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Posted to commits@storm.apache.org by pt...@apache.org on 2015/09/29 21:31:00 UTC
svn commit: r1705915 [3/7] - in /storm/site/publish: ./ contribute/
documentation/
Added: storm/site/publish/documentation/nimbus-ha-design.md
URL: http://svn.apache.org/viewvc/storm/site/publish/documentation/nimbus-ha-design.md?rev=1705915&view=auto
==============================================================================
--- storm/site/publish/documentation/nimbus-ha-design.md (added)
+++ storm/site/publish/documentation/nimbus-ha-design.md Tue Sep 29 19:31:00 2015
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+#Highly Available Nimbus design proposal
+##Problem Statement:
+Currently the storm master aka nimbus, is a process that runs on a single machine under supervision. In most cases the
+nimbus failure is transient and it is restarted by the supervisor. However sometimes when disks fail and networks
+partitions occur, nimbus goes down. Under these circumstances the topologies run normally but no new topologies can be
+submitted, no existing topologies can be killed/deactivated/activated and if a supervisor node fails then the
+reassignments are not performed resulting in performance degradation or topology failures. With this project we intend
+to resolve this problem by running nimbus in a primary backup mode to guarantee that even if a nimbus server fails one
+of the backups will take over.
+##Requirements:
+* Increase overall availability of nimbus.
+* Allow nimbus hosts to leave and join the cluster at will any time. A newly joined host should auto catch up and join
+the list of potential leaders automatically.
+* No topology resubmissions required in case of nimbus fail overs.
+* No active topology should ever be lost.
+
+##Leader Election:
+The nimbus server will use the following interface:
+
+```java
+public interface ILeaderElector {
+ /**
+ * queue up for leadership lock. The call returns immediately and the caller
+ * must check isLeader() to perform any leadership action.
+ */
+ void addToLeaderLockQueue();
+
+ /**
+ * Removes the caller from the leader lock queue. If the caller is leader
+ * also releases the lock.
+ */
+ void removeFromLeaderLockQueue();
+
+ /**
+ *
+ * @return true if the caller currently has the leader lock.
+ */
+ boolean isLeader();
+
+ /**
+ *
+ * @return the current leader's address , throws exception if noone has has lock.
+ */
+ InetSocketAddress getLeaderAddress();
+
+ /**
+ *
+ * @return list of current nimbus addresses, includes leader.
+ */
+ List<InetSocketAddress> getAllNimbusAddresses();
+}
+```
+On startup nimbus will check if it has code for all active topologies available locally. Once it gets to this state it
+will call addToLeaderLockQueue() function. When a nimbus is notified to become a leader it will check if it has all the
+code locally before assuming the leadership role. If any active topology code is missing, the node will not accept the
+leadership role instead it will release the lock and wait till it has all the code before requeueing for leader lock.
+
+The first implementation will be Zookeeper based. If the zookeeper connection is lost/resetted resulting in loss of lock
+or the spot in queue the implementation will take care of updating the state such that isLeader() will reflect the
+current status.The leader like actions must finish in less than minimumOf(connectionTimeout, SessionTimeout) to ensure
+the lock was held by nimbus for the entire duration of the action (Not sure if we want to just state this expectation
+and ensure that zk configurations are set high enough which will result in higher failover time or we actually want to
+create some sort of rollback mechanism for all actions, the second option needs a lot of code). If a nimbus that is not
+leader receives a request that only a leader can perform it will throw a RunTimeException.
+
+Following steps describes a nimbus failover scenario:
+* Letâs say we have 4 topologies running with 3 nimbus nodes and code-replication-factor = 2. We assume that the
+invariant âThe leader nimbus has code for all topologies locallyâ holds true at the beginning. nonleader-1 has code for
+the first 2 topologies and nonLeader-2 has code for the other 2 topologies.
+* Leader nimbus dies, hard disk failure so no recovery possible.
+* nonLeader-1 gets a zookeeper notification to indicate it is now the new leader. before accepting the leadership it
+checks if it has code available for all 4 topologies(these are topologies under /storm/storms/). It realizes it only has
+code for 2 topologies so it relinquishes the lock and looks under /storm/code-distributor/topologyId to find out from
+where can it download the code/metafile for the missing topologies. it finds entries for the leader nimbus and
+nonleader-2. It will try downloading from both as part of its retry mechanism.
+* nonLeader-2âs code sync thread also realizes that it is missing code for 2 topologies and follows the same process
+described in step-3 to download code for missing topologies.
+* eventually at least one of the nimbuses will have all the code locally and will accept leadership.
+This sequence diagram describes how leader election and failover would work with multiple components.
