Recently I have been trying to cut off expanses in one of the projects I ve been working. So we decided to move two of the t1.micro ec2 AWS instances to our dedicated server,which was already hosting VMS for other projects, as one KVM guest. First instance was the production MySQL DB server for the project while the other was the webserver(apache) hosting our php application. I thought it would be great to have the whole migration automated with chef in case we need to migrate later back to AWS or to another dedicated server.
Let’s say you wish to set the memcached CACHESIZE variable based on your system’s(node) memory.
By default CACHESIZE is defined as 64MB. You get the nodes total memory using the node[‘memory’][‘total’] which will return the memory in KB for example 1019492kB In this case you need to divide it with 1024 to get the size in MB. If you want to assign 10% of your total memory to memcached CACHESIZE then you ll have 1019492kB * 0.1 / 1024 = 99.559MB. You can remove the .559 using ruby’s to_i method.
So you can put the following in your cookbook to set your memcached cachesize. The only dependency is opscode memcached cookbook
node.set['memcached']['memory'] = (node['memory']['total'].to_i * 0.1 / 1024).to_i include_recipe 'memcached'