Re: [systemd-devel] type=notify not working as intended

[Lennart Poettering]

On Di, 15.08.17 09:29, Kalpa Gunarathna (ka...@sigscale.com) wrote:

> Hello all,
> 
> I have scripted a service unit as follow.
> 
> [Unit]
> Description="A test service"
> After=epmd.service epmd.socket
> 
> [Service]
> ExecStart=/home/otpuser/bin/start
> Type=notify
> NotifyAccess=all
> WorkingDirectory=~
> User=otpuser
> Group=otp
> Restart=always
> RestartSec=3
> 
> [Install]
> WantedBy=multi-user.target
> 
> 
> ExecStart directs to a shell script which starts a Erlang run_erl daemon.
> This daemon is forking a process which is the BEAM virtual machine. In the
> forked process Im sending "READY=1\nSTATUS=Initialized\nMAINPID="
> <> "\n to systemd via sd_notify. The problem is service
> is getting restarted constantly.

When you use Type=notify, then the main process of the daemon defines
the runtime of your service. That means you probably want to use the
shell's "exec" command to replace the shell script with your erlang
daemon. if you instead just fork it off, and exit in the shell script,
then systemd will notice that it exited and will consider the service
dead.

> journalctl give this
> 
> abc.service: Service hold-off time over, scheduling restart.
> Stopped "A test service.".
> 
> 
> Is it required to send READY=1 from the daemon it self ? or can systemd
> allow forked process of the daemon to send REDAY=1 notification?

It needs to come from any process that is witelisted using
NotifyAccess=. Note though that there's a bit of a race: if you send
READY=1 and immediately exit from the process doing that, then systemd
can't properly relate the message to the service (that's a race we
can#t fix without kernel support), except if the process is actually
the one systemd forked off. Hence, sd_notify(READY=1) works reliably only if 
either:

1. it is invoked by the immediate process systemd forked off

or

2. the process is long-running and stays around for longer after
   sending READY=1

Lennart

-- 
Lennart Poettering, Red Hat
___
systemd-devel mailing list
systemd-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/systemd-devel

Re: [systemd-devel] type=notify not working as intended

[Jouke Witteveen]

On Tue, Aug 15, 2017 at 5:59 AM, Kalpa Gunarathna  wrote:
> Hello all,
>
> I have scripted a service unit as follow.
>
> [Unit]
> Description="A test service"
> After=epmd.service epmd.socket
>
> [Service]
> ExecStart=/home/otpuser/bin/start
> Type=notify
> NotifyAccess=all
> WorkingDirectory=~
> User=otpuser
> Group=otp
> Restart=always
> RestartSec=3
>
> [Install]
> WantedBy=multi-user.target
>
>
> ExecStart directs to a shell script which starts a Erlang run_erl daemon.
> This daemon is forking a process which is the BEAM virtual machine. In the
> forked process Im sending "READY=1\nSTATUS=Initialized\nMAINPID="
> <> "\n to systemd via sd_notify. The problem is service
> is getting restarted constantly.
>
> journalctl give this
>
> abc.service: Service hold-off time over, scheduling restart.
> Stopped "A test service.".
>
>
> Is it required to send READY=1 from the daemon it self ? or can systemd
> allow forked process of the daemon to send REDAY=1 notification?
>
> It works when Type=forking and PIDFile is specified, but can we have
> Type=forking and without PIDFIle, notify READY=1 via forked process ?
>
> My systemd version
>
> $ systemd --version
> systemd 229
>

The service fails when the main process terminates before a READY=1
notification is received. Contrary to Reindl Haralds claim, this
notification is allowed to come from whatever process that is allowed
to send notifications, as controlled by NotifyAccess=. In order to not
give up on the service when the main process terminates, but wait for
the remaining processes in the cgroup, you should add
RemainAfterExit=yes to your unit.

Regards,
- Jouke
___
systemd-devel mailing list
systemd-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/systemd-devel

Re: [systemd-devel] type=notify not working as intended

[Reindl Harald]

Am 15.08.2017 um 05:59 schrieb Kalpa Gunarathna:

Hello all,

I have scripted a service unit as follow.

[Unit]
Description="A test service"
After=epmd.service epmd.socket

[Service]
ExecStart=/home/otpuser/bin/start
Type=notify
NotifyAccess=all
WorkingDirectory=~
User=otpuser
Group=otp
Restart=always
RestartSec=3

[Install]
WantedBy=multi-user.target


ExecStart directs to a shell script which starts a Erlang run_erl daemon.
This daemon is forking a process which is the BEAM virtual machine. In 
the forked process Im sending "READY=1\nSTATUS=Initialized\nMAINPID=" 
<> "\n to systemd via sd_notify. The problem is 
service is getting restarted constantly


MAINPID is supposed to send the notify
Type=notify needs to be explicit supported by the daemon

___
systemd-devel mailing list
systemd-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/systemd-devel

[systemd-devel] type=notify not working as intended

[Kalpa Gunarathna]

Hello all,

I have scripted a service unit as follow.

[Unit]
Description="A test service"
After=epmd.service epmd.socket

[Service]
ExecStart=/home/otpuser/bin/start
Type=notify
NotifyAccess=all
WorkingDirectory=~
User=otpuser
Group=otp
Restart=always
RestartSec=3

[Install]
WantedBy=multi-user.target


ExecStart directs to a shell script which starts a Erlang run_erl daemon.
This daemon is forking a process which is the BEAM virtual machine. In the
forked process Im sending "READY=1\nSTATUS=Initialized\nMAINPID="
<> "\n to systemd via sd_notify. The problem is service
is getting restarted constantly.

journalctl give this

abc.service: Service hold-off time over, scheduling restart.
Stopped "A test service.".


Is it required to send READY=1 from the daemon it self ? or can systemd
allow forked process of the daemon to send REDAY=1 notification?

It works when Type=forking and PIDFile is specified, but can we have
Type=forking and without PIDFIle, notify READY=1 via forked process ?

My systemd version

$ systemd --version
systemd 229
___
systemd-devel mailing list
systemd-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/systemd-devel