Discarding message in an old incarnation

Rickard Green rickard@REDACTED
Fri Aug 7 18:54:55 CEST 2020

fre 7 aug. 2020 kl. 15:38 skrev Matthew Evans <mattevans123@REDACTED>:

> Hi,
> We have a system running R19 that occasionally throws out this message:
> 2020-08-06 19:17:46 =ERROR REPORT====
> Discarding message {'$gen_cast',{compatibility_handling,3,3}} from <0.355.0> to <0.405.0> in an old incarnation (1) of this node (3)
> Can someone explain what it means? It's in a mesh, but all nodes
> are/should be running the same version.
> Many thanks

When a node is started it gets a value called ”creation” which is stored in
all pid, ports, and references that the node generates. If a node is
restarted with the same node name, the creation is changed. The creation
value is not printed when printing pids, ports, and references, so they can
look as the same while not being the same.

In your case your node is receiving a message to a process that existed on
a node with the same name but with a different creation. That is, a node
that previously existed.

Rickard Green
Rickard Green, Erlang/OTP, Ericsson AB
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