fetchFlagSettings doesnt update in memory flags or emit any events about js-client-sdk

[apucacao]

Hi @maxholman, sorry for the delay here. This looks like a bug. I've added it to the list, and we should have a fix out shortly. I'll let you know once we've released a fix.

[apucacao]

Hi @maxholman ,

Thanks for reaching out.

We only connect to the stream for updates if you subscribe to the change event. When updates from the stream arrive — and you bootstrapped using localStorage — the client will update that cache to ensure that on the next refresh localStorage contains the last known settings from the server.

Does that make sense?

Best,
Alexis

[maxholman]

Thanks @apucacao - gotcha.

How can I get my app to react to these changes that are not streamed in, and are also not in localStorage at bootstrap time?

Calling getFlags on ready returns the in-memory state which can be stale (not the same as localStorage or the server state)

It seems like the purpose of the change event is to notify subscribers simply that flags have changed.

Should it not be emitted both when changes arrive through the stream (as you mentioned) but also when fetchFlagSettings updates localStorage? They are both "changes"

[apucacao]

Ah, I see. Do you subscribe to change in your application? If you do, then you should get the latest settings from the server upon connecting to the stream. (We fetch once on connect.) Am I understanding correctly? Is that not working?

If you don't subscribe to change, then we have no way of letting you know that the latest settings we received were different from those you got from calling allFlags on ready. And to avoid discrepancies between calls to variation and the initial state you got on ready, we don't update the in-memory state.

[maxholman]

My change subscription is working as expected for when something comes across the stream.

After some more digging, it looks like stream.connect callback isn't firing for me on connect, but only when some inbound event arrives.

I'll see if I can troubleshoot more from here, but essentially this means that the fetchFlagSettings and updateSettings doesn't get called when the stream connects and therefore no change event occurs, causing the issue as described.

[maxholman]

Looks like there are no ping events occuring on the stream until I make a change on launchdarkly.com - so the onPing callback which is set via stream.connect() and updates the settings, doesnt fire when the stream connects.

[apucacao]

Right that makes sense. I'm wondering how your original scenario can become a problem though: if the in-memory state — which you got from allFlags on ready — becomes stale, then since you're connected to the stream, that should rectify itself rather quickly?

[maxholman]

This seems to be happening:

1. Client is initialised
2. flags is populated from localStorage
3. fetchFlagSettings called to get latest response from server
4. (async) localStorage is updated with latest response (no events are emitted and flags may be stale)
5. I register a change event listener
6. (async) Stream connects automatically due to event listener attach

At this point localStorage has the latest response, but flags is stale and reflects the state of localStorage on load.

I was expecting either:

a) Step 4 would emit a change event and update the in-memory flags, or
b) Step 6 should result in an initial ping event being received which then calls the stream.connect callback -> fetchFlagSettings -> updateSettings and finally emit('change')

Unfortunately neither of those happen so I am unable to get the absolute latest flags on load.

EDIT:

you should get the latest settings from the server upon connecting to the stream. (We fetch once on connect.)

I think this seems to be real issue, my client doesn't fetch on connect because it doesn't receive a ping.

[apucacao]

Hi @maxholman — we should be sending the initial ping even again. Have you tried this recently?

[maxholman]

Hi @apucacao - Just tried this again, still not seeing an initial ping and I still have the same issue I'm afraid