Thermos Uses bash, But Thermos Is Not bash</a>
+
+<ul>
+<li><a href="#bad">Bad</a></li>
+<li><a href="#good">Good</a></li>
+</ul></li>
+<li><a href="#rarely-use-functions-in-your-configurations">Rarely Use Functions In Your Configurations</a>
+
+<ul>
+<li><a href="#bad-1">Bad</a></li>
+<li><a href="#good-1">Good</a></li>
+</ul></li>
+</ul></li>
+</ul></li>
+</ul>
+
+<h2 id="the-basics">The Basics</h2>
+
+<p>To run a job on Aurora, you must specify a configuration file that tells
+Aurora what it needs to know to schedule the job, what Mesos needs to
+run the tasks the job is made up of, and what Thermos needs to run the
+processes that make up the tasks. This file must have
+a<code>.aurora</code> suffix.</p>
+
+<p>A configuration file defines a collection of objects, along with parameter
+values for their attributes. An Aurora configuration file contains the
+following three types of objects:</p>
+
+<ul>
+<li>Job</li>
+<li>Task</li>
+<li>Process</li>
+</ul>
+
+<p>A configuration also specifies a list of <code>Job</code> objects assigned
+to the variable <code>jobs</code>.</p>
+
+<ul>
+<li>jobs (list of defined Jobs to run)</li>
+</ul>
+
+<p>The <code>.aurora</code> file format is just Python. However, <code>Job</code>, <code>Task</code>,
+<code>Process</code>, and other classes are defined by a type-checked dictionary
+templating library called <em>Pystachio</em>, a powerful tool for
+configuration specification and reuse. Pystachio objects are tailored
+via {{}} surrounded templates.</p>
+
+<p>When writing your <code>.aurora</code> file, you may use any Pystachio datatypes, as
+well as any objects shown in the <a href="/documentation/0.12.0/configuration-reference/"><em>Aurora+Thermos Configuration
+Reference</em></a>, without <code>import</code> statements - the
+Aurora config loader injects them automatically. Other than that, an <code>.aurora</code>
+file works like any other Python script.</p>
+
+<p><a href="/documentation/0.12.0/configuration-reference/"><em>Aurora+Thermos Configuration Reference</em></a>
+has a full reference of all Aurora/Thermos defined Pystachio objects.</p>
+
+<h3 id="use-bottom-to-top-object-ordering">Use Bottom-To-Top Object Ordering</h3>
+
+<p>A well-structured configuration starts with structural templates (if
+any). Structural templates encapsulate in their attributes all the
+differences between Jobs in the configuration that are not directly
+manipulated at the <code>Job</code> level, but typically at the <code>Process</code> or <code>Task</code>
+level. For example, if certain processes are invoked with slightly
+different settings or input.</p>
+
+<p>After structural templates, define, in order, <code>Process</code>es, <code>Task</code>s, and
+<code>Job</code>s.</p>
+
+<p>Structural template names should be <em>UpperCamelCased</em> and their
+instantiations are typically <em>UPPER_SNAKE_CASED</em>. <code>Process</code>, <code>Task</code>,
+and <code>Job</code> names are typically <em>lower_snake_cased</em>. Indentation is typically 2
+spaces.</p>
+
+<h2 id="an-example-configuration-file">An Example Configuration File</h2>
+
+<p>The following is a typical configuration file. Don’t worry if there are
+parts you don’t understand yet, but you may want to refer back to this
+as you read about its individual parts. Note that names surrounded by
+curly braces {{}} are template variables, which the system replaces with
+bound values for the variables.</p>
+<pre class="highlight plaintext"><code># --- templates here ---
+class Profile(Struct):
+ package_version = Default(String, 'live')
+ java_binary = Default(String, '/usr/lib/jvm/java-1.7.0-openjdk/bin/java')
+ extra_jvm_options = Default(String, '')
+ parent_environment = Default(String, 'prod')
+ parent_serverset = Default(String,
+ '/foocorp/service/bird/{{parent_environment}}/bird')
+
+# --- processes here ---
+main = Process(
+ name = 'application',
+ cmdline = '{{profile.java_binary}} -server -Xmx1792m '
+ '{{profile.extra_jvm_options}} '
+ '-jar application.jar '
+ '-upstreamService {{profile.parent_serverset}}'
+)
+
+# --- tasks ---
+base_task = SequentialTask(
+ name = 'application',
+ processes = [
+ Process(
+ name = 'fetch',
+ cmdline = 'curl -O
+ https://packages.foocorp.com/{{profile.package_version}}/application.jar'),
+ ]
+)
+
+ # not always necessary but often useful to have separate task
+ # resource classes
+ staging_task = base_task(resources =
+ Resources(cpu = 1.0,
+ ram = 2048*MB,
+ disk = 1*GB))
+production_task = base_task(resources =
+ Resources(cpu = 4.0,
+ ram = 2560*MB,
+ disk = 10*GB))
+
+# --- job template ---
+job_template = Job(
+ name = 'application',
+ role = 'myteam',
+ contact = 'myteam-team@foocorp.com',
+ instances = 20,
+ service = True,
+ task = production_task
+)
+
+# -- profile instantiations (if any) ---
+PRODUCTION = Profile()
+STAGING = Profile(
+ extra_jvm_options = '-Xloggc:gc.log',
+ parent_environment = 'staging'
+)
+
+# -- job instantiations --
+jobs = [
+ job_template(cluster = 'cluster1', environment = 'prod')
+ .bind(profile = PRODUCTION),
+
+ job_template(cluster = 'cluster2', environment = 'prod')
+ .bind(profile = PRODUCTION),
+
+ job_template(cluster = 'cluster1',
+ environment = 'staging',
+ service = False,
+ task = staging_task,
+ instances = 2)
+ .bind(profile = STAGING),
+]
+</code></pre>
+
+<h2 id="defining-process-objects">Defining Process Objects</h2>
+
+<p>Processes are handled by the Thermos system. A process is a single
+executable step run as a part of an Aurora task, which consists of a
+bash-executable statement.</p>
+
+<p>The key (and required) <code>Process</code> attributes are:</p>
+
+<ul>
+<li> <code>name</code>: Any string which is a valid Unix filename (no slashes,
+NULLs, or leading periods). The <code>name</code> value must be unique relative
+to other Processes in a <code>Task</code>.</li>
+<li> <code>cmdline</code>: A command line run in a bash subshell, so you can use
+bash scripts. Nothing is supplied for command-line arguments,
+so <code>$*</code> is unspecified.</li>
+</ul>
+
+<p>Many tiny processes make managing configurations more difficult. For
+example, the following is a bad way to define processes.</p>
+<pre class="highlight plaintext"><code>copy = Process(
+ name = 'copy',
+ cmdline = 'curl -O https://packages.foocorp.com/app.zip'
+)
+unpack = Process(
+ name = 'unpack',
+ cmdline = 'unzip app.zip'
+)
+remove = Process(
+ name = 'remove',
+ cmdline = 'rm -f app.zip'
+)
+run = Process(
+ name = 'app',
+ cmdline = 'java -jar app.jar'
+)
+run_task = Task(
+ processes = [copy, unpack, remove, run],
+ constraints = order(copy, unpack, remove, run)
+)
+</code></pre>
+
+<p>Since <code>cmdline</code> runs in a bash subshell, you can chain commands
+with <code>&&</code> or <code>||</code>.</p>
+
+<p>When defining a <code>Task</code> that is just a list of Processes run in a
+particular order, use <code>SequentialTask</code>, as described in the <a href="#Task"><em>Defining</em>
+<code>Task</code> <em>Objects</em></a> section. The following simplifies and combines the
+above multiple <code>Process</code> definitions into just two.</p>
+<pre class="highlight plaintext"><code>stage = Process(
+ name = 'stage',
+ cmdline = 'curl -O https://packages.foocorp.com/app.zip && '
+ 'unzip app.zip && rm -f app.zip')
+
+run = Process(name = 'app', cmdline = 'java -jar app.jar')
+
+run_task = SequentialTask(processes = [stage, run])
+</code></pre>
+
+<p><code>Process</code> also has optional attributes to customize its behaviour. Details can be found in the <a href="/documentation/0.12.0/configuration-reference/#process-objects"><em>Aurora+Thermos Configuration Reference</em></a>.</p>
+
+<h2 id="getting-your-code-into-the-sandbox">Getting Your Code Into The Sandbox</h2>
+
+<p>When using Aurora, you need to get your executable code into its “sandbox”, specifically
+the Task sandbox where the code executes for the Processes that make up that Task.</p>
+
+<p>Each Task has a sandbox created when the Task starts and garbage
+collected when it finishes. All of a Task’s processes run in its
+sandbox, so processes can share state by using a shared current
+working directory.</p>
+
+<p>Typically, you save this code somewhere. You then need to define a Process
+in your <code>.aurora</code> configuration file that fetches the code from that somewhere
+to where the slave can see it. For a public cloud, that can be anywhere public on
+the Internet, such as S3. For a private cloud internal storage, you need to put in
+on an accessible HDFS cluster or similar storage.</p>
+
+<p>The template for this Process is:</p>
+<pre class="highlight plaintext"><code><name> = Process(
+ name = '<name>'
+ cmdline = '<command to copy and extract code archive into current working directory>'
+)
+</code></pre>
+
+<p>Note: Be sure the extracted code archive has an executable.</p>
+
+<h2 id="defining-task-objects">Defining Task Objects</h2>
+
+<p>Tasks are handled by Mesos. A task is a collection of processes that
+runs in a shared sandbox. It’s the fundamental unit Aurora uses to
+schedule the datacenter; essentially what Aurora does is find places
+in the cluster to run tasks.</p>
+
+<p>The key (and required) parts of a Task are:</p>
+
+<ul>
+<li><p><code>name</code>: A string giving the Task’s name. By default, if a Task is
+not given a name, it inherits the first name in its Process list.</p></li>
+<li><p><code>processes</code>: An unordered list of Process objects bound to the Task.
