merrimanr opened a new pull request #1516: METRON-2262: Upgrade to Curator 4.2.0
URL: https://github.com/apache/metron/pull/1516
 
 
   ## Contributor Comments
   This PR is based on 
[METRON-2261](https://github.com/apache/metron/pull/1515) and includes those 
changes.  It must be merged before this.
   
   This PR upgrades Curator to version 4.2.0 and fixes a couple bugs in 
`MaasIntegrationTest` that resulted from the upgrade.  There was an extra 
service unregister in the `ContainerRequestListener` class (should only be 
unregistered once) and another more complicated bug (described in the next 
section).
   
   ### Bug Fix
   After upgrading to Curator version 4.2.0, both tests in 
`MaasIntegrationTest` fail with this error:
   ```
   testMaaSWithoutDomain(org.apache.metron.maas.service.MaasIntegrationTest)  
Time elapsed: 214.791 sec  <<< FAILURE!
   java.lang.AssertionError
        at org.junit.Assert.fail(Assert.java:86)
        at org.junit.Assert.assertTrue(Assert.java:41)
        at org.junit.Assert.assertTrue(Assert.java:52)
        at 
org.apache.metron.maas.service.MaasIntegrationTest.testDSShell(MaasIntegrationTest.java:269)
        at 
org.apache.metron.maas.service.MaasIntegrationTest.testMaaSWithoutDomain(MaasIntegrationTest.java:113)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at 
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at 
org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
        at 
org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
        at 
org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
        at 
org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
        at 
org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:298)
        at 
org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:292)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.lang.Thread.run(Thread.java:748)
   ``` 
   The service is not properly unregistered, the test [waits for the service to 
be removed from the list of 
endpoints](https://github.com/apache/metron/blob/master/metron-analytics/metron-maas-service/src/test/java/org/apache/metron/maas/service/MaasIntegrationTest.java#L261)
 and then timeouts and fails.
   
   The root cause is a change in how the 
`org.apache.curator.x.discovery.details. ServiceDiscoveryImpl` class 
unregisters a service after the upgrade.  The list of services is maintained in 
2 places:  Zookeeper and an [internal 
Map](https://github.com/apache/curator/blob/apache-curator-4.2.0/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/details/ServiceDiscoveryImpl.java#L64)
 in `ServiceDiscoveryImpl`.  There are several read functions in 
`ServiceDiscoveryImpl` but then don't refresh the internal Map.  The internal 
Map is only updated when `registerService` and `unregisterService` are called. 
   
   Before the upgrade, a service is [removed from 
Zookeeper](https://github.com/apache/curator/blob/apache-curator-2.7.0/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/details/ServiceDiscoveryImpl.java#L218)
 then [removed from the internal 
Map](https://github.com/apache/curator/blob/apache-curator-2.7.0/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/details/ServiceDiscoveryImpl.java#L224).
   
   After the upgrade, the order is reversed.  The service is [removed from the 
internal 
Map](https://github.com/apache/curator/blob/apache-curator-4.2.0/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/details/ServiceDiscoveryImpl.java#L255)
 then [removed from 
Zookeeper](https://github.com/apache/curator/blob/apache-curator-4.2.0/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/details/ServiceDiscoveryImpl.java#L524).
  However there is a check that [ensures the service existed in the internal 
Map](https://github.com/apache/curator/blob/apache-curator-4.2.0/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/details/ServiceDiscoveryImpl.java#L511)
 before removing it for Zookeeper.  Services are registered in 
`org.apache.metron.maas.service.runner.Runner` and unregistered in 
`org.apache.metron.maas.service.callback.ContainerRequestListener`.  The latter 
runs in a different process so registered services are not in the internal Map. 
 This was not a problem before the upgrade because Zookeeper was updated 
regardless of the internal Map state.
   
   The fix proposed in this PR is to register a service immediately before 
unregistering it in `org.apache.metron.maas.discovery.ServiceDiscoverer`.  This 
populates the internal Map in `ServiceDiscoveryImpl` with the service so that 
the subsequent unregister call functions correctly.  A side effect of this 
would be writing duplicate data to Zookeeper.  The only other solution I can 
think of would be to rearchitect how and where services are 
registered/unregistered.
   
   ### Testing
   The `MaasIntegrationTest` (and all tests) should pass.  Upgrading Curator 
without the fixes in this PR should cause the error above.
   
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