Ring backend in mistral.rs

Mistral.rs provides a TCP-based ring backend for distributed tensor-parallel inference. This backend is enabled by compiling with the ring feature and implements collective operations over a ring topology using TCP sockets.

Prerequisites

Build with the ring feature enable, in addition to any others:
```
cargo build --release --features ring
```
Ensure the specified TCP ports are open and reachable between processes.
The world_size must be a power of 2 (2, 4, 8, 16, etc.) for correct operation.

Configuration

Create one JSON configuration file per process with the following fields:

Field	Type	Description
`master_ip`	string	Optional. IP address for master node.
`master_port`	integer	Optional. Port for master node.
`port`	integer	Local port to bind for incoming connections from the left neighbor.
`right_port`	integer	Port on which the right neighbor is listening (used to connect outgoing to the right).
`right_ip`	string	Optional. IP address of the right neighbor (defaults to `0.0.0.0`).
`rank`	integer	Rank of this process in `[0..world_size)`.
`world_size`	integer	Total number of processes in the ring. Must be a power of 2 (e.g., 2, 4, 8, 16, etc.).

This address and port should form a ring topology for each of the nodes. For example, the last node should point to the first node as its right neighbor.

Although all processes participate in collective communication, Rank 0 acts as the master node. For example, interactive mode or the server runs on Rank 0, while other ranks act as background workers.

Example ring topology:

+---------+         +---------+
| Rank 0  | ----->  | Rank 1  |
| IP: A   |         | IP: B   |
| Port: X |         | Port: Y |
+----+----+         +----+----+
     ^                   |
     |                   v
+----+----+         +----+----+
| Rank 3  | <-----  | Rank 2  |
| IP: D   |         | IP: C   |
| Port: W |         | Port: Z |
+---------+         +---------+

Each node connects to its right neighbor by IP and port, and the last node wraps around to the first.

Example for two processes:

ring_0.json:

{
  "master_ip": "0.0.0.0",
  "master_port": 1234,
  "port": 12345,
  "right_port": 12346,
  "rank": 0,
  "world_size": 2
}

ring_0.json:

{
  "master_ip": "0.0.0.0",
  "master_port": 1234,
  "port": 12346,
  "right_port": 12345,
  "rank": 1,
  "world_size": 2
}

Multi-Machine Example

To run on different machines, update the right_ip field in each config to the actual IP address of the neighbor process. For example, if you have two machines with IPs 192.168.1.10 and 192.168.1.11:

ring_0.json on Machine A (192.168.1.10):

{
  "port": 12345,
  "right_port": 12346,
  "right_ip": "192.168.1.11",
  "rank": 0,
  "world_size": 2
}

ring_1.json on Machine B (192.168.1.11):

{
  "port": 12346,
  "right_port": 12345,
  "right_ip": "192.168.1.10",
  "rank": 1,
  "world_size": 2
}

Make sure that the specified ports are open and that each machine can reach the other via TCP on those ports.

Usage

Set the RING_CONFIG environment variable to point to the JSON file for each process, then run your application built with the ring feature:

# Process 0 or computer 0
export RING_CONFIG=path/to/ring_0.json
cargo run --release --features ring -- ...

# Process 1 or computer 1
export RING_CONFIG=path/to/ring_1.json
cargo run --release --features ring -- ...

The ring backend will automatically handle collective communication for tensor-parallel inference.

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mistral.rs Documentation

Ring backend in mistral.rs

Prerequisites

Configuration

Multi-Machine Example

Usage