Unreliable storage subscriptions

[clangenb]

I am subscribing to storage double-map values via polkadot-js-api. In some cases, there seems to be no subscription updates, depending on the operation performed in the pallet.

• i get updates when double_map::remove_prefix is used, triggered by scheduler pallet
• i seem to consistently not get updates when double_map::insert is used triggered by an extrinsic

I could observe this so far for the ParticipantIndex

[brenzi]

I believe double map can't be subscribed with only the primary prefix. You can only subscribe to specific values, so insert doesn't trigger as it doesn't affect an existing value (only mutate would)
I think this behavior you describe works as designed

[brenzi]

hmm, but the change from None to Some participant index should trigger, actually

[clangenb]

I have asked in substrate-technical, let's see if an answer comes. We are not too reliant on this anyhow. I also doubt if a subscription makes sens in some cases where we only occasionally get updates. It might be better to fetch the updates, when necessary.

[brenzi]

well, a reactive design relies on subscriptions, not polling. So I do prefer the current model