Enhance builder info

[sajjaphani]

This PR handles to add/update additional information in the following API:

Existing package metadata APIs have been incorporated to return the size of the hart file. Below is an example:
https://bldr.habitat.sh/v1/depot/channels/core/stable/pkgs/7zip/latest?target=x86_64-linux

The APIs returns the below additional property JSON response:
{ ...., size: 1569, .... }

Change the channels API to include the promotion timestamp: /depot/pkgs/{origin}/{pkg}/{version}/{release}/channels
The API returns the below JSON response:
[ { name: 'unstable', created_at: '2022-01-05T11:09:34.245636', promoted_at: '2022-01-05T11:09:34.245636' }, { name: 'foo', created_at: '2022-01-05T11:09:37.385983', promoted_at: '2022-01-05T11:09:37.385983' } ]

Note: UI changes will be handled in a separate PR.

[mwrock]

Any reason why you would not add the size to do_get_package adding:

pkg_json["size"] = json!(req_state(&req).packages.size_of(&ident, target).await);

Note that the above won'r compile because size_of returns a Result but I'm just trying to convey the gist of how it might look.

This would eliminate the redundant code in the extra API and also cache the size along with the rest of the metadata in memcache.

[sajjaphani]

Any reason why you would not add the size to do_get_package adding:

pkg_json["size"] = json!(req_state(&req).packages.size_of(&ident, target).await);

Note that the above won'r compile because size_of returns a Result but I'm just trying to convey the gist of how it might look.

This would eliminate the redundant code in the extra API and also cache the size along with the rest of the metadata in memcache.

We could do that, but it requires us to change the signature of do_get_package and all the other functions that depend on this.

We also need to check and invalidate the cache entry for package metadata, where the size attribute is missing.

[mwrock]

How would you need to change the signature? It seems like you just need ident and target which do_get_package has. At least by the point in the function where it is ready to fetch the metadata it has a target and fully qualified ident.

Regarding cache invalidation, we could restart the memcache services after the release to clear out the cache.

[sajjaphani]

We need to change function do_get_package to async, and then handle calling this function async.

Restarting will eventually erases everything including sessions. Restarting Memcached service should also happen on on-prem end. Can we automate this?

[mwrock]

This looks good! I just think we need to remove the extra Size counter.

[mwrock]

Per our offline conversation, it does look like the on-prem upgrade process involves a supervisor restart: https://github.com/habitat-sh/on-prem-builder/blob/main/on-prem-docs/upgrading.md

[sajjaphani]

This looks good! I just think we need to remove the extra Size counter.

SizeRequest is update on call to size_of in s3.rs (AWS s3 API call), I think it may be good idea to have this metric.

[mwrock]

I was concerned the size counter would mirror the GetPackage counter but it looks like GetPackage will get called on every call to do_get_package but the size counter would only be called if the json was not cached. Sorry for the confusion. Feel free to add it back. Can you also squash the commits?

[sajjaphani]

Squashed all the commits and should be good now! @mwrock Can you take a quick look at this?