Samza的ApplicationMaster

时间：2021-04-09 20:51:11

当Samza ApplicationMaster启动时，它做以下的事情：

  1. 通过STREAMING_CONFIG环境变量从YARN获取配置信息(configuration)
  2. 在随机端口上 启动一个JMX server
  3. 实例化一个metrics registry和reporter来追踪计量信息
  4. 将AM向YARN的RM注册
  5. 使用每个stream的PartitionManager来获取总共的partition数量
  6. 从Samza的job configuration里获取总的container数量
  7. 将partition分给container(在Samza AM的dashboard里，称为Task Group)
  8. 为每个container向YARN发送一个ResourceRequest
  9. 每秒向YARN RM poll一次，检查allocated and released containers
SamzaAppMaster的实现
 
并不是提交AppMaster，只是向RM注册这个AppMaster。因为此时,AppMaster已经启动了。
1.在SamzaAppMasterLifecycle对象的onInit()方法中，使用amCient.registerApplicationMaster
2    val response = amClient.registerApplicationMaster (host , state.rpcPort, "%s:%d" format (host, state. trackingPort))
 
amClient对象的类：
 
org.apache.hadoop.yarn.client.api.async.AMRMClientAsync<T extends org.apache.hadoop.yarn.client.api.AMRMClient.ContainerRequest>
 

AMRMClientAsync handles communication with the ResourceManager and provides asynchronous updates on events such as container allocations and completions. It contains a thread that sends periodic heartbeats to the ResourceManager. It should be used by implementing a CallbackHandler:

 class MyCallbackHandler implements AMRMClientAsync.CallbackHandler {

   public void onContainersAllocated(List<Container> containers) {

     [run tasks on the containers]

   }

   public void onContainersCompleted(List<ContainerStatus> statuses) {

     [update progress, check whether app is done]

   }

   public void onNodesUpdated(List<NodeReport> updated) {}

   public void onReboot() {}

 }

The client's lifecycle should be managed similarly to the following:

 AMRMClientAsync asyncClient =

     createAMRMClientAsync(appAttId, 1000, new MyCallbackhandler());

 asyncClient.init(conf);

 asyncClient.start();

 RegisterApplicationMasterResponse response = asyncClient

    .registerApplicationMaster(appMasterHostname, appMasterRpcPort,

       appMasterTrackingUrl);

 asyncClient.addContainerRequest(containerRequest);

 [... wait for application to complete]

 asyncClient.unregisterApplicationMaster(status, appMsg, trackingUrl);

 asyncClient.stop();
这个类是用来做为一个Client和RM进行通信，并且注册一个用于回调的对象来处理container 的allocation和completion事件。它启动一个线程，周期性地发送hearbeat至ResourceManager

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