TaskInstance '__DS_COPY_TASK_RUNNER__' was canceled because it belongs to a 'drop' Task that was already running.

[songoo]

Hello.

I am using ember-data-copyable (0.2.1) to copy models, its very cool! And had no problems till today :( when I tried to copy same model in multiple times.

I have Promise.all(promises), in every of that promises I copy one or more models, but those are always the same models for all promises.

For example, I have 3 models (taskAsignments) , and I want copy all 3 of them in for example 6 promises.

What I encounter is, that all 3 models are copied in firstProcessedPromise and will fail in all other (five) promises with message :

TaskCancelation: TaskInstance 'DS_COPY_TASK_RUNNER' was canceled because it belongs to a 'drop' Task that was already running. For more information, see: http://ember-concurrency.com/#/docs/task-cancelation-help

I tried to rewrite Promise.all with reduce, so all 6 promises would be called in synchronized way, but result was same sadly. I also tried deep and not deep .copy with same result.

If possible please advice if have any idea.

[songoo]

I tried to replace .copy with manual (create record + calling all setters) copping and it went with no error. Also tried to get some info from ember slack, here is response, but not sure if it helps :

it’s hard to say without seeing some of the code, but that’s an error that will result from a promise rejection after a task instance has been coerced to a promise (usually by calling .then() or .catch() from a task instance, or by passing the task instance to something like an RSVP.hash or returning it from a route lifecycle hook).
this is mentioned in the docs here: http://ember-concurrency.com/api/global.html#didCancel

[roscorcoran]

I have this issue to when attempting to copy 2+ of the same model at once. Seems to be that only the last scheduled copy is performed all other copies are cancelled with the error outlined above.

[offirgolan]

Are you guys trying to copy the same model instance multiple times or are you copying different instances of the same model type?

[songoo]

Hi.
"same model instance multiple times", yes i get one assigment from database, then run 3 promises in same time and each of them will try to make its own copy of that exact assigment.

[offirgolan]

Makes sense. The copy task runner has a drop concurrency task policy. That means it will only execute the first request and ignore the rest until it's done running.

I need to investigate other concurrency policies before just removing this one due to unforeseen implications. In the mean time, you guys will need to chain your requests.

async copyModels(model) {
  await model.copy();
  await model.copy();
  await model.copy();
}

[songoo]

I also tried synchronous promises(with reduce), it did not help (and i was sure it will) .

[offirgolan]

Hmmmm thats pretty odd. I'll investigate this further in the next week or two. Pretty swamped at the moment.

[donaldwasserman]

@offirgolan Would you be willing to entertain a PR that makes it possible to allow a configurable set of concurrency options?

Something like:

model.copy({concurrencyPolicy: 'keepLatest'}) //because i can't spell Enqueue

I'm not familiar enough with the guts of EC to understand if you can dynamically apply .drop or whatever, but on the mixin side we could add a different layer of abstraction to do like

[COPY_TASK_<TYPE>]: task(function*() { return this.get('COPY_TASK').perform(options)).<TYPE>()

[offirgolan]

@donaldwasserman I would if there was a decent way of doing this. I'd rather not bomb the model's proto with a bunch of copy tasks for each concurrency policy.

ping @machty any thoughts on how I can support something like this?

[miguelcobain]

I think we shouldn't enforce any kind of concurrency policy ourselves and leave that choice to the user.

@offirgolan do you recall the reason to set the copy task concurrency policy to drop?