fix: [logrotate] rotation of logs would not happen

This is due to ``alpine`` version that stores the ``logrotate`` status
file in a different place than debian version.

apache/hooks/log_rotate-relation-joined

@@ -36,7 +36,7 @@ file_put "$DST" <<EOF
     create 640 root root
     sharedscripts
     postrotate
-         /bin/docker-send-signal \$${MASTER_BASE_SERVICE_NAME^^}_NAME SIGUSR1;
+         /bin/docker-send-signal ${MASTER_BASE_SERVICE_NAME} SIGUSR1;
     endscript
 }
 EOF

logrotate/build/Dockerfile

@@ -1,10 +1,12 @@
 FROM docker.0k.io/alpine
 
+## dependency of docker-send-signal
+RUN apk add curl
+RUN apk add jq
+
 RUN apk add logrotate && \
     sed -ri 's/^(\/var\/log\/messages \{\})$/# \1/g' /etc/logrotate.conf
 
-RUN apk add netcat-openbsd  ## dependency of docker-send-signal
-
 COPY src/ /
 
 ENTRYPOINT ["/entrypoint.sh"]

logrotate/build/src/bin/docker-send-signal

@@ -1,9 +1,18 @@
-#!/bin/bash
+#!/bin/sh
+
+docker_api() {
+    local url="$1"
+    shift
+    ## Note: the 'localhost' part is ignored by curl, but it is not
+    ## we can't remove it (like: http:/$url). If it does work on ubuntu's
+    ## curl, it doesn't work on alpine's curl.
+    curl -s --unix-socket /var/run/docker.sock "http://localhost/$url" "$@"
+}
 
 exname=$(basename "$0")
-usage="$exname [-h|--help] CONTAINER SIGNAL"
+usage="$exname [-h|--help] SERVICE SIGNAL"
 
-container=
+service=
 signal=
 while [ "$1" ]; do
     case "$1" in
@@ -12,7 +21,7 @@ while [ "$1" ]; do
             exit 0
         ;;
         *)
-            [ -z "$container" ] && { container=$1 ; shift ; continue ; }
+            [ -z "$service" ] && { service=$1 ; shift ; continue ; }
             [ -z "$signal" ] && { signal=$1 ; shift ; continue ; }
             echo "Unexpected argument '$1'." >&2
             exit 1
@@ -21,18 +30,36 @@ while [ "$1" ]; do
     shift
 done
 
-if [ -z "$container" ]; then
-    echo "You must provide a container name/id as first argument." >&2
+if [ -z "$service" ]; then
+    echo "You must provide a service name as first argument." >&2
     echo "$usage" >&2
     exit 1
 fi
 
 if [ -z "$signal" ]; then
-    echo "You must provide a signal to send to $container aargument." >&2
+    echo "You must provide a signal to send to $service aargument." >&2
     echo "$usage" >&2
     exit 1
 fi
 
-container_id="$(docker inspect --format="{{ .Id }}" "$container")"
 
-echo -e "POST /containers/$container_id/kill?signal=$signal HTTP/1.0\r\n" | nc -U /var/run/docker.sock
+if ! containers=$(
+        docker_api containers/json \
+                   -G --data-urlencode filters="{\"label\": [\"compose.service=$service\"]}"); then
+   echo "Curl toward socket for list of containers failed." >&2
+   exit 1
+fi
+if ! container_id=$(echo "$containers" | jq -r '.[0].Id'); then
+    echo "Failed to query following JSON:" >&2
+    echo "$containers" >&2
+    exit 1
+fi
+
+if [ "$container_id" -a "$container_id" != "null" ]; then
+    echo "Sending $signal to $service" >&2
+    docker_api "containers/${container_id}/kill" --data "signal=$signal"
+else
+    echo "No container found for service '$service'." >&2
+fi
+
+true

logrotate/build/src/entrypoint.sh

@@ -10,4 +10,4 @@ do
 done >> status.clean
 mv status.clean status
 
-/usr/sbin/logrotate /etc/logrotate.conf
+/usr/sbin/logrotate -s /var/lib/logrotate/status /etc/logrotate.conf

logrotate/metadata.yml

@@ -2,9 +2,8 @@ description: Log Rotation Service
 type: run-once
 data-resources:
   - /var/lib/logrotate
-## YYY: probably not useful anymore
-# charm-resources:
-#   - /etc/cron.daily/logrotate
+host-resources:
+  - /var/run/docker.sock   ## used by docker-send-signal for reloading containers
 provides:
   log-rotate:
     tech-dep: "reversed"