unexpected TaskCancelation in console

I’m seeing TaskCancelation: TaskCancelation errors in my fastboot logs. One of the tasks causing it is:

    loadIruWord: task(function * () {
        let result = yield get(this, 'store').findAll('iruWord');
        if (result !== null) {
            let filtered = this.filterWords(result, get(this, 'adjectivesToRemove'));
            set(this, 'words', filtered);
        }
        this.send('getIRUCount');
    }).on('init'),

Normally I would look for incorrect .then() usage, but I don’t see anything wrong with this task.

Narrowing down the task responsible, I start on the line triggering it value = new Error(TASK_CANCELATION_NAME);

and then go up the call stack to taskInstance.cancel(); in spliceTaskInstances

and taskInstance._origin._propertyName is the task in question loadIruWord

[machty]

@monovertex pointed out to me a subtler case which occurs when awaiting a task instance in an async function.

Still not sure what the root cause is in @kellyselden’s case, but for everyone’s benefit I wrote up an explanatory docs page about the issue and just released a new version of EC that includes a link to this page in the TaskCancelation error text.

[machty]

I’d recommend that anyone seeing these errors upgrade to the latest EC, which provides much more descriptive errors as to which task got canceled and why.

To reiterate: people should only be seeing this error if somewhere along the line, someone calls .then() on the TaskInstance returned from a someTask.perform(). Either this is your code (like in @Guaker13’s example), or it’s library code.

@kellyselden you mentioned this was fastboot; perhaps you’re passing loadIruWord.last (or something similar) to some component (or anyone who will call .then()) via the template, and since fastboot doesn’t know to wait for tasks to run to completion, it’s tearing down everything and canceling the task?