[erlang-questions] : : PID recycling
Tue Sep 9 13:14:26 CEST 2008
On Tue, Sep 09, 2008 at 10:38:54AM +0200, Zoltan Peter Toth wrote:
> What about the case when we have a number of erlang nodes on different
> hosts ?
> Will the epmd-s on the other hosts maintain the incarnation counter for
> a restarted host ?
> It seems to me that even if one host is restarted (or beam and epmd
> killed on it), the
> incarnation counter continues as if the local epmd was running. So I
> assume that
> those are the other epmd-s that keep track of that counter.
> (... or I just overlooked something ? )
The incarnation counter aka creation is kept in the local epmd.
Any erlang node only registers with the local epmd. When you
look up a node on a remote host you ask the remote epmd.
Epmd is mostly a local register on a host to map from node
to TCP/IP port number, and it also keeps the creation counter
(for the local nodes).
For a new node (also when epmd is new) the initial creation
is "randomized" in the interval 1..3 as current time in
seconds modulo 3 plus 1.
node->creation = (current_time(g) % 3) + 1; /* "random" 1-3 */
> Raimo Niskanen wrote:
> >On Mon, Sep 08, 2008 at 01:59:56PM +0200, Zoltan Peter Toth wrote:
> >>Hi Raimo !
> >>Thanks. So if a node completely restarts, i.e. epmd as well, then the
> >>cycling is lost,
> >>i.e. after 0 there will be 0 again after the reboot, right ?
> >Well, 1, since nodes with names use creation 1..3,
> >but you are right.
/ Raimo Niskanen, Erlang/OTP, Ericsson AB
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