Bun, Deno & other Runtimes

Using Bun, Deno and other Runtimes with PM2

PM2 is not limited to Node.js: it has first-class support for Bun and can manage applications running on Deno, Python, Ruby or any other interpreter.

Bun

PM2 supports Bun natively. When Bun is installed, TypeScript files are started with Bun automatically:

# .ts and .tsx files default to the bun interpreter
pm2 start app.ts

To run any application with Bun explicitly, set the interpreter:

pm2 start index.js --interpreter bun

Or in a configuration file:

module.exports = {
  apps: [{
    name: "api",
    script: "./app.ts",
    interpreter: "bun",
    node_args: "--smol"   // flags passed to the bun binary
  }]
}

All the usual PM2 features work with Bun applications: log management, restart strategies, max memory restart, graceful shutdown and monitoring.

Cluster Mode with Bun

Cluster mode follows the runtime of the PM2 daemon itself. To load-balance a Bun application over multiple cores, run PM2 with Bun (Bun >= 1.1.25 is required, as earlier versions lack cluster support):

# stop any daemon started with Node first
pm2 kill

# launch PM2 under the Bun runtime
bunx --bun pm2 start app.ts -i max

The daemon keeps the runtime it was first started with: use pm2 kill before switching between Node and Bun.

Deno

Deno applications run through PM2’s generic interpreter support, in fork mode:

pm2 start app.ts --interpreter="deno" --interpreter-args="run --allow-net"

Or in a configuration file:

module.exports = {
  apps: [{
    name: "deno-api",
    script: "./app.ts",
    interpreter: "deno",
    interpreter_args: "run --allow-net --allow-read"
  }]
}

Note that cluster mode is not available for Deno applications; scale them by starting several processes on different ports behind a reverse proxy.

Other Interpreters

PM2 picks the interpreter from the file extension:

Any other runtime works by setting --interpreter (CLI) or interpreter / interpreter_args (configuration file) explicitly:

pm2 start app.py --interpreter python3
pm2 start ./binary-file   # binaries run directly, no interpreter

Cluster mode is only available for Node.js and Bun applications; every other runtime uses fork mode. See also using transpilers with PM2.