[ejabberd] Clustering, data (state) sharing, and hooks firing on the cluster / nodes

Hisham Mardam Bey hisham.mardambey at gmail.com
Thu Nov 17 21:06:43 MSK 2011


Hi folks,

I'm fairly new to ejabberd and Erlang (3rd day using it as of writing
this email) and I am having fantastic results with both so far. We
want to use ejabberd where I work (dating site, we have up to around
8K people online wanting to chat). What we have so far is ejabberd
2.1.6-2.1 (via apt) coupled with Strophe JS for the web browsers.
We've written a couple of Erlang modules that update our system via
presence notifications when people join and leave. We've also got
another module that coordinates invitations between users and must
keep some state about who's said "yes" to who's invitation so that
subsequent chat messages between the 2 users can go through (other
wise the module's packet filter will drop it). The goal is to then use
this by adding a hook on fitler_packet and only let through chats that
have been approved and "registered" in the system.

My question is really about the last part, how one would go about
"sharing" such state across the cluster, and how do hooks work in a
cluster? I am still reading up on Erlang and ejabberd clustering and
how it works.

If I have multiple nodes in my cluster with users connected to
different nodes what is the recommended way of tracking such
invitation state? Also, if I use presence to figure out when a user
has left through a hook, will the presence hook fire only on the node
the user was connected to and left (presence changed)?

My plan is to read up some more on how Erlang and ejabberd handles
clustering then come back here and update this question. In the mean
time, any helpful information or resources explaining how this stuff
works are greatly appreciated.

hisham.

-- 
Hisham Mardam-Bey
http://hisham.cc/


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