Threads blocked trying to attach to the JVM

[yojs]

Fixes #: #565

Description of changes:

In this code all threads might be blocked behind one thread trying to
fill the jTidMap from a threaddump that contains all the thread related details that performanceAnalyzer uses. The thread dump is requires a JVM attach which has a default timeout of 10 seconds which is quite long. While one thread is busy attaching, all threads running ES operations might be stuck waiting for the same lock. Therefore, this change replaces a mandatory lock with a try-lock, so that the threads which cannot acquire the lock, moves past this and carry on. We will loose the metrics for this run, but that is better than stalling all ES operations.

Tests:

PA metrics is returning the metrics:

curl "localhost:9600/_opendistro/_performanceanalyzer/metrics?metrics=Latency,CPU_Utilization&agg=avg,max&dim=ShardID&nodes=all"
{"iAHcZIXUQMaOBPzRNsC-JA": {"timestamp": 1614637105000, "data": {"fields":[{"name":"ShardID","type":"VARCHAR"},{"name":"Latency","type":"DOUBLE"},{"name":"CPU_Utilization","type":"DOUBLE"}],"records":[[null,null,0.005394726328405913]]}}, "jLtljYrfQAuTVwUBgGtHNQ" :{"timestamp": 1614637105000, "data": {"fields":[{"name":"ShardID","type":"VARCHAR"},{"name":"Latency","type":"DOUBLE"},{"name":"CPU_Utilization","type":"DOUBLE"}],"records":[[null,null,0.002798561151079137]]}}}```

The writer metrics are being emitted in the /dev/shm file

```[root@7b746ade07bd performanceanalyzer]# cat 1614636875000
^heap_metrics
{"current_time":1614636875493}
{"MemType":"totYoungGC","GC_Collection_Event":0,"GC_Collection_Time":0,"Heap_Committed":-2,"Heap_Init":-2,"Heap_Max":-2,"Heap_Used":-2}
{"MemType":"totFullGC","GC_Collection_Event":0,"GC_Collection_Time":0,"Heap_Committed":-2,"Heap_Init":-2,"Heap_Max":-2,"Heap_Used":-2}
{"MemType":"PermGen","GC_Collection_Event":-2,"GC_Collection_Time":-2,"Heap_Committed":85696512,"Heap_Init":0,"Heap_Max":-1,"Heap_Used":80593424}
{"MemType":"Survivor","GC_Collection_Event":-2,"GC_Collection_Time":-2,"Heap_Committed":17891328,"Heap_Init":17891328,"Heap_Max":17891328,"Heap_Used":9578944}
{"MemType":"OldGen","GC_Collection_Event":-2,"GC_Collection_Time":-2,"Heap_Committed":357957632,"Heap_Init":357957632,"Heap_Max":357957632,"Heap_Used":55396840}
{"MemType":"Eden","GC_Collection_Event":-2,"GC_Collection_Time":-2,"Heap_Committed":143130624,"Heap_Init":143130624,"Heap_Max":143130624,"Heap_Used":37667024}
{"MemType":"NonHeap","GC_Collection_Event":-2,"GC_Collection_Time":-2,"Heap_Committed":118042624,"Heap_Init":7667712,"Heap_Max":-1,"Heap_Used":109184376}
{"MemType":"Heap","GC_Collection_Event":-2,"GC_Collection_Time":-2,"Heap_Committed":518979584,"Heap_Init":536870912,"Heap_Max":518979584,"Heap_Used":102642808}

If new tests are added, how long do the new ones take to complete

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[nisheedh]

Can you address my comments ?

[yojs]

Sorry for the delay in getting back to the comments.

[Bukhtawar]

Is there a better way to indicate whether an attach failed. Map being empty can happen else where in the code maybe

[Bukhtawar]

Thanks for the changes, LGTM