Add connection error/retry API and UI support

[texodus]

This PR adds a reconnect API to Perspective, as well as a UX to invoke a reconnect to <perspective-viewer>.

[greg-atomic]

Websockets can only handle auth during handshake. And auth tokens typically have an expiration time for security reasons. If a websocket is open for long enough then the token expires. The currently implemented reconnect function doesn't allow for updating the auth details in the new handshake, which happens at reconnect: it sends the old auth data that was used at the initial handshake. So the new reconnect functionality can't be used for this case: instead, one has to explicitly terminate and clean up the websocket connection and establish a brand new one to handle broken connections properly.

I'd suggest to change the reconnect function to enable for an updated URL to reconnect to as a parameter.

[texodus]

Websockets can only handle auth during handshake.

Perspective doesn't handle auth tokens at all. You will need to implement your own Client for a custom WebSocket protocol, there are no docs for this yet but you can follow the websocket.ts implementation in the repo

[greg-atomic]

Thanks for the quick response, really appreciate it! And I totally understand that you don't want to expand the scope of perspective with authentication. What I'm seeking is simply not making it impossible.

My problem is that this doesn't seem to be a typescript level, client wrapping question, but deeper in how rust handles websocket errors. The client's on_error function adds a non-removable error handler, which seems to keep firing even if one calls .terminate() on the client in typescript and deletes the client object.

As I can not use the reconnect function if there is authentication and expired tokens, I have no better idea than instantiating a new client. And what I see that the old on_error keeps firing because of the outdated url. And I also haven't found a way for cleaning up non-used clients, so if I go this route, after a while I see this error in the browser's console:

Uncaught (in promise) RangeError: WebAssembly.instantiate(): Out of memory: Cannot allocate Wasm memory for new instance

And I don't see how I could workaround that by creating a new websocket client in typescript.

I believe it would be the cleanest to support the suggested new url for reconnect: there's no need for a new client for any reasons, so we could simple avoid that, and on_error would also keep working as is now. A much less ideal, but still working solution could be able to remove the on_error handler from typescript, and have a way to delete the client and free up the wasm memory. This way one has to recreate the client in case of an error, refetch all data again, but at least it would work.

[texodus]

We would need to see your implementation, you have quite a lot more going on here well beyond the scope of this (merged, 3mo old) PR. Client doesn't tick on its own, it is continuing to throw errors because you are still calling methods on it in your application somewhere after calling Client::terminate (perhaps on a derived object) - and regardless, creating a new Client instance on disconnect (and enough of them to literally OOM the runtime as they are only a few bytes ...) is not the right way to do whatever it is you are trying to do (e.g. I do not understand what you expect to be the result of using the Client after explicitly terminating it).

Either way, this PR is not the appropriate venue - please reach out to us at Prospective, or you can open an Issue or Discussion if you have a self-contained, isolated reproduction of a specific issue or behavior you think is broken.