When attempting to troubleshoot a monitoring alert regarding memcached being offline/unavailable, checking the service it shows it is online and there are no logs to determine if there was indeed an issue at the time of the alert. Logging for memcached is not on even though there is a logfile directive in the configuration file /etc/memcached.conf
/etc/memcached.conf
# Ansible managed: /etc/ansible/roles/memcached_server/templates/memcached.conf modified on 2016-03-15 11:46:36 by root on infra01
-d
logfile /var/log/memcached.log
-m 1995
-p 11211
-u memcache
-l 172.29.237.146
-c 1024
-t 4
/etc/ansible/roles/memcached_server/templates/memcached.conf
# {{ ansible_managed }}
-d
logfile {{ memcached_log }}
-m {{ memcached_memory }}
-p {{ memcached_port }}
-u {{ memcached_user }}
-l {{ memcached_listen }}
-c {{ memcached_connections }}
-t {{ memcached_threads }}
Looking at the code, I believe memcached_log should be memcached_log_file and memcached_log_level should be added with '-v' as the default. Confirmation regarding the logging not being available with simply using logfile can be found here: https://docs.oracle.com/cd/E17952_01/refman-5.6-en/ha-memcached-using-logs.html
If you enable verbose mode, using the -v, -vv, or -vvv options, then the information output by memcached includes details of the operations being performed.
Without the verbose options, memcached normally produces no output during normal operating.
Output when using -v
The lowest verbosity level shows you:
Errors and warnings
Transient errors
Protocol and socket errors, including exhausting available connections
Each registered client connection, including the socket descriptor number and the protocol used.
Logg rotation and rsyslog redirection should also be implemented.