rust-parallel

Run commands in parallel, like a simple rust verision of GNU Parallel.

Just starting - more options to come :)

Goals:

• Use only safe rust.
• Use only asynchronous operations supported by tokio, 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 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 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 used for application error handling to propogate and format fatal errors.
• awaitgroup used to await completion of all async functions.
• clap command line argument parser.
• tokio asynchronous runtime for rust. From tokio this app uses:
  • async / await functions (aka coroutines)
  • Singleton CommandLineArgs instance using tokio::sync::OnceCell.
  • Asynchronous command execution using tokio::process::Command
  • Semaphore
• 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 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 <

$ 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 <

$ cat >./test2 <

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

```

With debug logs enabled:

$ cat test | RUST_LOG=debug rust-parallel 2022-11-29T03:44:17.993760Z DEBUG rust_parallel: begin main 2022-11-29T03:44:17.994436Z DEBUG rust_parallel::command_line_args: command_line_args = CommandLineArgs { jobs: 12, shell_enabled: false, inputs: [] } 2022-11-29T03:44:17.994476Z DEBUG rust_parallel::commands: begin spawn_commands 2022-11-29T03:44:17.994510Z DEBUG rust_parallel::commands: begin process_one_input input = Stdin 2022-11-29T03:44:17.994669Z DEBUG rust_parallel::commands: read line echo hi 2022-11-29T03:44:17.994721Z DEBUG rust_parallel::commands: read line echo there 2022-11-29T03:44:17.994752Z DEBUG rust_parallel::commands: read line echo how 2022-11-29T03:44:17.994775Z DEBUG rust_parallel::commands: read line echo are 2022-11-29T03:44:17.994777Z DEBUG rust_parallel::commands: begin run_command command = Command { _input: Stdin, _line_number: 1, command: "echo hi", shell_enabled: false } 2022-11-29T03:44:17.994803Z DEBUG rust_parallel::commands: read line echo you 2022-11-29T03:44:17.994793Z DEBUG rust_parallel::commands: begin run_command command = Command { _input: Stdin, _line_number: 2, command: "echo there", shell_enabled: false } 2022-11-29T03:44:17.994815Z DEBUG rust_parallel::commands: begin run_command command = Command { _input: Stdin, _line_number: 3, command: "echo how", shell_enabled: false } 2022-11-29T03:44:17.994832Z DEBUG rust_parallel::commands: begin run_command command = Command { _input: Stdin, _line_number: 4, command: "echo are", shell_enabled: false } 2022-11-29T03:44:17.994888Z DEBUG rust_parallel::commands: begin run_command command = Command { _input: Stdin, _line_number: 5, command: "echo you", shell_enabled: false } 2022-11-29T03:44:17.994902Z DEBUG rust_parallel::commands: end process_one_input input = Stdin 2022-11-29T03:44:17.999410Z DEBUG rust_parallel::commands: end spawn_commands 2022-11-29T03:44:17.999455Z DEBUG rust_parallel: before wait_group.wait wait_group = WaitGroup { count: 5 } 2022-11-29T03:44:17.999524Z DEBUG rust_parallel::commands: got command status = exit status: 0 hi 2022-11-29T03:44:17.999572Z DEBUG rust_parallel::commands: end run_command command = Command { _input: Stdin, _line_number: 1, command: "echo hi", shell_enabled: false } 2022-11-29T03:44:18.001264Z DEBUG rust_parallel::commands: got command status = exit status: 0 how 2022-11-29T03:44:18.001321Z DEBUG rust_parallel::commands: end run_command command = Command { _input: Stdin, _line_number: 3, command: "echo how", shell_enabled: false } 2022-11-29T03:44:18.003308Z DEBUG rust_parallel::commands: got command status = exit status: 0 there 2022-11-29T03:44:18.003353Z DEBUG rust_parallel::commands: end run_command command = Command { _input: Stdin, _line_number: 2, command: "echo there", shell_enabled: false } 2022-11-29T03:44:18.004760Z DEBUG rust_parallel::commands: got command status = exit status: 0 are 2022-11-29T03:44:18.004798Z DEBUG rust_parallel::commands: end run_command command = Command { _input: Stdin, _line_number: 4, command: "echo are", shell_enabled: false } 2022-11-29T03:44:18.006124Z DEBUG rust_parallel::commands: got command status = exit status: 0 you 2022-11-29T03:44:18.006158Z DEBUG rust_parallel::commands: end run_command command = Command { _input: Stdin, _line_number: 5, command: "echo you", shell_enabled: false } 2022-11-29T03:44:18.006277Z DEBUG rust_parallel: end main