Error in accept: Bad file descriptor

[Shahrier Akram]

Recently upgraded to Percona 5.7.12-log on a Debian box and the Percona server's been requiring frequent restarts every few hours to keep working. Further details here in stack overflow:

http://stackoverflow.com/questions/37796693/mysql-0-error-error-in-accept-bad-file-descriptor

ulimit is at 64k. It was at 1024 before. Raising the the opens_files_limit appears to have reduced the frequency of outage but not completely unfortunately. Any insights appreciated.

[Peter Zaitsev]

Hi,

What do you see as open_files status variable ?  Does it reach any high numbers ? 

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[edw...@ehibbert.org.uk]

I've just upgraded to Percona Cluster 5.7, and I see this too. The server spins logging that error until I manually restart it - which isn't great, so I'll need to rig up a monit script to restart it. It lasts a couple of hours before this happens under normal load.

I've increased the open files limit:

mysql> show global variables like 'open%';
+------------------+--------+
| Variable_name | Value |
+------------------+--------+
| open_files_limit | 100000 |
+------------------+--------+

Immediately after a restart, I see this:

mysql> show status like 'open%';
+--------------------------+-------+
| Variable_name | Value |
+--------------------------+-------+
| Open_files | 36 |
| Open_streams | 0 |
| Open_table_definitions | 231 |
| Open_tables | 2157 |
| Opened_files | 834 |
| Opened_table_definitions | 0 |
| Opened_tables | 1 |
+--------------------------+-------+

I don't yet know how this behaves over time, as when it's failed I've immediately panicked and restarted it rather than try to debug it.

[edw...@ehibbert.org.uk]

Well, this is a nice one.

In my case, the tight loop in the server was actually provoked by monit, which connects to 127.0.0.1 to check that the server is up.

If I shut down monit, the mysqld stays up.

If I then telnet localhost 3306 and disconnect, mysqld goes into a tight loop logging [ERROR] Error in accept: Bad file descriptor

[Roel Van de Paar]

Is https://mariadb.atlassian.net/browse/MDEV-8995 a solution?

[Roel Van de Paar]

If so, we could consider porting the patch.

[Edward Hibbert]

Thanks for your reply.  I don't think it's that - I have 5000 in my.cnf and that's what select @@max_connections\G shows.

As (now) described on http://stackoverflow.com/questions/37796693/mysql-0-error-error-in-accept-bad-file-descriptor/39967997#39967997 I have a hacky workaround by using unix sockets rather than TCP, which enables me to keep my servers running for more than an hour or so :-).   

I've not done work  on the MySQL code so I may be wrong, but the code I've included in that answer does look a bit like it retries in the hope that the problem will go away - which I can believe for EINTR, but doesn't seem to be the case with whatever is going on here.

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