Some handy Capistrano tasks for handling memcached. Assumes memcached runs locally on your app servers, YMMV

capistrano_memcached_tasks.rb

# This goes in config/deploy.rb
namespace :memcached do
  desc "Flush memcached"
  task :flush, :roles => [:app] do
    run("cd #{current_release} && RAILS_ENV=#{rails_env} /usr/bin/rake memcached:flush")
  end

  desc "Flush memcached if there are any pending migrations (hook this before db:migrate)"
  task :flush_if_pending_migrations, :roles => [:app] do
    output = capture("cd #{current_release} && RAILS_ENV=#{rails_env} /usr/bin/rake db:pending_migration_count"
)
    count = /(\d+) pending migrations/.match(output)
    if count[0] && count[0].to_i > 0
      puts "#{count[0].to_i} migrations will be run! Installing memcached:flush hook"
      after "deploy:migrate", "memcached:flush"
    end
  end
end

memcached.rake

# This goes in lib/tasks/memcached.rake
require 'socket'

namespace :memcached do
  desc "Flush memcached (running on localhost port 11211)"
  task :flush do
    socket = TCPSocket.new('127.0.0.1', 11211)
    socket.write("flush_all\r\n")
    result = socket.recv()
    if result == 'OK'
      puts "memcached flush."
    else
      STDERR.puts "Error flushing memcached: #{result}"
    end
    socket.close
  end
end