New metric: histogram for image push duration

[tvdfly]

Add a new metric that records how long we spend pushing the docker image to our registry during fly deploy. This will help us understand regional variations and overall performance of this action and inform registry performance work.

Potential attributes:

• builder type: local, remote
• builder region: for local use the closest region (e.g. where a request hits the fly-proxy edge), for remote use the remote builder machine's region

[ziscky]

Hey @tvdfly I would love to work on this. I can see some metrics being recorded here
Any pointers ?

[tvdfly]

Yep, the metrics.StartTiming() call will likely work here. We use it in a handful of places in the codebase that are good references: https://github.com/search?q=repo%3Asuperfly%2Fflyctl%20metrics.StartTiming&type=code

[utkarsh-shrivastav77]

Hi can I work on this issue