rust-parallel

Command-line utility to execute commands in parallel and display their output.

Like a simple rust version 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. Install Rust
2. Install the latest version of this app from crates.io: $ cargo install rust-parallel

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 <

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 <

$ cat >./test2 <

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

```

With debug logs enabled:

$ cat test | RUST_LOG=debug rust-parallel 2022-12-09T15:56:26.823431Z DEBUG rust_parallel: begin try_main 2022-12-09T15:56:26.824213Z DEBUG rust_parallel::command_line_args: command_line_args = CommandLineArgs { jobs: 12, shell_enabled: false, inputs: [] } 2022-12-09T15:56:26.824266Z DEBUG rust_parallel::command: begin spawn_commands 2022-12-09T15:56:26.824308Z DEBUG rust_parallel::command: begin process_one_input input = Stdin 2022-12-09T15:56:26.824502Z DEBUG rust_parallel::command: read line # input can contain comment lines (starting with #) and blank lines too 2022-12-09T15:56:26.824531Z DEBUG rust_parallel::command: read line 2022-12-09T15:56:26.824546Z DEBUG rust_parallel::command: read line echo hi 2022-12-09T15:56:26.824598Z DEBUG rust_parallel::command: read line echo there 2022-12-09T15:56:26.824631Z DEBUG rust_parallel::command: read line echo how 2022-12-09T15:56:26.824657Z DEBUG rust_parallel::command: read line echo are 2022-12-09T15:56:26.824681Z DEBUG rust_parallel::command: read line echo you 2022-12-09T15:56:26.824713Z DEBUG rust_parallel::command: begin run command = Command { 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 } 2022-12-09T15:56:26.824752Z DEBUG rust_parallel::command: begin run command = Command { 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 } 2022-12-09T15:56:26.824785Z DEBUG rust_parallel::command: end process_one_input input = Stdin 2022-12-09T15:56:26.824777Z DEBUG rust_parallel::command: begin run command = Command { 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 } 2022-12-09T15:56:26.824799Z DEBUG rust_parallel::command: begin run command = Command { 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 } 2022-12-09T15:56:26.824843Z DEBUG rust_parallel::command: end spawn_commands 2022-12-09T15:56:26.824826Z DEBUG rust_parallel::command: begin run command = Command { 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 } 2022-12-09T15:56:26.824911Z DEBUG rust_parallel: before wait_group.wait wait_group = WaitGroup { count: 5 } 2022-12-09T15:56:26.829988Z DEBUG rust_parallel::command: got command status = exit status: 0 hi 2022-12-09T15:56:26.830423Z DEBUG rust_parallel::command: end run command = Command { 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 } 2022-12-09T15:56:26.831294Z DEBUG rust_parallel::command: got command status = exit status: 0 how 2022-12-09T15:56:26.831589Z DEBUG rust_parallel::command: end run command = Command { 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 } 2022-12-09T15:56:26.833390Z DEBUG rust_parallel::command: got command status = exit status: 0 there 2022-12-09T15:56:26.833638Z DEBUG rust_parallel::command: end run command = Command { input: Stdin, line_number: 4, command: "echo there", shell_enabled: false } worker = WaitGroup { count: 3 } permit = OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 9 } }, permits: 1 } 2022-12-09T15:56:26.835139Z DEBUG rust_parallel::command: got command status = exit status: 0 are 2022-12-09T15:56:26.835412Z DEBUG rust_parallel::command: end run command = Command { input: Stdin, line_number: 6, command: "echo are", shell_enabled: false } worker = WaitGroup { count: 2 } permit = OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 10 } }, permits: 1 } 2022-12-09T15:56:26.836906Z DEBUG rust_parallel::command: got command status = exit status: 0 you 2022-12-09T15:56:26.837117Z DEBUG rust_parallel::command: end run command = Command { input: Stdin, line_number: 7, command: "echo you", shell_enabled: false } worker = WaitGroup { count: 1 } permit = OwnedSemaphorePermit { sem: Semaphore { ll_sem: Semaphore { permits: 11 } }, permits: 1 } 2022-12-09T15:56:26.874884Z DEBUG rust_parallel: end try_main