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Spring Cloud Stream - notice and handle errors in broker

I am fairly new to developing distributed applications with messaging, and to Spring Cloud Stream in particular. I am currently wondering about best practices on how to deal with errors on the broker side.
In our application, we need to both consume and produce messages from/to multiple sources/destinations like this:
Consumer side
For consuming, we have defined multiple #Beans of type java.util.function.Consumer. The configuration for those looks like this:
spring.cloud.stream.bindings.consumeA-in-0.destination=inputA
spring.cloud.stream.bindings.consumeA-in-0.group=$Default
spring.cloud.stream.bindings.consumeB-in-0.destination=inputB
spring.cloud.stream.bindings.consumeB-in-0.group=$Default
This part works quite well - wenn starting the application, the exchanges "inputA" and "inputB" as well as the queues "inputA.$Default" and "inputB.$Default" with corresponding binding are automatically created in RabbitMQ.
Also, in case of an error (e.g. a queue is suddenly not available), the application gets notified immediately with a QueuesNotAvailableException and continuously tries to re-establish the connection.
My only question here is: Is there some way to handle this exception in code? Or, what are best practices to deal with failures like this on broker side?
Producer side
This one is more problematic. Producing messages is triggered by some internal logic, we cannot use function #Beans here. Instead, we currently rely on StreamBridge to send messages. The problem is that this approach does not trigger creation of exchanges and queues on startup. So when our code calls streamBridge.send("outputA", message), the message is sent (result is true), but it just disappears into the void since RabbitMQ automatically drops unroutable messages.
I found that with this configuration, I can at least get RabbitMQ to create exchanges and queues as soon as the first message is sent:
spring.cloud.stream.source=produceA;produceB
spring.cloud.stream.default.producer.requiredGroups=$Default
spring.cloud.stream.bindings.produceA-out-0.destination=outputA
spring.cloud.stream.bindings.produceB-out-0.destination=outputB
I need to use streamBridge.send("produceA-out-0", message) in code to make it work, which is not too great since it means having explicit configuration hardcoded, but at least it works.
I also tried to implement the producer in a Reactor style as desribed in this answer, but in this case the exchange/queue also is not created on application startup and the sent message just disappears even though the return status of the sending method is "OK".
Failures on the broker side are not registered at all with this approach - when I simulate one e.g. by deleting the queue or the exchange, it is not registered by the application. Only when another message is sent, I get in the logs:
ERROR 21804 --- [127.0.0.1:32404] o.s.a.r.c.CachingConnectionFactory : Shutdown Signal: channel error; protocol method: #method<channel.close>(reply-code=404, reply-text=NOT_FOUND - no exchange 'produceA-out-0' in vhost '/', class-id=60, method-id=40)
But still, the result of StreamBridge#send was true in this case. But we need to know that sending did actually fail at this point (we persist the state of the sent object using this boolean return value). Is there any way to accomplish that?
Any other suggestions on how to make this producer scenario more robust? Best practices?
EDIT
I found an interesting solution to the producer problem using correlations:
...
CorrelationData correlation = new CorrelationData(UUID.randomUUID().toString());
messageHeaderAccessor.setHeader(AmqpHeaders.PUBLISH_CONFIRM_CORRELATION, correlation);
Message<String> message = MessageBuilder.createMessage(payload, messageHeaderAccessor.getMessageHeaders());
boolean sent = streamBridge.send(channel, message);
try {
final CorrelationData.Confirm confirm = correlation.getFuture().get(30, TimeUnit.SECONDS);
if (correlation.getReturned() == null && confirm.isAck()) {
// success logic
} else {
// failed logic
}
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
// failed logic
} catch (ExecutionException | TimeoutException e) {
// failed logic
}
using these additional configurations:
spring.cloud.stream.rabbit.default.producer.useConfirmHeader=true
spring.rabbitmq.publisher-confirm-type=correlated
spring.rabbitmq.publisher-returns=true
This seems to work quite well, although I'm still clueless about the return value of StreamBridge#send, it is always true and I cannot find information in which cases it would be false. But the rest is fine, I can get information on issues with the exchange or the queue from the correlation or the confirm.
But this solution is very much focused on RabbitMQ, which causes two problems:
our application should be able to connect to different brokers (e.g. Azure Service Bus)
in tests we use Kafka binder and I don't know how to configure the application context to make it work in this case, too
Any help would be appreciated.