+The value of the optional <code>constraints</code> attribute affects the
+contents as a whole. Currently, the only constraint, <code>order</code>, determines if
+the processes run in parallel or sequentially.</p></li>
+<li><p><code>resources</code>: A <code>Resource</code> object defining the Task’s resource
+ footprint. A <code>Resource</code> object has three attributes:
+ - <code>cpu</code>: A Float, the fractional number of cores the Task
+ requires.
+ - <code>ram</code>: An Integer, RAM bytes the Task requires.
+ - <code>disk</code>: An integer, disk bytes the Task requires.</p></li>
+</ul>
+
+<p>A basic Task definition looks like:</p>
+<pre class="highlight plaintext"><code>Task(
+ name="hello_world",
+ processes=[Process(name = "hello_world", cmdline = "echo hello world")],
+ resources=Resources(cpu = 1.0,
+ ram = 1*GB,
+ disk = 1*GB))
+</code></pre>
+
+<p>A Task has optional attributes to customize its behaviour. Details can be found in the <a href="/documentation/0.12.0/configuration-reference/#task-object"><em>Aurora+Thermos Configuration Reference</em></a></p>
+
+<h3 id="sequentialtask-running-processes-in-parallel-or-sequentially">SequentialTask: Running Processes in Parallel or Sequentially</h3>
+
+<p>By default, a Task with several Processes runs them in parallel. There
+are two ways to run Processes sequentially:</p>
+
+<ul>
+<li><p>Include an <code>order</code> constraint in the Task definition’s <code>constraints</code>
+attribute whose arguments specify the processes’ run order:</p>
+<pre class="highlight plaintext"><code>Task( ... processes=[process1, process2, process3],
+ constraints = order(process1, process2, process3), ...)
+</code></pre></li>
+<li><p>Use <code>SequentialTask</code> instead of <code>Task</code>; it automatically runs
+processes in the order specified in the <code>processes</code> attribute. No
+<code>constraint</code> parameter is needed:</p>
+<pre class="highlight plaintext"><code>SequentialTask( ... processes=[process1, process2, process3] ...)
+</code></pre></li>
+</ul>
+
+<h3 id="simpletask">SimpleTask</h3>
+
+<p>For quickly creating simple tasks, use the <code>SimpleTask</code> helper. It
+creates a basic task from a provided name and command line using a
+default set of resources. For example, in a .<code>aurora</code> configuration
+file:</p>
+<pre class="highlight plaintext"><code>SimpleTask(name="hello_world", command="echo hello world")
+</code></pre>
+
+<p>is equivalent to</p>
+<pre class="highlight plaintext"><code>Task(name="hello_world",
+ processes=[Process(name = "hello_world", cmdline = "echo hello world")],
+ resources=Resources(cpu = 1.0,
+ ram = 1*GB,
+ disk = 1*GB))
+</code></pre>
+
+<p>The simplest idiomatic Job configuration thus becomes:</p>
+<pre class="highlight plaintext"><code>import os
+hello_world_job = Job(
+ task=SimpleTask(name="hello_world", command="echo hello world"),
+ role=os.getenv('USER'),
+ cluster="cluster1")
+</code></pre>
+
+<p>When written to <code>hello_world.aurora</code>, you invoke it with a simple
+<code>aurora job create cluster1/$USER/test/hello_world hello_world.aurora</code>.</p>
+
+<h3 id="combining-tasks">Combining tasks</h3>
+
+<p><code>Tasks.concat</code>(synonym,<code>concat_tasks</code>) and
+<code>Tasks.combine</code>(synonym,<code>combine_tasks</code>) merge multiple Task definitions
+into a single Task. It may be easier to define complex Jobs
+as smaller constituent Tasks. But since a Job only includes a single
+Task, the subtasks must be combined before using them in a Job.
+Smaller Tasks can also be reused between Jobs, instead of having to
+repeat their definition for multiple Jobs.</p>
+
+<p>With both methods, the merged Task takes the first Task’s name. The
+difference between the two is the result Task’s process ordering.</p>
+
+<ul>
+<li><p><code>Tasks.combine</code> runs its subtasks’ processes in no particular order.
+The new Task’s resource consumption is the sum of all its subtasks’
+consumption.</p></li>
+<li><p><code>Tasks.concat</code> runs its subtasks in the order supplied, with each
+subtask’s processes run serially between tasks. It is analogous to
+the <code>order</code> constraint helper, except at the Task level instead of
+the Process level. The new Task’s resource consumption is the
+maximum value specified by any subtask for each Resource attribute
+(cpu, ram and disk).</p></li>
+</ul>
+
+<p>For example, given the following:</p>
+<pre class="highlight plaintext"><code>setup_task = Task(
+ ...
+ processes=[download_interpreter, update_zookeeper],
+ # It is important to note that {{Tasks.concat}} has
+ # no effect on the ordering of the processes within a task;
+ # hence the necessity of the {{order}} statement below
+ # (otherwise, the order in which {{download_interpreter}}
+ # and {{update_zookeeper}} run will be non-deterministic)
+ constraints=order(download_interpreter, update_zookeeper),
+ ...
+)
+
+run_task = SequentialTask(
+ ...
+ processes=[download_application, start_application],
+ ...
+)
+
+combined_task = Tasks.concat(setup_task, run_task)
+</code></pre>
+
+<p>The <code>Tasks.concat</code> command merges the two Tasks into a single Task and
+ensures all processes in <code>setup_task</code> run before the processes
+in <code>run_task</code>. Conceptually, the task is reduced to:</p>
+<pre class="highlight plaintext"><code>task = Task(
+ ...
+ processes=[download_interpreter, update_zookeeper,
+ download_application, start_application],
+ constraints=order(download_interpreter, update_zookeeper,
+ download_application, start_application),
+ ...
+)
+</code></pre>
+
+<p>In the case of <code>Tasks.combine</code>, the two schedules run in parallel:</p>
+<pre class="highlight plaintext"><code>task = Task(
+ ...
+ processes=[download_interpreter, update_zookeeper,
+ download_application, start_application],
+ constraints=order(download_interpreter, update_zookeeper) +
+ order(download_application, start_application),
+ ...
+)
+</code></pre>
+
+<p>In the latter case, each of the two sequences may operate in parallel.
+Of course, this may not be the intended behavior (for example, if
+the <code>start_application</code> Process implicitly relies
+upon <code>download_interpreter</code>). Make sure you understand the difference
+between using one or the other.</p>
+
+<h2 id="defining-job-objects">Defining Job Objects</h2>
+
+<p>A job is a group of identical tasks that Aurora can run in a Mesos cluster.</p>
+
+<p>A <code>Job</code> object is defined by the values of several attributes, some
+required and some optional. The required attributes are:</p>
+
+<ul>
+<li><p><code>task</code>: Task object to bind to this job. Note that a Job can
+only take a single Task.</p></li>
+<li><p><code>role</code>: Job’s role account; in other words, the user account to run
+the job as on a Mesos cluster machine. A common value is
+<code>os.getenv('USER')</code>; using a Python command to get the user who
+submits the job request. The other common value is the service
+account that runs the job, e.g. <code>www-data</code>.</p></li>
+<li><p><code>environment</code>: Job’s environment, typical values
+are <code>devel</code>, <code>test</code>, or <code>prod</code>.</p></li>
+<li><p><code>cluster</code>: Aurora cluster to schedule the job in, defined in
+<code>/etc/aurora/clusters.json</code> or <code>~/.clusters.json</code>. You can specify
+jobs where the only difference is the <code>cluster</code>, then at run time
+only run the Job whose job key includes your desired cluster’s name.</p></li>
+</ul>
+
+<p>You usually see a <code>name</code> parameter. By default, <code>name</code> inherits its
+value from the Job’s associated Task object, but you can override this
+default. For these four parameters, a Job definition might look like:</p>
+<pre class="highlight plaintext"><code>foo_job = Job( name = 'foo', cluster = 'cluster1',
+ role = os.getenv('USER'), environment = 'prod',
+ task = foo_task)
+</code></pre>
+
+<p>In addition to the required attributes, there are several optional
+attributes. Details can be found in the <a href="/documentation/0.12.0/configuration-reference/#job-objects">Aurora+Thermos Configuration Reference</a>.</p>
+
+<h2 id="the-jobs-list">The jobs List</h2>
+
+<p>At the end of your <code>.aurora</code> file, you need to specify a list of the
+file’s defined Jobs. For example, the following exports the jobs <code>job1</code>,
+<code>job2</code>, and <code>job3</code>.</p>
+<pre class="highlight plaintext"><code>jobs = [job1, job2, job3]
+</code></pre>
+
+<p>This allows the aurora client to invoke commands on those jobs, such as
+starting, updating, or killing them.</p>
+
+<h2 id="templating">Templating</h2>
+
+<p>The <code>.aurora</code> file format is just Python. However, <code>Job</code>, <code>Task</code>,
+<code>Process</code>, and other classes are defined by a templating library called
+<em>Pystachio</em>, a powerful tool for configuration specification and reuse.</p>
+
+<p><a href="/documentation/0.12.0/configuration-reference/">Aurora+Thermos Configuration Reference</a>
+has a full reference of all Aurora/Thermos defined Pystachio objects.</p>
+
+<p>When writing your <code>.aurora</code> file, you may use any Pystachio datatypes, as
+well as any objects shown in the <em>Aurora+Thermos Configuration
+Reference</em> without <code>import</code> statements - the Aurora config loader
+injects them automatically. Other than that the <code>.aurora</code> format
+works like any other Python script.</p>
+
+<h3 id="templating-1-binding-in-pystachio">Templating 1: Binding in Pystachio</h3>
+
+<p>Pystachio uses the visually distinctive {{}} to indicate template
+variables. These are often called “mustache variables” after the
+similarly appearing variables in the Mustache templating system and
+because the curly braces resemble mustaches.</p>
+
+<p>If you are familiar with the Mustache system, templates in Pystachio
+have significant differences. They have no nesting, joining, or
+inheritance semantics. On the other hand, when evaluated, templates
+are evaluated iteratively, so this affords some level of indirection.</p>
+
+<p>Let’s start with the simplest template; text with one
+variable, in this case <code>name</code>;</p>
+<pre class="highlight plaintext"><code>Hello {{name}}
+</code></pre>
+
+<p>If we evaluate this as is, we’d get back:</p>
+<pre class="highlight plaintext"><code>Hello
+</code></pre>
+
+<p>If a template variable doesn’t have a value, when evaluated it’s
+replaced with nothing. If we add a binding to give it a value:</p>
+<pre class="highlight json"><code><span style="background-color: #f8f8f8">{</span><span style="color: #bbbbbb"> </span><span style="color: #000080">"name"</span><span style="color: #bbbbbb"> </span><span style="background-color: #f8f8f8">:</span><span style="color: #bbbbbb"> </span><span style="color: #d14">"Tom"</span><span style="color: #bbbbbb"> </span><span style="background-color: #f8f8f8">}</span><span style="color: #bbbbbb">
+</span></code></pre>
+
+<p>We’d get back:</p>
+<pre class="highlight plaintext"><code>Hello Tom
+</code></pre>
+
+<p>Every Pystachio object has an associated <code>.bind</code> method that can bind
+values to {{}} variables. Bindings are not immediately evaluated.
