Adding delay between stop and start of a process in systemd

Question

I have a really strange issue with systemd. When I issue a systemctl restart it will start the new process before the previous one finishes.

This can be seen in the log, where the final shutdown message ("closing log") is logged after the startup message ("opening log").

Is there any way to add a delay between the stop and the start of process?

Answer 1

In your systemd service files, you can set RestartSec option to add a delay for restart. See example below:

[Service]
Restart=always
RestartSec=30

Check this link for more examples.

Answer 2

RestartSec seems to only be used if that particular service is the one being restarted via the systemctl restart command.

For example, I have two services, A and B.

[Unit]
Requires=network-online.target
[Service]
ExecStart=A-stuff
Restart=always

and

[Unit]
Requires=A.service
After=A.service
[Service]
ExecStart=B-stuff
Restart=always
RestartSec=30

If you do a systemctl restart B, it works as expected... but if you do a systemctl restart A, both services are stopped and immediately started again, with no delay.

Systemd is apparently only using the configuration values for the one service you specify, and ignoring them for any dependencies.

This is not as uncommon as it sounds. If B talks to a remote server, starting and stopping quickly may fail due to the remote end rejecting the client. But restarting A directly will happen whenever A is updated without a change to B.

You can probably work around this by adding the delay to A as well, but you shouldn't NEED to do this, as it breaks object isolation by making A know about B when it's not a dependency.

Answer 3

You may use ExecStopPost, which allows to run a command after the service stopping:

ExecStopPost=/bin/sleep 5

Then the service will wait for 5 seconds after each stopping (including manual restart or the service killing). It will not be possible to start it sooner then 5 seconds after its stopping.