add rust-toolchain file and bash script to update Docker, Travis and rustup-toolchain files with same version

[jxs]

closes linkerd/2482

Travis file is using the stable version, is there a special reason or can just be updated to the matching versions from Dockerfile and rustup-toolchain?

thanks 🙂

[hawkw]

This seems like it should probably have a #!/bin/bash shebang?

[jxs]

yes totally forgot it 😅

[hawkw]

Hey @jxs, thanks a lot!

Travis file is using the stable version, is there a special reason or can just be updated to the matching versions from Dockerfile and rustup-toolchain?

It's probably best for Travis to be using the same version as the Dockerfile , so I think you made the right call.

This change looks good to me, but I suspect that @olix0r will have opinions about bash scripts, so I'd like to get his approval before merging it.

[hawkw]

Can we add a comment here that this should be kept in sync with the rust-toolchain file and the Dockerfile? It could say something like "rather than updating this manually, run update-rust-version.sh...

[jxs]

added :) also added to the Dockerfile

[olix0r]

It's probably best for Travis to be using the same version as the Dockerfile , so I think you made the right call.

I think I disagree with this... I'd rather that we test and publish from the latest stable so that we discover issues eagerly, and also benefit from fixes. There may be a point in the future we we'd prefer to have more process around version updates, but it feels like a step backwards now.

[jxs]

@olix0r so, want me to update the bash script and remove the travis.yml file update?

[olix0r]

1.33.0 is out now ;)

[olix0r]

@jxs Yeah, let's do that for now, and we can add that back later if it seems important.

[hawkw]

It's probably best for Travis to be using the same version as the Dockerfile , so I think you made the right call.

I think I disagree with this... I'd rather that we test and publish from the latest stable so that we discover issues eagerly, and also benefit from fixes. There may be a point in the future we we'd prefer to have more process around version updates, but it feels like a step backwards now.

@olix0r What about having a travis build against the latest stable and one against the version built in the Dockerfile? We could use the latest stable build to be aware of upcoming breaking changes, and the pinned version build to verify that the dockerfile will actually build a working proxy image.

[olix0r]

@hawkw and I discussed this in realtime... I'll summarize:

The problem we care most about addressing is when a new developer is (1) running a very old rust version, so they cannot compile a recent proxy or (2, more likely) the user has a nightly that supports features we don't accept in our build.

For this case, we want a rust-toolchain to force users in case (1) to a newer minimum rust version and we want to force users in case (2) to use a stable rust.

To this end, I think it's okay if we continue to use stable in CI so that release artifacts are published from the most-recent Rust stable. We don't expect that newer rusts in CI will break existing code, so this is okay.

Then, we can manually bump rust-toolchain versions with the script when we take a new minimum version for development.

In summary: let's leave the travis.yml as it was (on master).

[jxs]

thanks for the feedback loop
updated!

[olix0r]

thank you @jxs !