Implement events logging feature

Record events (i.e. pluginhook's calls) as syslog entries and
provide a shortcut command to display the last part of the log
file.

A brief summary of the changes follows:

dokku:
 - New DOKKU_EVENTS_LOGFILE envvar to hold logfile location.

plugins/20_events/commands:
 - events output log entries, a tail's follow-like mode is
   provided too.
 - events:[on|off] enables/disables logging.
 - events:list lists events that are logged.

plugins/20_events/hook:
 - Generic hook that writes log entries. All the events are
   registered via symlink to this script.

plugins/common/functions:
 - dokku_log_event() writes log entries via logger.
 - dokku_log_pluginhook_call() formats log entries and writes
   them via dokku_log_event().

dokku

@@ -10,6 +10,8 @@ export PLUGIN_PATH=${PLUGIN_PATH:="/var/lib/dokku/plugins"}
 export DOKKU_NOT_IMPLEMENTED_EXIT=10
 export DOKKU_VALID_EXIT=0
 
+export DOKKU_EVENTS_LOGFILE=${DOKKU_EVENTS_LOGFILE:="/var/log/dokku.log"}
+
 source "$PLUGIN_PATH/common/functions"
 
 [[ -f $DOKKU_ROOT/dokkurc ]] && source $DOKKU_ROOT/dokkurc

plugins/20_events/backup-check

@@ -0,0 +1 @@
+hook

plugins/20_events/backup-export

@@ -0,0 +1 @@
+hook

plugins/20_events/backup-import

@@ -0,0 +1 @@
+hook

plugins/20_events/bind-external-ip

@@ -0,0 +1 @@
+hook

plugins/20_events/check-deploy

@@ -0,0 +1 @@
+hook

plugins/20_events/commands

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$(dirname $0)/../common/functions"
+
+find "$l_plugin_dir" -type l -printf "%f " | sort
+
+case "$1" in
+  events)
+    if [[ -f $DOKKU_EVENTS_LOGFILE ]] ; then
+      if [[ $2 == "-t" ]]; then
+        tail -f $DOKKU_EVENTS_LOGFILE
+      else
+        tail -n 100 $DOKKU_EVENTS_LOGFILE
+      fi
+    fi
+    ;;
+
+  events:on)
+    echo "Enabling dokku events logger"
+    [[ -d $DOKKU_ROOT/.dokkurc ]] || mkdir -p $DOKKU_ROOT/.dokkurc
+    echo "export DOKKU_EVENTS=1" > $DOKKU_ROOT/.dokkurc/DOKKU_EVENTS
+    ;;
+
+  events:off)
+    echo "Disabling dokku events logger"
+    rm -f $DOKKU_ROOT/.dokkurc/DOKKU_EVENTS
+    ;;
+
+  events:list)
+    if [[ "$DOKKU_EVENTS" ]]; then
+      dokku_col_log_info2_quiet "Events currently logged"
+      for hook in $(find $(dirname $0) -type l -printf "%f " | sort) ; do
+        dokku_col_log_msg "$hook"
+      done
+    else
+      dokku_log_warn "Events logger disabled"
+    fi
+    ;;
+
+  help | events:help)
+    cat && cat<<EOF
+    events [-t]                                     Show the last events (-t follows)
+    events:list                                     List logged events
+    events:on                                       Enable events logger
+    events:off                                      Disable events logger
+EOF
+    ;;
+
+  *)
+    exit $DOKKU_NOT_IMPLEMENTED_EXIT
+    ;;
+
+esac
+

plugins/20_events/dependencies

@@ -0,0 +1 @@
+hook

plugins/20_events/docker-args-build

@@ -0,0 +1 @@
+hook

plugins/20_events/docker-args-deploy

@@ -0,0 +1 @@
+hook

plugins/20_events/docker-args-run

@@ -0,0 +1 @@
+hook

plugins/20_events/git-post-pull

@@ -0,0 +1 @@
+hook

plugins/20_events/git-pre-pull

@@ -0,0 +1 @@
+hook

plugins/20_events/hook

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$(dirname $0)/../common/functions"
+
+[[ ! "$DOKKU_EVENTS" ]] || dokku_log_pluginhook_call "$(basename $0)" $@

plugins/20_events/install

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$(dirname $0)/../common/functions"
+
+if [[ ! -f  "$DOKKU_EVENTS_LOGFILE" ]]; then
+  touch "$DOKKU_EVENTS_LOGFILE"
+  # chown syslog:root might not work on SUSE
+  chown syslog:dokku "$DOKKU_EVENTS_LOGFILE"
+  chmod 664 "$DOKKU_EVENTS_LOGFILE"
+fi
+
+if [[ ! -f  "$DOKKU_RSYSLOG_FILTER" ]]; then
+  cat >"$DOKKU_RSYSLOG_FILTER" <<EOF
+:syslogtag, contains, "dokku" $DOKKU_EVENTS_LOGFILE
+EOF
+  service rsyslog reload
+
+[[ "$DOKKU_EVENTS" ]] && dokku_log_pluginhook_call "$(basename $0)" $@
+
+exit 0

plugins/20_events/nginx-hostname

@@ -0,0 +1 @@
+hook

plugins/20_events/nginx-pre-reload

@@ -0,0 +1 @@
+hook

plugins/20_events/post-build-buildstep

@@ -0,0 +1 @@
+hook

plugins/20_events/post-build-dockerfile

@@ -0,0 +1 @@
+hook

plugins/20_events/post-delete

@@ -0,0 +1 @@
+hook

plugins/20_events/post-deploy

@@ -0,0 +1 @@
+hook

plugins/20_events/post-domains-update

@@ -0,0 +1 @@
+hook

plugins/20_events/post-release-buildstep

@@ -0,0 +1 @@
+hook

plugins/20_events/post-release-dockerfile

@@ -0,0 +1 @@
+hook

plugins/20_events/pre-build-buildstep

@@ -0,0 +1 @@
+hook

plugins/20_events/pre-build-dockerfile

@@ -0,0 +1 @@
+hook

plugins/20_events/pre-delete

@@ -0,0 +1 @@
+hook

plugins/20_events/pre-deploy

@@ -0,0 +1 @@
+hook

plugins/20_events/pre-release-buildstep

@@ -0,0 +1 @@
+hook

plugins/20_events/pre-release-dockerfile

@@ -0,0 +1 @@
+hook

plugins/20_events/receive-app

@@ -0,0 +1 @@
+hook

plugins/20_events/update

@@ -0,0 +1 @@
+hook

plugins/common/functions

@@ -90,6 +90,17 @@ dokku_log_fail() {
   exit 1
 }
 
+dokku_log_event() {
+  logger -t dokku -i -- $@
+}
+
+dokku_log_pluginhook_call() {
+  local l_hook
+
+  l_hook="$1" ; shift
+  dokku_log_event "INVOKED: ${l_hook}( $@ )"
+}
+
 dokku_container_log_verbose_quiet() {
   CID=$1;
   shift