ReplicaCache#onCacheUpdated not triggered until you call cache.queryDocs()?

[michielbdejong]

ReplicaCache#onCacheUpdated not triggered until you call cache.queryDocs()?

[sgwilym]

Hi @michielbdejong. The goal of ReplicaCache is to provide a synchronous API to the (asynchronous) Replica, in order to be easily used by certain libraries or frameworks. It does this by watching for events from Replica, and seeing if they contain any documents which have been queried for previously. If a document satisfies this criteria, it adds it to an in-memory cache of documents.

The reason the page is rendering before any data is available is because ReplicaCache must synchronously return a result when it is queried.

1. On the first call, it does not have anything its cache, so it returns an empty result.
2. Then In the background it works to (asynchronously) retrieve the result, and fires an update when it has it.
3. This result is then added to ReplicaCache's in-memory cache of documents, so that it can be retrieved synchronously thereafter.

In short, the reason you do not see any results until you call cache.queryDocs is because the ReplicaCache does not know what you are interested in until you do.

[michielbdejong]

This is not a blocker for me, I can work around it now that I know about it, but it felt quirky so I'm simply curious why this works this way.

And thanks for this awesome project btw!

[michielbdejong]

Thanks, that makes a lot of sense now!