+
+
+
+##Nimbus state store:
+
+Currently the nimbus stores 2 kind of data
+* Meta information like supervisor info, assignment info which is stored in zookeeper
+* Actual topology configs and jars that is stored on nimbus hostâs local disk.
+
+To achieve fail over from primary to backup servers nimbus state/data needs to be replicated across all nimbus hosts or
+needs to be stored in a distributed storage. Replicating the data correctly involves state management, consistency checks
+and it is hard to test for correctness.However many storm users do not want to take extra dependency on another replicated
+storage system like HDFS and still need high availability.Eventually, we want to move to the bittorrent protocol for code
+distribution given the size of the jars and to achieve better scaling when the total number of supervisors is very high.
+The current file system based model for code distribution works fine with systems that have file system like structure
+but it fails to support a non file system based approach like bit torrent. To support bit torrent and all the file
+system based replicated storage systems we propose the following interface:
+
+```java
+/**
+ * Interface responsible to distribute code in the cluster.
+ */
+public interface ICodeDistributor {
+ /**
+ * Prepare this code distributor.
+ * @param conf
+ */
+ void prepare(Map conf);
+
+ /**
+ * This API will perform the actual upload of the code to the distributed implementation.
+ * The API should return a Meta file which should have enough information for downloader
+ * so it can download the code e.g. for bittorrent it will be a torrent file, in case of something
+ * like HDFS or s3 it might have the actual directory or paths for files to be downloaded.
+ * @param dirPath local directory where all the code to be distributed exists.
+ * @param topologyId the topologyId for which the meta file needs to be created.
+ * @return metaFile
+ */
+ File upload(Path dirPath, String topologyId);
+
+ /**
+ * Given the topologyId and metafile, download the actual code and return the downloaded file's list.
+ * @param topologyid
+ * @param metafile
+ * @param destDirPath the folder where all the files will be downloaded.
+ * @return
+ */
+ List<File> download(Path destDirPath, String topologyid, File metafile);
+
+ /**
+ * Given the topologyId, returns number of hosts where the code has been replicated.
+ */
+ int getReplicationCount(String topologyId);
+
+ /**
+ * Performs the cleanup.
+ * @param topologyid
+ */
+ void cleanup(String topologyid);
+
+ /**
+ * Close this distributor.
+ * @param conf
+ */
+ void close(Map conf);
+}
+```
+To support replication we will allow the user to define a code replication factor which would reflect number of nimbus
+hosts to which the code must be replicated before starting the topology. With replication comes the issue of consistency.
+We will treat zookeeperâs list of active topologies as our authority for topologies for which the code must exist on a
+nimbus host. Any nimbus host that does not have all the code for all the topologies which are marked as active in zookeeper
+will relinquish itâs lock so some other nimbus host could become leader. A background thread on all nimbus host will
+continuously try to sync code from other hosts where the code was successfully replicated so eventually at least one nimbus
+will accept leadership as long as at least one seed hosts exists for each active topology.
+
+Following steps describe code replication amongst nimbus hosts for a topology:
+* When client uploads jar, nothing changes.
+* When client submits a topology, leader nimbus calls code distributorâs upload function which will create a metafile stored
+locally on leader nimbus. Leader nimbus will write new entries under /storm/code-distributor/topologyId to notify all
+nonleader nimbuses that they should download this new code.
+* We wait on the leader nimbus to ensure at least N non leader nimbus has the code replicated, with a user configurable timeout.
+* When a non leader nimbus receives the notification about new code, it downloads the meta file from leader nimbus and then
+downloads the real code by calling code distributorâs download function with metafile as input.
+* Once non leader finishes downloading code, it will write an entry under /storm/code-distributor/topologyId to indicate
+it is one of the possible places to download the code/metafile in case the leader nimbus dies.
+* leader nimbus goes ahead and does all the usual things it does as part of submit topologies.
+
+The following sequence diagram describes the communication between different components involved in code distribution.
+
+
+
+##Thrift and Rest API
+In order to avoid workers/supervisors/ui talking to zookeeper for getting master nimbus address we are going to modify the
+`getClusterInfo` API so it can also return nimbus information. getClusterInfo currently returns `ClusterSummary` instance
+which has a list of `supervisorSummary` and a list of 'topologySummary` instances. We will add a list of `NimbusSummary`
+to the `ClusterSummary`. See the structures below:
+
+```thrift
+struct ClusterSummary {
+ 1: required list<SupervisorSummary> supervisors;
+ 3: required list<TopologySummary> topologies;
+ 4: required list<NimbusSummary> nimbuses;
+}
+
+struct NimbusSummary {
+ 1: required string host;
+ 2: required i32 port;
+ 3: required i32 uptime_secs;
+ 4: required bool isLeader;
+ 5: required string version;
+}
+```
+
+This will be used by StormSubmitter, Nimbus clients,supervisors and ui to discover the current leaders and participating
+nimbus hosts. Any nimbus host will be able to respond to these requests. The nimbus hosts can read this information once
+from zookeeper and cache it and keep updating the cache when the watchers are fired to indicate any changes,which should
+be rare in general case.
