commit ea3b86e8cd6ce8cebd0ccf41dcb2f6c4cb503929
Author: Andre Heber <a.heber@sabienzia.com>
Date:   Tue Aug 20 23:51:59 2024 +0200

    init

diff --git a/Dockerfile b/Dockerfile
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+++ b/Dockerfile
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+# Use Alpine as the base image
+FROM alpine:3.20.2
+
+# Install necessary packages & Go
+RUN apk add --no-cache \
+    alpine-base \
+    logrotate \
+    dcron \
+    go \
+    s6-overlay
+
+# Set up the s6-overlay configuration
+COPY etc /etc
+
+# Set up Go environment
+ENV GOPATH /go
+ENV PATH $GOPATH/bin:/usr/local/go/bin:$PATH
+
+# Copy the Go application
+COPY main.go /app/main.go
+
+# Build the Go application
+RUN go build -o /usr/local/bin/myapp /app/main.go
+
+# Set up syslog
+#COPY syslog.conf /etc/syslog.conf
+#RUN mkdir -p /var/log/syslog
+
+# Set up logrotate
+#COPY logrotate.conf /etc/logrotate.conf
+
+# Set up watchdog
+#COPY watchdog.conf /etc/watchdog.conf
+
+# Copy your application
+# COPY myapp /usr/local/bin/myapp
+
+# Set up s6 service for your app
+#COPY run /etc/services.d/myapp/run
+
+ENV LOG_LEVEL=WARNING
+
+# Use s6-overlay as the entrypoint
+ENTRYPOINT ["/init"]
diff --git a/README.md b/README.md
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+# Alpine with S6-Overlay
+
+I want a docker image that behaves more like a VM:
+
+1. I can start / stop many processes, also the main process (usually PID 1)
+   Why? To test things out. Changing environment variables, debugging with the coredump file or recompiling the app without crashing the container follows much more my development process
+2. Logging to a seperate file with logrotation
+   Why? Docker logs (and Kibana) are a pain in the ass!
+3. Watchdog: k8s restarts containers when they are crashing. That should be done by the s6-overlay.
+
+## Tested
+
+- [x] Starting & Stopping services with `s6-rc start myapp` and `s6-rc stop myapp`
+- [x] `docker exec` into the container and run myapp manually, it uses the env vars of the shell
+- [x] Logging: `/var/log/myapp/current` is filled
+- [ ] Logrotation
+- [ ] Cron
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diff --git a/etc/s6-overlay/s6-rc.d/myapp-log-prepare/dependencies.d/base b/etc/s6-overlay/s6-rc.d/myapp-log-prepare/dependencies.d/base
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index 0000000..e69de29
diff --git a/etc/s6-overlay/s6-rc.d/myapp-log-prepare/type b/etc/s6-overlay/s6-rc.d/myapp-log-prepare/type
new file mode 100644
index 0000000..3d92b15
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp-log-prepare/type
@@ -0,0 +1 @@
+oneshot
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diff --git a/etc/s6-overlay/s6-rc.d/myapp-log-prepare/up b/etc/s6-overlay/s6-rc.d/myapp-log-prepare/up
new file mode 100755
index 0000000..107f50f
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp-log-prepare/up
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+if { mkdir -p /var/log/myapp }
+if { chown nobody:nogroup /var/log/myapp }
+chmod 02755 /var/log/myapp
diff --git a/etc/s6-overlay/s6-rc.d/myapp-log/consumer-for b/etc/s6-overlay/s6-rc.d/myapp-log/consumer-for
new file mode 100644
index 0000000..de3fd5d
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+++ b/etc/s6-overlay/s6-rc.d/myapp-log/consumer-for
@@ -0,0 +1 @@
+myapp
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diff --git a/etc/s6-overlay/s6-rc.d/myapp-log/dependencies.d/myapp-log-prepare b/etc/s6-overlay/s6-rc.d/myapp-log/dependencies.d/myapp-log-prepare
new file mode 100644
index 0000000..e69de29
diff --git a/etc/s6-overlay/s6-rc.d/myapp-log/pipeline-name b/etc/s6-overlay/s6-rc.d/myapp-log/pipeline-name
new file mode 100644
index 0000000..11819eb
