[igorbernstein2]

Summary

When session_load == 0 across all scopes, ClientConfigurationManager.normalizeConfig clears session_configuration, resulting in an empty SessionPoolConfiguration.getDefaultInstance().

This change updates PoolSizer and SessionPoolImpl to handle an empty SessionPoolConfiguration cleanly:

• PoolSizer:
  • Guards pendingVRpcsPerSession > 0 in getScaleDelta() to prevent divide-by-zero (+Infinity -> Integer.MAX_VALUE and int overflow when inUseCount >= 1).
  • Updates handleGoAway and handleSessionClose from getScaleDelta() >= 0 to getScaleDelta() > 0 (since onSessionClosing / onSessionClosed already decrements expectedCapacity prior to consulting PoolSizer).
• SessionPoolImpl & SessionList:
  • Guards maybeScheduleCreateSessionRetry() with budget.getMaxConcurrentRequest() <= 0 so it does not spin on a 1ms retry timer when budget == 0.
  • Makes SessionHandle.onSessionClosing() idempotent with respect to expectedCapacity.
  • In the config listener, when newConfig is SessionPoolConfiguration.getDefaultInstance(), cancels retryCreateSessionFuture and gracefully closes all sessions (CLOSE_SESSION_REASON_DOWNSIZE); when newConfig is non-empty and poolState == PoolState.STARTED, scales back up via the pre-start loop.

[gemini-code-assist]

Code Review

This pull request adds robust handling for empty or disabled session pool configurations in the Google Cloud Bigtable client. Key changes include preventing division-by-zero errors in PoolSizer when pendingVRpcsPerSession is zero, updating SessionPoolImpl to properly cancel retry futures and close active sessions when the configuration is reset to default, and adding corresponding unit tests. The review feedback correctly identifies a compilation error in SessionPoolImpl.java where Future.cancel() is called without its required boolean argument, and suggests using cancel(false) instead.

[gemini-code-assist]

In Java, Future.cancel (and its sub-interfaces like ScheduledFuture) requires a boolean argument (mayInterruptIfRunning) to specify whether the executing thread should be interrupted. Calling cancel() with no arguments will result in a compilation error. Please use cancel(false) instead.

Suggested change

	retryCreateSessionFuture.cancel();
	retryCreateSessionFuture.cancel(false);