Asynchronous callback not working in VSTS gates Invoke REST API task

Question

I am using the Invoke REST API task in as a pre-deployment gate in my environment. The task has been configured to wait for a callback from my service (external to VSTS).

The problem is that when I try to call into VSTS to mark the task as completed I always get an error saying orchestration session xxxxxx_xxxxxx_xxxxxx not found for hub Gates. The same code when used with release or build definitions work fine but fails with this error when used with gates.

Here is a snippet of my code that makes the API call

var taskCompletedEvent = new TaskCompletedEvent(jobId, taskInstanceGuid, TaskResult.Succeeded);
taskClient.RaisePlanEventAsync(projectGuid, HUBNAME, planGuid, taskCompletedEvent).SyncResult();

Answer 1

This problem occurs because of a slight deviation on how gates are executed when compared to builds or releases. In general, the safest way to update such server side tasks using the callback mode would be by using the TaskClient maintained by the VSTS team itself, which takes care of all such quirks.

The slight change that can be made in the original code to make it work would be -

var taskCompletedEvent = new TaskCompletedEvent(taskInstanceId, Guid.Empty, TaskResult.Succeeded);
taskClient.RaisePlanEventAsync(projectGuid, HUBNAME, planGuid, taskCompletedEvent).SyncResult();

The difference lies in how the event is initialised. The TaskId parameter is not defined and JobId is not used anywhere. The recommendation is still to use the TaskClient on GitHub to ensure everything continues to work fine even when the VSTS Release Management team decides to fix this rather annoying difference.