is there any way to get better error messages from dbuslib.call_method?

[kurtbrose]

Trying to follow the example for starting a transient unit from here: https://github.com/facebookincubator/pystemd/blob/master/examples/start_transient_unit.py

        manager.Manager.StartTransientUnit(
            procname, b'fail',
            {
                b'Description': b'Carbonite Crawl %s on %s' % (name, target),
                b'ExecStart': [(cmd[0], cmd, False)],
                b'RemainAfterExit': True
            })

However, I'm getting the following error:

pystemd/dbuslib.pyx in pystemd.dbuslib.DBus.call_method()

TypeError: expected bytes, int found

> /home/fedora/carbonite/pystemd/dbuslib.pyx(389)pystemd.dbuslib.DBus.call_method()

Because it is cython, I don't know how far the loop got.

I can see the args getting passed in to call_method:

ipdb> args
self = <pystemd.systemd1.manager.Manager object at 0x7f0fd922f160>
interface_name = b'org.freedesktop.systemd1.Manager'
name = b'carbonite.crawl-test-auto-crawl.service'
smode = b'fail'
properties = {b'Description': b'Carbonite Crawl test-auto-crawl on ec2-52-26-199-38.us-west-2.compute.amazonaws.com', b'ExecStart': [(115, b'scrapy crawl sl_spider -a session_name=test-auto-crawl -a usernames=email-1024 -a password=wrong-password -a target=https://ec2-52-26-199-38.us-west-2.compute.amazonaws.com\n', False)], b'RemainAfterExit': True}
extra_units = None

I think putting the value and/or name of the argument causing the problem would improve debugability a lot.

EDIT: the bug was I forgot to split the byte-string into a list, so cmd[0] was returning an integer

[aleivag]

Hi @kurtbrose , thanks for summiting this.

it seems that you already solve this, may i also point to you to pystemd.run

import shlex
import pystemd.run
acmd = shlex.split(cmd) # or just have it as an array
unit = pystemd.run(acmd, remain_after_exit=True)

will return you a pystemd.systemd1.Unit object, that you can query for runtime information (and start/stop/restart/etc)

---

now about the request:

Yes it would be a nice addition, i was concentrating on making pystemd accept regular strings first (that is done, so i expect to put a new release today).

about this, i would definitely work on this. i still need to think exactly how to do it. The thing is that i dont want to assume anything about the used types, and i would much ratter let libsystemd0 reject types as they come, but with that said i can work on some sort of warning (hey you are putting a type X, but expected something from the family of type Y). let me think about it, and really thanks for the input.

Alvaro

[kurtbrose]

thanks!

[kurtbrose]

Thanks for the suggestion; psytemd.run is launching processes; now I'm trying to figure out how to monitor the running processes:

name = b'test.sleep.service'
pystemd.run([b'/usr/bin/sleep', b'10'], name=name)
unit = Unit(name, _autoload=True)
unit.Service.MainPID  # always 0?

Does this seem like the correct way to use the API?

[aleivag]

yes, MainPID shoudl be 0 when the process exit (or never started). you can do a few extra things:

unit = pystemd.run([b'/usr/bin/sleep', b'10'], remain_after_exit=True)
print('MainPID', unit.Service.MainPID)
print('SubState', unit.Unit.SubState)
print('LoadState', unit.Unit.LoadState)

you'll get

MainPID 3351
SubState b'running'
LoadState b'loaded'

By passing the remain_after_exit you make the unit to stay in memory after it finish, and allow pystemd.run to return a Unit file. if you don't specify, then when the unit finish (your 10 seconds), the unit will just go away.

there some (not the best i agree) documentation here https://github.com/facebookincubator/pystemd/blob/master/_docs/pystemd.run.md

[aleivag]

i just landed something that will help with the debug, is not the best thing, but its there... this will continue to be on our radar,