+
+## Configuration
+You can use nimbus ha with default configuration , however the default configuration assumes a single nimbus host so it
+trades off replication for lower topology submission latency. Depending on your use case you can adjust following configurations:
+* storm.codedistributor.class : This is a string representing fully qualified class name of a class that implements
+backtype.storm.codedistributor.ICodeDistributor. The default is set to "backtype.storm.codedistributor.LocalFileSystemCodeDistributor".
+This class leverages local file system to store both meta files and code/configs. This class adds extra load on zookeeper as even after
+downloading the code-distrbutor meta file it contacts zookeeper in order to figure out hosts from where it can download
+actual code/config and to get the current replication count. An alternative is to use
+"org.apache.storm.hdfs.ha.codedistributor.HDFSCodeDistributor" which relies on HDFS but does not add extra load on zookeeper and will
+make topology submission faster.
+* topology.min.replication.count : Minimum number of nimbus hosts where the code must be replicated before leader nimbus
+can mark the topology as active and create assignments. Default is 1.
+* topology.max.replication.wait.time.sec: Maximum wait time for the nimbus host replication to achieve the nimbus.min.replication.count.
+Once this time is elapsed nimbus will go ahead and perform topology activation tasks even if required nimbus.min.replication.count is not achieved.
+The default is 60 seconds, a value of -1 indicates to wait for ever.
+*nimbus.code.sync.freq.secs: frequency at which the background thread on nimbus which syncs code for locally missing topologies will run. default is 5 minutes.
+
+Note: Even though all nimbus hosts have watchers on zookeeper to be notified immediately as soon as a new topology is available for code
+download, the callback pretty much never results in code download. In practice we have observed that the desired replication is only achieved once the background-thread runs.
+So you should expect your topology submission time to be somewhere between 0 to (2 * nimbus.code.sync.freq.secs) for any nimbus.min.replication.count > 1.
\ No newline at end of file
Added: storm/site/publish/documentation/storm-eventhubs.html
URL: http://svn.apache.org/viewvc/storm/site/publish/documentation/storm-eventhubs.html?rev=1705915&view=auto
==============================================================================
--- storm/site/publish/documentation/storm-eventhubs.html (added)
+++ storm/site/publish/documentation/storm-eventhubs.html Tue Sep 29 19:31:00 2015
@@ -0,0 +1,203 @@
+<!DOCTYPE html>
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+ <h1 class="page-title">Azue Event Hubs Integration</h1>
+ <div class="row">
+ <div class="col-md-12">
+ <!-- Documentation -->
+
+<p class="post-meta"></p>
+
+<p>Storm spout and bolt implementation for Microsoft Azure Eventhubs</p>
+
+<h3 id="build">build</h3>
+<div class="highlight"><pre><code class="language-text" data-lang="text">mvn clean package
+</code></pre></div>
+<h3 id="run-sample-topology">run sample topology</h3>
+
+<p>To run the sample topology, you need to modify the config.properties file with
+the eventhubs configurations. Here is an example:</p>
+<div class="highlight"><pre><code class="language-text" data-lang="text">eventhubspout.username = [username: policy name in EventHubs Portal]
+eventhubspout.password = [password: shared access key in EventHubs Portal]
+eventhubspout.namespace = [namespace]
+eventhubspout.entitypath = [entitypath]
+eventhubspout.partitions.count = [partitioncount]
+
+# if not provided, will use storm's zookeeper settings
+# zookeeper.connectionstring=zookeeper0:2181,zookeeper1:2181,zookeeper2:2181
+
+eventhubspout.checkpoint.interval = 10
+eventhub.receiver.credits = 1024
+</code></pre></div>
+<p>Then you can use storm.cmd to submit the sample topology:
+ storm jar {jarfile} com.microsoft.eventhubs.samples.EventCount {topologyname} {spoutconffile}
+ where the {jarfile} should be: eventhubs-storm-spout-{version}-jar-with-dependencies.jar</p>
+
+<h3 id="run-eventhubsendclient">Run EventHubSendClient</h3>
+
+<p>We have included a simple EventHubs send client for testing purpose. You can run the client like this:
+ java -cp .\target\eventhubs-storm-spout-{version}-jar-with-dependencies.jar com.microsoft.eventhubs.client.EventHubSendClient
+ [username] [password] [entityPath] [partitionId] [messageSize] [messageCount]
+If you want to send messages to all partitions, use "-1" as partitionId.</p>
+
+<h3 id="windows-azure-eventhubs">Windows Azure Eventhubs</h3>
+<div class="highlight"><pre><code class="language-text" data-lang="text">http://azure.microsoft.com/en-us/services/event-hubs/
+</code></pre></div>
+
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Added: storm/site/publish/documentation/storm-hbase.html
URL: http://svn.apache.org/viewvc/storm/site/publish/documentation/storm-hbase.html?rev=1705915&view=auto
==============================================================================
