memcached restart starts a new memcached and doesn't kill the old one

Question

Hi all. I'm running my rails app in production mode and in staging mode on the same server, in different folders. They both use memcache-client which requires memcached to be running.

As yet i haven't set up a deploy script and so just do a deploy manually by sshing onto the server, going to the appropriate directory, updating the code, restarting memcached and then restarting unicorn (the processes which actually run the rails app). I restart memcached thus:

sudo /etc/init.d/memcached restart &

This starts a new memcached, but it doesn't kill the old one: check it out:

ip-<an-ip>:test.millionaire[subjects]$ ps afx | grep memcache
11176 pts/2    S+     0:00  |           \_ grep --color=auto memcache
10939 pts/3    R      8:13              \_ sudo /etc/init.d/memcached restart
 7453 ?        Sl     0:00 /usr/bin/memcached -m 64 -p 11211 -u nobody -l 127.0.0.1

ip-<an-ip>:test.millionaire[subjects]$ sudo /etc/init.d/memcached restart &
[1] 11187

ip-<an-ip>:test.millionaire[subjects]$ ps afx | grep memcache
11187 pts/2    T      0:00  |           \_ sudo /etc/init.d/memcached restart
11199 pts/2    S+     0:00  |           \_ grep --color=auto memcache
10939 pts/3    R      8:36              \_ sudo /etc/init.d/memcached restart
 7453 ?        Sl     0:00 /usr/bin/memcached -m 64 -p 11211 -u nobody -l 127.0.0.1

[1]+  Stopped                 sudo /etc/init.d/memcached restart
ip-<an-ip>:test.millionaire[subjects]$ sudo /etc/init.d/memcached restart &
[2] 11208
ip-<an-ip>:test.millionaire[subjects]$ ps afx | grep memcache
11187 pts/2    T      0:00  |           \_ sudo /etc/init.d/memcached restart
11208 pts/2    R      0:01  |           \_ sudo /etc/init.d/memcached restart
11218 pts/2    S+     0:00  |           \_ grep --color=auto memcache
10939 pts/3    R      8:42              \_ sudo /etc/init.d/memcached restart
 7453 ?        Sl     0:00 /usr/bin/memcached -m 64 -p 11211 -u nobody -l 127.0.0.1

What might be causing it is there's another memcached running - see the bottom line. I'm mystified as to where this is from and my instinct is to kill it but i thought i'dd better check with someone who actually knows more about memcached than i do.

Grateful for any advice - max

EDIT - solution

I figured this out after a bit of detective work with a colleague. In the rails console i typed CACHE.stats which prints out a hash of values, including "pid", which i could see was set to the instance of memcached which wasn;t started with memcached restart, ie this process:

7453 ?        Sl     0:00 /usr/bin/memcached -m 64 -p 11211 -u nobody -l 127.0.0.1

The memcached control script (ie that defines the start, stop and restart commands), is in /etc/init.d/memcached

A line in this says

# Edit /etc/default/memcached to change this.
ENABLE_MEMCACHED=no

So i looked in /etc/default/memcached, which was also set to ENABLE_MEMCACHED=no

So, this was basically preventing memcached from being stopped and started. I changed it to ENABLE_MEMCACHED=yes, then it would stop and start fine. Now when i stop and start memcached, it's the above process, the in-use memcached, that's stopped and started.

Answer 1

try using:

 killall memcached