memoryruins / ra-multiplex

share one rust-analyzer server instance between multiple LSP clients to save resources

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 has 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 through it.

The second binary ra-multiplex-server will listen on :27631 and spawn the rust-analyzer server, depending on the working directory the ra-multiplex client was spawned from it can reuse an already spawned rust-analyzer instance. It detects workspace root as the furthermost ancestor directory containing a Cargo.toml file. If the automatic workspace detection fails or if you're not using rust-analyzer as a server you can create a marker file .ra-multiplex-workspace-root in the directory you want to use as a workspace root, the first ancestor directory containing this file will be used.

Because neither LSP nor rust-analyzer itself support multiple clients per server ra-multiplex-server caches the handshake messages and modifies IDs of requests & responses to track which response belongs to which client. Because not all messages can be tracked this way it drops some, notably it drops any requests from the server, this appears to not be a problem with coc-rust-analyzer in neovim but YMMV.

If you have any 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:

$ which rust-analyzer
/home/user/.cargo/bin/rust-analyzer
$ 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 and port 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.
#
# ports below 1024 will typically require root privileges and should be
# avoided, the default was picked at random, this only needs to change if
# another application happens to collide with ra-multiplex.
listen = ["127.0.0.1", 27631] # localhost & some random unprivileged port

# ip address and port to which ra-multiplex will connect to
#
# this should usually just match the value of `listen`
connect = ["127.0.0.1", 27631] # same as `listen`

# 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"

# whether `ra-multiplex` client should process any arguments
#
# by default this is set to `false`, in this case `ra-multiplex` can be used as
# a drop-in replacement for `rust-analyzer` but no other server. for more
# information see the "Other LSP servers" section of the README.
arg_parsing = false

Other LSP servers

Using other servers requires a bit more setup. First enable the arg_parsing option in ~/.config/ra-multiplex/config.toml:

arg_parsing = true

Then for each server you want to use (including rust-analyzer) create a wrapper script that passes the right arguments like in the following example. We're using the standard cargo install directories so update the examples for your needs.

Wrapper script rust-analyzer-proxy:

#!/bin/sh
exec ~/.cargo/bin/ra-multiplex --server ~/.cargo/bin/rust-analyzer -- $@

Wrapper script clangd-proxy:

#!/bin/sh
exec ~/.cargo/bin/ra-multiplex --server /usr/bin/clangd -- --log=error $@

Configure LSP client to use the wrapper script, for CoC ~/.config/nvim/coc-settings.json:

{
    "rust-analyzer.serverPath": "/home/user/.cargo/bin/rust-analyzer-proxy",
    "clangd.path": "/home/user/.cargo/bin/clangd-proxy"
}