Retryable with not simple expressions

[ahoehma]

I'm doing this:

  @Transactional(transactionManager = "historyTransactionManager")
  @Retryable(
    retryFor = {
        org.springframework.dao.PessimisticLockingFailureException.class,
        org.springframework.dao.CannotAcquireLockException.class,
        org.springframework.dao.RecoverableDataAccessException.class,
        org.springframework.dao.DataAccessResourceFailureException.class,
        org.springframework.dao.InvalidDataAccessResourceUsageException.class,
        org.hibernate.exception.LockAcquisitionException.class
    },
    exceptionExpression = "#{@'historyJdbcRetryProperties'.save.enabled}",  // <<<<<<<<<<<<<<<<<<<<<<<<<<
    maxAttemptsExpression = "#{@'historyJdbcRetryProperties'.save.maxAttempts}", // <<<<<<<<<<<<<<<<<<<<<
    backoff = @Backoff(
      delayExpression = "#{@'historyJdbcRetryProperties'.save.backoffDelay}",// <<<<<<<<<<<<<<<<<<<<<<<<<<
      multiplierExpression = "#{@'historyJdbcRetryProperties'.save.backoffMultiplier}"))// <<<<<<<<<<<<<<<<<<<<
  @Timed(HistoryMetrics.TIMER_HISTORY_SAVE)
  @Override
  public ConfigurationHistory save(
      final String configurationId,
      final Configuration configuration,
      final ConfigurationActions configurationActions,
      final List<OrderNumber> orderNumbers,
      final @Nullable VariantTableNames variantTableNames) {
    log.trace("Save history for configuration-id '{}' with configuration '{}', actions '{}', orderNumbers '{}', variantTables '{}'",
        configurationId, configuration, configurationActions, orderNumbers, variantTableNames);
    checkNotNull(configurationId, "Missing configuration-id");
    checkNotNull(configuration, "Missing configuration");
    checkNotNull(configurationActions, "Missing actions");
    checkNotNull(orderNumbers, "Missing order numbers");
    return logTraceDumpSave(internalSave(configurationId, configuration, configurationActions, orderNumbers, variantTableNames));
  }

exceptionExpression = "#{@'historyJdbcRetryProperties'.save.enabled}"

Is my way to enable to disable particular retries. Please imagine I have not only the "save" method ... I have several other methods ... but the @retryable annotation looks almost identical ... only the "action-name" is different. So far so good :) It seems to work and I can enable or disable retry for specific actions.

maxAttemptsExpression = "#{@'historyJdbcRetryProperties'.save.maxAttempts}"
delayExpression = "#{@'historyJdbcRetryProperties'.save.backoffDelay}"
multiplierExpression = "#{@'historyJdbcRetryProperties'.save.backoffMultiplier}"

Same here - I want to control the max-attempts, delay and multiplier per "action".

But then I found this warning in my logs (org.springframework.retry.policy.ExpressionRetryPolicy):

#{...} syntax is not required for this run-time expression and is deprecated in favor of a simple expression string

I can't see which of my expressions are causing this warning.

And is my code soon or later broken ... imagine a new spring-retry release which drops support for complex expressions :O

Please share some hints/ideas with me.

Kind regards
Andreas

[artembilan]

The warning comes from the ExpressionRetryPolicy:

	/**
	 * Get expression based on the expression string. At the moment supports both literal
	 * and template expressions. Template expressions are deprecated.
	 * @param expression the expression string
	 * @return literal expression or template expression
	 */
	private static Expression getExpression(String expression) {
		if (isTemplate(expression)) {
			logger.warn("#{...} syntax is not required for this run-time expression "
					+ "and is deprecated in favor of a simple expression string");
			return new SpelExpressionParser().parseExpression(expression, PARSER_CONTEXT);
		}
		return new SpelExpressionParser().parseExpression(expression);
	}

This one is used from the AnnotationAwareRetryOperationsInterceptor, e.g.:

if (hasExceptionExpression) {
				simple = new ExpressionRetryPolicy(maxAttempts, policyMap, true, resolve(exceptionExpression),
						retryNotExcluded)
					.withBeanFactory(this.beanFactory);
			}

And that is done against: String exceptionExpression = (String) attrs.get("exceptionExpression");

And that is not about "complext expression", but rather how simpler they could be:

exceptionExpression = "@historyJdbcRetryProperties.save.enabled"

The problem that this expression in the ExpressionRetryPolicy is always evaluated at runtime:

	public boolean canRetry(RetryContext context) {
		Throwable lastThrowable = context.getLastThrowable();
		if (lastThrowable == null) {
			return super.canRetry(context);
		}
		else {
			return super.canRetry(context) && Boolean.TRUE
				.equals(this.expression.getValue(this.evaluationContext, lastThrowable, Boolean.class));
		}
	}

Unlike many others which are evaluated only at configuration phase.
Therefore no need in templating that exceptionExpression since it is always for runtime only.

I think we can improve that:

			logger.warn("#{...} syntax is not required for this run-time expression "
					+ "and is deprecated in favor of a simple expression string");

to include an expression itself and give a hint how that could be improved without SpEL template.

WDYT?

[ahoehma]

To include the expression itself would help a lot I think.

And I will try the simple version "@historyJdbcRetryProperties.save.enabled" as well!

Thanks.

[ahoehma]

Nice! The "simple" syntax is working :) I was not aware of that :) Many thanks @artembilan 💯