folsom_cowboy, a cowboy based wrapper for folsom

This is an application that exposes folsom metrics via http using cowboy. It is a port of folsom_webmachine to [cowboy].

installation

Just add the folsom_cowboy to your app, in addition to its dependencies: [cowboy], folsom.

    %% It's not typical to do this manually, but here's how:
    > lists:map(fun application:start/1,
            [cowlib, ranch, cowboy, folsom, folsom_cowboy]).

You can configure the port, transport, transport_options, num_acceptors, dispatch and enable_jsonp in the folsom_cowboy application environment. This is typically done in your application's sys.config, but can also be specified on the command line:

    $ erl -pa ebin deps/*/ebin -folsom_cowboy port 8888

• transport is the cowboy transport module (cowboy_tcp_transport or cowboy_ssl_transport)
• transport_options is the options list to pass to that module (port is handled separately), such as [{ip, {127, 0, 0, 1}}]
• num_acceptors is the number of acceptor processes to start for the listening socket (default is 100)
• dispatch is the cowboy_http_module dispatch tree, which you could use to change the URL scheme
• enable_jsonp if true enable a flavour of JSON with padding response (see below), false by default

api

Query the list of available metrics:

    $ curl http://localhost:5565/_metrics

Query a specific metric:

    $ curl http://localhost:5565/_metrics/name

Query Erlang VM metrics:

    $ curl http://localhost:5565/_memory

Query Erlang VM stats:

    $ curl http://localhost:5565/_statistics

Query Erlang VM information:

    $ curl http://localhost:5565/_system

output

    $ curl http://localhost:5565/_metrics/a
    {"value":{"min":1,"max":1000,"mean":322.2,"median":100,"variance":185259.19999999998,"standard_deviation":430.4174717643325,"skewness":1.2670136514902162,"kurtosis":-1.2908313302242205,"percentile":{"75":500,"95":1000,"99":1000,"999":1000},"histogram":{"10":2,"20":0,"30":0,"50":0,"100":1,"200":0,"300":0,"400":0,"500":1,"1000":1,"99999999999999":0}}}


     $ curl http://localhost:5565/_metrics/test

     {"value":{"1303483997384193":{"event":"asdfasdf"}}}


     $ curl http://localhost:5565/_memory
     {"total":11044608,"processes":3240936,"processes_used":3233888,"system":7803672,"atom":532137,"atom_used":524918,"binary":696984,"code":4358030,"ets":385192}

JSONP

If enabled, you can request JSONP responses by including the query-string parameter:

    $ curl http://localhost:5565/_metrics?jsonp=AvailableMetrics
    AvailableMetrics=[]

The returned javascript code is an assignment rather than a function call, so the parameter must be a valid javascript identified, in particular it must be a string of letters, digits or underscores, otherwise a 400 error is returned.