+Instead, they are evaluated only when the interpolated value of the
+object is necessary, e.g. for performing equality or serializing a
+message over the wire.</p>
+
+<p>Objects with and without mustache templated variables behave
+differently:</p>
+<pre class="highlight plaintext"><code>>>> Float(1.5)
+Float(1.5)
+
+>>> Float('{{x}}.5')
+Float({{x}}.5)
+
+>>> Float('{{x}}.5').bind(x = 1)
+Float(1.5)
+
+>>> Float('{{x}}.5').bind(x = 1) == Float(1.5)
+True
+
+>>> contextual_object = String('{{metavar{{number}}}}').bind(
+... metavar1 = "first", metavar2 = "second")
+
+>>> contextual_object
+String({{metavar{{number}}}})
+
+>>> contextual_object.bind(number = 1)
+String(first)
+
+>>> contextual_object.bind(number = 2)
+String(second)
+</code></pre>
+
+<p>You usually bind simple key to value pairs, but you can also bind three
+other objects: lists, dictionaries, and structurals. These will be
+described in detail later.</p>
+
+<h3 id="structurals-in-pystachio-aurora">Structurals in Pystachio / Aurora</h3>
+
+<p>Most Aurora/Thermos users don’t ever (knowingly) interact with <code>String</code>,
+<code>Float</code>, or <code>Integer</code> Pystashio objects directly. Instead they interact
+with derived structural (<code>Struct</code>) objects that are collections of
+fundamental and structural objects. The structural object components are
+called <em>attributes</em>. Aurora’s most used structural objects are <code>Job</code>,
+<code>Task</code>, and <code>Process</code>:</p>
+<pre class="highlight plaintext"><code>class Process(Struct):
+ cmdline = Required(String)
+ name = Required(String)
+ max_failures = Default(Integer, 1)
+ daemon = Default(Boolean, False)
+ ephemeral = Default(Boolean, False)
+ min_duration = Default(Integer, 5)
+ final = Default(Boolean, False)
+</code></pre>
+
+<p>Construct default objects by following the object’s type with (). If you
+want an attribute to have a value different from its default, include
+the attribute name and value inside the parentheses.</p>
+<pre class="highlight plaintext"><code>>>> Process()
+Process(daemon=False, max_failures=1, ephemeral=False,
+ min_duration=5, final=False)
+</code></pre>
+
+<p>Attribute values can be template variables, which then receive specific
+values when creating the object.</p>
+<pre class="highlight plaintext"><code>>>> Process(cmdline = 'echo {{message}}')
+Process(daemon=False, max_failures=1, ephemeral=False, min_duration=5,
+ cmdline=echo {{message}}, final=False)
+
+>>> Process(cmdline = 'echo {{message}}').bind(message = 'hello world')
+Process(daemon=False, max_failures=1, ephemeral=False, min_duration=5,
+ cmdline=echo hello world, final=False)
+</code></pre>
+
+<p>A powerful binding property is that all of an object’s children inherit its
+bindings:</p>
+<pre class="highlight plaintext"><code>>>> List(Process)([
+... Process(name = '{{prefix}}_one'),
+... Process(name = '{{prefix}}_two')
+... ]).bind(prefix = 'hello')
+ProcessList(
+ Process(daemon=False, name=hello_one, max_failures=1, ephemeral=False, min_duration=5, final=False),
+ Process(daemon=False, name=hello_two, max_failures=1, ephemeral=False, min_duration=5, final=False)
+ )
+</code></pre>
+
+<p>Remember that an Aurora Job contains Tasks which contain Processes. A
+Job level binding is inherited by its Tasks and all their Processes.
+Similarly a Task level binding is available to that Task and its
+Processes but is <em>not</em> visible at the Job level (inheritance is a
+one-way street.)</p>
+
+<h4 id="mustaches-within-structurals">Mustaches Within Structurals</h4>
+
+<p>When you define a <code>Struct</code> schema, one powerful, but confusing, feature
+is that all of that structure’s attributes are Mustache variables within
+the enclosing scope <em>once they have been populated</em>.</p>
+
+<p>For example, when <code>Process</code> is defined above, all its attributes such as
+{{<code>name</code>}}, {{<code>cmdline</code>}}, {{<code>max_failures</code>}} etc., are all immediately
+defined as Mustache variables, implicitly bound into the <code>Process</code>, and
+inherit all child objects once they are defined.</p>
+
+<p>Thus, you can do the following:</p>
+<pre class="highlight plaintext"><code>>>> Process(name = "installer", cmdline = "echo {{name}} is running")
+Process(daemon=False, name=installer, max_failures=1, ephemeral=False, min_duration=5,
+ cmdline=echo installer is running, final=False)
+</code></pre>
+
+<p>WARNING: This binding only takes place in one direction. For example,
+the following does NOT work and does not set the <code>Process</code> <code>name</code>
+attribute’s value.</p>
+<pre class="highlight plaintext"><code>>>> Process().bind(name = "installer")
+Process(daemon=False, max_failures=1, ephemeral=False, min_duration=5, final=False)
+</code></pre>
+
+<p>The following is also not possible and results in an infinite loop that
+attempts to resolve <code>Process.name</code>.</p>
+<pre class="highlight plaintext"><code>>>> Process(name = '{{name}}').bind(name = 'installer')
+</code></pre>
+
+<p>Do not confuse Structural attributes with bound Mustache variables.