On the consumer side, you can listen for an event such as the ListenerContainerConsumerFailedEvent.
https://docs.spring.io/spring-amqp/docs/current/reference/html/#consumer-events
On the producer side, producers only know about exchanges, not any queues bound to them; hence the requiredGroups property which causes the queue to be bound.
You only need spring.cloud.stream.default.producer.requiredGroups=$Default - you can send to arbitrary destinations using the StreamBridge and the infrastructure will be created.
#SpringBootApplication
public class So70769305Application {
public static void main(String[] args) {
SpringApplication.run(So70769305Application.class, args);
}
#Bean
ApplicationRunner runner(StreamBridge bridge) {
return args -> bridge.send("foo", "test");
}
}
spring.cloud.stream.default.producer.requiredGroups=$Default

i.grpc.internal.AbstractClientStream - Received data on closed stream meaning

I have a Spring boot application (v2.2.10.RELEASE) that subscribes to multiple topics in pubSub and pulls async data and sends it to somewhere else. I am not using SpringGCP, just native google libraries
this is my subscriber setting:
// Instantiate an asynchronous message receiver.
MessageReceiver receiver =
(PubsubMessage message, AckReplyConsumer consumer) -> {
messages.add(message);
consumer.ack();
};
Subscriber subscriber = Subscriber.newBuilder(subscriptionName, receiver)
.setParallelPullCount(2)
.setFlowControlSettings(flowControlSettings)
.setCredentialsProvider(credentialsProvider)
.setExecutorProvider(executorProvider)
//.setChannelProvider()
.build();
With high traffic and big messages (2 - 4 kb) I encounter this info message:
[grpc-default-worker-ELG-1-1] INFO i.grpc.internal.AbstractClientStream - Received data on closed stream
first of all, I don't fully understand what that means? all that I noticed was that when this happens the delivered duplicated messages increase. so I assumed it meant that pubSub tried to reach the subscriber with some messages but the subscriber for some reason was not ready so pubSub will try to deliver the messages again. and hence more duplicates, is that right?
would this problem be solved using the TransportChannelProvider in subscribers? my understanding of the poorly written documentation, that this will create a new channel for delivery when the current in-use channel is closed, hence get rid of the previous log message.
if yes, how do I define the channel target string? and where can I find A NameResolver-compliant URI for the mangagedChannel. the snippet I mean is this:
private TransportChannelProvider getChannelProvider() {
ManagedChannel channel = ManagedChannelBuilder.forTarget(target).usePlaintext(true).build();
return FixedTransportChannelProvider.create(GrpcTransportChannel.create(channel));
}
I am pretty new to GCP so sorry if my question is not coherent enough

Using a custom TransportChannelProvider won't solve this type of issue. This is more likely an issue deeper down in the stack, e.g., at the gRPC level. There have been some open issues for this type of error [1, 2].
With regard to why it is causing duplicates, it is possible that the messages are getting delivered via a stream that is already closed (which aligns with the error message) because they were trapped in a lower-level buffer at the gRPC layer and therefore ended up being duplicates of messages that were subsequently delivered and processed via another stream. This could be a version of the issue discussed in the documentation around large backlogs of small messages. There was a fix for this issue in v1.109.0 of the Java client library, so if you are using a version older than that, it is worth updating.
If duplicates continue to be an issue, it would be best to reach out to support with the name of your subscription and the message IDs of some of the duplicate messages so that they can look at the delivery patterns for those messages and further diagnose if these redeliveries are unexpected.

