add documentation about SIGABRT

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

contrib/systemd/README.md

@@ -12,8 +12,38 @@ updated: 2015-03-25
 
 ## Systemd units
 
-These unit files are meant to be used in the user session. You may drop them into `/etc/systemd/user` or `${XDG_DATA_HOME}/systemd/user` followed by `systemctl --user daemon-reload` to have systemd aware of the unit files.
+These unit files are meant to be used in the user session. You may drop them
+into `/etc/systemd/user` or `${XDG_DATA_HOME}/systemd/user` followed by
+`systemctl --user daemon-reload` to have systemd aware of the unit files.
 
-These files are meant to be triggered either manually using `systemctl --user start offlineimap.service` or by enabling the timer unit using `systemctl --user enable offlineimap.timer`. Additionally, specific accounts may be triggered by using `offlineimap@myaccount.timer` or `offlineimap@myaccount.service`.
+These files are meant to be triggered either manually using `systemctl --user
+start offlineimap.service` or by enabling the timer unit using `systemctl --user
+enable offlineimap.timer`. Additionally, specific accounts may be triggered by
+using `offlineimap@myaccount.timer` or `offlineimap@myaccount.service`.
+
+These unit files are installed as being enabled via a `mail.target` unit which
+is intended to be a catch-all for mail-related unit files. A simple
+`mail.target` file is also provided.
+
+## Signals
+
+Systemd supports a watchdog (via the WatchdogSec service file option) which
+will send the program a SIGABRT when the timer expires.
+
+Offlineimap handles it in the same manner as SIGUSR2, so that the current
+synchronisation is completed before the program exits safely.
+
+This makes offlineimap more flexible and robust for persistent setups that make
+use of holdconnectionopen and autorefresh options.
+
+For example, it may be useful in assisting with the occasional situation where
+offlineimap may not return successfully after a suspend and resume.
+
+To make use of this, users could add the following to the [Service] section of
+their systemd offlineimap service file (restart every 5 minutes):
+
+``` conf
+Restart=on-watchdog
+WatchdogSec=300
+```
 
-These unit files are installed as being enabled via a `mail.target` unit which is intended to be a catch-all for mail-related unit files. A simple `mail.target` file is also provided.

contrib/systemd/offlineimap.service

@@ -6,6 +6,8 @@ Type=oneshot
 ExecStart=/usr/bin/offlineimap -o -u syslog
 # Give 12 seconds for offlineimap to gracefully stop before hard killing it.
 TimeoutStopSec=12
+#Restart=on-watchdog
+#WatchdogSec=300
 
 [Install]
 WantedBy=mail.target

contrib/systemd/offlineimap@.service

@@ -4,6 +4,8 @@ Description=Offlineimap Service for account %i
 [Service]
 Type=oneshot
 ExecStart=/usr/bin/offlineimap -o -a %i -u syslog
+#Restart=on-watchdog
+#WatchdogSec=300
 
 [Install]
 WantedBy=mail.target

docs/offlineimap.txt

@@ -315,10 +315,10 @@ SIGHUP, SIGQUIT.
 accounts that are configured to 'autorefresh'. In effect, this will trigger a
 full sync of all accounts to be performed as soon as possible.
 
-* If sent a SIGUSR2, it will stop 'autorefresh' mode for all accounts. That
-is, accounts will abort any current sleep and will exit after a currently
-running synchronization has finished. This signal can be used to gracefully
-exit out of a running offlineimap "daemon".
+* If sent a SIGUSR2 or SIGABRT, it will stop 'autorefresh' mode for all
+accounts. That is, accounts will abort any current sleep and will exit after a
+currently running synchronization has finished. This signal can be used to
+gracefully exit out of a running offlineimap "daemon".
 
 * SIGTERM, SIGINT, SIGHUP are all treated to gracefully terminate as soon as
 possible. This means it will finish syncing the current folder in each