Feature Request: include source tablet alias in FullStatus RPC response

[timvaillancourt]

Feature Description

This issue requests that replicationdatapb.Status includes the tablet alias of a tablet's current primary replication source

Today it appears only the source_host and source_port of the PRIMARY are included in this response

The reason this is useful is VTOrc is having to use the source_host+source_port in sqlite3 queries to find the record of a replica's source, and these fields are unindexed. I considered just-indexing those 2 x fields (I think these fields used to be indexed), but using the tablet alias of the primary would use the Primary-Key and avoid another index, which I prefer. Also this information logically makes sense to be in this output (IMHO)

I propose this new field is topodata.TabletAlias source_alias = 26; or string source_alias = 26;. primary_alias would work too

cc @GuptaManan100 for feedback

Use Case(s)

VTOrc + any future use cases that benefit from an easy lookup of "what source alias is X tablet is replicating from?"

[timvaillancourt]

Updated to use term "source" only, not "primary", because those aren't always the same thing

[timvaillancourt]

Updated to use term "source" only, not "primary", because those aren't always the same thing

After more thought, perhaps both source_alias and primary_alias should be added 🤔. This would tell us both the primary and if there is any replication chaining, incorrect primary configured, etc

[GuptaManan100]

primary_alias is something that can be read from the topo server, so I don't think we need that. Source alias is something that I agree can be useful 👍

[timvaillancourt]

primary_alias is something that can be read from the topo server, so I don't think we need that. Source alias is something that I agree can be useful 👍

@GuptaManan100 just source_alias sounds good 👍

Any preference on storing this as topodata.TabletAlias vs string? I think I prefer the later

[GuptaManan100]

Latter is good!