HAProxy: Give me some logs on CentOS 6.5

HAProxy is frequently used as a load-balancer in front of a Galera cluster. While diagnosing an issue with HAProxy configuration, I realized that logging doesn’t work out of the box on CentOS 6.5. Here is a simple recipe to fix the issue.
If you look at the top of /etc/haproxy/haproxy.cfg, you will see something like:

Shell

 

 

 

defaults
    log globaldefaults
    log global

 

 

 

 

global log 127.0.0.1 local2 [...]

1 2 3

global     log         127.0.0.1 local2 [...]

This means that HAProxy will send its messages to rsyslog on 127.0.0.1. But by default, rsyslog doesn’t listen on any address, hence the issue.
Let’s edit /etc/rsyslog.conf and uncomment these lines:

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$ModLoad imudp $UDPServerRun 514

1 2	$ModLoad imudp $UDPServerRun 514

This will make rsyslog listen on UDP port 514 for all IP addresses. Optionally you can limit to 127.0.0.1 by adding:

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$UDPServerAddress 127.0.0.1

1	$UDPServerAddress 127.0.0.1

Now create a /etc/rsyslog.d/haproxy.conf file containing:

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local2.* /var/log/haproxy.log

1	local2.*    /var/log/haproxy.log

You can of course be more specific and create separate log files according to the level of messages:

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local2.=info /var/log/haproxy-info.log local2.notice /var/log/haproxy-allbutinfo.log

1 2	local2.=info     /var/log/haproxy-info.log local2.notice    /var/log/haproxy-allbutinfo.log

Then restart rsyslog and see that log files are created:

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# service rsyslog restart Shutting down system logger: [ OK ] Starting system logger: [ OK ] # ls -l /var/log | grep haproxy -rw-------. 1 root root 131 3 oct. 10:43 haproxy-allbutinfo.log -rw-------. 1 root root 106 3 oct. 10:42 haproxy-info.log

1 2 3 4 5 6 7

# service rsyslog restart Shutting down system logger:                               [  OK  ] Starting system logger:                                    [  OK  ]   # ls -l /var/log | grep haproxy -rw-------. 1 root   root      131  3 oct.  10:43 haproxy-allbutinfo.log -rw-------. 1 root   root      106  3 oct.  10:42 haproxy-info.log

Now you can start your debugging session!