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I have a systemd service, which is activated by a DBus service. The mechanism itself works:

  1. The systemd service is not running
  2. I send a call via DBus to the requested bus
  3. My service is started

The issue is that the message from step 2 is lost. I need to re-send the DBus call in order to get a response from the now-running service.

Is that behavior expected? Is there a way of queuing the message from 2 until the service is started, and delivering it then?

my dbus service file looks like this:

[D-BUS Service]
Name=d.d.service
Exec=/bin/false
SystemdService=dbus-example.service

And my service file like this:

[Unit]
Description=example dbus service

[Service]
ExecStart=/home/daniel/Projects/dbus/asdf.sh
Type=dbus
BusName=d.d.service
Environment=DISPLAY=:0
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  • Why is your service started through a shell script? What does the script contain? Commented Dec 4, 2024 at 7:38
  • The script starts a node process through asdf. The node process itself is long-running Commented Dec 4, 2024 at 11:32

1 Answer 1

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Is that behavior expected?

No, it's not.

Is there a way of queuing the message from 2 until the service is started, and delivering it then?

That's the default behavior. See specification.

If the messages are lost, I suspect your service is connecting to the bus twice: the first connection claims the name, receives queued messages and does nothing with them, and is immediately replaced by a second connection that re-claims the name and starts processing messages.

Use dbus-monitor or busctl monitor to verify this – watch for the RequestName method and the NameOwnerChanged signal. (If they are repeated twice, then the above explanation applies.)

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  • Thanks! I'll investigate Commented Dec 5, 2024 at 10:24

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