--- storm/site/publish/documentation/storm-hbase.html (added)
+++ storm/site/publish/documentation/storm-hbase.html Tue Sep 29 19:31:00 2015
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+ <li><a href="/contribute/BYLAWS.html">ByLaws</a></li>
+ </ul>
+ </li>
+ <li><a href="/2015/06/15/storm0100-beta-released.html" id="news">News</a></li>
+ </ul>
+ </nav>
+ </div>
+</div>
+
+
+
+ <div class="container-fluid">
+ <h1 class="page-title">Storm HBase Integration</h1>
+ <div class="row">
+ <div class="col-md-12">
+ <!-- Documentation -->
+
+<p class="post-meta"></p>
+
+<p>Storm/Trident integration for <a href="https://hbase.apache.org">Apache HBase</a></p>
+
+<h2 id="usage">Usage</h2>
+
+<p>The main API for interacting with HBase is the <code>org.apache.storm.hbase.bolt.mapper.HBaseMapper</code>
+interface:</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">public</span> <span class="kd">interface</span> <span class="nc">HBaseMapper</span> <span class="kd">extends</span> <span class="n">Serializable</span> <span class="o">{</span>
+ <span class="kt">byte</span><span class="o">[]</span> <span class="nf">rowKey</span><span class="o">(</span><span class="n">Tuple</span> <span class="n">tuple</span><span class="o">);</span>
+
+ <span class="n">ColumnList</span> <span class="nf">columns</span><span class="o">(</span><span class="n">Tuple</span> <span class="n">tuple</span><span class="o">);</span>
+<span class="o">}</span>
+</code></pre></div>
+<p>The <code>rowKey()</code> method is straightforward: given a Storm tuple, return a byte array representing the
+row key.</p>
+
+<p>The <code>columns()</code> method defines what will be written to an HBase row. The <code>ColumnList</code> class allows you
+to add both standard HBase columns as well as HBase counter columns.</p>
+
+<p>To add a standard column, use one of the <code>addColumn()</code> methods:</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">ColumnList</span> <span class="n">cols</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">ColumnList</span><span class="o">();</span>
+<span class="n">cols</span><span class="o">.</span><span class="na">addColumn</span><span class="o">(</span><span class="k">this</span><span class="o">.</span><span class="na">columnFamily</span><span class="o">,</span> <span class="n">field</span><span class="o">.</span><span class="na">getBytes</span><span class="o">(),</span> <span class="n">toBytes</span><span class="o">(</span><span class="n">tuple</span><span class="o">.</span><span class="na">getValueByField</span><span class="o">(</span><span class="n">field</span><span class="o">)));</span>
+</code></pre></div>
+<p>To add a counter column, use one of the <code>addCounter()</code> methods:</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">ColumnList</span> <span class="n">cols</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">ColumnList</span><span class="o">();</span>
+<span class="n">cols</span><span class="o">.</span><span class="na">addCounter</span><span class="o">(</span><span class="k">this</span><span class="o">.</span><span class="na">columnFamily</span><span class="o">,</span> <span class="n">field</span><span class="o">.</span><span class="na">getBytes</span><span class="o">(),</span> <span class="n">toLong</span><span class="o">(</span><span class="n">tuple</span><span class="o">.</span><span class="na">getValueByField</span><span class="o">(</span><span class="n">field</span><span class="o">)));</span>
+</code></pre></div>
+<p>When the remote HBase is security enabled, a kerberos keytab and the corresponding principal name need to be
+provided for the storm-hbase connector. Specifically, the Config object passed into the topology should contain
+{(âstorm.keytab.fileâ, â$keytabâ), ("storm.kerberos.principal", â$principalâ)}. Example:</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">Config</span> <span class="n">config</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">Config</span><span class="o">();</span>
+<span class="o">...</span>
+<span class="n">config</span><span class="o">.</span><span class="na">put</span><span class="o">(</span><span class="s">"storm.keytab.file"</span><span class="o">,</span> <span class="s">"$keytab"</span><span class="o">);</span>
+<span class="n">config</span><span class="o">.</span><span class="na">put</span><span class="o">(</span><span class="s">"storm.kerberos.principal"</span><span class="o">,</span> <span class="s">"$principle"</span><span class="o">);</span>
+<span class="n">StormSubmitter</span><span class="o">.</span><span class="na">submitTopology</span><span class="o">(</span><span class="s">"$topologyName"</span><span class="o">,</span> <span class="n">config</span><span class="o">,</span> <span class="n">builder</span><span class="o">.</span><span class="na">createTopology</span><span class="o">());</span>
+</code></pre></div>
+<h2 id="working-with-secure-hbase-using-delegation-tokens.">Working with Secure HBASE using delegation tokens.</h2>
+
+<p>If your topology is going to interact with secure HBase, your bolts/states needs to be authenticated by HBase.
