[erlang-questions] Mnesia and schema locks

[Loïc Hoguin]

Hello,

We are trying to debug an issue where we observe a lot of contention 
when a RabbitMQ node go down. It has a number of symptoms and we are in 
the middle of figuring things out.

One particular symptom occurs on the node that restarts, it gets stuck 
and there are two Mnesia locks:

[{{schema,rabbit_durable_route},read,{tid,879886,<6502.2299.18>}},
  {{schema,rabbit_exchange},read,{tid,879887,<6502.2302.18>}}]

The locks are only cleared when the other node in the cluster stops 
being so busy deleting data from a number of tables (another symptom) 
and things go back to normal.

Part of the problem is that while this is going on, the restarting node 
cannot be used, so I would like to understand what conditions can result 
in these locks staying up for so long. Any tips appreciated!

Thanks in advance,

-- 
Loïc Hoguin
https://ninenines.eu