Backoff annotation 'delayExpression' attribute is not always applied

[pstelzer1]

An annotation like this

   @Retryable(maxAttemptsExpression = "${application.config.maxRetryAttempts}",
      backoff = @Backoff(delayExpression = "${application.config.retryDelayTimeMs}"),
      retryFor = {MyRetryableException.class})
   public void myMethod(){
   ...
   }

does not result in a backoff delay pulled from the delayExpression as intended, but rather uses the default delay of 1000ms.

Debugging through the code, BackoffPolicyBuilder.build() correctly receives the delaySupplier with the value pulled from ${application.config.retryDelayTimeMs}, but only applies this field if a multiplier is present, or if a maxDelay is specified. If neither of these are true, then a FixedBackoffPolicy is instantiated, populated with the default delay of 1000ms and a sleeper, and returned.

FixedBackoffPolicy can support a backoff period supplier, but none is set in the BackoffPolicyBuilder.build() method.

This can be worked around by adding a multiplier of 1, or by adding a maxDelay to the backoff annotation, thus directing the BackoffPolicyBuilder to the sections of the build() method that take into account the delay expression. However, seems like a FixedBackoffPolicy can be generated that uses the specified delay expression, without having to set these other annotation attributes.

[artembilan]

Confirmed. This is a bug in the BackOffPolicyBuilder:

		FixedBackOffPolicy policy = new FixedBackOffPolicy();
		if (this.delay != null) {
			policy.setBackOffPeriod(this.delay);
		}
		if (this.sleeper != null) {
			policy.setSleeper(this.sleeper);
		}

As you see we don't take into account a this.delaySupplier as we do for other policies above.

Feel free to provide a contribution.

Thank you!

[pstelzer1]

This turns out to not be a bug.

Expressions are parsed correctly prior to invoking the BackoffPolicyBuilder, specifically in AnnotationAwareRetryOperationsInterceptor.getBackoffPolicy() line 408-414 and 418-424, but for spel expressions wrapped in #{...}, not for property expressions ${...}. (See the isTemplate() method.) If the property expression is wrapped in #{...}, then the expression is parsed correctly. Here is an example.

   @Retryable(maxAttemptsExpression = "#{${application.config.maxRetryAttempts}}",
      backoff = @Backoff(delayExpression = "#{${application.config.retryDelayTimeMs}}"),
      retryFor = {MyRetryableException.class})
   public void myMethod(){
   ...
   }

No fixes needed - the code works correctly once I set up the retry and backup expressions correctly.

Thanks!