Making sure a message published on a topic exchange is received by at least one consumer

TLDR; In the context of a topic exchange and queues created on the fly by the consumers, how to have a message redelivered / the producer notified when no consumer consumes the message?
I have the following components:
a main service, producing files. Each file has a certain category (e.g. pictures.profile, pictures.gallery)
a set of workers, consuming files and producing a textual output from them (e.g. the size of the file)
I currently have a single RabbitMQ topic exchange.
The producer sends messages to the exchange with routing_key = file_category.
Each consumer creates a queue and binds the exchange to this queue for a set of routing keys (e.g. pictures.* and videos.trending).
When a consumer has processed a file, it pushes the result in a processing_results queue.
Now - this works properly, but it still has a major issue. Currently, if the publisher sends a message with a routing key that no consumer is bound to, the message will be lost. This is because even if the queue created by the consumers is durable, it is destroyed as soon as the consumer disconnects since it is unique to this consumer.
Consumer code (python):
channel.exchange_declare(exchange=exchange_name, type='topic', durable=True)
result = channel.queue_declare(exclusive = True, durable=True)
queue_name = result.method.queue
topics = [ "pictures.*", "videos.trending" ]
for topic in topics:
channel.queue_bind(exchange=exchange_name, queue=queue_name, routing_key=topic)
channel.basic_consume(my_handler, queue=queue_name)
channel.start_consuming()
Loosing a message in this condition is not acceptable in my use case.
Attempted solution
However, "loosing" a message becomes acceptable if the producer is notified that no consumer received the message (in this case it can just resend it later). I figured out the mandatory field could help, since the specification of AMQP states:
This flag tells the server how to react if the message cannot be routed to a queue. If this flag is set, the server will return an unroutable message with a Return method.
This is indeed working - in the producer, I am able to register a ReturnListener :
rabbitMq.confirmSelect();
rabbitMq.addReturnListener( (int replyCode, String replyText, String exchange, String routingKey, AMQP.BasicProperties properties, byte[] body) -> {
log.info("A message was returned by the broker");
});
rabbitMq.basicPublish(exchangeName, "pictures.profile", true /* mandatory */, MessageProperties.PERSISTENT_TEXT_PLAIN, messageBytes);
This will as expected print A message was returned by the broker if a message is sent with a routing key no consumer is bound to.
Now, I also want to know when the message was correctly received by a consumer. So I tried registering a ConfirmListener as well:
rabbitMq.addConfirmListener(new ConfirmListener() {
void handleAck(long deliveryTag, boolean multiple) throws IOException {
log.info("ACK message {}, multiple = ", deliveryTag, multiple);
}
void handleNack(long deliveryTag, boolean multiple) throws IOException {
log.info("NACK message {}, multiple = ", deliveryTag, multiple);
}
});
The issue here is that the ACK is sent by the broker, not by the consumer itself. So when the producer sends a message with a routing key K:
If a consumer is bound to this routing key, the broker just sends an ACK
Otherwise, the broker sends a basic.return followed by a ACK
Cf the docs:
For unroutable messages, the broker will issue a confirm once the exchange verifies a message won't route to any queue (returns an empty list of queues). If the message is also published as mandatory, the basic.return is sent to the client before basic.ack. The same is true for negative acknowledgements (basic.nack).
So while my problem is theoretically solvable using this, it would make the logic of knowing if a message was correctly consumed very complicated (especially in the context of multi threading, persistence in a database, etc.):
send a message
on receive ACK:
if no basic.return was received for this message
the message was correctly consumed
else
the message wasn't correctly consumed
on receive basic.return
the message wasn't correctly consumed
Possible other solutions
Have a queue for each file category, i.e. the queues pictures_profile, pictures_gallery, etc. Not good since it removes a lot of flexibility for the consumers
Have a "response timeout" logic in the producer. The producer sends a message. It expects an "answer" for this message in the processing_results queue. A solution would be to resend the message if it hasn't been answered to after X seconds. I don't like it though, it would create some additional tricky logic in the producer.
Produce the messages with a TTL of 0, and have the producer listen on a dead-letter exchange. This is the official suggested solution to replace the 'immediate' flag removed in RabbitMQ 3.0 (see paragraph Removal of "immediate" flag). According to the docs of the dead letter exchanges, a dead letter exchange can only be configured per-queue. So it wouldn't work here
[edit] A last solution I see is to have every consumer create a durable queue that isn't destroyed when he disconnects, and have it listen on it. Example: consumer1 creates queue-consumer-1 that is bound to the message of myExchange having a routing key abcd. The issue I foresee is that it implies to find an unique identifier for every consumer application instance (e.g. hostname of the machine it runs on).
I would love to have some inputs on that - thanks!
Related to:
RabbitMQ: persistent message with Topic exchange (not applicable here since queues are created "on the fly")
Make sure the broker holds messages until at least one consumer gets it
RabbitMQ Topic Exchange with persisted queue
[edit] Solution
I ended up implementing something that uses a basic.return, as mentioned earlier. It is actually not so tricky to implement, you just have to make sure that your method producing the messages and the method handling the basic returns are synchronized (or have a shared lock if not in the same class), otherwise you can end up with interleaved execution flows that will mess up your business logic.

