How are timeouts surfaced in the rest API?

s-alty · March 19, 2020, 6:47pm

I see the /operations/wait endpoint supports a timeout param:
https://linuxcontainers.org/lxd/docs/master/rest-api#10operationsuuidwait

But it’s not clear to me how that timeout gets surfaced at the api level when it expires.

A cursory scan of the code shows that the timeout expiring causes this waitFinal method to return false:

github.com

lxc/lxd/blob/7a953a864728c4fae2600f0fbf0359e0f398783c/lxd/operations/operations.go#L452


	}


	// Wait until timeout
	if timeout > 0 {
		timer := time.NewTimer(time.Duration(timeout) * time.Second)
		select {
		case <-op.chanDone:
			return true, nil


		case <-timer.C:
			return false, nil
		}
	}


	return false, nil
}


// UpdateResources updates the resources of the operation. It returns an error
// if the operation is not pending or running, or the operation is read-only.
func (op *Operation) UpdateResources(opResources map[string][]string) error {
	if op.status != api.Pending && op.status != api.Running {

But I think it gets ignored by the caller:

github.com

lxc/lxd/blob/7a953a864728c4fae2600f0fbf0359e0f398783c/lxd/operations.go#L320


	id := mux.Vars(r)["id"]


	timeout, err := shared.AtoiEmptyDefault(r.FormValue("timeout"), -1)
	if err != nil {
		return response.InternalError(err)
	}


	// First check if the query is for a local operation from this node
	op, err := operations.OperationGetInternal(id)
	if err == nil {
		_, err = op.WaitFinal(timeout)
		if err != nil {
			return response.InternalError(err)
		}


		_, body, err := op.Render()
		if err != nil {
			return response.SmartError(err)
		}


		return response.SyncResponse(true, body)

Anyone know how to detect whether a timeout expired without the operation completing?

stgraber · March 19, 2020, 7:33pm

stgraber@castiana:~$ lxc query /1.0/operations/014b8909-5cec-4b73-903f-7b231fc4657d/wait?timeout=2
{
	"class": "task",
	"created_at": "2020-03-19T15:32:42.329637042-04:00",
	"description": "Creating container",
	"err": "",
	"id": "014b8909-5cec-4b73-903f-7b231fc4657d",
	"location": "none",
	"may_cancel": true,
	"metadata": {
		"download_progress": "rootfs: 51% (9.81MB/s)"
	},
	"resources": {
		"containers": [
			"/1.0/containers/blah"
		],
		"instances": [
			"/1.0/instances/blah"
		]
	},
	"status": "Running",
	"status_code": 103,
	"updated_at": "2020-03-19T15:32:55.088357752-04:00"
}

In this example, the timeout was hit and so you get the current operation state, which indicates it’s in fact still running per status and status_code.

s-alty · March 19, 2020, 7:52pm

Okay gotcha, so a 103 status code means the operation is still in progress.
https://linuxcontainers.org/lxd/docs/master/rest-api#status-codes

Thanks for the help.