This gem provides Rack middleware which adds an http header to the response. You can either add a hard coded header, or provide a block that will get evaluated at runtime.
# Add the host and build version to the header to make debugging production issues easier host_info = "#{`hostname`.split('.').first}; #{BUILD_VERSION}" Rails.configuration.middleware.insert_before(0, AddHttpHeader, 'X-Host-Info' => host_info) # Add debug info about the request only on errors Rails.configuration.middleware.insert_before(0, AddHttpHeader, 'X-Debug' => lambda{|env, status, headers| DebugInfo(env) if status >= 500})