Return build info under /loki/api/v1/status/buildinfo. (#3972)

* Return build info under `/version`.

Closes #3221

* Update documentation.

* Correct docs.

* Format version handler code.

* Ignore write error.

* Sort imports.

* Use `PrometheusVersion` struct.

* Set Go version.

docs/sources/api/_index.md

@@ -19,6 +19,7 @@ These endpoints are exposed by all components:
 - [`GET /ready`](#get-ready)
 - [`GET /metrics`](#get-metrics)
 - [`GET /config`](#get-config)
+- [`GET /loki/api/v1/status/buildinfo`](#get-buildinfo)
 
 These endpoints are exposed by the querier and the frontend:
 
@@ -823,6 +824,12 @@ and the current are returned. A value of `defaults` returns the default configur
 
 In microservices mode, the `/config` endpoint is exposed by all components.
 
+## `GET buildinfo`
+
+`/loki/api/v1/status/buildinfo` exposes the build information in a JSON object. The fields are `version`, `revision`, `branch`, `buildDate`, `buildUser`, and `goVersion`.
+
+In microservices mode, the `/version` endpoint is exposed by all components.
+
 ## Series
 
 The Series API is available under the following:

pkg/loki/loki.go

@@ -261,7 +261,10 @@ func (t *Loki) Run() error {
 	t.Server.HTTP.Path("/ready").Handler(t.readyHandler(sm))
 
 	// This adds a way to see the config and the changes compared to the defaults
-	t.Server.HTTP.Path("/config").HandlerFunc(configHandler(t.Cfg, newDefaultConfig()))
+	t.Server.HTTP.Path("/loki/api/v1/status/buildinfo").HandlerFunc(configHandler(t.Cfg, newDefaultConfig()))
+
+	// Each component serves its version.
+	t.Server.HTTP.Path("/version").HandlerFunc(versionHandler())
 
 	t.Server.HTTP.Path("/debug/fgprof").Handler(fgprof.Handler())
 

pkg/loki/version_handler.go

@@ -0,0 +1,31 @@
+package loki
+
+import (
+	"encoding/json"
+	"net/http"
+
+	prom "github.com/prometheus/prometheus/web/api/v1"
+
+	"github.com/grafana/loki/pkg/util/build"
+)
+
+func versionHandler() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		info := prom.PrometheusVersion{
+			Version:   build.Version,
+			Revision:  build.Revision,
+			Branch:    build.Branch,
+			BuildUser: build.BuildUser,
+			BuildDate: build.BuildDate,
+			GoVersion: build.GoVersion,
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+
+		// We ignore errors here, because we cannot do anything about them.
+		// Write will trigger sending Status code, so we cannot send a different status code afterwards.
+		// Also this isn't internal error, but error communicating with client.
+		_ = json.NewEncoder(w).Encode(info)
+	}
+}

pkg/loki/version_handler_test.go

@@ -0,0 +1,41 @@
+package loki
+
+import (
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/grafana/loki/pkg/util/build"
+)
+
+func TestVersionHandler(t *testing.T) {
+	build.Version = "0.0.1"
+	build.Branch = "main"
+	build.Revision = "foobar"
+	build.BuildDate = "yesterday"
+	build.BuildUser = "Turing"
+	build.GoVersion = "42"
+
+	req := httptest.NewRequest("GET", "http://test.com/config?mode=diff", nil)
+	w := httptest.NewRecorder()
+
+	h := versionHandler()
+	h(w, req)
+	resp := w.Result()
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+
+	expected := `{
+		"version":"0.0.1",
+		"branch":"main",
+		"buildDate":"yesterday",
+		"buildUser":"Turing",
+		"revision":"foobar",
+		"goVersion": "42"
+	}`
+	body, err := ioutil.ReadAll(resp.Body)
+	assert.NoError(t, err)
+	assert.JSONEq(t, expected, string(body))
+}

pkg/querier/queryrange/roundtrip.go

@@ -254,7 +254,7 @@ func NewLogFilterTripperware(
 	}, nil
 }
 
-// NewSeriesripperware creates a new frontend tripperware responsible for handling series requests
+// NewSeriesTripperware creates a new frontend tripperware responsible for handling series requests
 func NewSeriesTripperware(
 	cfg Config,
 	log log.Logger,

pkg/util/build/build.go

@@ -1,6 +1,10 @@
 package build
 
-import "github.com/prometheus/common/version"
+import (
+	"runtime"
+
+	"github.com/prometheus/common/version"
+)
 
 // Version information passed to Prometheus version package.
 // Package path as used by linker changes based on vendoring being used or not,
@@ -12,6 +16,7 @@ var (
 	Branch    string
 	BuildUser string
 	BuildDate string
+	GoVersion string
 )
 
 func init() {
@@ -20,4 +25,5 @@ func init() {
 	version.Branch = Branch
 	version.BuildUser = BuildUser
 	version.BuildDate = BuildDate
+	version.GoVersion = runtime.Version()
 }