Progressive release stops showing metrics when set to 100% target

[Bret Barker]

When using a progressive release [1], if you have been moving your release along 20%, 50%, 80% and watching the real-time metrics as users are refreshed with `snapcraft status`, all is well. However, as soon as you punch it to 100% it becomes non-progressive and you lose the ability to see the metrics.

Expected behavior: continue to show the metrics until 100% has been reached.

1. https://forum.snapcraft.io/t/progressive-releases/20913

[Sergio Schvezov (sergiusens)]

We agreed in the past the 100% would be equivalent to release. We can look at this.

[Maximiliano Bertacchini (maxiberta)]

Some background from the online docs: "Releasing a revision with a progressive percentage of 100 and releasing it without a progressive percentage are not equivalent. This behaviour is slightly surprising, but it’s a consequence of the fact that not all devices can ever get a progressive revision, since a device may only participate in a progressive release if we have a way to consistently identify it." [0]

Based on that, releases with progressive percentage of 100 are being implicitly transformed non-progressive (ie. nullified) to avoid that unintuitive situation.

Maybe we could make the internal logic smarter in that case by storing `100` explicitly instead of `null`, treating both `null` and `100` as non-progressive releases, but with the addition that those with `100` would still return progress stats.

[0] https://dashboard.snapcraft.io/docs/api/snap.html#progressive-releases

[Przemysław Suliga (suligap)]

Hi Sergio.

If we started to return "progressive"."current-percentage" for all returned channel-maps in the API responses (progressive or not) would snapcraft be backwards compatible with that change?

JSON schema wise it's legal now. Both scenarios would be possible:

1) Progressive.current-percentage being non-null, and progressive.percentage and progressive.paused being null -- this would indicate a non-progressive or 100% progressive release.

2) All progressive.current-percentage, progressive.percentage and progressive.paused being non null -- this is already the case for active progressive releases.

[Przemysław Suliga (suligap)]

Change that adds progressive.current-percentage (the field is non null now if there are any devices that reported this revision in a relevant channel) to all releases returned from https://dashboard.staging.snapcraft.io/docs/v2/en/snaps.html#snap-channel-map is deployed to staging.

[Przemysław Suliga (suligap)]

The above change is now deployed to production.

[Przemysław Suliga (suligap)]

SCA change released to production on 2021-06-18