chi-prometheus

Description

chi-prometheus is a Prometheus collectors for go-chi/chi.

Example metrics

# HELP chi_request_duration_milliseconds Time spent on the request partitioned by status code, method and HTTP path.
# TYPE chi_request_duration_milliseconds histogram
chi_request_duration_milliseconds_bucket{code="200",method="GET",path="/users/{firstName}",service="test",le="300"} 2
chi_request_duration_milliseconds_bucket{code="200",method="GET",path="/users/{firstName}",service="test",le="1200"} 2
chi_request_duration_milliseconds_bucket{code="200",method="GET",path="/users/{firstName}",service="test",le="5000"} 2
chi_request_duration_milliseconds_bucket{code="200",method="GET",path="/users/{firstName}",service="test",le="+Inf"} 2
chi_request_duration_milliseconds_sum{code="200",method="GET",path="/users/{firstName}",service="test"} 4
chi_request_duration_milliseconds_count{code="200",method="GET",path="/users/{firstName}",service="test"} 2
chi_request_duration_milliseconds_bucket{code="404",method="GET",path="/healthz",service="test",le="300"} 1
chi_request_duration_milliseconds_bucket{code="404",method="GET",path="/healthz",service="test",le="1200"} 1
chi_request_duration_milliseconds_bucket{code="404",method="GET",path="/healthz",service="test",le="5000"} 1
chi_request_duration_milliseconds_bucket{code="404",method="GET",path="/healthz",service="test",le="+Inf"} 1
chi_request_duration_milliseconds_sum{code="404",method="GET",path="/healthz",service="test"} 1
chi_request_duration_milliseconds_count{code="404",method="GET",path="/healthz",service="test"} 1
# HELP chi_requests_total Number of HTTP requests partitioned by status code, method and HTTP path.
# TYPE chi_requests_total counter
chi_requests_total{code="200",method="GET",path="/users/{firstName}",service="test"} 2
chi_requests_total{code="404",method="GET",path="/healthz",service="test"} 1

Requirement

chi-prometheus only works with go-chi/chi. Though you can set the middleware for other routers (multiplexers) including http.ServeMux, nothing happens.

Usage

chi-prometheus is used as a middleware. It also supports both a default registry and a custom registry. You can see full examples in middleware_test.go

Default registry

    r := chi.NewRouter()
    m := chiprometheus.New("test")
    # use DefaultRegisterer
    m.MustRegisterDefault()
    r.Use(m.Handler)
    r.Handle("/metrics", promhttp.Handler())
    r.Get("/healthz", [YOUR HandlerFunc])

Custom registry

    r := chi.NewRouter()
    # use your registry that works well with promauto
    # see also https://github.com/prometheus/client_golang/issues/716#issuecomment-590282553
    reg := prometheus.NewRegistry()
    if err := reg.Register(collectors.NewProcessCollector(collectors.ProcessCollectorOpts{})); err != nil {
        t.Error(err)
    }
    if err := reg.Register(collectors.NewGoCollector()); err != nil {
        t.Error(err)
    }
    m := chiprometheus.New("test")
    reg.MustRegister(m.Collectors()...)
    promh := promhttp.InstrumentMetricHandler(
        reg, promhttp.HandlerFor(reg, promhttp.HandlerOpts{}),
    )
    r.Use(m.Handler)
    r.Handle("/metrics", promh)
    r.Get("/healthz", [YOUR HandlerFunc])

Configuration

Latency histogram bucket is configurable with CHI_PROMETHEUS_LATENCY_BUCKETS. Default values are 300, 1200, 5000 (milliseconds).

You can override them as follows;

# comma separated string value
CHI_PROMETHEUS_LATENCY_BUCKETS="100,200,300,400"

Install

$ go get github.com/toshi0607/chi-prometheus

Comparison

There are great prior implementations for similar use cases.

zbindenren/negroni-prometheus

This is a router-agnostic Prometheus middleware implementation for an HTTP server. It is not actively developed and is archived by the owner.

766b/chi-prometheus

This is a Prometheus middleware taking advantage of a chi middleware library for chi. It is not actively developed, and I had to newly support the following features.

Go Modules
Custom registry
New features of prometheus/client_golang
Deleting the previous default codes (non-aggregation collector for paths, such as /users/{firstName})

So I decided to implement a new one instead of forking and adding some tweaks.

Licence

MIT file for details.

toshi0607/chi-prometheus