[ovirt-devel] [vdsm] Connection refused when talking to jsonrpc

[Nir Soffer]

On Tue, Nov 8, 2016 at 6:52 PM, Martin Sivak <msivak at redhat.com> wrote:
> Hi,
>
> mom-vdsm.service contains:
>
> Requires=vdsmd.service
> After=vdsmd.service

After does not mean much, since vdsm is not integrated with systemd.
Systemd does not wait until vdsm is ready to receive connections.

We can use systemd.daemon to notify systemd that vdsm is ready, making
dependencies more reliable.

See https://github.com/oVirt/ovirt-imageio/blob/master/daemon/ovirt_imageio_daemon/server.py#L44

> So when Shira restarted vdsm, mom was also restarted.
>
> [journalctl --unit vdsmd]
> Nov 08 18:25:27 RHEL7.2Server systemd[1]: Stopping Virtual Desktop
> Server Manager...
> Nov 08 18:25:27 RHEL7.2Server vdsmd_init_common.sh[3053]: vdsm:
> Running run_final_hooks
> Nov 08 18:25:27 RHEL7.2Server systemd[1]: Starting Virtual Desktop
> Server Manager...
>
> [journalctl --unit mom-vdsm]
> Nov 08 18:17:23 RHEL7.2Server systemd[1]: Starting MOM instance
> configured for VDSM purposes...
> Nov 08 18:25:16 RHEL7.2Server systemd[1]: Stopping MOM instance
> configured for VDSM purposes...
> Nov 08 18:25:29 RHEL7.2Server systemd[1]: Started MOM instance
> configured for VDSM purposes.
>
>
> But mom then immediately failed with:
>
> 2016-11-08 18:25:08,008 - mom.RPCServer - INFO - ping()
> 2016-11-08 18:25:08,010 - mom.RPCServer - INFO - getStatistics()
> 2016-11-08 18:25:17,028 - mom.RPCServer - INFO - RPC Server ending
> 2016-11-08 18:25:24,705 - mom.GuestManager - INFO - Guest Manager ending
> 2016-11-08 18:25:26,575 - mom.HostMonitor - INFO - Host Monitor ending
>
> 2016-11-08 18:25:29,869 - mom - INFO - MOM starting
> 2016-11-08 18:25:29,905 - mom.HostMonitor - INFO - Host Monitor starting
> 2016-11-08 18:25:29,905 - mom - INFO - hypervisor interface vdsmjsonrpcbulk
> 2016-11-08 18:25:30,029 - mom.vdsmInterface - ERROR - Cannot connect
> to VDSM! [Errno 111] Connection refused
> 2016-11-08 18:25:30,030 - mom - ERROR - Failed to initialize MOM threads
> Traceback (most recent call last):
>   File "/usr/lib/python2.7/site-packages/mom/__init__.py", line 29, in run
>     hypervisor_iface = self.get_hypervisor_interface()
>   File "/usr/lib/python2.7/site-packages/mom/__init__.py", line 217,
> in get_hypervisor_interface
>     return module.instance(self.config)
>   File "/usr/lib/python2.7/site-packages/mom/HypervisorInterfaces/vdsmjsonrpcbulkInterface.py",
> line 47, in instance
>     return JsonRpcVdsmBulkInterface()
>   File "/usr/lib/python2.7/site-packages/mom/HypervisorInterfaces/vdsmjsonrpcbulkInterface.py",
> line 29, in __init__
>     super(JsonRpcVdsmBulkInterface, self).__init__()
>   File "/usr/lib/python2.7/site-packages/mom/HypervisorInterfaces/vdsmjsonrpcInterface.py",
> line 43, in __init__
>     .orRaise(RuntimeError, 'No connection to VDSM.')
>   File "/usr/lib/python2.7/site-packages/mom/optional.py", line 28, in orRaise
>     raise exception(*args, **kwargs)
> RuntimeError: No connection to VDSM.
>
>
> The question here is, how much time does VDSM need to allow jsonrpc to
> connect and request a ping and list of VMs?

Even if we fix vdsm, mom (and any other client) should be more robust
and do not created so much noise when connection is refused. Client should
retry connection and log less dramatic warnings.

Adding devel at ovirt, vdsm-devel mailing was abandoned more then 2 years ago.

Nir