[GitHub] [phoenix] joshelser commented on a diff in pull request #1431: PHOENIX-6699 Phoenix metrics overwriting DefaultMetricsSystem in Regi…

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joshelser commented on code in PR #1431:
URL: https://github.com/apache/phoenix/pull/1431#discussion_r863210369


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phoenix-core/src/main/java/org/apache/phoenix/monitoring/MetricUtil.java:
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@@ -38,4 +46,22 @@ public static MetricsStopWatch getMetricsStopWatch(boolean isRequestMetricsEnabl
         return new MetricsStopWatch(true);
     }
 
+    // We need to cover the case when JmxCacheBuster has just stopped the HBase metrics
+    // system, and not accidentally overwrite the DefaultMetricsSystem singleton.
+    // See PHOENIX-6699
+    public static boolean isDefaultMetricsInitialized() {
+        try {
+            MetricsSystemImpl metrics = (MetricsSystemImpl) DefaultMetricsSystem.instance();
+            Field prefixField = MetricsSystemImpl.class.getDeclaredField("prefix");

Review Comment:
   > we could just to check if we are and RS/Master process, and skip the initialization, but I don't know a way to do that.
   
   I'm not coming up with any static state that you could look at to try to determine if you're in the context of a RS or Master, shy of _hoping_ that the classpath client side doesnt' have the `HRegionServer.class` in it (or similar).
   
   The other thing I thought of was looking at `RpcServer.getCurrentCall()`. Normally, there is a corresponding user RPC which would result in this returning the current RPC. But, this method would return empty during a compaction (e.g. updating Phoenix stats) where there is no active HBase Call.
   
   Could we somehow separate the Phoenix client-side-only metrics from the execution pathway of the Phoenix server-side metrics? I imagine this is no easier to do.



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