[improve][broker] Added synchronized for sendMessages in Non-Persistent message dispatchers

[sandeep-mst]

Fixes #24379

Motivation

We have observed inconsistency with the usage of synchronized keyword while dispatching messages to the consumer across different dispatchers.
The following are not using synchronized keyword while filtering and sending messages to the consumers.

• NonPersistentDispatcherSingleActiveConsumer#sendMessages
• NonPersistentStickyKeyDispatcherMultipleConsumers#sendMessages

The rest of the dispatchers including all the persistent dispatchers and NonPersistentDispatcherMultipleConsumers use synchronized while sending messages. This causes inconsistencies across different dispatchers while running server-side filters with multiple producers and a single consumer as it will get multi-threaded. This is even more a case when server-side filter code is not thread-safe.

Modifications

Added synchronized keyword at the following two method calls.

• NonPersistentDispatcherSingleActiveConsumer#sendMessages
• NonPersistentStickyKeyDispatcherMultipleConsumers#sendMessages

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:
cognitree#24

[lhotari]

LGTM

[lhotari]

Thanks for fixing this issue @sandeep-mst

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.24%. Comparing base (bbc6224) to head (71166c7).
Report is 1132 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #24386      +/-   ##
============================================
+ Coverage     73.57%   74.24%   +0.67%     
+ Complexity    32624    32298     -326     
============================================
  Files          1877     1867      -10     
  Lines        139502   145267    +5765     
  Branches      15299    16610    +1311     
============================================
+ Hits         102638   107855    +5217     
+ Misses        28908    28870      -38     
- Partials       7956     8542     +586     

Flag	Coverage Δ
inttests	26.75% <ø> (+2.16%)	⬆️
systests	23.32% <ø> (-1.00%)	⬇️
unittests	73.73% <ø> (+0.89%)	⬆️

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

Files with missing lines	Coverage Δ
...t/NonPersistentDispatcherSingleActiveConsumer.java	87.50% <ø> (+0.40%)	⬆️
...ersistentStickyKeyDispatcherMultipleConsumers.java	75.28% <ø> (+5.01%)	⬆️

... and 1086 files with indirect coverage changes

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