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ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java
 (line 570)
<https://reviews.apache.org/r/47961/#comment200332>

    These values feel too small, especially when multiple users are logged on.



ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java
 (line 2506)
<https://reviews.apache.org/r/47961/#comment200339>

    Should we set a default value of say 1000?



ambari-server/src/main/java/org/apache/ambari/server/controller/metrics/RestMetricsPropertyProvider.java
 (line 256)
<https://reviews.apache.org/r/47961/#comment200337>

    Why was the try { moved down here as opposed to immediately inside the for 
loop?



ambari-server/src/test/java/org/apache/ambari/server/configuration/ConfigurationTest.java
 (line 792)
<https://reviews.apache.org/r/47961/#comment200341>

    IMO, this type of test doesn't add much value since anyone that changes the 
value will simply go ahead and change the test anyway. Instead, we should 
assert that the default values are within a reasonable range.


- Alejandro Fernandez


On May 27, 2016, 7:18 p.m., Jonathan Hurley wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/47961/
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> 
> (Updated May 27, 2016, 7:18 p.m.)
> 
> 
> Review request for Ambari, Alejandro Fernandez, Nate Cole, Robert Levas, 
> Robert Nettleton, and Srimanth Gunturi.
> 
> 
> Bugs: AMBARI-16913
>     https://issues.apache.org/jira/browse/AMBARI-16913
> 
> 
> Repository: ambari
> 
> 
> Description
> -------
> 
> Incoming requests from the web client (or from any REST API) will eventually 
> be routed to the property provider / subresource framework. It is here were 
> any JMX data is queried for within the context of the REST request. In large 
> clusters, these requests can backup quite easily (even with a massive 
> threadpool), causing UX degradations in the web client:
> 
> ```
> Thread [qtp-ambari-client-38]
>       
> JMXPropertyProvider(ThreadPoolEnabledPropertyProvider).populateResources(Set<Resource>,
>  Request, Predicate) line: 168   
>       JMXPropertyProvider.populateResources(Set<Resource>, Request, 
> Predicate) line: 156      
>       StackDefinedPropertyProvider.populateResources(Set<Resource>, Request, 
> Predicate) line: 200     
>       ClusterControllerImpl.populateResources(Type, Set<Resource>, Request, 
> Predicate) line: 155      
>       QueryImpl.queryForResources() line: 407 
>       QueryImpl.execute() line: 217   
>       ReadHandler.handleRequest(Request) line: 69     
>       GetRequest(BaseRequest).process() line: 145     
> ```
> 
> Consider one of the calls made by the web client:
> ```
> GET api/v1/clusters/c1/components/?
> ServiceComponentInfo/category=MASTER&
> fields=
> ServiceComponentInfo/service_name,
> host_components/HostRoles/display_name,
> host_components/HostRoles/host_name,
> host_components/HostRoles/state,
> host_components/HostRoles/maintenance_state,
> host_components/HostRoles/stale_configs,
> host_components/HostRoles/ha_state,
> host_components/HostRoles/desired_admin_state,
> host_components/metrics/jvm/memHeapUsedM,
> host_components/metrics/jvm/HeapMemoryMax,
> host_components/metrics/jvm/HeapMemoryUsed,
> host_components/metrics/jvm/memHeapCommittedM,
> host_components/metrics/mapred/jobtracker/trackers_decommissioned,
> host_components/metrics/cpu/cpu_wio,
> host_components/metrics/rpc/client/RpcQueueTime_avg_time,
> host_components/metrics/dfs/FSNamesystem/*,
> host_components/metrics/dfs/namenode/Version,
> host_components/metrics/dfs/namenode/LiveNodes,
> host_components/metrics/dfs/namenode/DeadNodes,
> host_components/metrics/dfs/namenode/DecomNodes,
> host_components/metrics/dfs/namenode/TotalFiles,
> host_components/metrics/dfs/namenode/UpgradeFinalized,
> host_components/metrics/dfs/namenode/Safemode,
> host_components/metrics/runtime/StartTime
> ```
> 
> This query is essentially saying that for every {{MASTER}}, get metrics from 
> them. The problem is that in a large cluster, there could be 100 masters, yet 
> the metrics being asked for are only for NameNode. As a result, the JMX 
> endpoints for all 100 masters are queried - *live* - as part of the request.
> 
> There are two inherent flaws with this approach:
> 
> - Even with millisecond JMX response times, multiplying this by 100's and 
> then adding parsing overhead causes a noticeable delay in the web client as 
> the federated requests are blocking the main UX request
> 
> - Although there is a threadpool which scales up to service these requests - 
> that only really works for 1 user. With multiple users logged in, you'd need 
> 100's upon 100's of threads pulling in the same JMX data
> 
> This data should never be queried for directly as part of the incoming REST 
> requests. Instead, an autonomous pool of threads should be constantly 
> retrieving these point-in-time metrics and updating a cache. The cache is 
> then used to service all live REST requests. 
> - On the first request to a resource, a cache miss occurs and no data is 
> returned. I think this is acceptable since metrics take a few moments to 
> populate anyway right now. As the web client polls, the next request should 
> pickup the newly cached metrics.
> - Only URLs which are being asked for by incoming REST requests should be 
> considered for retrieval. After sometime, if they haven't been requested, 
> then the headless threadpool can stop trying to update their data
> - All JMX data will be parsed and stored in-memory, in an expiring cache
> 
> 
> Diffs
> -----
> 
>   ambari-server/src/main/java/org/apache/ambari/server/AmbariService.java 
> 186e272 
>   
> ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java
>  7cfaf61 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/AmbariManagementController.java
>  d6b9d0e 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/AmbariManagementControllerImpl.java
>  f4a615c 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/AmbariServer.java
>  99a6cab 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/ControllerModule.java
>  617553b 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/internal/AbstractProviderModule.java
>  04a8f0a 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/internal/StackDefinedPropertyProvider.java
>  6c40d14 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/jmx/JMXPropertyProvider.java
>  1ccc5df 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/metrics/MetricPropertyProviderFactory.java
>  PRE-CREATION 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/metrics/RestMetricsPropertyProvider.java
>  6f2a134 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/metrics/ThreadPoolEnabledPropertyProvider.java
>  6f4a6ea 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/utilities/BufferedThreadPoolExecutorCompletionService.java
>  4d6daa6 
>   
> ambari-server/src/main/java/org/apache/ambari/server/controller/utilities/ScalingThreadPoolExecutor.java
>  7a5e479 
>   
> ambari-server/src/main/java/org/apache/ambari/server/state/services/MetricsRetrievalService.java
>  PRE-CREATION 
>   
> ambari-server/src/test/java/org/apache/ambari/server/configuration/ConfigurationTest.java
>  5d65ea7 
>   
> ambari-server/src/test/java/org/apache/ambari/server/controller/internal/StackDefinedPropertyProviderTest.java
>  32e84cb 
>   
> ambari-server/src/test/java/org/apache/ambari/server/controller/metrics/RestMetricsPropertyProviderTest.java
>  f78024f 
>   
> ambari-server/src/test/java/org/apache/ambari/server/controller/test/BufferedThreadPoolExecutorCompletionServiceTest.java
>  f47068c 
> 
> Diff: https://reviews.apache.org/r/47961/diff/
> 
> 
> Testing
> -------
> 
> PENDING
> 
> 
> Thanks,
> 
> Jonathan Hurley
> 
>

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