How to Avoid Recompiling protobuf-src with System-installed Protobuf in libp2p?

[vinay10949]

Hi everyone,

I'm working on project that includes libp2p (version 0.54.1) in a workspace. I’ve noticed that during the build process, protobuf-src is being compiled from source, which significantly increases the build time. This is happening despite having Protobuf installed system-wide and setting the PROTOC environment variable to point to the system's protoc binary.

Setup Details:

• Rust version: 1.71
• libp2p version: 0.54.1
• OS: Ubuntu 22.04
• Installed Protobuf:
  • sudo apt install protobuf-compiler libprotobuf-dev
  • protoc --version outputs libprotoc 3.21.9

Configuration:

I have set the PROTOC environment variable:

export PROTOC=/usr/bin/protoc

Problem:

Despite having Protobuf installed system-wide, the protobuf-src crate still compiles from source during the cargo build process. This has been significantly increasing my build time. I’ve checked the libp2p documentation but couldn’t find any specific flags or features that disable Protobuf-related functionality.

What I’ve Tried:

• Setting the PROTOC environment variable: This doesn't stop protobuf-src from being compiled.
• Disabling Protobuf in libp2p features: There are no clear flags to disable Protobuf usage in libp2p that I could find.
• Precompiling .proto files: I considered precompiling .proto files and committing the generated Rust code, but I’m unsure how to integrate this cleanly with libp2p.

Question:

Has anyone encountered this issue or have suggestions on how to force libp2p to use the system-installed Protobuf binaries, or avoid compiling protobuf-src entirely? If libp2p or one of its dependencies (like prost-build) is causing this, is there a workaround?

Impact:

This is especially problematic in CI environments, where build times are critical. Any tips to reduce build time would be greatly appreciated!

[drHuangMHT]

I don't see protobuf-src or protobuf-sys in our dependency tree(via cargo tree -i <package name>). And we don't use prost or prost-build in most packages we publish, except an example where we showcase how to collect metrics. Can you check your dependency tree using cargo tree to see the dependents of protobuf-src(you will need -i flag to invert the tree)?