Make wasm runtime cache size configurable

[librelois]

Polkadot companion: paritytech/polkadot#4466

What does it do?

Makes configurable the maximum number of different runtime versions that can be kept in cache.

What important points should reviewers know?

Before this PR, the cache had an array of 2 VersionedRuntime, with a custom implementation of a "Last Recent Usage" cache strategy which consisted in swapping a runtime in 1st position when it was used.
This custom implementation is not compliant if the cache contains more than 2 elements, then a full LRU algorithm is needed, that's why I use the lru crate which does this very well.

skip check-dependent-cumulus

[crystalin]

@bkchr sorry to ping you, but not sure who can do a review of this one.

[bkchr]

Sorry for the late review. I left some comments

[librelois]

Sorry for the late review. I left some comments

Thanks for the review, I applied your feedback

[bkchr]

2 nitpicks, otherwise seems to look good.

[bkchr]

It also doesn't compile.

[librelois]

It also doesn't compile.

Fixed

[bkchr]

It also doesn't compile.

Fixed

There are still warnings. Cargo fmt is also not happy.

[librelois]

There are still warnings. Cargo fmt is also not happy.

Sorry about that, it should be fine now.

[bkchr]

There are still warnings. Cargo fmt is also not happy.

Sorry about that, it should be fine now.

I need to inform you, that CI is still not happy 🙈

[librelois]

@bkchr It seems that the CI is green now. There is no need of companion PR on polkadot or cumulus.

[bkchr]

@librelois for polkadot we need a companion. See the error. Cumulus should be fine and can be ignored.

[librelois]

@librelois for polkadot we need a companion. See the error. Cumulus should be fine and can be ignored.

Can one of you take care of the polkadot companion PR or should I do it myself? And in this last case, how to proceed? (I have never made a "polkadot companion" PR).

[arkpar]

The docs should probably specify that --runtime-cache-size is capped at 255. Btw what happens if the users sets --runtime-cache-size=1000?

[librelois]

The docs should probably specify that --runtime-cache-size is capped at 255. Btw what happens if the users sets --runtime-cache-size=1000?

runtime_cache_size is of type u8 so it is structopt that will fail to parse the value and will print an error to the user.

[bkchr]

@librelois for polkadot we need a companion. See the error. Cumulus should be fine and can be ignored.

Can one of you take care of the polkadot companion PR or should I do it myself? And in this last case, how to proceed? (I have never made a "polkadot companion" PR).

You need to create a pr to polkadot that fixes the compilation with your branch. Then you need to mention it as polkadot companion: link in the description of this pr.

[librelois]

You need to create a pr to polkadot that fixes the compilation with your branch. Then you need to mention it as polkadot companion: link in the description of this pr.

It's done

[bkchr]

@librelois can you please merge master into this branch? 🙈

[librelois]

@bkchr Looking at the log of the gitlab-check-dependent-polkadot job, there seems to be a problem in your CI:

$ ./pipeline-scripts/check_dependent_project.sh paritytech substrate --substrate "$DEPENDENT_REPO" "$GITHUB_PR_TOKEN" "$CARGO_UPDATE_CRATES"
check_dependent_project
========================
This check ensures that this project's dependents do not suffer downstream breakages from new code
changes.
From https://gitlab.parity.io/parity/substrate
 * branch              master     -> FETCH_HEAD
fatal: It seems that there is already a rebase-apply directory, and
I wonder if you are in the middle of another rebase.  If that is the
case, please try
	git rebase (--continue | --abort | --skip)
If that is not the case, please
	rm -fr ".git/rebase-apply"
and run me again.  I am stopping in case you still have something
valuable there.

[bkchr]

bot merge

[paritytech-processbot]

Error: Github API says "Allow edits from maintainers" is not enabled for paritytech/polkadot#4466. The bot would use that permission to push the lockfile update after merging this PR. Please check https://docs.github.com/en/github/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork.

[librelois]

Please check https://docs.github.com/en/github/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork.

I don't have any checkboxes like "Allow edits from maintainers":

Maybe I need to redo the companion PR from a personal fork instead of the purestake fork.

[FlorianFranzen]

@librelois Would have been nice it that new parameter was also documented in code and that I did not have to read this issue to understand what it is for, e.g. see also the missing rust docs.