rust-parallel 0.1.12

Run commands in parallel
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# rust-parallel

Run commands in parallel, like a simple rust verision of [GNU Parallel](https://www.gnu.org/software/parallel/).

Just starting - more options to come :)

[![Crates.io][crates-badge]][crates-url]

[crates-badge]: https://img.shields.io/crates/v/rust-parallel.svg
[crates-url]: https://crates.io/crates/rust-parallel

# Goals:
* Use only safe rust.
* Use only asynchronous operations supported by [tokio](https://tokio.rs), do not use any blocking operations.
* Support arbitrarily large number of input lines, avoid `O(number of input lines)` memory usage.  In support of this:
  * [`tokio::sync::Semaphore`](https://docs.rs/tokio/latest/tokio/sync/struct.Semaphore.html) is used carefully to limit the number of commands that can be run, and to limit memory usage while waiting for commands to finish.  Do not spawn tasks for all input lines immediately to limit memory usage.
  * [`awaitgroup::WaitGroup`](https://crates.io/crates/awaitgroup) is used to wait for all async functions to finish.  Internally this is just a counter and uses a constant amount of memory.
* Support running commands on local machine only, not on remote machines.

# Tech Stack:
* [anyhow](https://github.com/dtolnay/anyhow) used for application error handling to propogate and format fatal errors.
* [awaitgroup](https://crates.io/crates/awaitgroup) used to await completion of all async functions.
* [clap](https://docs.rs/clap/latest/clap/) command line argument parser.
* [tokio](https://tokio.rs/) asynchronous runtime for rust.  From tokio this app uses:
  * `async` / `await` functions (aka coroutines)
  * Singleton `CommandLineArgs` instance using [`tokio::sync::OnceCell`](https://docs.rs/tokio/latest/tokio/sync/struct.OnceCell.html).
  * Asynchronous command execution using [`tokio::process::Command`](https://docs.rs/tokio/latest/tokio/process/struct.Command.html)
  * Semaphore
* [tracing](https://docs.rs/tracing/latest/tracing/) used for debug and warning logs.

# Installation:
1. Clone this git repo
2. Build options:
   * `cargo build -v` faster build, slower runtime performance, executable in `target/debug/rust-parallel`
   * `cargo build --release` slower build, faster runtime performance, executable in `target/release/rust-parallel`
3. Below demos assume you have put the `rust-parallel` executable in your `PATH`.

# Usage:
```
$ rust-parallel -h

Run commands in parallel

Usage: rust-parallel [OPTIONS] [INPUTS]...

Arguments:
  [INPUTS]...  Input file or - for stdin.  Defaults to stdin if no inputs are specified

Options:
  -j, --jobs <JOBS>    Maximum number of commands to run in parallel, defauts to num cpus [default: 12]
  -s, --shell-enabled  Use /bin/sh -c shell to run commands
  -h, --help           Print help information
  -V, --version        Print version information
```

# Demos:

Small demo of 5 echo commands:

```
$ cat >./test <<EOL
# input can contain comment lines (starting with #) and blank lines too

echo hi
echo there
echo how
echo are
echo you
EOL

$ cat test | rust-parallel -j5
are
hi
there
how
you
```

Using `awk` to form commands:

```
$ head -100 /usr/share/dict/words| awk '{printf "md5 -s %s\n", $1}' | rust-parallel
MD5 ("Abba") = 5fa1e1f6e07a6fea3f2bb098e90a8de2
MD5 ("abaxial") = ac3a53971d52d9ce3277eadf03f13a5e
MD5 ("abaze") = 0b08c52aa63d947b6a5601ee975bc3a4
MD5 ("abaxile") = 21f5fc27d7d34117596e41d8c001087e
MD5 ("abbacomes") = 76640eb0c929bc97d016731bfbe9a4f8
MD5 ("abbacy") = 08aeac72800adc98d2aba540b6195921
MD5 ("Abbadide") = 7add1d6f008790fa6783bc8798d8c803
MD5 ("abb") = ea01e5fd8e4d8832825acdd20eac5104
```

Using input file.  Multiple inputs can be specified, `-` means stdin:

```
$ cat >./test1 <<EOL
echo hi
echo there
echo how
EOL

$ cat >./test2 <<EOL
echo are
echo you
EOL

$ cat test2 | rust-parallel test1 -
there
how
hi
are
you

