embed homepage in a Go app (#33)

the entire './public' folder that Hugo produces is embedded into a
variable of 'embed.FS' type and served directly using the default http
mux that Go std offers.

ci, pre-commit, Dockerfile and compose file have all been updated
accordingly.

nginx is no longer needed to front the site files, which enabled
switching to a SCRATCH image containing just a single statically linked
"homepage" app that has all files (html, css, js) embedded.
the containers are otherwise empty (as the name SCRATCH suggests), which
further decreases potential attack surface area.

Co-authored-by: surtur <a_mirre@utb.cz>
Reviewed-on: #33

.drone.yml

@@ -31,6 +31,13 @@ steps:
       - uname -r
       - hadolint --version
 
+  - name: golang
+    pull: always
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    commands:
+      - uname -r
+      - go version
+
 ---
 kind: pipeline
 type: docker
@@ -47,6 +54,9 @@ trigger:
 depends_on:
   - pull
 
+environment:
+  CGO_ENABLED: 0
+
 steps:
   - name: hugo-extended
     pull: if-not-exists
@@ -57,6 +67,44 @@ steps:
       - hugo version
       - hugo --gc=true --minify
 
+  - name: go fmt
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    volumes:
+      - name: gopath
+        path: /go
+    depends_on:
+      - clone
+    commands:
+      - go fmt
+
+  - name: go vet
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    volumes:
+      - name: gopath
+        path: /go
+    depends_on:
+      - go fmt
+    commands:
+      - go vet
+
+  - name: go build
+    pull: if-not-exists
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    volumes:
+      - name: gopath
+        path: /go
+    depends_on:
+      - go vet
+      # wait until the site is output into './public'.
+      - hugo-extended
+    commands:
+      - go build -v -ldflags "-s -w -X main.Version=${DRONE_COMMIT}" .
+
+volumes:
+  - name: gopath
+    temp: {}
+
+
 ---
 kind: pipeline
 type: docker
@@ -178,6 +226,9 @@ node:
 depends_on:
   - build
 
+environment:
+  CGO_ENABLED: 0
+
 steps:
   - name: hugo-extended
     pull: if-not-exists
@@ -204,12 +255,47 @@ steps:
       - hadolint --version
       - hadolint Dockerfile
 
+  - name: go fmt
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    volumes:
+      - name: gopath
+        path: /go
+    depends_on:
+      - clone
+    commands:
+      - go fmt
+
+  - name: go vet
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    volumes:
+      - name: gopath
+        path: /go
+    depends_on:
+      - go fmt
+    commands:
+      - go vet
+
+  - name: go build
+    image: docker.io/library/golang:1.18.5-alpine3.16
+    volumes:
+      - name: gopath
+        path: /go
+    depends_on:
+      - go vet
+      # wait until the site is output into './public'.
+      - hugo-extended
+    commands:
+      - go build -v -ldflags "-s -w -X main.Version=${DRONE_COMMIT}" .
+
   - name: build
     pull: always
     image: tmaier/docker-compose:latest
     depends_on:
       - rm-intermediate
       - hadolint
+      - go fmt
+      - go vet
+      - go build
     volumes:
       - name: s
         path: /var/run/docker.sock
@@ -237,6 +323,8 @@ volumes:
   - name: s
     host:
       path: /var/run/docker.sock
+  - name: gopath
+    temp: {}
 
 
 ---

.pre-commit-config.yaml

@@ -19,4 +19,11 @@ repos:
         language: system
         entry: yamllint .
         pass_filenames: false
+  - repo: https://github.com/dnephin/pre-commit-golang
+    rev: v0.5.0
+    hooks:
+      - id: go-mod-tidy
+      - id: go-unit-tests
+      - id: golangci-lint
+      - id: go-build
 ...

Dockerfile

@@ -1,28 +1,25 @@
-FROM immawanderer/fedora-hugo:linux-amd64 AS hugobuild
-RUN mkdir -pv /homepage
-COPY . /homepage
+FROM docker.io/immawanderer/fedora-hugo:linux-amd64 AS hugobuild
 
 WORKDIR /homepage
 
+COPY . .
+
 RUN git submodule init \
 	&& git submodule update --recursive \
-&& hugo version
-# "DL3059 info: Multiple consecutive `RUN` instructions.
-# Consider consolidation."
-# hadolint ignore=DL3059
-RUN hugo --minify --gc=true
+	&& hugo version \
+	&& hugo --minify --gc=true --cleanDestinationDir
 
-WORKDIR /
+FROM docker.io/library/golang:1.18.5-alpine3.16 AS gobuild
+COPY --from=hugobuild /homepage/ /homepage/
 
-FROM nginx:mainline-alpine
-COPY --from=hugobuild /homepage/public/ /usr/share/nginx/html
+WORKDIR /homepage
 
-# tripple slash reference
-# https://stackoverflow.com/questions/5190966/using-sed-to-insert-tabs/5191165#5191165
-RUN sed -i -e 's/^worker_processes  auto;/worker_processes auto;/'\
- -e "/^events {$/ a \\\tmulti_accept on;\n\tuse epoll;"\
- -e "/^http {$/ a \\\tserver_tokens off;\n\tetag off;\n"\
- -e 's/#tcp_nopush/tcp_nopush/'\
- -e "/tcp_nopush/ a \\\ttcp_nodelay on;\n\terror_page 404 /404.html;"\
- -e "s/^    */$(printf '\t')/"\
- /etc/nginx/nginx.conf
+ARG VCS_REF=development
+
+RUN CGO_ENABLED=0 GOFLAGS='-trimpath -mod=readonly -modcacherw' \
+	go build -o homepage-app -v -ldflags "-s -w -X main.version=$VCS_REF" .
+
+FROM scratch
+COPY --from=gobuild /homepage/homepage-app /homepage
+
+ENTRYPOINT ["/homepage"]

docker-compose.yml

@@ -10,7 +10,7 @@ services:
       - internal-nw
       - default
     ports:
-      - 127.0.0.1:1314:80
+      - 127.0.0.1:1314:1314
     restart: always
     volumes:
       # So that traefik can listen to the Docker events
@@ -26,7 +26,7 @@ services:
     restart: always
     labels:
       - traefik.enable=true
-      - traefik.http.services.homepage.loadbalancer.server.port=80
+      - traefik.http.services.homepage.loadbalancer.server.port=1314
       - traefik.http.routers.homepage.rule=Host(`localhost`) || Host(`127.0.0.1`) || Host(`homepage`) || Host(`6426tqrh4y5uobmo5y2csaip3m3avmjegd2kpa24sadekpxglbm34aqd.onion`)
       # ref: https://stackoverflow.com/a/61976953
       # ref: https://github.com/traefik/traefik/issues/563

go.mod

@@ -0,0 +1,3 @@
+module git.dotya.ml/dotya.ml/homepage
+
+go 1.18

main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"embed"
+	"io/fs"
+	"log"
+	"net/http"
+)
+
+var version = "development"
+
+//go:embed public/*
+var embeddedPublic embed.FS
+
+func main() {
+	root, err := fs.Sub(embeddedPublic, "public")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fs := http.FileServer(http.FS(root))
+
+	http.Handle("/", fs)
+
+	log.Printf("app built from revision '%s'\n", version)
+	log.Print("Listening on :1314...")
+
+	err = http.ListenAndServe(":1314", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+}