[rabbitmq-discuss] TTLs in 2.5.1

[Emile Joubert]

Hi Aaron,

On 20/12/11 03:29, Aaron Westendorf wrote:
> We're running Rabbit 2.5.1 in a 2 node cluster and need  to implement
> message TTLs to mitigate some pressing problems. If anyone could help
> us out with some questions we have that would be most appreciated.
> 
> Are they fully supported in this version?

Yes, support for per-queue message TTL was introduced in rabbit 2.2.0.

> If we're going to enable TTLs, is there a pressing need to upgrade or
> can we stay on 2.5.1?

We would always recommend running the latest version. In this case you
do not need to upgrade specifically to get this feature.

> Is there anything special to note about them in a 2.5.1 cluster?

No. per-queue TTL is a queue-specific feature and queues exist only on a
single node in a 2.5.1 cluster.

> Do we need to turn on client qos, or will rabbit change its consumer
> delivery rules on TTL'd messages?

You do not need to set QoS for messages to expire.

> Are there any recommended lower bounds on this value?

This depends on your usage and hardware performance characteristics. You
should test and validate in a comparable environment before deploying to
production.

A value larger than the average latency makes sense.

> What kind of effect should we expect message TTL to have on resource
> requirements?

I would expect perhaps a small improvement since it is easier for the
broker to expire a message than to deliver.

> Will this significantly impact the memory footprint specifically?

The effect would be similar to a consumer that works at the combined
rate of the publishers.

> Anything special about TTL in the case where rabbit is already under
> very high load?