[erlang-questions] Internode connections
Tue Mar 13 14:16:33 CET 2007
t ty wrote:
> If two nodes are interconnected (net_adm:ping/1 succeeds) and the
> network connection between both nodes go down, what is the longest
> time period which can pass before each node says the other is dead.
> Hints to code to look at would be fine.
Somewhere between 45 to 75 seconds. Look into the docs on the
net_ticktime net_kernel's option:
> Reason: I had two interconnected nodes lose connections to each other
> over the weekend. The servers are the same LAN but different subnet.
> The servers were running the entire time, however over this weekend we
> had a Daylight Saving Time change. I suspect one server might had the
> time change occur before the other and the time to live got all weird.
If you are not starting the emulator with the +c switch, it normally
compensates for sudden changes in the system time by gradually adjusting
time to catch up with the wall clock. I don't know for sure if
net_ticktime is driven by a timer that's based on the internal clock
values (i.e. erlang:now/0) rather then the wall clock, but have no
reason to believe it wouldn't be.
> End result, mnesia dropped its peer and I'm left with an inconsistant
If you are running a replicated database, you need to design the system
that it would monitor network partitioning, and automatically restart
the replicated nodes. Please read this thread:
we also use this technique and it is indeed quite effective. I wish
that mnesia had this feature built-in.
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