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp-log/pipeline-name
@@ -0,0 +1 @@
+myapp-pipeline
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diff --git a/etc/s6-overlay/s6-rc.d/myapp-log/run b/etc/s6-overlay/s6-rc.d/myapp-log/run
new file mode 100755
index 0000000..1c9c705
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp-log/run
@@ -0,0 +1,2 @@
+#!/bin/sh
+exec logutil-service /var/log/myapp
diff --git a/etc/s6-overlay/s6-rc.d/myapp-log/type b/etc/s6-overlay/s6-rc.d/myapp-log/type
new file mode 100644
index 0000000..1780f9f
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp-log/type
@@ -0,0 +1 @@
+longrun
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diff --git a/etc/s6-overlay/s6-rc.d/myapp/dependencies.d/base b/etc/s6-overlay/s6-rc.d/myapp/dependencies.d/base
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index 0000000..e69de29
diff --git a/etc/s6-overlay/s6-rc.d/myapp/finish b/etc/s6-overlay/s6-rc.d/myapp/finish
new file mode 100755
index 0000000..8a878d4
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp/finish
@@ -0,0 +1,9 @@
+#!/bin/sh
+
+if test "$1" -eq 256 ; then
+  e=$((128 + $2))
+else
+  e="$1"
+fi
+
+echo "$e" > /run/s6-linux-init-container-results/exitcode
diff --git a/etc/s6-overlay/s6-rc.d/myapp/producer-for b/etc/s6-overlay/s6-rc.d/myapp/producer-for
new file mode 100644
index 0000000..7e6d3c5
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp/producer-for
@@ -0,0 +1 @@
+myapp-log
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diff --git a/etc/s6-overlay/s6-rc.d/myapp/run b/etc/s6-overlay/s6-rc.d/myapp/run
new file mode 100755
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--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp/run
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+#!/command/with-contenv sh
+exec 2>&1
+exec s6-setuidgid daemon /usr/local/bin/myapp
diff --git a/etc/s6-overlay/s6-rc.d/myapp/type b/etc/s6-overlay/s6-rc.d/myapp/type
new file mode 100644
index 0000000..1780f9f
--- /dev/null
+++ b/etc/s6-overlay/s6-rc.d/myapp/type
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+longrun
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diff --git a/etc/s6-overlay/s6-rc.d/user/contents.d/myapp b/etc/s6-overlay/s6-rc.d/user/contents.d/myapp
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index 0000000..e69de29
diff --git a/etc/s6-overlay/s6-rc.d/user/contents.d/myapp-pipeline b/etc/s6-overlay/s6-rc.d/user/contents.d/myapp-pipeline
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diff --git a/go.mod b/go.mod
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+++ b/go.mod
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+module example.com/loglevel
+
+go 1.22.3
diff --git a/main.go b/main.go
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+++ b/main.go
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+package main
+
+import (
+	"log"
+	"os"
+	"time"
+)
+
+func main() {
+	// Configure logging to include timestamp
+	log.SetFlags(log.Ldate | log.Ltime | log.Lmicroseconds)
+
+	// Read LOG_LEVEL from environment variable
+	logLevel := os.Getenv("LOG_LEVEL")
+	if logLevel == "" {
+		logLevel = "INFO" // Default log level
+	}
+
+	log.Printf("Starting application with LOG_LEVEL: %s", logLevel)
+
+	// Infinite loop to log every 2 seconds
+	for {
+		log.Printf("Current LOG_LEVEL: %s", logLevel)
+		time.Sleep(2 * time.Second)
+	}
+}
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diff --git a/run b/run
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+++ b/run
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+#!/usr/bin/with-contenv sh
+
+# Start your application
+exec /usr/local/bin/myapp
+
+# Touch the watchdog file
+touch /var/run/myapp.touch
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