I have a use case where I publish to a topic and listen via Queues in solace. Due to the increased number of Queues , we have decided to create temporary queues. When I tried with a temp Queue, I was able to publish and subscribe directly. But I'm unable to attach a topic endpoint to the queue. Is it possible t attach a topic endpoint to a temp Queue in Solace, if so how to do it?
Yes, it is possible. Which API are you using? Assuming it is the Solace Java API, then to add a topic subscription to a queue you can use the JCSMPSession.addSubscription(...) method. For other Solace APIs see the documentation here: https://docs.solace.com/Solace-PubSub-Messaging-APIs/API-Developer-Guide/Adding-Topic-Subscriptio.htm
The process is same whether the queue is temporary or durable.
Queue queue = JCSMPFactory.onlyInstance().createQueue("Q/tutorial/topicToQueueMapping");
Topic tutorialTopic = JCSMPFactory.onlyInstance().createTopic("T/mapped/topic/sample");
session.addSubscription(queue, tutorialTopic, JCSMPSession.WAIT_FOR_CONFIRM);
In the add subscription method above pass in your temporary queue object reference.
Related
The SimpleMessageListenerContainerFactory in spring-cloud-aws provides a way to configure the MaxNumberOfMessages to pull from an SQS queue. See spring cloud docs
If an application is listening to more than one queue. How can the MaxNumberOfMessages be set differently for each queue?
I'm using MassTransit AmazonSQS and I would want to know if there is any way of removing/deleting the queues and the topics that got created by MassTransit,for which there is no more need to exist, like when the message is renamed or when there are no more messages being published to that queue. Are there some attributes to set on the topic/queue so that after a certain period of inactivity the AWS resources created by MassTransit are removed automatically?
I am aware of the "AutoDelete" configuration property, but I use it with temporary queues and these get removed successfully, but in the case of a durable queue, how do we ensure the resources are removed when they're not in use after a certain period (both AWS topics and queues)?
MassTransit will not remove any topics, subscriptions, or queues. It will only create missing entities.
It is your responsibility to remove any topics, subscriptions, or queues that are no longer in use. From a code perspective, if a queue isn't being used, MassTransit probably doesn't know about it anyway.
I tried using parallel requests but the due to retention by AWS, it does not allow to poll back the same queue unless previously polled messages are deleted.
I however achieved doing the same using the FIFO, but not the standard queue.
Thanks in Advance!
:)
When you say "it does not allow to poll back the same queue unless previously polled messages are deleted", I assume you're talking about the inflight messages per queue limit, which is pretty high at 120,000:
For most standard queues (depending on queue traffic and message backlog), there can be a maximum of approximately 120,000 inflight messages (received from a queue by a consumer, but not yet deleted from the queue). If you reach this limit, Amazon SQS returns the OverLimit error message. To avoid reaching the limit, you should delete messages from the queue after they're processed. You can also increase the number of queues you use to process your messages. To request a limit increase, file a support request.
The expected use case of SQS is to have workers that receive a message, do some work, then delete the message. If you're not following this pattern, I'd strongly recommend reevaluating whether SQS is the right tool for what you're trying to do.
However, if you really have a valid use case for having more than 120K messages inflight at once, you'll need to describe your use case to AWS and get their approval to increase that limit.
Iam sending messages to the queue and using amazon sqs queuing system in a rails application. But since the queue follows FIFO process, it will get the next items in the same fashion. Suppose if I have 100 items in a queue, how can I retrieve the 35th item from the queue and process it. As far as I know, there is no such method that amazon sqs provides for doing it. So is there any other method/workaround where I can achieve the this functionality.
There is no method to do that; SQS does not guarantee order of items in the queue due to its geographically redundant nature; it can't even guarantee FIFO. If you absolutely must process things in order, and need the ability to 'look ahead' in the queue, SQS may not be your best choice. Perhaps a custom made queue in something like DynamoDB may be work better.
SQS is designed to guarantee at-least-once delivery and does not take into account the order of messages. So the simple answer to your question on whether you can do that, is no.
A work around would depend on your use-case:
To split work among different processes handling queue messages and making sure they don't both process the same item - Different queues is one approach, or prefixing every message with an identifier denoting which process is supposed to work on it. For example, if I have 4 daemons's running, I could prefix every message in the queue with the ID of the process which should work on it - 1,2,3 or 4. Every process would only process messages with the number corresponding to it's ID.
Order of arrival is critical - In this case, you're better off not using SQS because it wasn't to be used this way. CloudAMQP is a cloud based service that is based off RabbitMQ which is a true FIFO queue and would suit this case better than SQS.
I'm using an Amazon SQS queue to send notifications to an external system.
If the HTTP request fails when using SQS' SendMessage, I don't know whether the message has been queued or not. My default policy would be to retry posting the message to the queue, but there's a risk to post the message twice, which might not be acceptable depending on the use case.
Is there a way to have SQS refuse the message if there is a duplicate on the message body (or some kind of message metadata, such as a unique ID we could provide) so that we could retry until the message is accepted, and be confident that there won't be a duplicate if the first request had been already queued, but the response had been lost?
No, there's no such mechanism in SQS. Going further, it is also possible that a message will be delivered twice or more (at-least-once delivery semantics). So even if such a mechanism existed, you wouldn't be able to guarantee that the message isn't delivered multiple times.
See: http://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/DistributedQueues.html
For exactly-once deliveries, you need some form of transactions (and HTTP isn't a transactional protocol) both on the sending and receiving end.
AFAIK, right now SQS does support what was asked!
Please see the "What's new" post entitled Amazon SQS Introduces FIFO Queues with Exactly-Once Processing and Lower Prices for Standard Queues
According to SQS FAQ:
FIFO queues provide exactly-once processing, which means that each message is delivered once and remains available until a consumer processes it and deletes it. Duplicates are not introduced into the queue.
There's also an AWS Blog post with a bit more insight on the subject:
These queues are designed to guarantee that messages are processed exactly once, in the order that they are sent, and without duplicates.
......
Exactly-once processing applies to both single-consumer and multiple-consumer scenarios. If you use FIFO queues in a multiple-consumer environment, you can configure your queue to make messages visible to other consumers only after the current message has been deleted or the visibility timeout expires. In this scenario, at most one consumer will actively process messages; the other consumers will be waiting until the first consumer finishes or fails.
Duplicate messages can sometimes occur when a networking issue outside of SQS prevents the message sender from learning the status of an action and causes the sender to retry the call. FIFO queues use multiple strategies to detect and eliminate duplicate messages. In addition to content-based deduplication, you can include a MessageDeduplicationId when you call SendMessage for a FIFO queue. The ID can be up to 128 characters long, and, if present, takes higher precedence than content-based deduplication.