+The approach described above requires that all potential worker hosts have "storm.keytab.file" on them. If you have
+multiple topologies on a cluster , each with different hbase user, you will have to create multiple keytabs and distribute
+it to all workers. Instead of doing that you could use the following approach:</p>
+
+<p>Your administrator can configure nimbus to automatically get delegation tokens on behalf of the topology submitter user.
+The nimbus need to start with following configurations:</p>
+
+<p>nimbus.autocredential.plugins.classes : ["org.apache.storm.hbase.security.AutoHBase"]
+nimbus.credential.renewers.classes : ["org.apache.storm.hbase.security.AutoHBase"]
+hbase.keytab.file: "/path/to/keytab/on/nimbus" (This is the keytab of hbase super user that can impersonate other users.)
+hbase.kerberos.principal: "<a href="mailto:superuser@EXAMPLE.com">superuser@EXAMPLE.com</a>"
+nimbus.credential.renewers.freq.secs : 518400 (6 days, hbase tokens by default expire every 7 days and can not be renewed,
+if you have custom settings for hbase.auth.token.max.lifetime in hbase-site.xml than you should ensure this value is
+atleast 1 hour less then that.)</p>
+
+<p>Your topology configuration should have:
+topology.auto-credentials :["org.apache.storm.hbase.security.AutoHBase"] </p>
+
+<p>If nimbus did not have the above configuration you need to add it and then restart it. Ensure the hbase configuration
+files(core-site.xml,hdfs-site.xml and hbase-site.xml) and the storm-hbase jar with all the dependencies is present in nimbus's classpath.
+Nimbus will use the keytab and principal specified in the config to authenticate with HBase. From then on for every
+topology submission, nimbus will impersonate the topology submitter user and acquire delegation tokens on behalf of the
+topology submitter user. If topology was started with topology.auto-credentials set to AutoHBase, nimbus will push the
+delegation tokens to all the workers for your topology and the hbase bolt/state will authenticate with these tokens.</p>
+
+<p>As nimbus is impersonating topology submitter user, you need to ensure the user specified in storm.kerberos.principal
+has permissions to acquire tokens on behalf of other users. To achieve this you need to follow configuration directions
+listed on this link</p>
+
+<p><a href="http://hbase.apache.org/book/security.html#security.rest.gateway">http://hbase.apache.org/book/security.html#security.rest.gateway</a></p>
+
+<p>You can read about setting up secure HBase here:<a href="http://hbase.apache.org/book/security.html">http://hbase.apache.org/book/security.html</a>.</p>
+
+<h3 id="simplehbasemapper">SimpleHBaseMapper</h3>
+
+<p><code>storm-hbase</code> includes a general purpose <code>HBaseMapper</code> implementation called <code>SimpleHBaseMapper</code> that can map Storm
+tuples to both regular HBase columns as well as counter columns.</p>
+
+<p>To use <code>SimpleHBaseMapper</code>, you simply tell it which fields to map to which types of columns.</p>
+
+<p>The following code create a <code>SimpleHBaseMapper</code> instance that:</p>
+
+<ol>
+<li>Uses the <code>word</code> tuple value as a row key.</li>
+<li>Adds a standard HBase column for the tuple field <code>word</code>.</li>
+<li>Adds an HBase counter column for the tuple field <code>count</code>.</li>
+<li>Writes values to the <code>cf</code> column family.</li>
+</ol>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">SimpleHBaseMapper</span> <span class="n">mapper</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">SimpleHBaseMapper</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">withRowKeyField</span><span class="o">(</span><span class="s">"word"</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">withColumnFields</span><span class="o">(</span><span class="k">new</span> <span class="nf">Fields</span><span class="o">(</span><span class="s">"word"</span><span class="o">))</span>
