Fixing TraceContext NPE issue

[xiangfu0]

Description

When query timed out it's possible that one thread tries to register the trace after the request is already unregistered. So need to check null before putting the trace.

Sample stacktrace:

2022/02/04 00:01:06.604 ERROR [ServerQueryExecutorV1Impl] [pqr-7] Exception processing requestId 1193
java.lang.RuntimeException: Caught exception while running CombinePlanNode.
        at org.apache.pinot.core.plan.CombinePlanNode.run(CombinePlanNode.java:164) 
        at org.apache.pinot.core.plan.InstanceResponsePlanNode.run(InstanceResponsePlanNode.java:41) 
        at org.apache.pinot.core.plan.GlobalPlanImplV0.execute(GlobalPlanImplV0.java:45) 
        at org.apache.pinot.core.query.executor.ServerQueryExecutorV1Impl.processQuery(ServerQueryExecutorV1Impl.java:290) 
        at org.apache.pinot.core.query.executor.ServerQueryExecutorV1Impl.processQuery(ServerQueryExecutorV1Impl.java:192) 
        at org.apache.pinot.core.query.executor.QueryExecutor.processQuery(QueryExecutor.java:60) 
        at org.apache.pinot.core.query.scheduler.QueryScheduler.processQueryAndSerialize(QueryScheduler.java:154) 
        at org.apache.pinot.core.query.scheduler.QueryScheduler.lambda$createQueryFutureTask$0(QueryScheduler.java:138) 
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?]
        at shaded.com.google.common.util.concurrent.TrustedListenableFutureTask$TrustedFutureInterruptibleTask.runInterruptibly(TrustedListenableFutureTask.java:111)
        at shaded.com.google.common.util.concurrent.InterruptibleTask.run(InterruptibleTask.java:58)
        at shaded.com.google.common.util.concurrent.TrustedListenableFutureTask.run(TrustedListenableFutureTask.java:75)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
        at java.lang.Thread.run(Thread.java:829) [?:?]
Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
        at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:?]
        at java.util.concurrent.FutureTask.get(FutureTask.java:205) ~[?:?]
5:10
        at org.apache.pinot.core.plan.CombinePlanNode.run(CombinePlanNode.java:154) 
        ... 15 more
Caused by: java.lang.NullPointerException
        at org.apache.pinot.core.util.trace.TraceContext.registerThreadToRequest(TraceContext.java:140) 
        at org.apache.pinot.core.util.trace.TraceCallable.call(TraceCallable.java:41) 
        ... 8 more

Upgrade Notes

Does this PR prevent a zero down-time upgrade? (Assume upgrade order: Controller, Broker, Server, Minion)

• Yes (Please label as backward-incompat, and complete the section below on Release Notes)

Does this PR fix a zero-downtime upgrade introduced earlier?

• Yes (Please label this as backward-incompat, and complete the section below on Release Notes)

Does this PR otherwise need attention when creating release notes? Things to consider:

• New configuration options
• Deprecation of configurations
• Signature changes to public methods/interfaces
• New plugins added or old plugins removed

• Yes (Please label this PR as release-notes and complete the section on Release Notes)

Release Notes

Documentation

[codecov-commenter]

Codecov Report

Merging #8126 (e994021) into master (7d74c8c) will increase coverage by 0.08%.
The diff coverage is 66.66%.

@@             Coverage Diff              @@
##             master    #8126      +/-   ##
============================================
+ Coverage     71.33%   71.41%   +0.08%     
  Complexity     4302     4302              
============================================
  Files          1624     1624              
  Lines         84140    84142       +2     
  Branches      12596    12597       +1     
============================================
+ Hits          60021    60094      +73     
+ Misses        20013    19947      -66     
+ Partials       4106     4101       -5     

Flag	Coverage Δ
integration1	29.01% <0.00%> (+0.20%)	⬆️
integration2	27.56% <0.00%> (-0.05%)	⬇️
unittests1	67.94% <66.66%> (-0.01%)	⬇️
unittests2	14.18% <0.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...org/apache/pinot/core/util/trace/TraceContext.java	73.58% <66.66%> (-0.93%)	⬇️
...a/org/apache/pinot/common/utils/ServiceStatus.java	60.00% <0.00%> (-7.15%)	⬇️
...he/pinot/segment/local/segment/store/IndexKey.java	70.00% <0.00%> (-5.00%)	⬇️
...core/query/pruner/SelectionQuerySegmentPruner.java	86.36% <0.00%> (-2.28%)	⬇️
...core/startree/operator/StarTreeFilterOperator.java	85.31% <0.00%> (-2.10%)	⬇️
.../pinot/server/starter/helix/BaseServerStarter.java	57.98% <0.00%> (-1.97%)	⬇️
...apache/pinot/controller/api/upload/ZKOperator.java	74.40% <0.00%> (-1.60%)	⬇️
...e/pinot/broker/broker/helix/BaseBrokerStarter.java	75.67% <0.00%> (-1.09%)	⬇️
.../aggregation/function/ModeAggregationFunction.java	88.10% <0.00%> (-0.55%)	⬇️
...va/org/apache/pinot/controller/ControllerConf.java	58.53% <0.00%> (-0.41%)	⬇️
... and 22 more

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