[systemd-devel] Query regarding NOTIFY_SOCKET

[Michael Biebl]

I suggest reading https://www.freedesktop.org/software/systemd/man/daemon.html

It's not necessary to fork for a new-style daemon and actually discouraged.

2016-11-08 14:28 GMT+01:00 Raghavendra. H. R <raghuhr84 at gmail.com>:
> Hi Tomasz,
>
> Thanks for pointing out the mistake. I actually missed the line
> "Type=notify" in the mail.
> I found the journalctl logs and from that I can make out the real problem is
> not about NOTIFY_SOCKET. It is about child process in my application Myapp.
>
> Below given is my Service file.
>
> [Unit]
> Description=Sd_notify example
>
> [Service]
> Type=notify
> ExecStart=/etc/Myapp
>
> [Install]
> WantedBy=multi-user.target
>
> And in Myapp code my application is using fork() to create a child process.
> Because of which notification is not working correctly.
>
> This is error log
>
> localhost systemd[1]: sd_example.service: Got notification message from PID
> 1270, but reception only permitted for main PID 1106
>
> Is there any way from which we can force sd_notify to make use of Parent PID
> instead of child process. My sd_notify is after the fork() call, so I doubt
> sd_notify is called from child process.
>
> MyApp code snippet
>
>         int count = 0;
>         cpid = fork();
>
>         if (cpid < 0)
>         {
>             printf("vfork failed.");
>         }
>
>         if (cpid == 0)
>         {
>             count++;
>             if(count == 1)
> {
> ret = sd_notify(0, "READY=1");
> printf("Return value = %d \n");
> }
> }
>
>
> Regards,
> Raghavendra H R
>
> --
> Regards,
>
> Raghavendra. H. R
> (Raghu)
>
> On Tue, Nov 8, 2016 at 5:15 PM, Tomasz Torcz <tomek at pipebreaker.pl> wrote:
>>
>> On Tue, Nov 08, 2016 at 05:01:59PM +0530, Raghavendra. H. R wrote:
>> > Hi All,
>> >
>> > I'm a newbie in Systemd init system and I'm exploring sd_notify which is
>> > basically used for notification purpose in SystemD.
>>
>>   It is written “systemd” (all lowercase).
>>
>> > I have created one unit file which is of type "notify" and in my
>> > application I have written sd_notify(0, "READY=1"); from which SystemD
>> > can
>> > be notified that my process in totally up and running.
>> >
>> > Below given is my Service file.
>> >
>> > *[Unit]*
>> > *Description=Sd_notify example*
>> >
>> > *[Service]*
>> > *ExecStart=/etc/Myapp*
>>
>>
>>   This is not 'unit of type notify'. This is unit of type 'simple'.
>> Please read "man systemd.service" and paragraph Type= and choose
>> correctly.
>>
>>
>> > Need help in understanding what value should be set in the environment
>> > varaible NOTIFY_SOCKET.
>> > But there's no much information/documentation available on
>> > NOTIFY_SOCKET.
>>
>>   NOTIFY_SOCKET is filled-in by systemd and it is available when you
>> correctly defined unit type.  If you want to check it's value, you can
>> user getenv() inside you program and print the value.
>>   I think amount of documentation about NOTIFY_SOCKET is enough, if
>> you think there's something specific missing, let us know.
>>
>>
>> --
>> Tomasz Torcz               "Never underestimate the bandwidth of a station
>> xmpp: zdzichubg at chrome.pl    wagon filled with backup tapes." -- Jim Gray
>>
>> _______________________________________________
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>> systemd-devel at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/systemd-devel
>
>
>
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