Merge pull request #425 from sundbry/syslog-shutdown

Start syslog-ng before runit, and stop after runit.

README.md

@@ -57,6 +57,7 @@ You can configure the stock `ubuntu` image yourself from your Dockerfile, so why
      * [Environment variable dumps](#envvar_dumps)
      * [Modifying environment variables](#modifying_envvars)
      * [Security](#envvar_security)
+   * [System logging](#logging)
    * [Upgrading the operating system inside the container](#upgrading_os)
  * [Container administration](#container_administration)
    * [Running a one-shot command in a new container](#oneshot)
@@ -303,6 +304,14 @@ If you are sure that your environment variables don't contain sensitive data, th
     RUN chmod 755 /etc/container_environment
     RUN chmod 644 /etc/container_environment.sh /etc/container_environment.json
 
+<a name="logging"></a>
+### System logging
+
+Baseimage-docker uses syslog-ng to provide a syslog facility to the container. Syslog-ng is not managed as an runit service (see below). Syslog messages are forwarded to the console via the service at /etc/service/syslog-forwarder.
+
+#### Log startup/shutdown sequence
+In order to ensure that all application log messages are captured by syslog-ng, syslog-ng is started separately before the runit supervisor process, and shutdown after runit exits. This uses the [startup script facility](#running_startup_scripts) provided by this image. This avoids a race condition which would exist if syslog-ng were managed as an runit service, where runit kills syslog-ng in parallel with the container's other services, causing log messages to be dropped during a graceful shutdown if syslog-ng exits while logs are still being produced by other services.
+
 <a name="upgrading_os"></a>
 ### Upgrading the operating system inside the container
 

image/services/syslog-ng/syslog-ng.init

@@ -0,0 +1,34 @@
+#!/bin/bash
+set -e
+
+# If /dev/log is either a named pipe or it was placed there accidentally,
+# e.g. because of the issue documented at https://github.com/phusion/baseimage-docker/pull/25,
+# then we remove it.
+if [ ! -S /dev/log ]; then rm -f /dev/log; fi
+if [ ! -S /var/lib/syslog-ng/syslog-ng.ctl ]; then rm -f /var/lib/syslog-ng/syslog-ng.ctl; fi
+
+PIDFILE="/var/run/syslog-ng.pid"
+SYSLOGNG_OPTS=""
+
+[ -r /etc/default/syslog-ng ] && . /etc/default/syslog-ng
+
+syslogng_wait() {
+    if [ "$2" -ne 0 ]; then
+        return 1
+    fi
+
+    RET=1
+    for i in $(seq 1 30); do
+        status=0
+        syslog-ng-ctl stats >/dev/null 2>&1 || status=$?
+        if [ "$status" != "$1" ]; then
+            RET=0
+            break
+        fi
+        sleep 1s
+    done
+    return $RET
+}
+
+/usr/sbin/syslog-ng --pidfile "$PIDFILE" -F $SYSLOGNG_OPTS &
+syslogng_wait 1 $?

image/services/syslog-ng/syslog-ng.runit

@@ -1,32 +0,0 @@
-#!/bin/sh
-set -e
-
-# If /dev/log is either a named pipe or it was placed there accidentally,
-# e.g. because of the issue documented at https://github.com/phusion/baseimage-docker/pull/25,
-# then we remove it.
-if [ ! -S /dev/log ]; then rm -f /dev/log; fi
-if [ ! -S /var/lib/syslog-ng/syslog-ng.ctl ]; then rm -f /var/lib/syslog-ng/syslog-ng.ctl; fi
-
-SYSLOGNG_OPTS=""
-
-[ -r /etc/default/syslog-ng ] && . /etc/default/syslog-ng
-
-case "x$CONSOLE_LOG_LEVEL" in
-  x[1-8])
-    dmesg -n $CONSOLE_LOG_LEVEL
-    ;;
-  x)
-    ;;
-  *)
-    echo "CONSOLE_LOG_LEVEL is of unaccepted value."
-    ;;
-esac
-
-if [ ! -e /dev/xconsole ]
-then
-  mknod -m 640 /dev/xconsole p
-  chown root:adm /dev/xconsole
-  [ -x /sbin/restorecon ] && /sbin/restorecon $XCONSOLE
-fi
-
-exec syslog-ng -F -p /var/run/syslog-ng.pid $SYSLOGNG_OPTS

image/services/syslog-ng/syslog-ng.sh

@@ -7,8 +7,8 @@ SYSLOG_NG_BUILD_PATH=/bd_build/services/syslog-ng
 
 ## Install a syslog daemon.
 $minimal_apt_get_install syslog-ng-core
-mkdir /etc/service/syslog-ng
-cp $SYSLOG_NG_BUILD_PATH/syslog-ng.runit /etc/service/syslog-ng/run
+cp $SYSLOG_NG_BUILD_PATH/syslog-ng.init /etc/my_init.d/10_syslog-ng.init
+cp $SYSLOG_NG_BUILD_PATH/syslog-ng.shutdown /etc/my_init.post_shutdown.d/10_syslog-ng.shutdown
 mkdir -p /var/lib/syslog-ng
 cp $SYSLOG_NG_BUILD_PATH/syslog_ng_default /etc/default/syslog-ng
 touch /var/log/syslog

image/services/syslog-ng/syslog-ng.shutdown

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+PIDFILE="/var/run/syslog-ng.pid"
+
+syslogng_wait() {
+    if [ "$2" -ne 0 ]; then
+        return 1
+    fi
+
+    RET=1
+    for i in $(seq 1 30); do
+        status=0
+        syslog-ng-ctl stats >/dev/null 2>&1 || status=$?
+        if [ "$status" != "$1" ]; then
+            RET=0
+            break
+        fi
+        sleep 1s
+    done
+    return $RET
+}
+
+kill $(cat "$PIDFILE")
+syslogng_wait 0 $?