Rebuild to use crond and pre-compiled binary

The build process of the binary patched with the cron runner was too
instable as coredns is not properly vendoring their dependencies. This
way the binary is stable (provided by coredns) and the cron is taken
over by alpine crond.

Signed-off-by: Knut Ahlers <knut@ahlers.me>

Dockerfile

@@ -1,27 +1,14 @@
-FROM golang:alpine
-
-ARG COREDNS_VERSION=v1.0.5
-
-ADD ./build.sh /usr/local/bin/build.sh
-ADD ./cron_generate.go /src/cron_generate.go
-RUN set -ex \
- && apk --no-cache add git bash \
- && bash /usr/local/bin/build.sh
-
 FROM alpine
 
 LABEL maintainer Knut Ahlers <knut@ahlers.me>
 
-COPY --from=0 /go/bin/coredns /usr/local/bin/
-
-ADD ./requirements.txt /src/requirements.txt
-RUN set -ex \
- && apk --no-cache add python3 bind-tools \
- && pip3 install -r /src/requirements.txt
-
 ADD . /src
 WORKDIR /src
 
+RUN set -ex \
+ && apk --no-cache add bash \
+ && /src/build.sh
+
 EXPOSE 53/udp 53
 
 VOLUME ["/src/zones"]
@@ -29,5 +16,5 @@ VOLUME ["/src/zones"]
 HEALTHCHECK --interval=30s --timeout=5s \
   CMD dig +short @localhost health.server.test TXT || exit 1
 
-ENTRYPOINT ["/usr/local/bin/coredns"]
+ENTRYPOINT ["/src/docker-entrypoint.sh"]
-CMD ["--"]
+CMD ["coredns"]

build.sh

@@ -1,28 +1,33 @@
 #!/bin/bash
 set -euxo pipefail
 
-# Download sourcecode
+# Install build utilities
-mkdir -p /go/src/github.com/coredns
+apk --no-cache add curl
-git clone https://github.com/coredns/coredns.git /go/src/github.com/coredns/coredns
 
-# Ensure version pinning
+# Install dependencies
-cd /go/src/github.com/coredns/coredns
+apk --no-cache add python3 bind-tools
-git reset --hard ${COREDNS_VERSION}
 
-# Copy cron drop-in
+# Get latest versions of tools using latestver
-cp /src/cron_generate.go .
+COREDNS_VERSION=$(curl -sSfL 'https://lv.luzifer.io/catalog-api/coredns/latest.txt?p=version')
+DUMB_INIT_VERSION=$(curl -sSfL 'https://lv.luzifer.io/catalog-api/dumb-init/latest.txt?p=version')
 
-# Get dependencies and build
+[ -z "${COREDNS_VERSION}" ] && { exit 1; }
-go get -d -v
+[ -z "${DUMB_INIT_VERSION}" ] && { exit 1; }
 
-# Force downgrades not being pinned
+# Install tools
-CWD=$(pwd)
+curl -sSfL https://github.com/coredns/coredns/releases/download/v${COREDNS_VERSION}/coredns_${COREDNS_VERSION}_linux_amd64.tgz | \
-cd ${GOPATH}/src/github.com/mholt/caddy              && git checkout -q v0.10.10
+  tar -x -z -C /usr/local/bin
-cd ${GOPATH}/src/github.com/miekg/dns                && git checkout -q v1.0.4
-cd ${GOPATH}/src/github.com/prometheus/client_golang && git checkout -q v0.8.0
-cd ${GOPATH}/src/golang.org/x/net                    && git checkout -q release-branch.go1.9
-cd ${GOPATH}/src/golang.org/x/text                   && git checkout -q e19ae1496984b1c655b8044a65c0300a3c878dd3
-cd "${CWD}"
 
-# Do the compile
+curl -sSfLo /usr/local/bin/dumb-init https://github.com/Yelp/dumb-init/releases/download/v${DUMB_INIT_VERSION}/dumb-init_${DUMB_INIT_VERSION}_amd64
-go install
+chmod +x /usr/local/bin/dumb-init
+
+# Install requirements for python3 scripts
+pip3 install -r /src/requirements.txt
+
+# Create cron to update zones periodically
+echo "*       *       *       *       *       run-parts /etc/periodic/1min" >> /var/spool/cron/crontabs/root
+mkdir -p /etc/periodic/1min
+ln -s /src/zonefile_cron /etc/periodic/1min/zonefile_cron
+
+# Cleanup
+apk --no-cache del curl

cron_generate.go

@@ -1,44 +0,0 @@
-package main
-
-import (
-	"context"
-	"os/exec"
-	"time"
-
-	"github.com/Sirupsen/logrus"
-	"github.com/robfig/cron"
-)
-
-func init() {
-	c := cron.New()
-	c.AddFunc("0 * * * * *", generateZonefiles)
-	c.Start()
-
-	go generateZonefiles()
-}
-
-func generateZonefiles() {
-	logger := logrus.WithFields(logrus.Fields{
-		"fkt": "generateZonefiles",
-	})
-
-	var (
-		iw = logger.WriterLevel(logrus.InfoLevel)
-		ew = logger.WriterLevel(logrus.ErrorLevel)
-	)
-
-	defer iw.Close()
-	defer ew.Close()
-
-	ctx, cancel := context.WithTimeout(context.Background(), 59*time.Second)
-	defer cancel()
-
-	cmd := exec.CommandContext(ctx, "/usr/bin/python3", "generateZonefiles.py")
-	cmd.Stdout = iw
-	cmd.Stderr = ew
-	cmd.Dir = "/src"
-
-	if err := cmd.Run(); err != nil {
-		logger.WithError(err).Error("Command execution failed")
-	}
-}

docker-entrypoint.sh

@@ -0,0 +1,12 @@
+#!/usr/local/bin/dumb-init /bin/bash
+set -euxo pipefail
+
+if [ "${1:-}" = 'coredns' ]; then
+  # Start crond in the background
+  crond
+
+  # Start coredns
+  exec "$@"
+fi
+
+exec "$@"

zonefile_cron

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -euxo pipefail
+
+cd /src
+exec /usr/bin/python3 generateZonefiles.py