[GitHub] [fluo-muchos] ctubbsii commented on a change in pull request #274: Updates to enable launch of EC2 instances via user-defined templates

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ctubbsii commented on a change in pull request #274: Updates to enable launch of EC2 instances via user-defined templates
URL: https://github.com/apache/fluo-muchos/pull/274#discussion_r320999232
 
 

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 File path: conf/templates/README.md
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+## Muchos EC2 Cluster Templates
+
+Cluster templates are intended to provide greater flexibility, if needed,
+with respect to instance type selection and launch configuration for
+your EC2 hosts. For example, cluster templates may be ideal for use
+cases that require distinct, per-host launch configurations, and
+for use cases that require hosts to have persistent, EBS-backed data
+volumes (rather than ephemeral volumes, the muchos default for EC2
+clusters)
+
+If you are already familiar with muchos and with the basics of EC2
+launch requests, then creating your own launch templates will be simple
+and straightforward.
+
+Please follow the guidance provided here to ensure compatibility between
+your custom templates and muchos automation
+
+## Configuration
+
+### Select a cluster template in *muchos.props*
+```
+[ec2]
+...
+cluster_template = example
+...
+```
+The configured value must match the name of a subdirectory under
+`conf/templates`
+
+```
+~$ ls -1a fluo-muchos/conf/templates/example
+.
+..
+devices
+metrics.json
+namenode.json
+resourcemanager.json
+zookeeper.json
+worker.json
+```
+The subdirectory will contain one or more user-defined EC2 launch
+templates (*\*.json*) for your various host types, and it will
+include a *devices* file specifying the desired mount points for all
+data volumes (excluding root volumes, as they are mounted
+automatically)
+
+### Defining EC2 launch templates and device mounts for your hosts
+
+#### Launch Templates: *{service-name}.json* files
+
+Each JSON file represents a standard EC2 launch request, and each file
+name must match one of the predefined muchos service names, as
+defined in the **nodes** section of *muchos.props*. E.g.,
+```
+... 
+[nodes]
+leader1 = namenode,resourcemanager,accumulomaster
+leader2 = metrics,zookeeper
+worker1 = worker
+worker2 = worker
+worker3 = worker
+worker4 = worker
+```
+In template mode, the first service listed for a given host denotes the
+template to be selected for its launch.
+
+Based on the example given above:
+* **leader1** selects **namenode.json**
 
 Review comment:
   Perhaps instead, we can have some configuration syntax that uses an explicit **{templatename}**?
   
   Something like:
   ```ini
   [nodes]
   leader1 = namenode,resourcemanager;template={name}
   ```
   
   If unspecified, the template name could be `default` or `worker` or whatever makes things easiest.

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