Lint all network sync calls

vronin · July 25, 2023, 2:20pm

Just stumbled on a pretty bad bug. We have an async application. And unfortunately, the DNS resolution in one place was done synchronously by to_socket_addrs.

It all worked well when DNS was resolved fast, and it started to exhibit very unpleasant behavior when DNS began to act up.

BTW. The documentation is quite clear: "Note that this function may block the current thread while resolution is performed.". However, it took a while to figure out what was going on.

I am worried that

It's too easy to introduce in another place a call to_socket_addrs
There could be other sync network calls that I should be aware of.

So, the question is. Do you know any tools or configurations to check for things like that? (My guess is I am not the first "lucky" person to stumble on these problems).

Michael-F-Bryan · July 26, 2023, 6:04am

It sounds like you might be looking for Clippy's disallowed_method and disallowed_type lints.

From there, just make sure you run clippy as part of your CI. This is what I include in the GitHub Actions for every project I work on, nowadays:

github.com

wasmerio/wasmer-toml/blob/de8e65b9cc69780668474ae58030f930470da440/.github/workflows/ci.yml#L31-L43


      
          lints:
            name: Linting and Formatting
            runs-on: ubuntu-latest
            steps:
              - uses: actions/checkout@v2
              - name: Rust Cache
                uses: Swatinem/rust-cache@v2
              - name: Setup Rust
                uses: dsherret/rust-toolchain-file@v1
              - name: Check Formatting
                run: cargo fmt --all --verbose --check
              - name: Clippy
                run: cargo clippy --workspace --verbose