```

With debug logs enabled:

```
$ cat test | RUST_LOG=debug rust-parallel
2022-12-07T01:03:25.580138Z DEBUG rust_parallel: begin main
2022-12-07T01:03:25.580847Z DEBUG rust_parallel::command_line_args: command_line_args = CommandLineArgs { jobs: 12, shell_enabled: false, inputs: [] }
2022-12-07T01:03:25.580890Z DEBUG rust_parallel::commands: begin spawn_commands
2022-12-07T01:03:25.580928Z DEBUG rust_parallel::commands: begin process_one_input input = Stdin
2022-12-07T01:03:25.581111Z DEBUG rust_parallel::commands: read line # input can contain comment lines (starting with #) and blank lines too
2022-12-07T01:03:25.581138Z DEBUG rust_parallel::commands: read line
2022-12-07T01:03:25.581151Z DEBUG rust_parallel::commands: read line echo hi
2022-12-07T01:03:25.581197Z DEBUG rust_parallel::commands: read line echo there
2022-12-07T01:03:25.581225Z DEBUG rust_parallel::commands: read line echo how
2022-12-07T01:03:25.581247Z DEBUG rust_parallel::commands: read line echo are
2022-12-07T01:03:25.581273Z DEBUG rust_parallel::commands: read line echo you
2022-12-07T01:03:25.581310Z DEBUG rust_parallel::commands: begin run command = CommandInvocation { _input: Stdin, _line_number: 3, command: "echo hi", shell_enabled: false, _worker: WaitGroup { count: 5 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 7 } }, permits: 1 } }
2022-12-07T01:03:25.581315Z DEBUG rust_parallel::commands: begin run command = CommandInvocation { _input: Stdin, _line_number: 4, command: "echo there", shell_enabled: false, _worker: WaitGroup { count: 5 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 7 } }, permits: 1 } }
2022-12-07T01:03:25.581355Z DEBUG rust_parallel::commands: begin run command = CommandInvocation { _input: Stdin, _line_number: 6, command: "echo are", shell_enabled: false, _worker: WaitGroup { count: 5 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 7 } }, permits: 1 } }
2022-12-07T01:03:25.581365Z DEBUG rust_parallel::commands: end process_one_input input = Stdin
2022-12-07T01:03:25.581380Z DEBUG rust_parallel::commands: begin run command = CommandInvocation { _input: Stdin, _line_number: 7, command: "echo you", shell_enabled: false, _worker: WaitGroup { count: 5 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 7 } }, permits: 1 } }
2022-12-07T01:03:25.581344Z DEBUG rust_parallel::commands: begin run command = CommandInvocation { _input: Stdin, _line_number: 5, command: "echo how", shell_enabled: false, _worker: WaitGroup { count: 5 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 7 } }, permits: 1 } }
2022-12-07T01:03:25.581456Z DEBUG rust_parallel::commands: end spawn_commands
2022-12-07T01:03:25.581479Z DEBUG rust_parallel: before wait_group.wait wait_group = WaitGroup { count: 5 }
2022-12-07T01:03:25.588049Z DEBUG rust_parallel::commands: got command status = exit status: 0
you
2022-12-07T01:03:25.588166Z DEBUG rust_parallel::commands: end run command = CommandInvocation { _input: Stdin, _line_number: 7, command: "echo you", shell_enabled: false, _worker: WaitGroup { count: 5 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 7 } }, permits: 1 } }
2022-12-07T01:03:25.589906Z DEBUG rust_parallel::commands: got command status = exit status: 0
how
2022-12-07T01:03:25.589973Z DEBUG rust_parallel::commands: end run command = CommandInvocation { _input: Stdin, _line_number: 5, command: "echo how", shell_enabled: false, _worker: WaitGroup { count: 4 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 8 } }, permits: 1 } }
2022-12-07T01:03:25.591461Z DEBUG rust_parallel::commands: got command status = exit status: 0
are
2022-12-07T01:03:25.591510Z DEBUG rust_parallel::commands: end run command = CommandInvocation { _input: Stdin, _line_number: 6, command: "echo are", shell_enabled: false, _worker: WaitGroup { count: 3 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 9 } }, permits: 1 } }
2022-12-07T01:03:25.593118Z DEBUG rust_parallel::commands: got command status = exit status: 0
hi
2022-12-07T01:03:25.593148Z DEBUG rust_parallel::commands: end run command = CommandInvocation { _input: Stdin, _line_number: 3, command: "echo hi", shell_enabled: false, _worker: WaitGroup { count: 2 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 10 } }, permits: 1 } }
2022-12-07T01:03:25.594342Z DEBUG rust_parallel::commands: got command status = exit status: 0
there
2022-12-07T01:03:25.594367Z DEBUG rust_parallel::commands: end run command = CommandInvocation { _input: Stdin, _line_number: 4, command: "echo there", shell_enabled: false, _worker: WaitGroup { count: 1 }, _permit: OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 11 } }, permits: 1 } }
2022-12-07T01:03:25.594457Z DEBUG rust_parallel: end main
```