Purge old messages when out of memory

[AlexeyKupershtokh]

Hello.

As I can see in the push_stream_shared_memory_size description:

The size of the memory chunk this module will use to store published messages, channels and other shared structures. When this memory is full any new request for publish a message or subscribe a channel will receive an 500 Internal Server Error response.

What is supposed to do when you get 500 trying to publish a mesasge?

I would prefer to have another option of the module behavior. I think it should (optionally) free memory when it needs more by freeing old messages. This way push_stream_message_ttl would have logic more like "try to keep messages for push_stream_message_ttl but can also delete them earlier".

E.g. this policy is available in Redis ( http://oldblog.antirez.com/post/redis-as-LRU-cache.html ):

Another way to use Redis as a cache is the maxmemory directive, a feature that allows specifying a maximum amount of memory to use. When new data is added to the server, and the memory limit was already reached, the server will remove some old data deleting a volatile key, that is, a key with an EXPIRE (a timeout) set, even if the key is still far from expiring automatically.

What do you think?

[joaoafrmartins]

Hello @wandenberg @AlexeyKupershtokh! +1

[misiek08]

It's a must have.

Some API to delete stored messages will be great too, but it's more advanced feature, so just freeing memory as needed will be ok.

[tomquas]

yes please. would be tremendously useful in my current setup.