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Log error if there are no event handlers registered
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We see this error all the time
```
no handler registered for event
event.Message=, event.Annotations=, event.Timestamp=0001-01-01T00:00:00Z, event.TaskName=, event.AllocID=, event.TaskID=,
```

So we're handling an even with all default fields. I noted that this can
happen if only err is set as in

```
func (d *driverPluginClient) handleTaskEvents(reqCtx context.Context, ch chan *TaskEvent, stream proto.Driver_TaskEventsClient) {
	defer close(ch)
	for {
		ev, err := stream.Recv()
		if err != nil {
			if err != io.EOF {
				ch <- &TaskEvent{
					Err: grpcutils.HandleReqCtxGrpcErr(err, reqCtx, d.doneCtx),
				}
			}
```

In this case Err fails to be serialized by the logger, see this test

```

	ev := &drivers.TaskEvent{
		Err: fmt.Errorf("errz"),
	}
	i.logger.Warn("ben test", "event", ev)
	i.logger.Warn("ben test2", "event err str", ev.Err.Error())
	i.logger.Warn("ben test3", "event err", ev.Err)
	ev.Err = nil
	i.logger.Warn("ben test4", "nil error", ev.Err)

2021-10-06T22:37:56.736Z INFO nomad.stdout {"@Level":"warn","@message":"ben test","@module":"client.driver_mgr","@timestamp":"2021-10-06T22:37:56.643900Z","driver":"mock_driver","event":{"TaskID":"","TaskName":"","AllocID":"","Timestamp":"0001-01-01T00:00:00Z","Message":"","Annotations":null,"Err":{}}}
2021-10-06T22:37:56.736Z INFO nomad.stdout {"@Level":"warn","@message":"ben test2","@module":"client.driver_mgr","@timestamp":"2021-10-06T22:37:56.644226Z","driver":"mock_driver","event err str":"errz"}
2021-10-06T22:37:56.736Z INFO nomad.stdout {"@Level":"warn","@message":"ben test3","@module":"client.driver_mgr","@timestamp":"2021-10-06T22:37:56.644240Z","driver":"mock_driver","event err":"errz"}
2021-10-06T22:37:56.736Z INFO nomad.stdout {"@Level":"warn","@message":"ben test4","@module":"client.driver_mgr","@timestamp":"2021-10-06T22:37:56.644252Z","driver":"mock_driver","nil error":null}
```

Note in the first example err is set to an empty object and the error is
lost.

What we want is the last two examples which call out the err field
explicitly so we can see what it is in this case
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Ben Buzbee committed Oct 11, 2021
1 parent 215bf04 commit 337c5d7
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3 changes: 3 additions & 0 deletions .changelog/11280.txt
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
```release-note:improvement
client/plugins/drivermanager: log if there is an error in a driver event
```
3 changes: 2 additions & 1 deletion client/pluginmanager/drivermanager/instance.go
Original file line number Diff line number Diff line change
Expand Up @@ -481,5 +481,6 @@ func (i *instanceManager) handleEvent(ev *drivers.TaskEvent) {
return
}

i.logger.Warn("no handler registered for event", "event", ev)
i.logger.Warn("no handler registered for event", "event", ev, "error", ev.Err)

}

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