add build details to binary (#866)

* poc

* finish JSON, remove uneeded methods, update docker file, finish script details

* build.Details didn't need to be exported

* typo

* somehow missed this

* should default to false

* Fix some things

remove commit SHA as build script will now create a hybrid for version
as in the push-docker-images.sh script, code shamelessly stolen.

change JSON function to Data and return a struct, the caller can do what
they like with that data, i.e. marshall JSON for a response body.

* add struct tags

* use build script in docker image

* newline in build.sh

* use previously generated version for binary build

* Working docker args

removed script build.sh, was not really needed.

date is generated automatically during docker build process.

VERSION will be set to 'Not Specified', or the version set during
our CI docker build/push step. A user can set their own version during
build using ldflags.

* remove old comment re: script

* Yikes

Almost forgot to remove my testing junk

* GitHub on my phone is hard

cmd/proxy/Dockerfile

@@ -8,7 +8,9 @@ WORKDIR $GOPATH/src/github.com/gomods/athens
 
 COPY . .
 
-RUN GO111MODULE=on CGO_ENABLED=0 go build -mod=vendor -o /bin/athens-proxy ./cmd/proxy
+ARG VERSION="Not Specified"
+
+RUN GO111MODULE=on CGO_ENABLED=0 go build -mod=vendor -ldflags "-X github.com/gomods/athens/pkg/build.version=$VERSION -X github.com/gomods/athens/pkg/build.buildDate=$(date -u +%Y-%m-%d-%H:%M:%S-%Z)" -o /bin/athens-proxy ./cmd/proxy
 
 FROM alpine
 

cmd/proxy/main.go

@@ -2,19 +2,27 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"log"
+	"os"
 	"path/filepath"
 
 	"github.com/gomods/athens/cmd/proxy/actions"
+	"github.com/gomods/athens/pkg/build"
 	"github.com/gomods/athens/pkg/config"
 )
 
 var (
 	configFile = flag.String("config_file", filepath.Join("..", "..", "config.dev.toml"), "The path to the config file")
+	version    = flag.Bool("version", false, "Print version information and exit")
 )
 
 func main() {
 	flag.Parse()
+	if *version {
+		fmt.Println(build.String())
+		os.Exit(0)
+	}
 	if configFile == nil {
 		log.Fatal("Invalid config file path provided")
 	}

pkg/build/build.go

@@ -0,0 +1,37 @@
+// Package build provides details of the built binary
+// The details are set using ldflags.
+//
+// The ldflags can be set manually for testing locally:
+// `go build -ldflags "-X github.com/gomods/athens/pkg/build.version=$(git describe --tags) -X github.com/gomods/athens/pkg/build.buildDate=$(date -u +%Y-%m-%d-%H:%M:%S-%Z)"`
+package build
+
+import (
+	"fmt"
+)
+
+// Details represents known data for a given build
+type Details struct {
+	Version string `json:"version,omitempty"`
+	Date    string `json:"date,omitempty"`
+}
+
+var version, buildDate string
+
+// String returns build details as a string with formatting
+// suitable for console output.
+//
+// i.e.
+// Build Details:
+//         Version:        v0.1.0-155-g1a20f8b
+//         Date:           2018-11-05-14:33:14-UTC
+func String() string {
+	return fmt.Sprintf("Build Details:\n\tVersion:\t%s\n\tDate:\t\t%s", version, buildDate)
+}
+
+// Data returns build details as a struct
+func Data() Details {
+	return Details{
+		Version: version,
+		Date:    buildDate,
+	}
+}

scripts/push-docker-images.sh

@@ -34,7 +34,7 @@ fi
 
 REPO_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )/.." >/dev/null && pwd )/"
 
-docker build -t ${REGISTRY}proxy:${VERSION} -f ${REPO_DIR}cmd/proxy/Dockerfile ${REPO_DIR}
+docker build --build-arg VERSION=${VERSION} -t ${REGISTRY}proxy:${VERSION} -f ${REPO_DIR}cmd/proxy/Dockerfile ${REPO_DIR}
 
 # Apply the mutable tag to the immutable version
 docker tag ${REGISTRY}proxy:${VERSION} ${REGISTRY}proxy:${MUTABLE_TAG}