+ <span class="o">.</span><span class="na">withCounterFields</span><span class="o">(</span><span class="k">new</span> <span class="nf">Fields</span><span class="o">(</span><span class="s">"count"</span><span class="o">))</span>
+ <span class="o">.</span><span class="na">withColumnFamily</span><span class="o">(</span><span class="s">"cf"</span><span class="o">);</span>
+</code></pre></div>
+<h3 id="hbasebolt">HBaseBolt</h3>
+
+<p>To use the <code>HBaseBolt</code>, construct it with the name of the table to write to, an a <code>HBaseMapper</code> implementation:</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">HBaseBolt</span> <span class="n">hbase</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">HBaseBolt</span><span class="o">(</span><span class="s">"WordCount"</span><span class="o">,</span> <span class="n">mapper</span><span class="o">);</span>
+</code></pre></div>
+<p>The <code>HBaseBolt</code> will delegate to the <code>mapper</code> instance to figure out how to persist tuple data to HBase.</p>
+
+<h3 id="hbasevaluemapper">HBaseValueMapper</h3>
+
+<p>This class allows you to transform the HBase lookup result into storm Values that will be emitted by the <code>HBaseLookupBolt</code>.</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">public</span> <span class="kd">interface</span> <span class="nc">HBaseValueMapper</span> <span class="kd">extends</span> <span class="n">Serializable</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="n">List</span><span class="o"><</span><span class="n">Values</span><span class="o">></span> <span class="nf">toTuples</span><span class="o">(</span><span class="n">Result</span> <span class="n">result</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span><span class="o">;</span>
+ <span class="kt">void</span> <span class="nf">declareOutputFields</span><span class="o">(</span><span class="n">OutputFieldsDeclarer</span> <span class="n">declarer</span><span class="o">);</span>
+<span class="o">}</span>
+</code></pre></div>
+<p>The <code>toTuples</code> method takes in a HBase <code>Result</code> instance and expects a List of <code>Values</code> instant.
+Each of the value returned by this function will be emitted by the <code>HBaseLookupBolt</code>.</p>
+
+<p>The <code>declareOutputFields</code> should be used to declare the outputFields of the <code>HBaseLookupBolt</code>.</p>
+
+<p>There is an example implementation in <code>src/test/java</code> directory.</p>
+
+<h3 id="hbaseprojectioncriteria">HBaseProjectionCriteria</h3>
+
+<p>This class allows you to specify the projection criteria for your HBase Get function. This is optional parameter
+for the lookupBolt and if you do not specify this instance all the columns will be returned by <code>HBaseLookupBolt</code>.</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">HBaseProjectionCriteria</span> <span class="kd">implements</span> <span class="n">Serializable</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="n">HBaseProjectionCriteria</span> <span class="nf">addColumnFamily</span><span class="o">(</span><span class="n">String</span> <span class="n">columnFamily</span><span class="o">);</span>
+ <span class="kd">public</span> <span class="n">HBaseProjectionCriteria</span> <span class="nf">addColumn</span><span class="o">(</span><span class="n">ColumnMetaData</span> <span class="n">column</span><span class="o">);</span>
+</code></pre></div>
+<p><code>addColumnFamily</code> takes in columnFamily. Setting this parameter means all columns for this family will be included
+ in the projection.</p>
+
+<p><code>addColumn</code> takes in a columnMetaData instance. Setting this parameter means only this column from the column familty
+ will be part of your projection.