I believe that an alternate exchange would be the best fit for your use case for the part regarding the identification of not routed messages.
Whenever an exchange with a configured AE cannot route a message to any queue, it publishes the message to the specified AE instead.
Basically upon creation of the "main" exchange, you configure an alternate exchange for it.
For the referenced alternate exchange, I tend to go with a fanout, then create a queue (notroutedq) binded to it.
This means any message that is not published to at least one of the queues bound to your "main" exchange will end up in the notroutedq
Now regarding your statement:
because even if the queue created by the consumers is durable, it is destroyed as soon as the consumer disconnects since it is unique to this consumer.
Seems that you have configured your queues with auto-delete set to true.
If so, in case of disconnect, as you stated, the queue is destroyed and the messages still present on the queue are lost, case not covered by the alternate exchange configuration.
It's not clear from your use case description whether you'd expect in some cases for a message to end up in more than one queue, seemed more a case of one queue per type of processing expected (while keeping the grouping flexible). If indeed the queue split is related to type of processing, I do not see the benefit of setting the queue with auto-delete, expect maybe not having to do any cleanup maintenance when you want to change the bindings.
Assuming you can go with durable queues, then a dead letter exchange (would again go with fanout) with a binding to a dlq would cover the missing cases.
not routed covered by alternate exchange
correct processing already handled by your processing_result queue
problematic processing or too long to be processed covered by the dead letter exchange, in which case the additional headers added upon dead lettering the message can even help to identify the type of actions to take

Parse byteBuffer in Websphere MQ Exit

I'm trying to build a custom mq exit to archive messages that hit a queue. I have the following code.
class MyMqExits implements WMQSendExit, WMQReceiveExit{
#Override
public ByteBuffer channelReceiveExit(MQCXP arg0, MQCD arg1, ByteBuffer arg2) {
// TODO Auto-generated method stub
if ( arg2){
def _bytes = arg2.array()
def results = new String(_bytes)
println results;
}
return arg2;
}
...
The content of the message (header/body) is in the byte buffer, along with some unreadable binary information. How can I parse the message (including the body and the queue name) from arg2? We've gone through IBM's documentation, but haven't found an object or anything that makes this easy.

Assuming the following two points:
1) Your sender application has not hard coded the queue name where it puts messages. So you can change the application configuration to send messages to a different object.
2) MessageId of the archived message is not important, only message body is important.
Then one alternative I can think of is to create an Alias queue that resolves to a Topic and use two subscribers to receive messages.
1) Subscriber 1: An administratively defined durable subscriber with a queue provided to receive messages. Provide the same queue name from which your existing consumer application is receiving messages.
2) Subscriber 2: Another administratively defined durable subscriber with queue provided. You can write a simple java application to get messages from this queue and archive.
3) Both subscribers subscribe to the same topic.
Here are steps:
// Create a topic
define topic(ANY.TOPIC) TOPICSTR('/ANY_TOPIC')
// Create an alias queue that points to above created topic
define qalias(QA.APP) target(ANY.TOPIC) targtype(TOPIC)
// Create a queue for your application that does business logic. If one is available already then no need to create.
define ql(Q.BUSLOGIC)
// Create a durable subscription with destination queue as created in previous step.
define sub(SB.BUSLOGIC) topicstr('/ANY_TOPIC') dest(Q.BUSLOGIC)
// Create a queue for application that archives messages.
define ql(Q.ARCHIVE)
// Create another subscription with destination queue as created in previous step.
define sub(SB.ARCHIVE) topicstr('/ANY_TOPIC') dest(Q.ARCHIVE)
Write a simple MQ Java/JMS application to get messages from Q.ARCHIVE and archive messages.

