My Question is regarding Replay in Solace

Piyush Poply

Hi , I have following questions on Replay

Want to know more about the replay Queues that gets created once we enable the replay on our VPN. One of the queues has name like Replay Log which stores all the persistant messages getting send to the VPN , what about the other queue having name like REPLAY_TOPICS what exactly is the significane of that.

My Second question is with respect to a Replay from a consumer side, I am currently aware that through JCSMP we can set replay to flow properties and start our consumer to get replay messages in the queue , but with this approach we have to restart/rebind our consumer flow every time we need replay to be done. Is there any other way through which we can do replay on a trigger and we dont need to disturb our consumer flow. I am also aware of the SEMP endpoints but that is something we dont have access to in our organization.

My last question is , Is there a way to do Replay on Non exclusive endpoints without using SEMP Admin API (as mentioned we dont have access to that), As per my reading it is restricted to use Replay on Non exclusive endpoints from Consumer side.

amackenzie

Hi @Piyush Poply ,

1. The REPLAY_TOPICs queue is about keeping track of the subscriptions that you want to be tracked in the replay log. This was introduced in a recent broker release. Prior to that, all guaranteed messages would be tracked in the replay log. This feature allows you to only replay topics that are "important" rather than filling the replay log with messages you will not need to replay.
2. Replay depends on disconnecting consumer flows as otherwise you would get into race conditions and unpredictable results. The SEMP endpoints will also cause your flows to unbind/rebind.
3. The reason API-initiated replay is limited to exclusive queues is because a single consumer does not have the right/ability to unbind flows in other consumer clients that might/would be connected to the non-exclusive queue. From SEMP or Broker Manager UI, this is a management user and does have the right to do so.

Andrew

Piyush Poply

Thanks @amackenzie For clearing out all the queries I posted,   

On the first question regarding REPLAY_TOPIC queue, is there any documentation which we can refer and use this functionality of messages getting replayed only for topics having subscription to this queue.  I tried to find out in Solace documentation but couldn't.  

Currently In our version of Solace, we can see this queue having no subscription and all the messages having mode persistent are getting pushed to the replay queue. 

amackenzie

Hello @Piyush Poply ,

The feature to allow configuration of a topic filter to select which messages are referenced in the replay log was introduced in broker v10.0.0 (April 2022).

The configuration is straightforward if you are used to topic subscriptions and can be configured in the CLI using instructions here.

There is also support in Broker Manager via the Replay -> Subscriptions page:

I hope that helps.