CosmosDBMongoTrigger should support more options (as per CosmosTrigger)

[asos-martinsmith]

I would expect to see

• StartFromBeginning/StartFromTime attributes
• LeaseContainerPrefix
• PreferredLocations

When using function apps with the CosmosTrigger I regularly have a requirement to just process changes from some specific time.

The GetChangeStreamTokens command supports a startAtOperationTime parameter so the first two should be simple to implement.

Ability to specify a StartFromTime is useful for numerous cases - one such use case is restoring a database to a point in time and then using the change feed process to upsert changes since the point in time of the restore in order to get an up-to-date copy.

The ability to set a new LeaseContainerPrefix in conjunction with StartFromTime allows re-processing to start again from a specific point and is useful for recovering after errors. For the Mongo API case this may also be useful for regenerating leases if (due to partition splits or merges) the leases calculated at startup get very out of synch with the physical partitions that exist.

Also it appears as though the leases collection can't currently be used to hold leases from multiple collections.

IMO the implementation for the NoSQL API change feed processor should have been followed more closely (in that the documents need a prefix that uniquely identifies the account/database/collection/lease prefix it relates to rather than just catering for one).