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https://reviews.apache.org/r/48722/
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(Updated June 16, 2016, 6:43 p.m.)


Review request for Ambari, Andrew Onischuk, Laszlo Puskas, Robert Levas, Sandor 
Magyari, and Sumit Mohanty.


Changes
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1. Introduced ambari agent config properties (ambari-agent.ini) for a minimum 
and maximum heartbeat internals
2. The computed heartbeat intervals is used all the time not just when there 
are still pending tasks(stages)


Bugs: AMBARI-17248
    https://issues.apache.org/jira/browse/AMBARI-17248


Repository: ambari


Description
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Commands to be executed by ambari-agents are being sent down by the server in 
the response message to agent heartbeat messages. 
The server processes the received heartbeat, it checks if there are next 
commands scheduled to be executed by ambari-agent and adds those to the 
heartbeat response for the ambari-agent.
The server organises the commands that can be executed in parallel into stages. 
Ambari server ensures that only the commands of a single stage is scheduled to 
be executed by the agent and starts scheduling the commands of the next stage 
only after all commands of current stage has finished successfully.
The processing of command status received with the heartbeat message happens 
asynchronously to heartbeat response in HeartBeatProcessor and ActionScheduler 
creation thus when the heartbeat response is created the commands for the next 
stage are not scheduled yet. This means that the next commands will be sent to 
agent only with the next heartbeat.
Agents currently sends a heartbeat to the server on command a completion or at 
a timeout = self.netutil.HEARTBEAT_IDDLE_INTERVAL_SEC – 
self.netutil.MINIMUM_INTERVAL_BETWEEN_HEARTBEATS interval which is ~10 seconds 
if there are no commands to be executed.
This means that when the server receives a heartbeat triggered by the 
completion of the last command from the current stage the server will send the 
commands for the next stage only 10 seconds later when the next heartbeat is 
received. This leads to agents spending considerable amount of time idle when 
there are multiple stages to be executed.
Agents should heartbeat at a higher rate while there are still pending stages 
to be executed.


Diffs (updated)
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  ambari-agent/conf/unix/ambari-agent.ini 8f2ab1b 
  ambari-agent/conf/windows/ambari-agent.ini df88be6 
  ambari-agent/src/main/python/ambari_agent/AmbariConfig.py 89a881a 
  ambari-agent/src/main/python/ambari_agent/Controller.py e981a76 
  ambari-agent/src/main/python/ambari_agent/NetUtil.py 80bf3ae 
  ambari-agent/src/test/python/ambari_agent/TestNetUtil.py d72e319 
  ambari-agent/src/test/python/ambari_agent/examples/ControllerTester.py 
8103872 
  
ambari-server/src/main/java/org/apache/ambari/server/agent/HeartBeatHandler.java
 35a37e3 
  
ambari-server/src/main/java/org/apache/ambari/server/agent/HeartBeatResponse.java
 1ab7ae9 
  ambari-server/src/main/java/org/apache/ambari/server/state/Cluster.java 
ac0ddd2 
  ambari-server/src/main/java/org/apache/ambari/server/state/Clusters.java 
bd9de13 
  
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClusterImpl.java
 3d2388e 
  
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClustersImpl.java
 c26e1e9 
  
ambari-server/src/test/java/org/apache/ambari/server/state/cluster/ClusterImplTest.java
 627ade9 

Diff: https://reviews.apache.org/r/48722/diff/


Testing
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Manual testing.

Unit tests in succeeded.


Thanks,

Sebastian Toader

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