How long will messages published to a Redis channel stay there ? Also, is there is a way to configure the max. lifetime of a message per channel ? Is there a way to control the channel size or does the channel continues to store messages as long as the Redis server has free memory ?
Redis pub/sub doesn't persist published messages. What you are looking for seems more like a message queue which can be implemented using a combination of pub/sub and lists. For more information see pattern sections in RPOPLPUSH command.
Related
We are currently using RabbitMQ Dynamic Shovels to forward messages to Azure Event Hub. Recently we setup a new Queue to be forwarded to Event Hub. Some messages in this Queue have a size of over 1MB which is the limit for messages on Event Hub. Because of this limit the messages bounce back and are sent again a few times each second. This creates a lot of network traffic which can be an issue.
Is there any way to send messages that bounce back to a DLX (dead letter exchange) or to a different queue? We have looked for some Dynamic Shovel options but could not find any that would be of any use.
Thank you Jesse Squire. Posting your suggestion as an answer to help other community members.
Generally, for cases when your payload is (or may be) larger than the allowable size, we recommend considering the claim check pattern where you store your payload in some other durable store (such as Blob storage) and then publish the event with a body that points to that resource.
You can refer to Dead-lettering dead-lettered messages in RabbitMQ.
You can also open an issue on GitHub: rabbitmq-server
I am working on a node JS app that connect to redis server and subscribe to a channel to get the messages.
There is a bit of confusion, should we really enable "key space notifications" on redis config to get the events in client
The same scenario I have tried using rdis cli, with which i see "key space notifications" are not enabled at the same time I have subscribed to a channel with a pattern, so when ever I publish a message from the other client, I am able to capture that event in subscribed client.
Is the "key space notifications" mandatory , but the POC says other way.
Does any one know what should be the right approach here, subscribing to channel is suffice to get messages, and its nothing to do with "key-space-notifications" ??
From Redis Keyspace Notifications
Keyspace notifications allow clients to subscribe to Pub/Sub channels in order to receive events affecting the Redis data set in some way.
Examples of events that can be received are:
All the commands affecting a given key.
All the keys receiving an LPUSH operation.
All the keys expiring in the database 0.
Events are delivered using the normal Pub/Sub layer of Redis, so clients implementing Pub/Sub are able to use this feature without modifications.
So, if you need just pub/sub, there is no need of extra configuration regarding Keyspace Notifications
I have few questions, I could not find the answers from Redis tutorial
1) how can I view/check values of a Redis PubSub channel? Monitor command is there to debug Redis, but I want to check what previously has pushed to channel.
2) What is the exact differece between channel and a queue?
3) how can I monitor Redis cluster in a free web based application?
1) You cannot view/check values that were published on a channel in the past. You can think of pubsub as fire and forget. Redis publishes a messages on a channel to clients which have subscribed to it, but does not persist the message for future reference. You can only monitor the messages published in realtime
2) Channel is a reference used by Redis to know which clients have subscribed to received messages published on that channel.
Queue is a data structure which stores values, these values can be accessed in future in FIFO order. So if you are using a queue for messaging, the messages will remain in the queue until you explicitly delete them
3) IMO there isn't any great free monitoring tool for Redis out there. See some available options here
As a side, regarding questions 1) and 2) : in case you are looking for reliable messaging, check out Redis Streams.
When my web app subscribes to a Redis channel (mostly on Application_Start), it should automatically load the current channel content, but not wait for the next publish within this channel.
I couldn't find any way to achieve this - but as this "problem" appears to be so common and trivial I guess there must be an easy solution for this?
In the web app I'm using StackExchange.Redis (in case that's relevant). Who can help? Thx in advance!
The answer is no, there is no option to do this using Redis pub/sub functionality, Redis don't actually store messages which being published to the channel, so you can't retrieve them when you connect to channel.
Take a look at RabbitMQ with their persistent queues and message acknowledgements, which they have out of the box.
As there's obviously no comfortable option available in Redis, I'm now publishing the channel message also as a regular key-value. So the clients take it from key-value store before subscribing to the channel.
I'm using NServiceBus 4.x with RabbitMQ 3.2.x as my transport.
I made the assumption that by using RabbitMQ as my transport I would be given the competing consumer model as an option. I understand that NServiceBus employs the "Fannout" exchange type for all exchanges and does not support round robin at this time. However is there a way to configure NServiceBus to take advantage of the levels of indirection via Exchanges and channels that RabbitMQ offers.
I have several consumers I would like to compete for messages from a given queue. What I am observing is subscribers' blocking access to further message retrieval from the queue until the message is consumed. So having more then one consumer at this point does me no good other then redundancy.
After reading some documentation on RabbitMQ I'm assuming that it's normal to block until the Ack receipt is sent from the subscriber. But I had assumed that subscriber #2 would have free access to the queue to fetch another message.
There is mention of increasing the prefetch count on RabbitMQ channel.
Example:
channel.BasicQos(0,prefetchcount,false)
I don't see anywhere that I can change this setting via configuration in NServiceBus. Furthermore as I read what prefetch does I'm really not sure this what i'm looking for.
Is it possible to use RabbitMQ with out a distirbutor type pattern used with MSMQ? Or should I move to MassTransit or Rebus?
Put prefetchcount=2 in your connection string. Any value above 1 will tell the broker to allow more than X unacked message to go out. You need to fiddle with this setting to find the optimum for your scenario.