[Arathorn]

The main alternative is probably Matrix currently (Disclaimer: i work on it). The advantages are that it's a pretty simple HTTP API, and there are good SDKs for JS, iOS & Android. The biggest disadvantage is probably that the UI SDKs (matrix-react-sdk, matrix-ios-kit and matrix-android-sdk) have ended up quite entangled in the Riot client codebase, and we need to decouple them so that they can be better used to implement custom chat/collaboration components.

[nerdponx]

Last I checked, the Synapse homeserver was heavy on resource consumption and therefore tough to run at home on, say, a RPi. How much progress has been made towards more usable homeservers?

[majewsky]

I have a Synapse running (among other things) on a 1/1 VM. It's at the top of `top` (heh) when sorting by memory:

  PID USER      PR  NI    VIRT    RES %CPU %MEM     TIME+ S COMMAND                                                                                                                                                 
  486 synapse   20   0  510,1m  81,7m  0,0  8,2   3:03.73 S python2.7
  ...

There are six user accounts on that Synapse and few activity (less than 100 messages per day).

When I first installed it to play around with it, I joined #matrix:matrix.org and it brought Synapse to a grinding halt. Took quite some time to catch up with the thousands of peers it suddenly had to federate with, and I ultimately cleared Synapse's database to make it forget about all these peers.

For comparison, I also have a Prosody (i.e. an XMPP server) on the same box, which has about 10 user accounts and my own account is joined to a few moderately busy MUCs, so the number of messages is at least one order of magnitude higher. Yet memory usage is about one order of magnitude smaller (CPU usage is too infrequent to compare, but look at the "TIME" column for an initial comparison):

  $ psgrep 'prosody\|synapse'
  USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  synapse    486  0.1  8.1 522332 83664 ?        Ssl  Aug13   3:04 /usr/bin/python2.7 -m synapse.app.homeserver --config-path=/etc/synapse/homeserver.yaml --log-config=/etc/synapse/log_config.yaml
  prosody    574  0.0  1.0  52408 10476 ?        S    Aug13   0:27 lua5.1 /usr/lib/prosody/../../bin/prosody

[ryukafalz]

Synapse does a lot more than Prosody though. If a Prosody server hosting a MUC goes down, the MUC is down. If the Matrix homeserver that created a room goes down, the room's still there as long as there are other servers participating. That decentralization does have its tradeoffs.

It's also the first Matrix server, so there's that. Its replacement is in progress: https://github.com/matrix-org/dendrite

[majewsky]

Oh nice. That should have a lot less footprint indeed, both in terms of CPU usage and # of dependencies. (Not entirely sure about memory usage, but that should also be better for a compiled language.)

[Arathorn]

yup, synapse is heavy (as the rest of the thread says). this is mainly due to the DB schema being a bit naive, and it caching everything in RAM to speed things up. There are also some operations it does which spike RAM usage (which is then never reclaimed, thanks to Python2's malloc being a bit dumb). As others have said, Synapse is doing a lot more than something like Prosody. Dendrite on the other hand should be good for running on an RPi - we should have an idea this week, where the first monolithic Dendrite binary is due to land.