From 99f94fc73513ca9a9eccd859ce61487f7379a7b1 Mon Sep 17 00:00:00 2001
From: Till <2353100+S7evinK@users.noreply.github.com>
Date: Tue, 11 Jul 2023 13:56:25 +0200
Subject: [PATCH] Add revision to version string (#3147)

Since the removal of `build.sh`, we don't include any information about
the revision Dendrite was build from. Since go1.18, the revision a
binary was build from is automatically included, so we can try to get
that instead.

This also adds a `dendrite_up` metric showing the current version
(`dendrite_up{version="0.13.1+c796f20"} 1`)

Closes #2993
---
 .dockerignore        |  3 +--
 Dockerfile           |  2 +-
 cmd/dendrite/main.go | 11 +++++++++++
 internal/version.go  | 30 ++++++++++++++++++++++++++++--
 4 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/.dockerignore b/.dockerignore
index 76547e9ee..80ccf937c 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,3 +1,2 @@
 bin
-*.wasm
-.git
\ No newline at end of file
+*.wasm
\ No newline at end of file
diff --git a/Dockerfile b/Dockerfile
index 2487ea5bc..4ee20933a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@
 # base installs required dependencies and runs go mod download to cache dependencies
 #
 FROM --platform=${BUILDPLATFORM} docker.io/golang:1.20-alpine AS base
-RUN apk --update --no-cache add bash build-base curl
+RUN apk --update --no-cache add bash build-base curl git
 
 #
 # build creates all needed binaries
diff --git a/cmd/dendrite/main.go b/cmd/dendrite/main.go
index 66eb88f87..7b2bebc0b 100644
--- a/cmd/dendrite/main.go
+++ b/cmd/dendrite/main.go
@@ -26,6 +26,7 @@ import (
 	"github.com/matrix-org/dendrite/setup/jetstream"
 	"github.com/matrix-org/dendrite/setup/process"
 	"github.com/matrix-org/gomatrixserverlib/fclient"
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/sirupsen/logrus"
 
 	"github.com/matrix-org/dendrite/appservice"
@@ -187,6 +188,16 @@ func main() {
 		}
 	}
 
+	upCounter := prometheus.NewCounter(prometheus.CounterOpts{
+		Namespace: "dendrite",
+		Name:      "up",
+		ConstLabels: map[string]string{
+			"version": internal.VersionString(),
+		},
+	})
+	upCounter.Add(1)
+	prometheus.MustRegister(upCounter)
+
 	// Expose the matrix APIs directly rather than putting them under a /api path.
 	go func() {
 		basepkg.SetupAndServeHTTP(processCtx, cfg, routers, httpAddr, nil, nil)
diff --git a/internal/version.go b/internal/version.go
index c42b20390..eedc3327c 100644
--- a/internal/version.go
+++ b/internal/version.go
@@ -2,6 +2,7 @@ package internal
 
 import (
 	"fmt"
+	"runtime/debug"
 	"strings"
 )
 
@@ -19,6 +20,8 @@ const (
 	VersionMinor = 13
 	VersionPatch = 1
 	VersionTag   = "" // example: "rc1"
+
+	gitRevLen = 7 // 7 matches the displayed characters on github.com
 )
 
 func VersionString() string {
@@ -37,7 +40,30 @@ func init() {
 	if branch != "" {
 		parts = append(parts, branch)
 	}
-	if len(parts) > 0 {
-		version += "+" + strings.Join(parts, ".")
+
+	defer func() {
+		if len(parts) > 0 {
+			version += "+" + strings.Join(parts, ".")
+		}
+	}()
+
+	// Try to get the revision Dendrite was build from.
+	// If we can't, e.g. Dendrite wasn't built (go run) or no VCS version is present,
+	// we just use the provided version above.
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return
+	}
+
+	for _, setting := range info.Settings {
+		if setting.Key == "vcs.revision" {
+			revLen := len(setting.Value)
+			if revLen >= gitRevLen {
+				parts = append(parts, setting.Value[:gitRevLen])
+			} else {
+				parts = append(parts, setting.Value[:revLen])
+			}
+			break
+		}
 	}
 }