[sakthivelmanii]

Problem

When AbstractLazyInitializer.get() is invoked and initialize() throws an exception, the failure was previously permanently cached in this.error with this.initialized = true regardless of whether the error was transient or retryable. In MultiplexedSessionDatabaseClient.getDialect() and DatabaseClientImpl.getStatementFactory(), an initial transient failure during session creation or query execution (DEADLINE_EXCEEDED, RESOURCE_EXHAUSTED, or UNAVAILABLE) caused all subsequent calls to immediately rethrow the cached exception without retrying, even after multiplexed session creation succeeded on retry.

Solution

Update AbstractLazyInitializer to cache only resource-not-found exceptions (DatabaseNotFoundException, InstanceNotFoundException, SessionNotFoundException) and non-retryable errors. Retryable SpannerException errors (matching MultiplexedSessionDatabaseClient.RETRYABLE_ERROR_CODES: DEADLINE_EXCEEDED, RESOURCE_EXHAUSTED, UNAVAILABLE) are rethrown without setting initialized = true so subsequent get() calls retry initialization.

• Make MultiplexedSessionDatabaseClient.RETRYABLE_ERROR_CODES package-private so AbstractLazyInitializer shares the same retryable error set.
• In DatabaseClientImpl.statementFactorySupplier.initialize(), unwrap ExecutionException.getCause() in SpannerExceptionFactory.asSpannerException and convert TimeoutException via SpannerExceptionFactory.propagateTimeout (DEADLINE_EXCEEDED).
• Add unit tests in LazySpannerInitializerTest and DatabaseClientImplTest covering retryable error recovery, non-retryable error caching, and concurrent retries.

[gemini-code-assist]

Code Review

This pull request updates AbstractLazyInitializer to allow retrying initialization when transient, retryable errors occur, rather than caching them indefinitely. It also refactors exception handling in DatabaseClientImpl when retrieving the database dialect and exposes RETRYABLE_ERROR_CODES from MultiplexedSessionDatabaseClient. Comprehensive tests have been added to verify recovery behavior. The review feedback suggests simplifying the shouldCacheError method in AbstractLazyInitializer by removing redundant checks for specific exception subclasses, as they are already covered by the more general SpannerException check.

[gemini-code-assist]

The explicit checks for DatabaseNotFoundException, InstanceNotFoundException, and SessionNotFoundException are redundant. These classes all extend SpannerException and have the error code ErrorCode.NOT_FOUND. Since NOT_FOUND is not present in MultiplexedSessionDatabaseClient.RETRYABLE_ERROR_CODES (which only contains DEADLINE_EXCEEDED, RESOURCE_EXHAUSTED, and UNAVAILABLE), the subsequent SpannerException check will naturally return true for them. Removing these redundant checks simplifies the code and reduces unnecessary class coupling.

  private static boolean shouldCacheError(Exception e) {
    if (e instanceof SpannerException) {
      return !MultiplexedSessionDatabaseClient.RETRYABLE_ERROR_CODES.contains(
          ((SpannerException) e).getErrorCode());
    }
    return true;
  }

[sakthivelmanii]

Simplified shouldCacheError to rely on the SpannerException check directly.