Cosmos Driver: Prime metadata caches at client creation time

[analogrelay]

The Cosmos DB SDK really depends on having full metadata for a container in order to perform operations. Right now, that metadata is lazy-loaded, which means a lot of operations can take a longer amount of time because the cache needs to be populated on the first request. We normally refresh the cache in the background, so it's only this cache priming operation that takes longer.

In order to simplify the clients a bit, and make that behavior clearer to users, let's make DatabaseClient::container_client and CosmosClient::database_client async, and have them perform the cache priming IN the actual creation function.

We're already making these functions async, but this work item track doing the cache priming in those now-async functions.

[FabianMeiswinkel]

IMO also allowing to get teh pk-def from container_client would be good (synchronously) - once we initialized the container async we have it, PK-def is immutable - so we can avoid having to rely on lazy async options in many places

[analogrelay]

I suspect we'd store a full subset of "Immutable" properties on ContainerProperties.

One thing to watch out for though is container re-creation. If the user believes the client is created based on the Container Name, and deletes and recreates the container, what should happen with existing ContainerClient instances? Should they be forced to remain coupled to the original RID mapped to that name (and thus break when the container is deleted)? Should they refresh their metadata?

[FabianMeiswinkel]

That is what i had initially - but removed due to dead code :-)

I don't think we need anything put PK-def - but sure -we can extend for any of the immutabel properties (UniqueKey is also immutable for example)

The colelction delete+recreate enforcement is something I will take care of in the browser - we need to always capture the ecpected CollectionRid in a request header to achieve that. To eventually support renames we would need to add a similar rntbd header for expected id when using rid for addressing