[TEZ-4350] Remove synchronized from DAGAppMaster.serviceInit, serviceStart, serviceStop - ASF JIRA

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Details

Type: Improvement
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 0.9.3, 0.10.2
Component/s: None
Labels:
None

Description

according to AbstractService.serviceInit javadoc

   * This method will only ever be called once during the lifecycle of
   * a specific service instance.
   *
   * Implementations do not need to be synchronized as the logic
   * in {@link #init(Configuration)} prevents re-entrancy.

moreover, it generates findbugs alerts for every field that is accessed somewhere else in DAGAppMaster in an unsynchronized fashion:

Code	Warning
IS	Inconsistent synchronization of org.apache.tez.dag.app.DAGAppMaster.webUIService; locked 57% of time
Bug type IS2_INCONSISTENT_SYNC (click for details)
In class org.apache.tez.dag.app.DAGAppMaster
Field org.apache.tez.dag.app.DAGAppMaster.webUIService
Synchronized 57% of the time
Unsynchronized access at DAGAppMaster.java:[line 2623]
Unsynchronized access at DAGAppMaster.java:[line 2623]
Synchronized access at DAGAppMaster.java:[line 568]
Synchronized access at DAGAppMaster.java:[line 569]
Synchronized access at DAGAppMaster.java:[line 578]
Synchronized access at DAGAppMaster.java:[line 656]

I cannot see any value now in having it synchronized (most probably this wasn't the case 8 years ago at the time of ~~TEZ-537~~)

UPDATE: double-checked, AbstractService lifecycle methods are protected with a lock since ~~YARN-530~~