ra-multiplex  

Multiplex server for rust-analyzer allows multiple LSP clients (editor windows) to share a single rust-analyzer instance per cargo workspace.

How it works

The project two binaries, ra-multiplex which is a thin wrapper that acts like rust-analyzer but only connects to a TCP socket at 127.0.0.1:27631 and pipes stdin and stdout to it.

The second binary ra-multiplex-server will listen on :27631 and spawn the rust-analyzer server, but depending on the working directory the ra-multiplex client was spawned from it might reuse an already spawned rust-analyzer instance.

Because this is not really a supported mode of operation by either LSP or rust-analyzer itself the ra-multiplex-server caches some messages and modifies request/response ids in order to make most of LSP work.

The project is still work in progress so it'll probably block some LSP functionality or break randomly or something, but it was tested and works well enough with coc-rust-analyzer client in neovim, it should theoretically work with other clients and editors too. If you have problems you're welcome to open issues on this repository.

How to use

Build the project with

$ cargo build --release

Run the ra-multiplex-server, make sure that rust-analyzer is in your PATH, with optional logging.

$ which rust-analyzer
/home/user/.cargo/bin/rust-analyzer
$ RUST_LOG=info target/release/ra-multiplex-server

Configure your editor to use ra-multiplex as rust-analyzer, for example for CoC in neovim edit ~/.config/nvim/coc-settings.json, add:

{
    "rust-analyzer.serverPath": "/path/to/ra-multiplex",
}

Configuration

Configuration is stored in a TOML file in your system's default configuration directory, for example ~/.config/ra-multiplex/config.toml. If you're not sure where that is on your system starting either ra-multiplex or ra-multiplex-server without a config file present will print a warning with the expected path.

Note that the configuration file is likely not necessary and ra-multiplex should be usable with all defaults.

Example configuration file:

# this is an example configuration file for ra-multiplex
#
# all configuration options here are set to their default value they'll have if
# they're not present in the file or if the config file is missing completely.

# time in seconds after which a rust-analyzer server instance with no clients
# connected will get killed to save system memory.
#
# you can set this option to `false` for infinite timeout
instance_timeout = 300 # after 5 minutes

# time in seconds how long to wait between the gc task checks for disconnected
# clients and possibly starts a timeout task. the value must be at least 1.
gc_interval = 10 # every 10 seconds

# ip address on which ra-multiplex-server listens
#
# the default "127.0.0.1" only allows connections from localhost which is
# preferred since the protocol doesn't worry about security.
# ra-multiplex-server expects the filesystem structure and contents to be the
# same on its machine as on ra-multiplex's machine. if you want to run the
# server on a different computer it's theoretically possible but at least for
# now you're on your own.
listen = "127.0.0.1" # localhost

# tcp port number on which ra-multiplex-server listens
#
# ports below 1024 will typically require root privileges and should be
# avoided, this only needs to change if another application happens to collide
# with ra-multiplex.
port = 27631 # random unprivileged port

# default log filters
#
# RUST_LOG env variable overrides this option, both use the same syntax which
# is documented in the `env_logger` documentation here:
# <https://docs.rs/env_logger/0.9.0/env_logger/index.html#enabling-logging>
log_filters = "info"