A receive exit is not going to give you the whole message. Send and receive exits operate on the transmission buffers sent/received by channels. These will contain various protocol flows which are not documented because the protocol is not public, and part of those protocol flows will be chunks of the messages broken down to fit into 32Kb chunks.
You don't give enough information in your question for me to know what type of channel you are using, but I'm guessing it's on the client side since you are writing it in Java and that is the only environment where that is applicable.
Writing the exit at the client side, you'll need to be careful you deal with the cases where the message is not successfully put to the target queue, and you'll need to manage syncpoints etc.
If you were using QMgr-QMgr channels, you should use a message exit to capture the MQXR_MSG invocations where the whole message is given to you. If you put any further messages in a channel message exit, the messages you put are included in the channel's Syncpoint and so committed if the original messages were committed.
Since you are using client-QMgr channels, you could look at an API Exit on the QMgr end (currently client side API Exits are only supported for C clients) and catch all the MQPUT calls. This exit would also give you the MQPUT return codes so you could code your exit to look out for, and deal with failed puts.
Of course, writing an exit is a complicated task, so it may be worth finding out if there are any pre-written tools that could do this for you instead of starting from scratch.

I fully agree with Morag & Shashi, wrong approach. There is an open source project called Message Multiplexer (MMX) that will get a message from a queue and output it to one or more queues. Context information is maintained across the message put(s). For more info on MMX go to: http://www.capitalware.com/mmx_overview.html
If you cannot change the source or target queues to insert MMX into the mix then an API Exit may do the trick. Here is a blog posting about message replication via an API Exit: http://www.capitalware.com/rl_blog/?p=3304

This is quite an old question but it's worth replying with an update that's relevant to MQ 9.2.3 or later. There is a new feature called Streaming Queues (see https://www.ibm.com/docs/en/ibm-mq/9.2?topic=scenarios-streaming-queues) and one of the use-cases it is designed to support is putting a copy of every message sent to a given queue, to an alternative queue. Another application can then consume the duplicate messages and archive them separately to the application that is processing the original messages.

RabbitMQ - Get total count of messages enqueued

I have a Java client which monitors RabbitMQ queue. I am able to get the count of messages currently in queue with this code
#Resource
RabbitAdmin rabbitAdmin;
..........
DeclareOk declareOk = rabbitAdmin.getRabbitTemplate().execute(new ChannelCallback<DeclareOk>() {
public DeclareOk doInRabbit(Channel channel) throws Exception {
return channel.queueDeclarePassive("test.pending");
}
});
return declareOk.getMessageCount();
I want to get some more additional details like -
Message body of currently enqueued items.
Total number of messages that was enqueued in the queue since the queue was created.
Is there any way to retrieve these data in Java client?

With AMQP protocol (including RabbitMQ implementation) you can't get such info with 100% guarantee.
The closest number to messages count is messages count returned with queue.declare-ok (AMQP.Queue.DeclareOk in java AMQP client library).
Whilst messages count you receive with queue.declare-ok may match exact messages number enqueues, you can't rely on it as it doesn't count messages which waiting acknowledges or published to queue during transaction but not committed yet.
It really depends what kind of precission do you need.
As to enqueued messages body, you may want to manually extract all messages in queue, view their body and put them back to queue. This is the only way to do what you want.
You can get some information about messages count with Management Plugin, RabbitMQ Management HTTP API and rabbitmqctl util (see list_queues, list_channels).
You can't get total published messages count since queue was created and I think nobody implement such stats while it useless (FYI, with messages flow in average 10k per second you will not even reach uint64 in a few thousand years).

AMQP.Queue.DeclareOk dok = channel.queueDeclare(QUEUE_NAME, true, false, false, queueArgs);
dok.getMessageCount();

To access queue details via http api,
http://public-domain-name:15672/api/queues/%2f/queue_name
To access queue details via command from localhost cli promt,
curl -i -u guest_uname:guest_password http://localhost:15672/api/queues/%2f/queue_name
Where,
%2f is default vhost "/"