[fix][broker] Fix the wrong value of BrokerSrevice.maxUnackedMsgsPerDispatcher

[aloyszhang]

Motivation

Pulsar has the limit of max unacked messages at

• broker level
• subscription level
• consumer level

In the product environment(maxUnackedMessagesPerBroker > 0), we met the subscription blocked unexpectedly even if we have set the limit of max un-ack for subscription and consumer big enough.

After troubleshooting, this is caused by the wrong default value of maxUnackedMessagesPerSubscriptionOnBrokerBlocked which is 0.16 now.

For example, if set maxUnackedMessagesPerBroker to 60000, the BrokerService#maxUnackedMsgsPerDispatcher should be 60000 * 1/6 = 10000 by default, but now it's 600

 this.maxUnackedMessages = pulsar.getConfiguration().getMaxUnackedMessagesPerBroker();
            this.maxUnackedMsgsPerDispatcher = maxUnackedMessages
                    * pulsar.getConfiguration().getMaxUnackedMessagesPerSubscriptionOnBrokerBlocked() / 100;

Modifications

• correct the value of maxUnackedMsgsPerDispatcher
• modify the related tests

Verifying this change

• Make sure that the change passes the CI checks.

This change is already covered by existing tests, such as (please describe tests).

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:

aloyszhang#22

[github-actions]

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (69a45a1) 73.43% compared to head (7c0de10) 73.54%.
Report is 26 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #21765      +/-   ##
============================================
+ Coverage     73.43%   73.54%   +0.10%     
+ Complexity    32798    32288     -510     
============================================
  Files          1897     1858      -39     
  Lines        140647   138146    -2501     
  Branches      15489    15141     -348     
============================================
- Hits         103290   101605    -1685     
+ Misses        29283    28674     -609     
+ Partials       8074     7867     -207     

Flag	Coverage Δ
inttests	24.16% <0.00%> (+<0.01%)	⬆️
systests	23.71% <0.00%> (-1.05%)	⬇️
unittests	72.84% <100.00%> (+0.10%)	⬆️

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

Files	Coverage Δ
...rg/apache/pulsar/broker/service/BrokerService.java	80.99% <100.00%> (-0.16%)	⬇️

... and 133 files with indirect coverage changes

[aloyszhang]

@Technoboy- @codelipenghui @poorbarcode
PTAL, thanks

[aloyszhang]

@315157973 @Technoboy- Apply the comment, PTAL again.