Provide writing of a single object to the metabase

[cthulhu-rider]

Is your feature request related to a problem? Please describe.

I can't add single object (e.g. stored in file) to the metabase using CLI. The only thing I can do is to re-sync the metabase with the blobstor on neofs-node startup.

Describe the solution you'd like

$ neofs-lens meta write --obj $OBJ_PATH --path $META_DST
Object has been successfully written to the metabase.

Describe alternatives you've considered

Not yet.

Additional context

I tried to push an object into a node by writing it into the node's FSTree. That wasn't enough since I also needed to add a record to the metabase. I could also turn any shard to degraded mode, but that wasn't an option in my case. So the only thing I could do is to restart storage node with metabase re-sync.

[carpawell]

How about a new RPC to the control service? It could check the correctness of the object (marshaling, required fields check, etc) and put it according to Storage Engine rules (correct shard, correct indexing, correct notification/lock/removal flows). No need to perform more than one action (put to FTTree (or blobovniczas?), put to meta), and no need to think about any internal object relations.

Looks weird but anyway we already allow dropping any object if you control the node despite any policy/logic/other thoughts.

[carpawell]

And, moreover, that CLI has been called "lens" for some reason.

[cthulhu-rider]

And, moreover, that CLI has been called "lens" for some reason.

lens name does not block the application to perform writing operations. The name was chosen as pretty short and laconic, but not to limit functionality.

[cthulhu-rider]

How about a new RPC to the control service?

@carpawell Control service LGTM to prevent application shutdown (its process locks all metabases). What about "offline" cases? I think simple read-write command can also be useful.

[carpawell]

lens name does not block the application to perform writing operations

Well, i was not thinking about naming only: the general purpose for that CLI looked as read-only for me but i could be wrong.

What about "offline" cases?

If we are possible to face such cases, neofs-lens meta write could be useful of course. But generally speaking, do not know when it could happen.