I am creating a bulk video processing system using spring-boot. Here the user will provide all the video related information through an xlsx sheet and we will process the videos in the backend. I am using the Rabbitmq for queuing up the request.
Let say a user has uploaded a sheet with 100 rows,then there will be 100 messages in the Rabbitmq queue. In the back-end, we are auto-scaling the subscribers (servers). So we will start with one subscriber-only and based on the load (number of messages in the queue) we will scale up to 15 subscribers.
But our producer is very fast and it allocating all the messages to our first subscriber (before other subscribers are coming up) and all our new subscriber are not getting any messages from the queue.
If all the subscribers are available before producer started pushing the messages then it is allocating the messages to all servers.
Please provide me a solution of how can our new subscribers pull the messages from the queue that were produced earlier.
You are probably being affected by the listener container prefetchCount property - it defaults to 250 with recent versions (since 2.0).
So the first consumer will get up to 250 messages when it starts.
It sounds like you should reduce it to a small number, even all the way down to 1 so only one message is outstanding at each consumer.
Related
I have a publisher that sends messages to a consumer that moves a motor.
The motor has a work queue which I cannot access, and it works slower than the rate of the incoming messages, so I'm trying to control the traffic on the consumer.
To keep updated and relevant data coming to the motor without the queue filling up and creating a traffic jam, I set the RabbitMQ queue size limit to 5 and basicQos to 1.
The idea is that the RabbitMQ queue will drop the old messages when it is filled up, so the newest commands are at the front of the queue.
Also by setting basicQos to 1 I ensure that the consumer doesn't grab all messages from the queue and bombards the motor at once, which is exactly what i'm trying to avoid since I can't do anything once the command was sent to the motor.
This way the consumer takes messages from the queue one by one, while new messages replace the old ones on the queue.
Practically this moves the bottleneck to the RabbitMQ queue instead of the motor's queue.
I also cannot check the motor's work queue, so all traffic control must be done on the consumer.
I added messageId and tested, and found out many messages are still coming and going long after the publisher is being shut down.
I'm expecting around 5 messages after shutdown since that's the size of the queue, but i'm getting hundreds.
I also added a few seconds of sleep inside the callback to make sure this isn't the robot queue that's acting up, but i'm still getting many messages after shutdown, and I can see in the logs the callback is being called every time so it's definitely still getting messages from somewhere.
Please help.
Thanks.
Moving the acknowledgment to the end of the callback solved the problem.
I'm guessing that by setting basicQos to 1 it did execute the callback for each message one after another, but in the background it kept grabbing messages from the queue.
So even when the publisher was shutdown, the consumer still had messages that were taken from the queue in it, and those messages were the ones that I saw being executed.
I'm confused how rabbitmq works when a new consumer comes online.
I understand when there are currently x number of consumers connected, and then a producer sends a message the consumers will receive these messages.
But say consumerX was down, and now comes online or it is a brand new consumer. Is it possible for it to replay messages in the past 24 hours?
This is a normal behavior for RabbitMQ.
Please read:
https://www.rabbitmq.com/tutorials/tutorial-two-python.html
Is it possible for it to replay messages in the past 24 hours?
It depends on how you set things up.
If you have queues that don't auto-delete, they'll just keep collecting messages and waiting around for a consumer to connect.
I've had instances w/ thousands of messages stuck in a queue because my consumer was crashing. As soon as I fixed my code, the messages started consuming again.
But, if you're letting your queues get deleted when your consumers die, then you're in a bit of trouble.
There is a plugin to read the last ## of messages from an exchange, but it doesn't work in a time-based manner... just the last ## of messages: https://github.com/rabbitmq/rabbitmq-recent-history-exchange
We're seeing an issue where consumers of our message queues are picking up messages from queues at the top of the alphabetical range. We have two applications: a producer, and a subscriber. We're using RabbitMQ 3.6.1.
