How do you know if memcached is doing anything?

Question

I'm testing out using memcached to cache django views. How can I tell if memcached is actually caching anything from the Linux command line?

Answer 1

Can you use curl to fetch a page a few hundred times and time the results? You could also look at running a process on the server that simulates heavy CPU/disk load while doing this.

Answer 2

You could use telnet and the stats command e.g.:

# telnet localhost [memcacheport]
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
stats
STAT pid 2239
STAT uptime 10228704
STAT time 1236714928
STAT version 1.2.3
STAT pointer_size 32
STAT rusage_user 2781.185813
STAT rusage_system 2187.764726
STAT curr_items 598669
STAT total_items 31363235
STAT bytes 37540884
STAT curr_connections 131
STAT total_connections 8666
STAT connection_structures 267
STAT cmd_get 27
STAT cmd_set 30694598
STAT get_hits 16
STAT get_misses 11
STAT evictions 0
STAT bytes_read 2346004016
STAT bytes_written 388732988
STAT limit_maxbytes 268435456
STAT threads 4
END

Answer 3

Simple way to test for memcache working was to sneak in a commented out timestamp on every page served up. If the timestamp stayed the same on multiple requests to a page, then the page was being cached by memcache.

In Django settings, I also setup the cache mechanism to use a file cache on the filesystem (really slow), but after hitting up the pages I could see that there were actual cache files being placed in the file path so I could confirm caching was active in Django.

I used both these steps to work out my caching problem. I actually did not have caching turned on correctly in Django. The newer method to activate caching is using the 'django.middleware.cache.CacheMiddleware' middleware (not the middleware with two middleware pieces that have to be the first/last middleware settings.)

Answer 4

Start memcache not as a daemon but normal, so just run 'memcached -vv' for very verbose. You will see when get's and sets come in to the memcache server.