# README

XStats

Package xstats is a generic client for service instrumentation.

xstats is inspired from Go-kit's metrics package but it takes a slightly different path. Instead of having to create an instance for each metric, xstats use a single instance to log every metrics you want. This reduces the boiler plate when you have a lot a metrics in your app. It's also easier in term of dependency injection.

Talking about dependency injection, xstats comes with a xhandler.Handler integration so it can automatically inject the xstats client within the net/context of each request. Each request's xstats instance have its own tags storage ; This let you inject some per request contextual tags to be included with all observations sent within the lifespan of the request.

xstats is pluggable and comes with integration for expvar, StatsD and DogStatsD, the Datadog augmented version of StatsD with support for tags. More integration may come later (PR welcome).

Supported Clients

Install

go get github.com/rs/xstats

Usage

// Defines interval between flushes to statsd server
flushInterval := 5 * time.Second

// Connection to the statsd server
statsdWriter, err := net.Dial("udp", "127.0.0.1:8126")
if err != nil {
    log.Fatal(err)
}

// Create the stats client
s := xstats.New(dogstatsd.New(statsdWriter, flushInterval))

// Global tags sent with all metrics (only with supported clients like datadog's)
s.AddTags("role:my-service", "dc:sv6")

// Send some observations
s.Count("requests", 1, "tag")
s.Timing("something", 5*time.Millisecond, "tag")

Integration with github.com/rs/xhandler:

var xh xhandler.HandlerC

// Here is your handler
xh = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    // Get the xstats request's instance from the context. You can safely assume it will
    // be always there, if the handler is removed, xstats.FromContext will return a nop
    // instance.
    m := xstats.FromRequest(r)

    // Count something
    m.Count("requests", 1, "route:index")
})

// Install the metric handler with dogstatsd backend client and some env tags
flushInterval := 5 * time.Second
tags := []string{"role:my-service"}
statsdWriter, err := net.Dial("udp", "127.0.0.1:8126")
if err != nil {
    log.Fatal(err)
}
xh = xstats.NewHandler(dogstatsd.New(statsdWriter, flushInterval), tags, xh)

// Root context
ctx := context.Background()
h := xhandler.New(ctx, xh)
http.Handle("/", h)

if err := http.ListenAndServe(":8080", nil); err != nil {
    log.Fatal(err)
}

Testing

func TestFunc(t *testing.T) {
    m := mock.New()
    s := xstats.New(m)
    m.On("Timing", "something", 5*time.Millisecond, "tag")
    s.Timing("something", 5*time.Millisecond, "tag")
    s.AssertExpectations(t)
}