How to setup error channel for PubSub consumer binding with explicit subscription name?

I have consumer binding defined like:

spring.cloud.stream.gcp:
  pubsub:
    bindings:
      ongoing-messages-input:
         consumer:
         subscriptionName: my-pull-transactions

I define error handler like this:

    @ServiceActivator(inputChannel = "ongoing-messages-input.errors")
    public void handleError(Message<MessagingException> failedMessage) {

The framework creates an error channel out-of-box my-pull-transactions.errors, i.e. based on subscription name.

I want it to be ongoing-messages-input.errors how to achieve this? It should work as well, all error message from this channel goes to my custom channel.

I can’t rely on the subscription name as this is a dynamic value for me and depends on the environment.

I tried:

• Define

spring.cloud.stream:
  bindings:
    ongoing-messages-input: #channel name
      destination: my-topic-name #topic name
      binder: pubsub

• Customize error channel name like this:

    @Bean
    public ConsumerEndpointCustomizer<PubSubInboundChannelAdapter> messageChannelAdapter() {
        return (endpoint, destinationName, group) -> endpoint.setErrorChannelName("ongoing-messages-input.errors");
    }

I get the error:

java.lang.IllegalArgumentException: 'beanFactory' must not be null
	at org.springframework.util.Assert.notNull(Assert.java:201)
	at org.springframework.integration.support.channel.ChannelResolverUtils.getChannelResolver(ChannelResolverUtils.java:49)
	at org.springframework.integration.context.IntegrationObjectSupport.getChannelResolver(IntegrationObjectSupport.java:257)
	at org.springframework.integration.endpoint.MessageProducerSupport.getErrorChannel(MessageProducerSupport.java:126)
	at com.google.cloud.spring.pubsub.integration.inbound.PubSubInboundChannelAdapter.getErrorChannel(PubSubInboundChannelAdapter.java:161)
	at org.springframework.integration.endpoint.MessageProducerSupport.sendErrorMessageIfNecessary(MessageProducerSupport.java:252)
	at org.springframework.integration.endpoint.MessageProducerSupport.sendMessage(MessageProducerSupport.java:211)

To fix this I tried to define channel bean with a correspondent name - no result:

    @Bean(name = "ongoing-messages-input.errors")
    public MessageChannel errorChannel() {
        return new QueueChannel();
    }

Suggestion, it would be really helpful if PubSubInboundChannelAdapter has a method to return input channel name, as it has reference to this bean. Even fixing this bug, inside ConsumerEndpointCustomizer there is no way to properly resolve the new name in case of multiple binders. In my example, I have to hardcode, which is not good.

Workaround: Propagate bean factory:

@Bean
    public ConsumerEndpointCustomizer<PubSubInboundChannelAdapter> messageChannelAdapter(ConfigurableApplicationContext applicationContext) {
        return (endpoint, destinationName, group) -> {
            endpoint.setErrorChannelName("ongoing-messages-input.errors");
            endpoint.setBeanFactory(applicationContext.getBeanFactory());
        };
    }

I think this workaround should be fixed somewhere in com.google.cloud.spring.stream.binder.pubsub.PubSubMessageChannelBinder #createConsumerEndpoint as this class has a reference to app context and a method to get bean factory already.

The suggestion still is open, as it will be a problem for multiple consumer bindings. I’m open to contribute ✌️

[dzou]

Ok, I see what you’re saying.

• pubSubInboundChannelAdapter.getChannelName() seems fine to add, I would be okay with the contribution.
• This endpoint.setBeanFactory(applicationContext.getBeanFactory()); seems to make sense but will have to double check to make sure it doesn’t cause a regression.

Let us check-in with Spring team on how to override error channel.

@artembilan – Do you have any advice regarding how a user might easily override the default error channel destination for a Spring stream channel binder? We configure a Pub/Sub stream error handler like this. I’m wondering if there is a standard way in Spring to let users to override this destination or easily forward messages from the default error channel to a custom one.

[dzou]

Fixed by #515