+Attributes are implicitly converted to Mustache variables but not vice
+versa.</p>
+
+<h3 id="templating-2-structurals-are-factories">Templating 2: Structurals Are Factories</h3>
+
+<h4 id="a-second-way-of-templating">A Second Way of Templating</h4>
+
+<p>A second templating method is both as powerful as the aforementioned and
+often confused with it. This method is due to automatic conversion of
+Struct attributes to Mustache variables as described above.</p>
+
+<p>Suppose you create a Process object:</p>
+<pre class="highlight plaintext"><code>>>> p = Process(name = "process_one", cmdline = "echo hello world")
+
+>>> p
+Process(daemon=False, name=process_one, max_failures=1, ephemeral=False, min_duration=5,
+ cmdline=echo hello world, final=False)
+</code></pre>
+
+<p>This <code>Process</code> object, “<code>p</code>”, can be used wherever a <code>Process</code> object is
+needed. It can also be reused by changing the value(s) of its
+attribute(s). Here we change its <code>name</code> attribute from <code>process_one</code> to
+<code>process_two</code>.</p>
+<pre class="highlight plaintext"><code>>>> p(name = "process_two")
+Process(daemon=False, name=process_two, max_failures=1, ephemeral=False, min_duration=5,
+ cmdline=echo hello world, final=False)
+</code></pre>
+
+<p>Template creation is a common use for this technique:</p>
+<pre class="highlight plaintext"><code>>>> Daemon = Process(daemon = True)
+>>> logrotate = Daemon(name = 'logrotate', cmdline = './logrotate conf/logrotate.conf')
+>>> mysql = Daemon(name = 'mysql', cmdline = 'bin/mysqld --safe-mode')
+</code></pre>
+
+<h3 id="advanced-binding">Advanced Binding</h3>
+
+<p>As described above, <code>.bind()</code> binds simple strings or numbers to
+Mustache variables. In addition to Structural types formed by combining
+atomic types, Pystachio has two container types; <code>List</code> and <code>Map</code> which
+can also be bound via <code>.bind()</code>.</p>
+
+<h4 id="bind-syntax">Bind Syntax</h4>
+
+<p>The <code>bind()</code> function can take Python dictionaries or <code>kwargs</code>
+interchangeably (when “<code>kwargs</code>” is in a function definition, <code>kwargs</code>
+receives a Python dictionary containing all keyword arguments after the
+formal parameter list).</p>
+<pre class="highlight plaintext"><code>>>> String('{{foo}}').bind(foo = 'bar') == String('{{foo}}').bind({'foo': 'bar'})
+True
+</code></pre>
+
+<p>Bindings done “closer” to the object in question take precedence:</p>
+<pre class="highlight plaintext"><code>>>> p = Process(name = '{{context}}_process')
+>>> t = Task().bind(context = 'global')
+>>> t(processes = [p, p.bind(context = 'local')])
+Task(processes=ProcessList(
+ Process(daemon=False, name=global_process, max_failures=1, ephemeral=False, final=False,
+ min_duration=5),
+ Process(daemon=False, name=local_process, max_failures=1, ephemeral=False, final=False,
+ min_duration=5)
+))
+</code></pre>
+
+<h4 id="binding-complex-objects">Binding Complex Objects</h4>
+
+<h5 id="lists">Lists</h5>
+<pre class="highlight plaintext"><code>>>> fibonacci = List(Integer)([1, 1, 2, 3, 5, 8, 13])
+>>> String('{{fib[4]}}').bind(fib = fibonacci)
+String(5)
+</code></pre>
+
+<h5 id="maps">Maps</h5>
+<pre class="highlight plaintext"><code>>>> first_names = Map(String, String)({'Kent': 'Clark', 'Wayne': 'Bruce', 'Prince': 'Diana'})
+>>> String('{{first[Kent]}}').bind(first = first_names)
+String(Clark)
+</code></pre>
+
+<h5 id="structurals">Structurals</h5>
+<pre class="highlight plaintext"><code>>>> String('{{p.cmdline}}').bind(p = Process(cmdline = "echo hello world"))
+String(echo hello world)
+</code></pre>
+
+<h3 id="structural-binding">Structural Binding</h3>
+
+<p>Use structural templates when binding more than two or three individual
+values at the Job or Task level. For fewer than two or three, standard
+key to string binding is sufficient.</p>
+
+<p>Structural binding is a very powerful pattern and is most useful in
+Aurora/Thermos for doing Structural configuration. For example, you can
+define a job profile. The following profile uses <code>HDFS</code>, the Hadoop
+Distributed File System, to designate a file’s location. <code>HDFS</code> does
+not come with Aurora, so you’ll need to either install it separately
+or change the way the dataset is designated.</p>
+<pre class="highlight plaintext"><code>class Profile(Struct):
+ version = Required(String)
+ environment = Required(String)
+ dataset = Default(String, hdfs://home/aurora/data/{{environment}}')
+
+PRODUCTION = Profile(version = 'live', environment = 'prod')
+DEVEL = Profile(version = 'latest',
+ environment = 'devel',
+ dataset = 'hdfs://home/aurora/data/test')
+TEST = Profile(version = 'latest', environment = 'test')
+
+JOB_TEMPLATE = Job(
+ name = 'application',
+ role = 'myteam',
+ cluster = 'cluster1',
+ environment = '{{profile.environment}}',
+ task = SequentialTask(
+ name = 'task',
+ resources = Resources(cpu = 2, ram = 4*GB, disk = 8*GB),
+ processes = [
+ Process(name = 'main', cmdline = 'java -jar application.jar -hdfsPath
+ {{profile.dataset}}')
+ ]
+ )
+ )
+
+jobs = [
+ JOB_TEMPLATE(instances = 100).bind(profile = PRODUCTION),
+ JOB_TEMPLATE.bind(profile = DEVEL),
+ JOB_TEMPLATE.bind(profile = TEST),
+ ]
+</code></pre>
+
+<p>In this case, a custom structural “Profile” is created to self-document
+the configuration to some degree. This also allows some schema
+“type-checking”, and for default self-substitution, e.g. in
+<code>Profile.dataset</code> above.</p>
+
+<p>So rather than a <code>.bind()</code> with a half-dozen substituted variables, you
+can bind a single object that has sensible defaults stored in a single
+place.</p>
+
+<h2 id="configuration-file-writing-tips-and-best-practices">Configuration File Writing Tips And Best Practices</h2>
+
+<h3 id="use-as-few-aurora-files-as-possible">Use As Few .aurora Files As Possible</h3>
+
+<p>When creating your <code>.aurora</code> configuration, try to keep all versions of
+a particular job within the same <code>.aurora</code> file. For example, if you
+have separate jobs for <code>cluster1</code>, <code>cluster1</code> staging, <code>cluster1</code>
+testing, and<code>cluster2</code>, keep them as close together as possible.</p>
+
+<p>Constructs shared across multiple jobs owned by your team (e.g.
+team-level defaults or structural templates) can be split into separate
+<code>.aurora</code>files and included via the <code>include</code> directive.</p>
+
+<h3 id="avoid-boilerplate">Avoid Boilerplate</h3>
+
+<p>If you see repetition or find yourself copy and pasting any parts of
+your configuration, it’s likely an opportunity for templating. Take the
+example below:</p>
+
+<p><code>redundant.aurora</code> contains:</p>
+<pre class="highlight plaintext"><code>download = Process(
+ name = 'download',
+ cmdline = 'wget http://www.python.org/ftp/python/2.7.3/Python-2.7.3.tar.bz2',
+ max_failures = 5,
+ min_duration = 1)
+
+unpack = Process(
+ name = 'unpack',
+ cmdline = 'rm -rf Python-2.7.3 && tar xzf Python-2.7.3.tar.bz2',
+ max_failures = 5,
+ min_duration = 1)
+
+build = Process(
+ name = 'build',
+ cmdline = 'pushd Python-2.7.3 && ./configure && make && popd',
+ max_failures = 1)
+
+email = Process(
+ name = 'email',
+ cmdline = 'echo Success | mail feynman@tmc.com',
+ max_failures = 5,
+ min_duration = 1)
+
+build_python = Task(
+ name = 'build_python',
+ processes = [download, unpack, build, email],
+ constraints = [Constraint(order = ['download', 'unpack', 'build', 'email'])])
+</code></pre>
+
+<p>As you’ll notice, there’s a lot of repetition in the <code>Process</code>
+definitions. For example, almost every process sets a <code>max_failures</code>
+limit to 5 and a <code>min_duration</code> to 1. This is an opportunity for factoring
+into a common process template.</p>
+
+<p>Furthermore, the Python version is repeated everywhere. This can be
+bound via structural templating as described in the <a href="#AdvancedBinding">Advanced Binding</a>
+section.</p>
+
+<p><code>less_redundant.aurora</code> contains:</p>
+<pre class="highlight plaintext"><code>class Python(Struct):
+ version = Required(String)
+ base = Default(String, 'Python-{{version}}')
+ package = Default(String, '{{base}}.tar.bz2')
+
+ReliableProcess = Process(
+ max_failures = 5,
+ min_duration = 1)
+
+download = ReliableProcess(
+ name = 'download',
+ cmdline = 'wget http://www.python.org/ftp/python/{{python.version}}/{{python.package}}')
+
+unpack = ReliableProcess(
+ name = 'unpack',
+ cmdline = 'rm -rf {{python.base}} && tar xzf {{python.package}}')
+
+build = ReliableProcess(
+ name = 'build',
+ cmdline = 'pushd {{python.base}} && ./configure && make && popd',
+ max_failures = 1)
+
+email = ReliableProcess(
+ name = 'email',
+ cmdline = 'echo Success | mail {{role}}@foocorp.com')
+
+build_python = SequentialTask(
+ name = 'build_python',
+ processes = [download, unpack, build, email]).bind(python = Python(version = "2.7.3"))
+</code></pre>
+
+<h3 id="thermos-uses-bash-but-thermos-is-not-bash">Thermos Uses bash, But Thermos Is Not bash</h3>
+
+<h4 id="bad">Bad</h4>
+
+<p>Many tiny Processes makes for harder to manage configurations.</p>
+<pre class="highlight plaintext"><code>copy = Process(
+ name = 'copy',
+ cmdline = 'rcp user@my_machine:my_application .'
