postfix can't connect with mysql table when using unix socket. postmap succeeds though? [closed]

Question

Postfix is throwing up an error saying:

Jul 9 14:41:26 tmail postfix/trivial-rewrite[4342]: warning: connect to mysql server unix:/var/run/mysqld/mysqld.sock: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) Jul 9 14:41:26 tmail postfix/trivial-rewrite[4342]: fatal: mysql:/etc/postfix/mysql-yaa-aliases.cf(0,lock|fold_fix): table lookup problem

In main.cf I have:

virtual_alias_maps = mysql:/etc/postfix/mysql-yaa-aliases.cf

In mysql-yaa-aliases.cf I have:

hosts = unix:/var/run/mysqld/mysqld.sock
# hosts = 127.0.0.1
user = yaa_admin
password = ********
dbname = yaa
query = SELECT dest FROM yaa_active_aliases WHERE address='%s'

If I use 127.0.0.1 it works (not ideal as I would prefer the speed of a socket.) Also if I test the socket with postmap it works:

# postmap -q "[email protected]" mysql:/etc/postfix/mysql-yaa-aliases.cf
[email protected], [email protected]

When I use strace on the trivial-rewrite daemon I get:

connect(11, {sa_family=AF_FILE, path="/var/run/mysqld/mysqld.sock"}, 110) = -1 ENOENT (No such file or directory)

Whereas strace using postmap I get:

connect(4, {sa_family=AF_FILE, path="/var/run/mysqld/mysqld.sock"}, 110) = 0

BTW - Currently running Postfix 2.7, but the fault still shows with 2.9

Ozonize

BTW postmap tests succeed with both unix: and 127.0.0.1 lines – Majormajordomo

Answer 1

FOUND IT :) - trivial-rewrite takes place in a chroot jail, therefore the socket file REALLY doesn't exist.

The solution (thanks to https://serverfault.com/questions/229389 for helping me with this) is to add this to the /etc/fstab:

/var/run/mysqld /var/spool/postfix/var/run/mysqld bind defaults,bind 0 0

Thus allowing Postfix to keep its chroot config, and giving it access to the mysql socket.

Ozonize

How about using as host value 127.0.0.1? It helped me to solve this issue. It uses TCP connection which doesn't write socket (unlike localhost value on unix). – Klotz

I think using a TCP connection is a better solution. Would be worthy of being a separate answer to this question. EDIT: I see, the question's closed. Oh well, I got my answer ;-) – Eme

@Klotz I am trying to use 127.0.0.1 but still get the error Can't connect to MySQL server on <my_ip_address> . Any pointers? – Liverish

@Klotz Very old comments, but worth answering. When both methods are possible, unix sockets are always preferable. There was a time when it would be considered wrong to use TCPIP over unix sockets for a local connection. Today CPUs are fast enough that more people use that shortcut. But engaging the TCP/IP stack for local connections is still wasteful and even with some localhost shortcuts in the system still adds significant overhead. jasonbarnabe.wordpress.com/2014/10/01/… – Leblanc