https://github.com/cdaringe/swaperooni

Hot swap a child process in response to user provided events with signal proxying
https://github.com/cdaringe/swaperooni

docker hot-reload init init-system

Last synced: 8 months ago
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Hot swap a child process in response to user provided events with signal proxying

• Host: GitHub
• URL: https://github.com/cdaringe/swaperooni
• Owner: cdaringe
• Created: 2023-12-31T04:16:10.000Z (about 2 years ago)
• Default Branch: main
• Last Pushed: 2024-08-01T03:22:01.000Z (over 1 year ago)
• Last Synced: 2024-10-31T07:48:27.083Z (over 1 year ago)
• Topics: docker, hot-reload, init, init-system
• Language: Rust
• Homepage:
• Size: 1.09 MB
• Stars: 2
• Watchers: 3
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: readme.md

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README

          
# swaperooni

Hot-reload a child process without tearing down the parent PID. Proxies signals

into the child process.



[![Rust](https://github.com/cdaringe/swaperooni/actions/workflows/rust.yml/badge.svg)](https://github.com/cdaringe/swaperooni/actions/workflows/rust.yml)

- if the child exits, `swaperooni` exits with the same code.

- if a swap request is issued, the child is torn down, and new child brought up.

Supports two hot-reload request options:

- `ipc` - send a newline delimited command string from the child to the swaperooni socket. See [examples/ipc_bash_hopscotch/main.sh](examples/ipc_bash_hopscotch/main.sh).

- `poll` - monitor the `mtime` of a file. on change, re-execute it.

**swaperooni is not a supervisor.** `swaperooni` is similar to [tini](https://github.com/krallin/tini).

## Why

Because you can. Generally, avoid using this, and use a supervisor/orchestrator.

You may have cases where swapping child PIDs is more desirable (e.g. oddball docker/k8s environments).

## How

See the examples.

- `SOCKET_PATH=demo.sock cargo run ipc -- bash examples/ipc_bash_hopscotch/a.sh`

  - program `a` runs momentarily, then requests to be swapped for program `b`. `b` requests program `c`, and `c` gracefully exits.

- `SOCKET_PATH=demo.sock cargo run ipc -- node examples/ipc_node_counter/index.mjs 0`

  - run a node.js process. the process asks swaperooni to run itself again, but with different params (a counter)

- `cargo run poll --poll-interval-ms=1000 -- examples/poll_countdown/main.sh 5`

  - poll for entrypoint change and re-run it.

## Performance

Well, it is <1MB and does nothing _most_ of the time.