+ )
+
+ unpack = Process(
+ name = 'unpack',
+ cmdline = 'unzip app.zip'
+ )
+
+ remove = Process(
+ name = 'remove',
+ cmdline = 'rm -f app.zip'
+ )
+
+ run = Process(
+ name = 'app',
+ cmdline = 'java -jar app.jar'
+ )
+
+ run_task = Task(
+ processes = [copy, unpack, remove, run],
+ constraints = order(copy, unpack, remove, run)
+ )
+</code></pre>
+
+<h4 id="good">Good</h4>
+
+<p>Each <code>cmdline</code> runs in a bash subshell, so you have the full power of
+bash. Chaining commands with <code>&&</code> or <code>||</code> is almost always the right
+thing to do.</p>
+
+<p>Also for Tasks that are simply a list of processes that run one after
+another, consider using the <code>SequentialTask</code> helper which applies a
+linear ordering constraint for you.</p>
+<pre class="highlight plaintext"><code>stage = Process(
+ name = 'stage',
+ cmdline = 'rcp user@my_machine:my_application . && unzip app.zip && rm -f app.zip')
+
+run = Process(name = 'app', cmdline = 'java -jar app.jar')
+
+run_task = SequentialTask(processes = [stage, run])
+</code></pre>
+
+<h3 id="rarely-use-functions-in-your-configurations">Rarely Use Functions In Your Configurations</h3>
+
+<p>90% of the time you define a function in a <code>.aurora</code> file, you’re
+probably Doing It Wrong™.</p>
+
+<h4 id="bad">Bad</h4>
+<pre class="highlight plaintext"><code>def get_my_task(name, user, cpu, ram, disk):
+ return Task(
+ name = name,
+ user = user,
+ processes = [STAGE_PROCESS, RUN_PROCESS],
+ constraints = order(STAGE_PROCESS, RUN_PROCESS),
+ resources = Resources(cpu = cpu, ram = ram, disk = disk)
+ )
+
+ task_one = get_my_task('task_one', 'feynman', 1.0, 32*MB, 1*GB)
+ task_two = get_my_task('task_two', 'feynman', 2.0, 64*MB, 1*GB)
+</code></pre>
+
+<h4 id="good">Good</h4>
+
+<p>This one is more idiomatic. Forced keyword arguments prevents accidents,
+e.g. constructing a task with “32*MB” when you mean 32MB of ram and not
+disk. Less proliferation of task-construction techniques means
+easier-to-read, quicker-to-understand, and a more composable
+configuration.</p>
+<pre class="highlight plaintext"><code>TASK_TEMPLATE = SequentialTask(
+ user = 'wickman',
+ processes = [STAGE_PROCESS, RUN_PROCESS],
+)
+
+task_one = TASK_TEMPLATE(
+ name = 'task_one',
+ resources = Resources(cpu = 1.0, ram = 32*MB, disk = 1*GB) )
+
+task_two = TASK_TEMPLATE(
+ name = 'task_two',
+ resources = Resources(cpu = 2.0, ram = 64*MB, disk = 1*GB)
+)
+</code></pre>
+
+</div>
+
+ </div>
+ </div>
+ <div class="container-fluid section-footer buffer">
+ <div class="container">
+ <div class="row">
+ <div class="col-md-2 col-md-offset-1"><h3>Quick Links</h3>
+ <ul>
+ <li><a href="/downloads/">Downloads</a></li>
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+ <li><a href="http://www.apache.org/foundation/thanks.html">Thanks</a></li>
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+ </div>
+ <div class="col-md-6">
+ <p class="disclaimer">Copyright 2014 <a href="http://www.apache.org/">Apache Software Foundation</a>. Licensed under the <a href="http://www.apache.org/licenses/">Apache License v2.0</a>. The <a href="https://www.flickr.com/photos/trondk/12706051375/">Aurora Borealis IX photo</a> displayed on the homepage is available under a <a href="https://creativecommons.org/licenses/by-nc-nd/2.0/">Creative Commons BY-NC-ND 2.0 license</a>. Apache, Apache Aurora, and the Apache feather logo are trademarks of The Apache Software Foundation.</p>
+ </div>
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+
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+ <ul class="nav navbar-nav navbar-right">
+ <li><a href="/documentation/latest/">Documentation</a></li>
+ <li><a href="/community/">Community</a></li>
+ <li><a href="/downloads/">Downloads</a></li>
+ <li><a href="/blog/">Blog</a></li>
+ </ul>
+ </div>
+ </div>
+</div>
+
+ <div class="container-fluid">
+ <div class="container content">
+ <div class="col-md-12 documentation">
+<h5 class="page-header text-uppercase">Documentation
+<select onChange="window.location.href='/documentation/' + this.value + '/cron-jobs/'"
+ value="0.12.0">
+ <option value="0.12.0"
+ selected="selected">
+ 0.12.0
+ (latest)
+ </option>
+ <option value="0.11.0"
+ >
+ 0.11.0
+ </option>
+ <option value="0.10.0"
+ >
+ 0.10.0
+ </option>
+ <option value="0.9.0"
+ >
+ 0.9.0
+ </option>
+ <option value="0.8.0"
+ >
+ 0.8.0
+ </option>
+ <option value="0.7.0-incubating"
+ >
+ 0.7.0-incubating
+ </option>
+ <option value="0.6.0-incubating"
+ >
+ 0.6.0-incubating
+ </option>
+ <option value="0.5.0-incubating"
+ >
+ 0.5.0-incubating
+ </option>
+</select>
+</h5>
+<h1 id="cron-jobs">Cron Jobs</h1>
+
+<p>Aurora supports execution of scheduled jobs on a Mesos cluster using cron-style syntax.</p>
+
+<ul>
+<li><a href="#overview">Overview</a></li>
+<li><a href="#collision-policies">Collision Policies</a>
+
+<ul>
+<li><a href="#kill_existing">KILL_EXISTING</a></li>
+<li><a href="#cancel_new">CANCEL_NEW</a></li>
+</ul></li>
+<li><a href="#failure-recovery">Failure recovery</a></li>
+<li><a href="#interacting-with-cron-jobs-via-the-aurora-cli">Interacting with cron jobs via the Aurora CLI</a>
+
+<ul>
+<li><a href="#cron-schedule">cron schedule</a></li>
+<li><a href="#cron-deschedule">cron deschedule</a></li>
+<li><a href="#cron-start">cron start</a></li>
+<li><a href="#job-killall-job-restart-job-kill">job killall, job restart, job kill</a></li>
+</ul></li>
+<li><a href="#technical-note-about-syntax">Technical Note About Syntax</a></li>
+<li><a href="#caveats">Caveats</a>
+
+<ul>
+<li><a href="#failovers">Failovers</a></li>
+<li><a href="#collision-policy-is-best-effort">Collision policy is best-effort</a></li>
+<li><a href="#timezone-configuration">Timezone Configuration</a></li>
+</ul></li>
+</ul>
+
+<h2 id="overview">Overview</h2>
+
+<p>A job is identified as a cron job by the presence of a
+<code>cron_schedule</code> attribute containing a cron-style schedule in the
+<a href="/documentation/0.12.0/configuration-reference/#job-objects"><code>Job</code></a> object. Examples of cron schedules
+include “every 5 minutes” (<code>*/5 * * * *</code>), “Fridays at 17:00” (<code>* 17 * * FRI</code>), and
+“the 1st and 15th day of the month at 03:00” (<code>0 3 1,15 *</code>).</p>
+
+<p>Example (available in the <a href="/documentation/0.12.0/vagrant/">Vagrant environment</a>):</p>
+<pre class="highlight plaintext"><code>$ cat /vagrant/examples/job/cron_hello_world.aurora
+# cron_hello_world.aurora
+# A cron job that runs every 5 minutes.
+jobs = [
+ Job(
+ cluster = 'devcluster',
+ role = 'www-data',
+ environment = 'test',
+ name = 'cron_hello_world',
+ cron_schedule = '*/5 * * * *',
+ task = SimpleTask(
+ 'cron_hello_world',
+ 'echo "Hello world from cron, the time is now $(date --rfc-822)"'),
+ ),
+]
+</code></pre>
+
+<h2 id="collision-policies">Collision Policies</h2>
+
+<p>The <code>cron_collision_policy</code> field specifies the scheduler’s behavior when a new cron job is
+triggered while an older run hasn’t finished. The scheduler has two policies available,
+<a href="#kill_existing">KILL_EXISTING</a> and <a href="#cancel_new">CANCEL_NEW</a>.</p>
+
+<h3 id="kill_existing">KILL_EXISTING</h3>
+
+<p>The default policy - on a collision the old instances are killed and a instances with the current
+configuration are started.</p>
+
+<h3 id="cancel_new">CANCEL_NEW</h3>
+
+<p>On a collision the new run is cancelled.</p>
+
+<p>Note that the use of this flag is likely a code smell - interrupted cron jobs should be able
+to recover their progress on a subsequent invocation, otherwise they risk having their work queue
+grow faster than they can process it.</p>
+
+<h2 id="failure-recovery">Failure recovery</h2>
+
+<p>Unlike with services, which aurora will always re-execute regardless of exit status, instances of
+cron jobs retry according to the <code>max_task_failures</code> attribute of the
+<a href="/documentation/0.12.0/configuration-reference/#task-objects">Task</a> object. To get “run-until-success” semantics,
+set <code>max_task_failures</code> to <code>-1</code>.</p>
+
+<h2 id="interacting-with-cron-jobs-via-the-aurora-cli">Interacting with cron jobs via the Aurora CLI</h2>
+
+<p>Most interaction with cron jobs takes place using the <code>cron</code> subcommand. See <code>aurora cron -h</code>
+for up-to-date usage instructions.</p>
+
+<h3 id="cron-schedule">cron schedule</h3>
+
+<p>Schedules a new cron job on the Aurora cluster for later runs or replaces the existing cron template
+with a new one. Only future runs will be affected, any existing active tasks are left intact.</p>
+<pre class="highlight plaintext"><code>$ aurora cron schedule devcluster/www-data/test/cron_hello_world /vagrant/examples/jobs/cron_hello_world.aurora
+</code></pre>
+
+<h3 id="cron-deschedule">cron deschedule</h3>
+
+<p>Deschedules a cron job, preventing future runs but allowing current runs to complete.</p>
+<pre class="highlight plaintext"><code>$ aurora cron deschedule devcluster/www-data/test/cron_hello_world
+</code></pre>
+
+<h3 id="cron-start">cron start</h3>
+
+<p>Start a cron job immediately, outside of its normal cron schedule.</p>
+<pre class="highlight plaintext"><code>$ aurora cron start devcluster/www-data/test/cron_hello_world
+</code></pre>
+
+<h3 id="job-killall-job-restart-job-kill">job killall, job restart, job kill</h3>
+
+<p>Cron jobs create instances running on the cluster that you can interact with like normal Aurora
+tasks with <code>job kill</code> and <code>job restart</code>.</p>
+
+<h2 id="technical-note-about-syntax">Technical Note About Syntax</h2>
+
+<p><code>cron_schedule</code> uses a restricted subset of BSD crontab syntax. While the
+execution engine currently uses Quartz, the schedule parsing is custom, a subset of FreeBSD
+<a href="http://www.freebsd.org/cgi/man.cgi?crontab(5)">crontab(5)</a> syntax. See
+<a href="https://github.com/apache/aurora/blob/master/src/main/java/org/apache/aurora/scheduler/cron/CrontabEntry.java#L106-L124">the source</a>
+for details.</p>
+
+<h2 id="caveats">Caveats</h2>
+
+<h3 id="failovers">Failovers</h3>
+
+<p>No failover recovery. Aurora does not record the latest minute it fired
+triggers for across failovers. Therefore it’s possible to miss triggers
+on failover. Note that this behavior may change in the future.</p>
+
+<p>It’s necessary to sync time between schedulers with something like <code>ntpd</code>.