+The following code creates a projectionCriteria which specifies a projection criteria that:</p>
+
+<ol>
+<li>includes count column from column family cf.</li>
+<li>includes all columns from column family cf2.</li>
+</ol>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">HBaseProjectionCriteria</span> <span class="n">projectionCriteria</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">HBaseProjectionCriteria</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">addColumn</span><span class="o">(</span><span class="k">new</span> <span class="n">HBaseProjectionCriteria</span><span class="o">.</span><span class="na">ColumnMetaData</span><span class="o">(</span><span class="s">"cf"</span><span class="o">,</span> <span class="s">"count"</span><span class="o">))</span>
+ <span class="o">.</span><span class="na">addColumnFamily</span><span class="o">(</span><span class="s">"cf2"</span><span class="o">);</span>
+</code></pre></div>
+<h3 id="hbaselookupbolt">HBaseLookupBolt</h3>
+
+<p>To use the <code>HBaseLookupBolt</code>, Construct it with the name of the table to write to, an implementation of <code>HBaseMapper</code>
+and an implementation of <code>HBaseRowToStormValueMapper</code>. You can optionally specify a <code>HBaseProjectionCriteria</code>. </p>
+
+<p>The <code>HBaseLookupBolt</code> will use the mapper to get rowKey to lookup for. It will use the <code>HBaseProjectionCriteria</code> to
+figure out which columns to include in the result and it will leverage the <code>HBaseRowToStormValueMapper</code> to get the
+values to be emitted by the bolt.</p>
+
+<p>You can look at an example topology LookupWordCount.java under <code>src/test/java</code>.</p>
+
+<h2 id="example:-persistent-word-count">Example: Persistent Word Count</h2>
+
+<p>A runnable example can be found in the <code>src/test/java</code> directory.</p>
+
+<h3 id="setup">Setup</h3>
+
+<p>The following steps assume you are running HBase locally, or there is an <code>hbase-site.xml</code> on the
+classpath pointing to your HBase cluster.</p>
+
+<p>Use the <code>hbase shell</code> command to create the schema:</p>
+<div class="highlight"><pre><code class="language-text" data-lang="text">> create 'WordCount', 'cf'
+</code></pre></div>
+<h3 id="execution">Execution</h3>
+
+<p>Run the <code>org.apache.storm.hbase.topology.PersistenWordCount</code> class (it will run the topology for 10 seconds, then exit).</p>
+
+<p>After (or while) the word count topology is running, run the <code>org.apache.storm.hbase.topology.WordCountClient</code> class
+to view the counter values stored in HBase. You should see something like to following:</p>
+<div class="highlight"><pre><code class="language-text" data-lang="text">Word: 'apple', Count: 6867
+Word: 'orange', Count: 6645
+Word: 'pineapple', Count: 6954
+Word: 'banana', Count: 6787
+Word: 'watermelon', Count: 6806
+</code></pre></div>
+<p>For reference, the sample topology is listed below:</p>
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">PersistentWordCount</span> <span class="o">{</span>
+ <span class="kd">private</span> <span class="kd">static</span> <span class="kd">final</span> <span class="n">String</span> <span class="n">WORD_SPOUT</span> <span class="o">=</span> <span class="s">"WORD_SPOUT"</span><span class="o">;</span>
+ <span class="kd">private</span> <span class="kd">static</span> <span class="kd">final</span> <span class="n">String</span> <span class="n">COUNT_BOLT</span> <span class="o">=</span> <span class="s">"COUNT_BOLT"</span><span class="o">;</span>
+ <span class="kd">private</span> <span class="kd">static</span> <span class="kd">final</span> <span class="n">String</span> <span class="n">HBASE_BOLT</span> <span class="o">=</span> <span class="s">"HBASE_BOLT"</span><span class="o">;</span>
+
+
+ <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span>
+ <span class="n">Config</span> <span class="n">config</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">Config</span><span class="o">();</span>
+
+ <span class="n">WordSpout</span> <span class="n">spout</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">WordSpout</span><span class="o">();</span>
+ <span class="n">WordCounter</span> <span class="n">bolt</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">WordCounter</span><span class="o">();</span>
+
+ <span class="n">SimpleHBaseMapper</span> <span class="n">mapper</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">SimpleHBaseMapper</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">withRowKeyField</span><span class="o">(</span><span class="s">"word"</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">withColumnFields</span><span class="o">(</span><span class="k">new</span> <span class="nf">Fields</span><span class="o">(</span><span class="s">"word"</span><span class="o">))</span>
+ <span class="o">.</span><span class="na">withCounterFields</span><span class="o">(</span><span class="k">new</span> <span class="nf">Fields</span><span class="o">(</span><span class="s">"count"</span><span class="o">))</span>
+ <span class="o">.</span><span class="na">withColumnFamily</span><span class="o">(</span><span class="s">"cf"</span><span class="o">);</span>
+
+ <span class="n">HBaseBolt</span> <span class="n">hbase</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">HBaseBolt</span><span class="o">(</span><span class="s">"WordCount"</span><span class="o">,</span> <span class="n">mapper</span><span class="o">);</span>
