[erlang-questions] ETS tables and pubsub

Christopher Meiklejohn <>
Wed Nov 13 18:50:19 CET 2013


On Wednesday, November 13, 2013 at 12:19 AM, Barco You wrote:
> Why don't you use gproc?

Last time I checked, gproc isn’t super reliable under failure conditions in global distribution mode.

Garret and Ulf have discussed it on erlang-questions [1], section 10 of Ulf’s Erlang Workshop paper [2] covers quite a bit about it, and I’ve also written about it [3].

[1] http://erlang.org/pipermail/erlang-questions/2012-July/067749.html
[2] http://svn.ulf.wiger.net/gproc/doc/erlang07-wiger.pdf
[3] http://christophermeiklejohn.com/erlang/2013/06/05/erlang-gproc-failure-semantics.html

- Chris

> On Wed, Nov 13, 2013 at 2:38 AM, akonsu < (mailto:)> wrote:
> > I have a pubsub system which has a single publisher process that maintains all its subscriber processes' Pid's in an ETS table.
> >  
> > The publisher monitors its subscribers and when the publisher receives DOWN message, it removes the subscriber Pid from the table.  
> >  
> > The table entries are tuples of the form {MonitorRef, SubscriberPid}, and the MonitorRef is used as the key.
> >  
> > Now I would like to make sure that if the publisher dies, and gets restarted by its supervisor, the subscriber table is preserved. So I created a process that creates the ETS table, sets the table's heir to self(), and then gives away the table to the publisher.  
> >  
> > The problem is that I do not know how to handle transfer of the table from the heir to the publisher:
> >  
> > when publisher receives the table, the table contains a list of tuples {MonitorRef, SubscriberPid}, but the MonitorRefs were created by the previous publisher instance, so when the new publisher receives ETS_TRANSFER it needs to monitor all these SubscriberPids again.  
> >  
> > what is the best way to do it? Loop over all ETS entries, attach a monitor to each and reenter the new MonitorRefs into the table? This might be slow, no? Maybe my architecture can be improved? Any advice?  
> >  
> > thanks
> > Konstantin
> >  
> >  
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