Let's say that the message queues are setup like so:
Our first application, the producer, puts say 100 messages/second onto each queue:
Our second application, the subscriber, has five unique consumer methods that can deal with messages on each respective queue. Each method binds to it's respective queue. A subscriber has a prefetch of 1 meaning it can only hold one message at a time, regardless of queue. We may run numerous instances of the subscriber like so:
So the situation is thus: each queue is receiving 100 msg/sec, and we have four instances of subscriber consuming these messages, so each queue has four consumers. Let's say that the consumer methods can deal with 25 msg/sec each.
What happens is that instead of all the queues being consumed equally, the alphabetically higher queues instead get priority. It's seems as though when the subscriber becomes ready, RabbitMQ looks down the list of queues that this particular ready channel is bound to, and picks the first queue with pending messages.
In our situation, A_QUEUE will have every message consumed. B_QUEUE may have some consumed in certain race conditions, but C_QUEUE/D_QUEUE and especially E_QUEUE will rarely get touched.
If we turn off the publisher, the queues will eventually drain, top to bottom.
Is it possible to configure either RabbitMQ itself or possibly even the channel to use some sort of round robin distribution policy or maybe even random policy so that when a channel has numerous bound queues, all with messages pending, the distribution is even?
to clarify: you have a single subscriber application with multiple consumers in it, right?
I'm guessing you're using a single RabbitMQ Connection within the subscriber app.
Are you also re-using a single RabbitMQ Channel for all of your consumers? If so, that would be a problem. Be sure to use a new Channel for each consumer you start.
Maybe the picture is wrong, but if it's not then your setup is wrong. You don't need 4 queues if you are going to have subscribers that listen to each and every queue. You'd just need one queue, that has multiple instances of the same subscriber consuming from it.
Now to answer, yes (but no need to configure, as long as prefetch is 1), actually rabbitmq does distribute messages evenly. You can find about about that here, and on the same place actually how your setup should look like. Here is a quote from the link.
RabbitMQ just dispatches a message when the message enters the queue.
It doesn't look at the number of unacknowledged messages for a
consumer. It just blindly dispatches every n-th message to the n-th
consumer.
I am developing an app. and I am using activemq. Is there any way to do that one producer always send messages to one broker but on the opposite side there 3 consumers.Each consumer listens broker and can take any of message from queue.Is this possible?
I am using activemq for writing my app. logs to db.As u know writing logs to db is time taking process.That's why consumer is more and more slow than producer.For ex. I send 100.000 message(huge objects).Producer finishes sending messages in 20 mins.But When the producer finished, consumer has finished 4.000 message processing yet.
Yes, what you are describing is possible. In fact, you can have any number of consumers listening on a single queue. The messages are dispatched in a round-robin fashion between consumers.
What you should be aware of is that ActiveMQ performs much better sending small messages than large ones. If you need to send very large payloads (e.g. 100mb), you are far better off saving the message to a location that is accessible by both the producer and consumers (e.g. a network file system), and sending the location of the message instead. The consumer can then use that to read the message manually. This way you get a relatively small amount of traffic through the message broker.
I am trying to do some stress testing on AMQ 5.5.1.
I have created a queue and using Jmeter Point-to-point to send JMS requests to the queue. Kindly note I haven't configured any consumer so mesages just get stacked up and actually stored in KahaDB store.
I notice if I have used 200 users in the Thread group - it creates exactly 400 threads on ActiveMQ that I can see via jconsole.
Jmeter slowly(actually quite fast) keeps on pushing messages to the queue as I can see the queue size gradually increasing and doesn't do it at one go.
I am using ProducerFlowControl as false and using the default hybrid store cursor on (though I haven't got a ready consumer at the moment).
I am also using Persistent Delivery.
My questions are:
What is restricting Jmeter from pushing all the 200 messages at one go? Is it ActiveMQ or I need to configure something in jmeter to be able to send 200 at one go. I did notice as soon as I start the test on Jmeter straight away 400 threads are created on ActiveMQ which makes me think it establishes connections at one go for 200 users with activemq but messages are pushed in batches but not together.
Why are there 2 threads per consumer on activemq and why do all the threads remain active until all messages have been pushed. Ideally if the users were pushing messages one by one as soon as they have done so and got an acknowledgement back it should have died out. But all 200 X 2 threads die at the same time when all messages have finally been pushed.
Any help is appreciated.