KaveriTech Technical Blog

Installation

1. Follow this link to install and configure memcached.
2. Start the memcache server using either

memcached -vv

or

/etc/init.d/memcached start

Integrating memcached with your rails application

1. Install memcache-client

gem install memcache-client

2.   Add the below line to  end of your config/environment.rb file.

CACHE = MemCache.new(’127.0.0.1′)

3.  Add the following method to your application controller / application helper or where ever you want according to your needs.

def perform_cache(key)
begin
unless output = CACHE.get(key)
output = yield
CACHE.set(key, output, 15.minutes)
end
rescue => e
logger.info “MEMCACHE ERROR+++++++++++++++++++++++++++++++++++++++”
logger.info “ERROR : #{e.message}”
logger.info “MEMCACHE ERROR+++++++++++++++++++++++++++++++++++++++”
output = yield
end
return output
end

The above method performs the caching based on a unique key. If the value for that key already exists, it will return the output from the stored cache or  else it will execute the block you are using when calling the above method and generate a new value from the executed block for the particular key and store it in the cache.
You can set a timer to expire the cached data.(15 mins in my case.)
If you don’t want to expire the cache based on timer, simply remove the third parameter we are passing to ’set’ method.
The above method also handles the exception,in case your memcache server is down for some reason.

4. Cache your complex queries as follows.

my_key = Digest::MD5.hexdigest(request.request_uri)
output = perform_cache(my_key) { ClassName.method_name(…)  #Your query/method }

Note : The key generated should be always unique. I am using the URL as the key, Since the URL is pretty long we can take the MD5 hash of it and use it as the key.

That’s it, You are ready to go.