+Clock skew could cause double or missed triggers in the case of a failover.</p>
+
+<h3 id="collision-policy-is-best-effort">Collision policy is best-effort</h3>
+
+<p>Aurora aims to always have <em>at least one copy</em> of a given instance running at a time - it’s
+an AP system, meaning it chooses Availability and Partition Tolerance at the expense of
+Consistency.</p>
+
+<p>If your collision policy was <code>CANCEL_NEW</code> and a task has terminated but
+Aurora has not noticed this Aurora will go ahead and create your new
+task.</p>
+
+<p>If your collision policy was <code>KILL_EXISTING</code> and a task was marked <code>LOST</code>
+but not yet GCed Aurora will go ahead and create your new task without
+attempting to kill the old one (outside the GC interval).</p>
+
+<h3 id="timezone-configuration">Timezone Configuration</h3>
+
+<p>Cron timezone is configured indepdendently of JVM timezone with the <code>-cron_timezone</code> flag and
+defaults to UTC.</p>
+
+</div>
+
+ </div>
+ </div>
+ <div class="container-fluid section-footer buffer">
+ <div class="container">
+ <div class="row">
+ <div class="col-md-2 col-md-offset-1"><h3>Quick Links</h3>
+ <ul>
+ <li><a href="/downloads/">Downloads</a></li>
+ <li><a href="/community/">Mailing Lists</a></li>
+ <li><a href="http://issues.apache.org/jira/browse/AURORA">Issue Tracking</a></li>
+ <li><a href="/documentation/latest/contributing/">How To Contribute</a></li>
+ </ul>
+ </div>
+ <div class="col-md-2"><h3>The ASF</h3>
+ <ul>
+ <li><a href="http://www.apache.org/licenses/">License</a></li>
+ <li><a href="http://www.apache.org/foundation/sponsorship.html">Sponsorship</a></li>
+ <li><a href="http://www.apache.org/foundation/thanks.html">Thanks</a></li>
+ <li><a href="http://www.apache.org/security/">Security</a></li>
+ </ul>
+ </div>
+ <div class="col-md-6">
+ <p class="disclaimer">Copyright 2014 <a href="http://www.apache.org/">Apache Software Foundation</a>. Licensed under the <a href="http://www.apache.org/licenses/">Apache License v2.0</a>. The <a href="https://www.flickr.com/photos/trondk/12706051375/">Aurora Borealis IX photo</a> displayed on the homepage is available under a <a href="https://creativecommons.org/licenses/by-nc-nd/2.0/">Creative Commons BY-NC-ND 2.0 license</a>. Apache, Apache Aurora, and the Apache feather logo are trademarks of The Apache Software Foundation.</p>
+ </div>
+ </div>
+ </div>
+
+ </body>
+</html>
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+++ aurora/site/publish/documentation/0.12.0/deploying-aurora-scheduler/index.html Fri Mar 4 02:43:01 2016
@@ -0,0 +1,548 @@
+<!DOCTYPE html>
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <meta name="viewport" content="width=device-width, initial-scale=1">
+ <title>Apache Aurora</title>
+ <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css">
+ <link href="/assets/css/main.css" rel="stylesheet">
+ <!-- Analytics -->
+ <script type="text/javascript">
+ var _gaq = _gaq || [];
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+ </head>
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+ <div class="container-fluid section-header">
+ <div class="container">
+ <div class="nav nav-bar">
+ <a href="/"><img src="/assets/img/aurora_logo_dkbkg.svg" width="300" alt="Transparent Apache Aurora logo with dark background"/></a>
+ <ul class="nav navbar-nav navbar-right">
+ <li><a href="/documentation/latest/">Documentation</a></li>
+ <li><a href="/community/">Community</a></li>
+ <li><a href="/downloads/">Downloads</a></li>
+ <li><a href="/blog/">Blog</a></li>
+ </ul>
+ </div>
+ </div>
+</div>
+
+ <div class="container-fluid">
+ <div class="container content">
+ <div class="col-md-12 documentation">
+<h5 class="page-header text-uppercase">Documentation
+<select onChange="window.location.href='/documentation/' + this.value + '/deploying-aurora-scheduler/'"
+ value="0.12.0">
+ <option value="0.12.0"
+ selected="selected">
+ 0.12.0
+ (latest)
+ </option>
+ <option value="0.11.0"
+ >
+ 0.11.0
+ </option>
+ <option value="0.10.0"
+ >
+ 0.10.0
+ </option>
+ <option value="0.9.0"
+ >
+ 0.9.0
+ </option>
+ <option value="0.8.0"
+ >
+ 0.8.0
+ </option>
+ <option value="0.7.0-incubating"
+ >
+ 0.7.0-incubating
+ </option>
+ <option value="0.6.0-incubating"
+ >
+ 0.6.0-incubating
+ </option>
+ <option value="0.5.0-incubating"
+ >
+ 0.5.0-incubating
+ </option>
+</select>
+</h5>
+<h1 id="deploying-the-aurora-scheduler">Deploying the Aurora Scheduler</h1>
+
+<p>When setting up your cluster, you will install the scheduler on a small number (usually 3 or 5) of
+machines. This guide helps you get the scheduler set up and troubleshoot some common hurdles.</p>
+
+<ul>
+<li><a href="#installing-aurora">Installing Aurora</a>
+
+<ul>
+<li><a href="#creating-the-distribution-zip-file-optional">Creating the Distribution .zip File (Optional)</a></li>
+<li><a href="#installing-aurora-1">Installing Aurora</a></li>
+</ul></li>
+<li><a href="#configuring-aurora">Configuring Aurora</a>
+
+<ul>
+<li><a href="#a-note-on-configuration">A Note on Configuration</a></li>
+<li><a href="#replicated-log-configuration">Replicated Log Configuration</a></li>
+<li><a href="#initializing-the-replicated-log">Initializing the Replicated Log</a></li>
+<li><a href="#storage-performance-considerations">Storage Performance Considerations</a></li>
+<li><a href="#network-considerations">Network considerations</a></li>
+<li><a href="#considerations-for-running-jobs-in-docker">Considerations for running jobs in docker</a></li>
+<li><a href="#security-considerations">Security Considerations</a></li>
+<li><a href="#configuring-resource-oversubscription">Configuring Resource Oversubscription</a></li>
+<li><a href="#process-logs">Process Logs</a></li>
+</ul></li>
+<li><a href="#running-aurora">Running Aurora</a>
+
+<ul>
+<li><a href="#maintaining-an-aurora-installation">Maintaining an Aurora Installation</a></li>
+<li><a href="#monitoring">Monitoring</a></li>
+<li><a href="#running-stateful-services">Running stateful services</a></li>
+<li><a href="#dedicated-attribute">Dedicated attribute</a>
+
+<ul>
+<li><a href="#syntax">Syntax</a></li>
+<li><a href="#example">Example</a></li>
+</ul></li>
+</ul></li>
+<li><a href="#best-practices">Best practices</a>
+
+<ul>
+<li><a href="#diversity">Diversity</a></li>
+</ul></li>
+<li><a href="#common-problems">Common problems</a>
+
+<ul>
+<li><a href="#replicated-log-not-initialized">Replicated log not initialized</a></li>
+<li><a href="#symptoms">Symptoms</a></li>
+<li><a href="#solution">Solution</a></li>
+<li><a href="#scheduler-not-registered">Scheduler not registered</a></li>
+<li><a href="#symptoms-1">Symptoms</a></li>
+<li><a href="#solution-1">Solution</a></li>
+</ul></li>
+<li><a href="#changing-scheduler-quorum-size">Changing Scheduler Quorum Size</a>
+
+<ul>
+<li><a href="#preparation">Preparation</a></li>
+<li><a href="#adding-new-schedulers">Adding New Schedulers</a></li>
+</ul></li>
+</ul>
+
+<h2 id="installing-aurora">Installing Aurora</h2>
+
+<p>The Aurora scheduler is a standalone Java server. As part of the build process it creates a bundle
+of all its dependencies, with the notable exceptions of the JVM and libmesos. Each target server
+should have a JVM (Java 8 or higher) and libmesos (0.25.0) installed.</p>
+
+<h3 id="creating-the-distribution-zip-file-optional">Creating the Distribution .zip File (Optional)</h3>
+
+<p>To create a distribution for installation you will need build tools installed. On Ubuntu this can be
+done with <code>sudo apt-get install build-essential default-jdk</code>.</p>
+<pre class="highlight plaintext"><code>git clone http://git-wip-us.apache.org/repos/asf/aurora.git
+cd aurora
+./gradlew distZip
+</code></pre>
+
+<p>Copy the generated <code>dist/distributions/aurora-scheduler-*.zip</code> to each node that will run a scheduler.</p>
+
+<h3 id="installing-aurora">Installing Aurora</h3>
+
+<p>Extract the aurora-scheduler zip file. The example configurations assume it is extracted to
+<code>/usr/local/aurora-scheduler</code>.</p>
+<pre class="highlight plaintext"><code>sudo unzip dist/distributions/aurora-scheduler-*.zip -d /usr/local
+sudo ln -nfs "$(ls -dt /usr/local/aurora-scheduler-* | head -1)" /usr/local/aurora-scheduler
+</code></pre>
+
+<h2 id="configuring-aurora">Configuring Aurora</h2>
+
+<h3 id="a-note-on-configuration">A Note on Configuration</h3>
+
+<p>Like Mesos, Aurora uses command-line flags for runtime configuration. As such the Aurora
+“configuration file” is typically a <code>scheduler.sh</code> shell script of the form.</p>
+<pre class="highlight shell"><code><span style="color: #999988;font-style: italic">#!/bin/bash</span>
+<span style="color: #008080">AURORA_HOME</span><span style="color: #000000;font-weight: bold">=</span>/usr/local/aurora-scheduler
+
+<span style="color: #999988;font-style: italic"># Flags controlling the JVM.</span>
+<span style="color: #008080">JAVA_OPTS</span><span style="color: #000000;font-weight: bold">=(</span>
+ -Xmx2g
+ -Xms2g
+ <span style="color: #999988;font-style: italic"># GC tuning, etc.</span>
+<span style="color: #000000;font-weight: bold">)</span>
+
+<span style="color: #999988;font-style: italic"># Flags controlling the scheduler.</span>
+<span style="color: #008080">AURORA_FLAGS</span><span style="color: #000000;font-weight: bold">=(</span>
+ -http_port<span style="color: #000000;font-weight: bold">=</span>8081
+ <span style="color: #999988;font-style: italic"># Log configuration, etc.</span>
+<span style="color: #000000;font-weight: bold">)</span>
+
+<span style="color: #999988;font-style: italic"># Environment variables controlling libmesos</span>
+<span style="color: #0086B3">export </span><span style="color: #008080">JAVA_HOME</span><span style="color: #000000;font-weight: bold">=</span>...
