CachingSessionFactory slowness if setPoolSize is called without initializing initial sessionCacheSize

[gauravbrills]

Version :
5.5.10

Migrating from 5.1.13 and 5.5.10

Describe the bug

We were doing a spring 2.6 migratoin and hence also upgrading spring integration version to 5.5.10 . Our existing code used to initialize CachingSessionFactory as below

      CachingSessionFactory<LsEntry> csf = new CachingSessionFactory<LsEntry>(sf ); 
       scsf.setPoolSize(connectionInfo.getPoolSize());
      // Refer https://github.com/spring-projects/spring-integration/pull/2606
      csf.setTestSession(true);
      csf.setSessionWaitTimeout(props.getSftp()
            .getSessionWaitTimeout());

Post migrating we observed that the setPoolSize method was degrading our performance and in itself taking aroudn 30 seconds . This is mainly due to the method calling SimplePool.setPoolSize which as the poolsize was not initialized keeps a default pool size as Integer.MAX_VALUE and hence when setPoolSize tries to reduce the pool size it goes into a long loop in order to clear it up . The same worked in the old version as the old code used to break in case there was nothing returned on poll .

Diff here v5.1.13.RELEASE...v5.5.10#diff-1da249bba02f27de259b1f47687338cb6204ca4754afd457ef82a1d17c912ca1

To Reproduce

The below code

      CachingSessionFactory<LsEntry> csf = new CachingSessionFactory<LsEntry>(sf ); 
       scsf.setPoolSize(connectionInfo.getPoolSize());
      // Refer https://github.com/spring-projects/spring-integration/pull/2606
      csf.setTestSession(true);
      csf.setSessionWaitTimeout(props.getSftp()
            .getSessionWaitTimeout());

Expected behavior

I think the design makes sense to clear the pool but it could lead to performance issues in case the poolsize is not initialized at the start like CachingSessionFactory<LsEntry> csf = new CachingSessionFactory<LsEntry>(sf, connectionInfo.getPoolSize()); . There could be a fix or this needs to be documented in code so people take care in case of upgrades.

Sample

      CachingSessionFactory<LsEntry> csf = new CachingSessionFactory<LsEntry>(sf ); 
       scsf.setPoolSize(connectionInfo.getPoolSize());
      // Refer https://github.com/spring-projects/spring-integration/pull/2606
      csf.setTestSession(true);
      csf.setSessionWaitTimeout(props.getSftp()
            .getSessionWaitTimeout());

[artembilan]

I see your point, @gauravbrills .

If you have a possible fix in mind, feel free to contribute it or share over here.
I will think how that while (delta < 0) { algorithm could be changed...

[gauravbrills]

Sure we were working on patching our code but I will add PR once I get time next week