Embed partial ExecutedActionMetadata in ExecuteOperationMetadata

[roitk]

The ExecutedActionMetadata contains a lot of interesting information about the work that was done, such as the worker the job was run on, timestamps for various execution milestones, and so on. This information is currently only available after the work is complete, in the ActionResult. However, I think some of these things would be useful to look at while the execution is running as well, especially in the context of UI tools that can show the status of ongoing work (e.g. bgd-browser).

Unfortunately, there isn't currently a place to put this in the longrunning Operation that clients get back when waiting for a job. The only metadata field is used by the ExecuteOperationMetadata message, which has a very limited set of fields. So this PR just adds an ExecutedActionMetadata field in ExecuteOperationMetadata.

[peterebden]

I like the idea of this - it seems useful to find out where an action is executing (presumably this can be found out on the server side but this makes it easier to see it on the client).

I'm a little dubious about the Any though. It seems tricky for a client to know how to interpret it - there is prior art with the auxiliary_metadata field, but it seems like that is more likely to be both populated & read by the server side, which probably agrees about what it wants to put in there.
Maybe it will be sufficient to have some de facto options for this?

[roitk]

Maybe it will be sufficient to have some de facto options for this?

Any thoughts on default fields? I'd personally like (at least) the worker name and the various milestones in the ExecutedActionMetadata to show up here, which could be populated as the job passes through those stages.

[peterebden]

Yup, I agree on those. I think ExecutedActionMetadata is fairly close, although I also agree with your points before about where it's not so ideal.
On balance maybe that's a good place to start since it already exists and we don't have to define a new message? So just something like "Servers MAY choose to populate this field with a partially complete ExecutedActionMetadata message" would give a hint on how to interpret the contents.

[roitk]

On balance maybe that's a good place to start since it already exists and we don't have to define a new message? So just something like "Servers MAY choose to populate this field with a partially complete ExecutedActionMetadata message" would give a hint on how to interpret the contents.

I think that's a good compromise. Updated the comment.

[EricBurnett]

This LGTM as well. @sstriker I see you assigned yourself: anything more needed here?

[sstriker]

This LGTM as well. @sstriker I see you assigned yourself: anything more needed here?

No, we're good to go.