+
+
+ <span class="c1">// wordSpout ==> countBolt ==> HBaseBolt</span>
+ <span class="n">TopologyBuilder</span> <span class="n">builder</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">TopologyBuilder</span><span class="o">();</span>
+
+ <span class="n">builder</span><span class="o">.</span><span class="na">setSpout</span><span class="o">(</span><span class="n">WORD_SPOUT</span><span class="o">,</span> <span class="n">spout</span><span class="o">,</span> <span class="mi">1</span><span class="o">);</span>
+ <span class="n">builder</span><span class="o">.</span><span class="na">setBolt</span><span class="o">(</span><span class="n">COUNT_BOLT</span><span class="o">,</span> <span class="n">bolt</span><span class="o">,</span> <span class="mi">1</span><span class="o">).</span><span class="na">shuffleGrouping</span><span class="o">(</span><span class="n">WORD_SPOUT</span><span class="o">);</span>
+ <span class="n">builder</span><span class="o">.</span><span class="na">setBolt</span><span class="o">(</span><span class="n">HBASE_BOLT</span><span class="o">,</span> <span class="n">hbase</span><span class="o">,</span> <span class="mi">1</span><span class="o">).</span><span class="na">fieldsGrouping</span><span class="o">(</span><span class="n">COUNT_BOLT</span><span class="o">,</span> <span class="k">new</span> <span class="nf">Fields</span><span class="o">(</span><span class="s">"word"</span><span class="o">));</span>
+
+
+ <span class="k">if</span> <span class="o">(</span><span class="n">args</span><span class="o">.</span><span class="na">length</span> <span class="o">==</span> <span class="mi">0</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">LocalCluster</span> <span class="n">cluster</span> <span class="o">=</span> <span class="k">new</span> <span class="nf">LocalCluster</span><span class="o">();</span>
+ <span class="n">cluster</span><span class="o">.</span><span class="na">submitTopology</span><span class="o">(</span><span class="s">"test"</span><span class="o">,</span> <span class="n">config</span><span class="o">,</span> <span class="n">builder</span><span class="o">.</span><span class="na">createTopology</span><span class="o">());</span>
+ <span class="n">Thread</span><span class="o">.</span><span class="na">sleep</span><span class="o">(</span><span class="mi">10000</span><span class="o">);</span>
+ <span class="n">cluster</span><span class="o">.</span><span class="na">killTopology</span><span class="o">(</span><span class="s">"test"</span><span class="o">);</span>
+ <span class="n">cluster</span><span class="o">.</span><span class="na">shutdown</span><span class="o">();</span>
+ <span class="n">System</span><span class="o">.</span><span class="na">exit</span><span class="o">(</span><span class="mi">0</span><span class="o">);</span>
+ <span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
+ <span class="n">config</span><span class="o">.</span><span class="na">setNumWorkers</span><span class="o">(</span><span class="mi">3</span><span class="o">);</span>
+ <span class="n">StormSubmitter</span><span class="o">.</span><span class="na">submitTopology</span><span class="o">(</span><span class="n">args</span><span class="o">[</span><span class="mi">0</span><span class="o">],</span> <span class="n">config</span><span class="o">,</span> <span class="n">builder</span><span class="o">.</span><span class="na">createTopology</span><span class="o">());</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</code></pre></div>
+
+
+ </div>
+ </div>
+ </div>
+<footer>
+ <div class="container-fluid">
+ <div class="row">
+ <div class="col-md-3">
+ <div class="footer-widget">
+ <h5>Meetups</h5>
+ <ul class="latest-news">
+
+ <li><a href="http://www.meetup.com/Apache-Storm-Apache-Kafka/">Apache Storm & Apache Kafka</a> <span class="small">(Sunnyvale, CA)</span></li>
+
+ <li><a href="http://www.meetup.com/Apache-Storm-Kafka-Users/">Apache Storm & Kafka Users</a> <span class="small">(Seattle, WA)</span></li>
+
+ <li><a href="http://www.meetup.com/New-York-City-Storm-User-Group/">NYC Storm User Group</a> <span class="small">(New York, NY)</span></li>
+
+ <li><a href="http://www.meetup.com/Bay-Area-Stream-Processing">Bay Area Stream Processing</a> <span class="small">(Emeryville, CA)</span></li>
+
+ <li><a href="http://www.meetup.com/Boston-Storm-Users/">Boston Realtime Data</a> <span class="small">(Boston, MA)</span></li>
+
+ <li><a href="http://www.meetup.com/storm-london">London Storm User Group</a> <span class="small">(London, UK)</span></li>
+
+ <!-- <li><a href="http://www.meetup.com/Apache-Storm-Kafka-Users/">Seatle, WA</a> <span class="small">(27 Jun 2015)</span></li> -->
+ </ul>
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+ <div class="footer-widget">
+ <h5>About Storm</h5>
+ <p>Storm integrates with any queueing system and any database system. Storm's spout abstraction makes it easy to integrate a new queuing system. Likewise, integrating Storm with database systems is easy.</p>
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+ <p align="center">Copyright © 2015 <a href="http://www.apache.org">Apache Software Foundation</a>. All Rights Reserved.
+ <br>Apache Storm, Apache, the Apache feather logo, and the Apache Storm project logos are trademarks of The Apache Software Foundation.
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