Heroku/Memcache/Rack::Cache Stats

Question

I am trying to wrap my brain around Rack::Cache, Rails 3.2, Memcache, and Heroku. I think I've got it all working together, as outlined here: http://myownpirateradio.com/2012/01/01/getting-heroku-cedar-and-rails-3-1-asset-pipeline-to-play-nicely-together/

All that said, I am unsure if Memcached is actually doing what it should. Is there any way to get stats on Memcached or to see if a request was cached by Memcached? I put the current time on a page, and can see that it is getting cached (headers look good too), but how do I know it is all working with Memcached, as opposed to the file store?

Thanks.

Answer 1

You can get stats on memcached by doing:

$ heroku run console
Running console attached to terminal... up, run.1
Loading production environment (Rails 3.1.3)
irb(main):001:0> Rails.cache.stats
Dalli/SASL authenticating as app590983%40heroku.com
Dalli/SASL: Authenticated
=> {"mc5.ec2.northscale.net:11211"=>{"evictions"=>"0", "curr_items"=>"627",
    "total_items"=>"1257", "bytes"=>"2294318", "reclaimed"=>"0", 
    "engine_maxbytes"=>"5242880", "bucket_conns"=>"2", "pid"=>"319", 
    "uptime"=>"6710022", "time"=>"1330731177", "version"=>"1.4.4_207_g19c6b9e", 
    "libevent"=>"1.4.11-stable", "pointer_size"=>"64", 
    "rusage_user"=>"34354.590000", "rusage_system"=>"31381.520000", 
    "daemon_connections"=>"10", "curr_connections"=>"1211", 
    "total_connections"=>"14127919", "connection_structures"=>"1764", 
    "cmd_get"=>"9476", "cmd_set"=>"1257", "cmd_flush"=>"0", "auth_cmds"=>"24", 
    "auth_errors"=>"0", "get_hits"=>"8093", "get_misses"=>"1383", 
    "delete_misses"=>"0", "delete_hits"=>"0", "incr_misses"=>"0", 
    "incr_hits"=>"0", "decr_misses"=>"0", "decr_hits"=>"0", "cas_misses"=>"0", 
    "cas_hits"=>"0", "cas_badval"=>"0", "bytes_read"=>"21983909", 
    "bytes_written"=>"85267718", "limit_maxbytes"=>"67108864", 
    "rejected_conns"=>"0", "threads"=>"4", "conn_yields"=>"0"}}

PS: I think you might need to be using the Dalli gem for this to work, but that is the recommended client anyway.

You can also run Rails.cache.class to see which backend is Rails using.