+<span style="color: #0086B3">export </span><span style="color: #008080">GLOG_v</span><span style="color: #000000;font-weight: bold">=</span>1
+<span style="color: #0086B3">export </span><span style="color: #008080">LIBPROCESS_PORT</span><span style="color: #000000;font-weight: bold">=</span>8083
+
+<span style="color: #008080">JAVA_OPTS</span><span style="color: #000000;font-weight: bold">=</span><span style="color: #d14">"</span><span style="color: #000000;font-weight: bold">${</span><span style="color: #008080">JAVA_OPTS</span><span style="background-color: #f8f8f8">[*]</span><span style="color: #000000;font-weight: bold">}</span><span style="color: #d14">"</span> <span style="color: #0086B3">exec</span> <span style="color: #d14">"</span><span style="color: #008080">$AURORA_HOME</span><span style="color: #d14">/bin/aurora-scheduler"</span> <span style="color: #d14">"</span><span style="color: #000000;font-weight: bold">${</span><span style="color: #008080">AURORA_FLAGS</span><span style="background-color: #f8f8f8">[@]</span><span style="color: #000000;font-weight: bold">}</span><span style="color: #d14">"</span>
+</code></pre>
+
+<p>That way Aurora’s current flags are visible in <code>ps</code> and in the <code>/vars</code> admin endpoint.</p>
+
+<p>Examples are available under <code>examples/scheduler/</code>. For a list of available Aurora flags and their
+documentation run</p>
+<pre class="highlight plaintext"><code>/usr/local/aurora-scheduler/bin/aurora-scheduler -help
+</code></pre>
+
+<h3 id="replicated-log-configuration">Replicated Log Configuration</h3>
+
+<p>All Aurora state is persisted to a replicated log. This includes all jobs Aurora is running
+including where in the cluster they are being run and the configuration for running them, as
+well as other information such as metadata needed to reconnect to the Mesos master, resource
+quotas, and any other locks in place.</p>
+
+<p>Aurora schedulers use ZooKeeper to discover log replicas and elect a leader. Only one scheduler is
+leader at a given time - the other schedulers follow log writes and prepare to take over as leader
+but do not communicate with the Mesos master. Either 3 or 5 schedulers are recommended in a
+production deployment depending on failure tolerance and they must have persistent storage.</p>
+
+<p>In a cluster with <code>N</code> schedulers, the flag <code>-native_log_quorum_size</code> should be set to
+<code>floor(N/2) + 1</code>. So in a cluster with 1 scheduler it should be set to <code>1</code>, in a cluster with 3 it
+should be set to <code>2</code>, and in a cluster of 5 it should be set to <code>3</code>.</p>
+
+<table><thead>
+<tr>
+<th>Number of schedulers (N)</th>
+<th><code>-native_log_quorum_size</code> setting (<code>floor(N/2) + 1</code>)</th>
+</tr>
+</thead><tbody>
+<tr>
+<td>1</td>
+<td>1</td>
+</tr>
+<tr>
+<td>3</td>
+<td>2</td>
+</tr>
+<tr>
+<td>5</td>
+<td>3</td>
+</tr>
+<tr>
+<td>7</td>
+<td>4</td>
+</tr>
+</tbody></table>
+
+<p><em>Incorrectly setting this flag will cause data corruption to occur!</em></p>
+
+<p>See <a href="/documentation/0.12.0/storage-config/#scheduler-storage-configuration-flags">this document</a> for more replicated
+log and storage configuration options.</p>
+
+<h2 id="initializing-the-replicated-log">Initializing the Replicated Log</h2>
+
+<p>Before you start Aurora you will also need to initialize the log on a majority of the schedulers.</p>
+<pre class="highlight plaintext"><code>mesos-log initialize --path="/path/to/native/log"
+</code></pre>
+
+<p>The <code>--path</code> flag should match the <code>--native_log_file_path</code> flag to the scheduler.
+Failing to do this will result the following message when you try to start the scheduler.</p>
+<pre class="highlight plaintext"><code>Replica in EMPTY status received a broadcasted recover request
+</code></pre>
+
+<h3 id="storage-performance-considerations">Storage Performance Considerations</h3>
+
+<p>See <a href="/documentation/0.12.0/scheduler-storage/">this document</a> for scheduler storage performance considerations.</p>
+
+<h3 id="network-considerations">Network considerations</h3>
+
+<p>The Aurora scheduler listens on 2 ports - an HTTP port used for client RPCs and a web UI,
+and a libprocess (HTTP+Protobuf) port used to communicate with the Mesos master and for the log
+replication protocol. These can be left unconfigured (the scheduler publishes all selected ports
+to ZooKeeper) or explicitly set in the startup script as follows:</p>
+<pre class="highlight plaintext"><code># ...
+AURORA_FLAGS=(
+ # ...
+ -http_port=8081
+ # ...
+)
+# ...
+export LIBPROCESS_PORT=8083
+# ...
+</code></pre>
+
+<h3 id="considerations-for-running-jobs-in-docker-containers">Considerations for running jobs in docker containers</h3>
+
+<p>In order for Aurora to launch jobs using docker containers, a few extra configuration options
+must be set. The <a href="http://mesos.apache.org/documentation/latest/docker-containerizer/">docker containerizer</a>
+must be enabled on the mesos slaves by launching them with the <code>--containerizers=docker,mesos</code> option.</p>
+
+<p>By default, Aurora will configure Mesos to copy the file specified in <code>-thermos_executor_path</code>
+into the container’s sandbox. If using a wrapper script to launch the thermos executor,
+specify the path to the wrapper in that argument. In addition, the path to the executor pex itself
+must be included in the <code>-thermos_executor_resources</code> option. Doing so will ensure that both the
+wrapper script and executor are correctly copied into the sandbox. Finally, ensure the wrapper
+script does not access resources outside of the sandbox, as when the script is run from within a
+docker container those resources will not exist.</p>
+
+<p>In order to correctly execute processes inside a job, the docker container must have python 2.7
+installed.</p>
+
+<p>A scheduler flag, <code>-global_container_mounts</code> allows mounting paths from the host (i.e., the slave)
+into all containers on that host. The format is a comma separated list of host<em>path:container</em>path[:mode]
+tuples. For example <code>-global_container_mounts=/opt/secret_keys_dir:/mnt/secret_keys_dir:ro</code> mounts
+<code>/opt/secret_keys_dir</code> from the slaves into all launched containers. Valid modes are <code>ro</code> and <code>rw</code>.</p>
+
+<p>If you would like to supply your own parameters to <code>docker run</code> when launching jobs in docker
+containers, you may use the following flags:</p>
+<pre class="highlight plaintext"><code>-allow_docker_parameters
+-default_docker_parameters
+</code></pre>
+
+<p><code>-allow_docker_parameters</code> controls whether or not users may pass their own configuration parameters
+through the job configuration files. If set to <code>false</code> (the default), the scheduler will reject
+jobs with custom parameters. <em>NOTE</em>: this setting should be used with caution as it allows any job
+owner to specify any parameters they wish, including those that may introduce security concerns
+(<code>privileged=true</code>, for example).</p>
+
+<p><code>-default_docker_parameters</code> allows a cluster operator to specify a universal set of parameters that
+should be used for every container that does not have parameters explicitly configured at the job
+level. The argument accepts a multimap format:</p>
+<pre class="highlight plaintext"><code>-default_docker_parameters="read-only=true,tmpfs=/tmp,tmpfs=/run"
+</code></pre>
+
+<h3 id="process-logs">Process Logs</h3>
+
+<h4 id="log-destination">Log destination</h4>
+
+<p>By default, Thermos will write process stdout/stderr to log files in the sandbox. Process object configuration
+allows specifying alternate log file destinations like streamed stdout/stderr or suppression of all log output.
