Add a CONNECT event to informer. #614

brendandburns · 2021-03-19T15:25:44Z

Fixes #609

drubin · 2021-03-19T15:29:52Z

src/cache.ts

@@ -1,4 +1,4 @@
-import { ADD, DELETE, ERROR, Informer, ListPromise, ObjectCallback, UPDATE } from './informer';
+import { ADD, CONNECT, DELETE, ERROR, Informer, ListPromise, ObjectCallback, UPDATE } from './informer';


Does it make sense to add a disconnect here too while we are at it?

I think connect + error is sufficient. There shouldn't be a disconnect w/o an error that isn't followed immediately by another connect.

drubin · 2021-03-19T15:31:24Z

src/informer.ts

 export const ADD: string = 'add';
 export const UPDATE: string = 'update';
 export const DELETE: string = 'delete';
+
+// These are issued when a watch connects, reconnects or sees an error


I see we are only testing for one of these conditions, what about reconnect or errors?

Added a test for reconnect. There was already a test for errors. I clarified this comment also.

dominykas · 2021-03-22T16:11:16Z

src/cache.ts

@@ -97,6 +98,7 @@ export class ListWatch<T extends KubernetesObject> implements ObjectCache<T>, In
            // do not auto-restart
            return;
        }
+        this.callbackCache[CONNECT].forEach((elt: ObjectCallback<T>) => elt({} as T));


Is {} as T the right thing to do? I would expect no params passed to the callback here (not sure if TypeScript allows expressing that though...)

This also caught me off guard for the ERROR event - error is an instance of Error, not T.

This was legacy left over from when the callbacks only dealt with objects not errors and connects. I refactored the callback type signature to make it better.

brendandburns · 2021-03-24T23:56:01Z

Comments addressed, please re-check.

Thanks!

dominykas · 2021-03-25T10:03:38Z

src/cache.ts

@@ -102,13 +113,14 @@ export class ListWatch<T extends KubernetesObject> implements ObjectCache<T>, In
    private async doneHandler(err: any): Promise<any> {
        this._stop();
        if (err) {
-            this.callbackCache[ERROR].forEach((elt: ObjectCallback<T>) => elt(err));
+            this.callbackCache[ERROR].forEach((elt: ObjectCallback<T>) => elt(undefined, err));


Hmmm. This makes it a breaking change? It also has the error at the end, which may be unintuitive to folks used to Node's error-first callbacks... But moving the error first would be even more breaking...

Not sure what's the best approach here... Not saying this shouldn't got ahead, it's easy enough to adapt as a user of the library, but still.

Would be a travesty in TypeScript world to allow on() to have overloads to accept different parameter types? i.e. allow on(verb: string, fn: ObjectCallback<T>): void; as well as on(verb: string, fn: ErrorCallback): void;? While it wouldn't enforce the correct callback type based on the verb, it would at least be non-breaking? Not sure if there's a better way to express this in TS...

I did also try it that way:

on(verb: string, fn: ObjectCallback<T> | ErrorCallback | ConnectCallback)

But I felt like that was even messier, because suddenly the user can accidentally pass a ConnectCallback to a on('add', ...)

Maybe we could do:

export type Callback<T extends KubernetesObject> = (err: any, obj: T | null) => void; // Deprecated export type ObjectCallback<T extends KubernetesObject> = (obj: T) => void; ... on(verb: string, fn: ObjectCallback | Callback) ...

wdyt? That has the benefit of not being a breaking change, and also adding in the more node-style callbacks.

~~Although, I'm not actually sure that TS can handle that since those two callback types may be indistinguishable...~~

I made the types more concrete so I think TS can handle it based on the # of parameters.

Would TS handle that at runtime or just compile time?

Did TS ever get enums? If the first param for on() was enum, rather than a string, then it could have multiple signatures based on enum type... Which would probably still be a breaking change from TS perspective, but possibly the old string signature could still be there, just with any callback so that people can upgrade their code eventually, even if they would lose out a little bit in terms of potentially accidentally passing the wrong callback?

Also I wonder if passing the wrong callback is even a problem for people using TS, because surely someone must have noticed by now that the callback for the error event is not right? i.e. this could mean that making changes here is not that disruptive, even if the changes are breaking when looking at it strictly?

This is a common pattern (on() with different callbacks for different event types) - surely someone must have solved this by now? This is used in node itself (in streams and elsewhere): https://github.com/DefinitelyTyped/DefinitelyTyped/blob/1d52dcdeea0c4006bb63c28ff60b919f3f5fc3a6/types/node/stream.d.ts#L84-L91 🤔

was there a follow-up on this @brendandburns ?

Thanks for the pointer! I fixed this using type overloading.

brendandburns · 2021-04-23T19:25:20Z

Comments addressed, please take another look!

dominykas

👏

k8s-ci-robot · 2021-04-28T11:13:44Z

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drubin · 2021-05-02T19:26:43Z

/lgtm

Thanks for fixing the comments

k8s-ci-robot requested a review from drubin March 19, 2021 15:25

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. approved Indicates a PR has been approved by an approver from all required OWNERS files. size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Mar 19, 2021

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Add a CONNECT event to informer.

0cc04fe

brendandburns force-pushed the stop branch from 17c724a to 0cc04fe Compare March 24, 2021 23:55

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Updates.

7d88ed6

brendandburns force-pushed the stop branch from 463bb00 to 7d88ed6 Compare April 23, 2021 19:23

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Add a CONNECT event to informer. #614

Add a CONNECT event to informer. #614

brendandburns commented Mar 19, 2021

drubin Mar 19, 2021

brendandburns Mar 24, 2021

drubin Mar 19, 2021

brendandburns Mar 24, 2021

dominykas Mar 22, 2021

brendandburns Mar 24, 2021

brendandburns commented Mar 24, 2021

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drubin commented May 2, 2021

		@@ -1,4 +1,4 @@
		import { ADD, DELETE, ERROR, Informer, ListPromise, ObjectCallback, UPDATE } from './informer';
		import { ADD, CONNECT, DELETE, ERROR, Informer, ListPromise, ObjectCallback, UPDATE } from './informer';

Add a CONNECT event to informer. #614

Add a CONNECT event to informer. #614

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brendandburns commented Mar 19, 2021

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