+Default behavior can be configured for the entire cluster with the following flag (through the <code>-thermos_executor_flags</code>
+argument to the Aurora scheduler):</p>
+<pre class="highlight plaintext"><code>--runner-logger-destination=both
+</code></pre>
+
+<p><code>both</code> configuration will send logs to files and stream to parent stdout/stderr outputs.</p>
+
+<p>See <a href="/documentation/0.12.0/configuration-reference/#logger">this document</a> for all destination options.</p>
+
+<h4 id="log-rotation">Log rotation</h4>
+
+<p>By default, Thermos will not rotate the stdout/stderr logs from child processes and they will grow
+without bound. An individual user may change this behavior via configuration on the Process object,
+but it may also be desirable to change the default configuration for the entire cluster.
+In order to enable rotation by default, the following flags can be applied to Thermos (through the
+-thermos<em>executor</em>flags argument to the Aurora scheduler):</p>
+<pre class="highlight plaintext"><code>--runner-logger-mode=rotate
+--runner-rotate-log-size-mb=100
+--runner-rotate-log-backups=10
+</code></pre>
+
+<p>In the above example, each instance of the Thermos runner will rotate stderr/stdout logs once they
+reach 100 MiB in size and keep a maximum of 10 backups. If a user has provided a custom setting for
+their process, it will override these default settings.</p>
+
+<h2 id="running-aurora">Running Aurora</h2>
+
+<p>Configure a supervisor like <a href="http://mmonit.com/monit/">Monit</a> or
+<a href="http://supervisord.org/">supervisord</a> to run the created <code>scheduler.sh</code> file and restart it
+whenever it fails. Aurora expects to be restarted by an external process when it fails. Aurora
+supports an active health checking protocol on its admin HTTP interface - if a <code>GET /health</code> times
+out or returns anything other than <code>200 OK</code> the scheduler process is unhealthy and should be
+restarted.</p>
+
+<p>For example, monit can be configured with</p>
+<pre class="highlight plaintext"><code>if failed port 8081 send "GET /health HTTP/1.0\r\n" expect "OK\n" with timeout 2 seconds for 10 cycles then restart
+</code></pre>
+
+<p>assuming you set <code>-http_port=8081</code>.</p>
+
+<h2 id="security-considerations">Security Considerations</h2>
+
+<p>See <a href="/documentation/0.12.0/security/">security.md</a>.</p>
+
+<h2 id="configuring-resource-oversubscription">Configuring Resource Oversubscription</h2>
+
+<p><strong>WARNING</strong>: This feature is currently in alpha status. Do not use it in production clusters!
+See <a href="/documentation/0.12.0/configuration-reference/#revocable-jobs">this document</a> for more feature details.</p>
+
+<p>Set these scheduler flag to allow receiving revocable Mesos offers:</p>
+<pre class="highlight plaintext"><code>-receive_revocable_resources=true
+</code></pre>
+
+<p>Specify a tier configuration file path:</p>
+<pre class="highlight plaintext"><code>-tier_config=path/to/tiers/config.json
+</code></pre>
+
+<p>Example <a href="https://github.com/apache/aurora/blob/#{git_tag}/src/test/resources/org/apache/aurora/scheduler/tiers-example.json">tier configuration file</a>).</p>
+
+<h3 id="maintaining-an-aurora-installation">Maintaining an Aurora Installation</h3>
+
+<h3 id="monitoring">Monitoring</h3>
+
+<p>Please see our dedicated <a href="/documentation/0.12.0/monitoring/">monitoring guide</a> for in-depth discussion on monitoring.</p>
+
+<h3 id="running-stateful-services">Running stateful services</h3>
+
+<p>Aurora is best suited to run stateless applications, but it also accommodates for stateful services
+like databases, or services that otherwise need to always run on the same machines.</p>
+
+<h4 id="dedicated-attribute">Dedicated attribute</h4>
+
+<p>The Mesos slave has the <code>--attributes</code> command line argument which can be used to mark a slave with
+static attributes (not to be confused with <code>--resources</code>, which are dynamic and accounted).</p>
+
+<p>Aurora makes these attributes available for matching with scheduling
+<a href="/documentation/0.12.0/configuration-reference/#specifying-scheduling-constraints">constraints</a>. Most of these
+constraints are arbitrary and available for custom use. There is one exception, though: the
+<code>dedicated</code> attribute. Aurora treats this specially, and only allows matching jobs to run on these
+machines, and will only schedule matching jobs on these machines.</p>
+
+<p>See the <a href="/documentation/0.12.0/resources/#resource-quota">section</a> about resource quotas to learn how quotas apply to
+dedicated jobs.</p>
+
+<h5 id="syntax">Syntax</h5>
+
+<p>The dedicated attribute has semantic meaning. The format is <code>$role(/.*)?</code>. When a job is created,
+the scheduler requires that the <code>$role</code> component matches the <code>role</code> field in the job
+configuration, and will reject the job creation otherwise. The remainder of the attribute is
+free-form. We’ve developed the idiom of formatting this attribute as <code>$role/$job</code>, but do not
+enforce this.</p>
+
+<h5 id="example">Example</h5>
+
+<p>Consider the following slave command line:</p>
+<pre class="highlight plaintext"><code>mesos-slave --attributes="dedicated:db_team/redis" ...
+</code></pre>
+
+<p>And this job configuration:</p>
+<pre class="highlight plaintext"><code>Service(
+ name = 'redis',
+ role = 'db_team',
+ constraints = {
+ 'dedicated': 'db_team/redis'
+ }
+ ...
+)
+</code></pre>
+
+<p>The job configuration is indicating that it should only be scheduled on slaves with the attribute
+<code>dedicated:db_team/redis</code>. Additionally, Aurora will prevent any tasks that do <em>not</em> have that
+constraint from running on those slaves.</p>
+
+<h2 id="best-practices">Best practices</h2>
+
+<h3 id="diversity">Diversity</h3>
+
+<p>Data centers are often organized with hierarchical failure domains. Common failure domains
+include hosts, racks, rows, and PDUs. If you have this information available, it is wise to tag
+the mesos-slave with them as
+<a href="https://mesos.apache.org/documentation/attributes-resources/">attributes</a>.</p>
+
+<p>When it comes time to schedule jobs, Aurora will automatically spread them across the failure
+domains as specified in the
+<a href="/documentation/0.12.0/configuration-reference/#specifying-scheduling-constraints">job configuration</a>.</p>
+
+<p>Note: in virtualized environments like EC2, the only attribute that usually makes sense for this
+purpose is <code>host</code>.</p>
+
+<h2 id="common-problems">Common problems</h2>
+
+<p>So you’ve started your first cluster and are running into some issues? We’ve collected some common
+stumbling blocks and solutions here to help get you moving.</p>
+
+<h3 id="replicated-log-not-initialized">Replicated log not initialized</h3>
+
+<h4 id="symptoms">Symptoms</h4>
+
+<ul>
+<li>Scheduler RPCs and web interface claim <code>Storage is not READY</code></li>
+<li>Scheduler log repeatedly prints messages like</li>
+</ul>
+<pre class="highlight plaintext"><code> I1016 16:12:27.234133 26081 replica.cpp:638] Replica in EMPTY status
+ received a broadcasted recover request
+ I1016 16:12:27.234256 26084 recover.cpp:188] Received a recover response
+ from a replica in EMPTY status
+</code></pre>
+
+<h4 id="solution">Solution</h4>
+
+<p>When you create a new cluster, you need to inform a quorum of schedulers that they are safe to
+consider their database to be empty by <a href="#initializing-the-replicated-log">initializing</a> the
+replicated log. This is done to prevent the scheduler from modifying the cluster state in the event
+of multiple simultaneous disk failures or, more likely, misconfiguration of the replicated log path.</p>
+
+<h3 id="scheduler-not-registered">Scheduler not registered</h3>
+
+<h4 id="symptoms">Symptoms</h4>
+
+<p>Scheduler log contains</p>
+<pre class="highlight plaintext"><code>Framework has not been registered within the tolerated delay.
+</code></pre>
+
+<h4 id="solution">Solution</h4>
+
+<p>Double-check that the scheduler is configured correctly to reach the master. If you are registering
+the master in ZooKeeper, make sure command line argument to the master:</p>
+<pre class="highlight plaintext"><code>--zk=zk://$ZK_HOST:2181/mesos/master
+</code></pre>
+
+<p>is the same as the one on the scheduler:</p>
+<pre class="highlight plaintext"><code>-mesos_master_address=zk://$ZK_HOST:2181/mesos/master
+</code></pre>
+
+<h2 id="changing-scheduler-quorum-size">Changing Scheduler Quorum Size</h2>
+
+<p>Special care needs to be taken when changing the size of the Aurora scheduler quorum.
+Since Aurora uses a Mesos replicated log, similar steps need to be followed as when
+<a href="http://mesos.apache.org/documentation/latest/operational-guide">changing the mesos quorum size</a>.</p>
+
+<h3 id="preparation">Preparation</h3>
+
+<p>Increase <a href="/documentation/0.12.0/storage-config/#-native_log_quorum_size">-native<em>log</em>quorum_size</a> on each
+existing scheduler and restart them. When updating from 3 to 5 schedulers, the quorum size
+would grow from 2 to 3.</p>
+
+<h3 id="adding-new-schedulers">Adding New Schedulers</h3>
+
+<p>Start the new schedulers with <code>-native_log_quorum_size</code> set to the new value. Failing to
+first increase the quorum size on running schedulers can in some cases result in corruption
+or truncating of the replicated log used by Aurora. In that case, see the documentation on
+<a href="/documentation/0.12.0/storage-config/#recovering-from-a-scheduler-backup">recovering from backup</a>.</p>
+
+</div>
+
+ </div>
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