Crate permit[][src] version license: Apache 2.0 unsafe forbidden pipeline status


permit::Permit is a struct for cancelling operations.

Use Cases

  • Graceful server shutdown
  • Cancel operations that take too long
  • Stop in-flight operations when revoking authorization


  • Subordinate permits. Revoking a permit also revokes its subordinates, recursively.
  • Drop a permit to revoke its subordinates, recursively.
  • Wait for all subordinate permits to drop.
  • Implements Future. You can await a permit and return when it is revoked.
  • Similar to Golang’s context
  • Depends only on std.
  • forbid(unsafe_code)
  • 100% test coverage



  • async_ctx
    • Good API
    • Async only
  • io-context
    • Holds Any values
    • Unmaintained
  • ctx
    • Holds an Any value
    • API is a direct copy of Golang’s context, even where that doesn’t make sense for Rust. For example, to cancel, one must copy the context and call a returned Box<Fn>.
    • Unmaintained


Graceful shutdown:

let top_permit = permit::Permit::new();
// Start some worker threads.
for _ in 0..5 {
    let permit = top_permit.new_sub();
    std::thread::spawn(move || {
        while !permit.is_revoked() {
            // ...
// Revoke all thread permits and wait for them to
// finish and drop their permits.

Cargo Geiger Safety Report


  • v0.1.4 - Fix bug where revoke() and then wait() would not wait.
  • v0.1.3
    • Don’t keep or wake stale std::task::Waker structs.
    • Eliminate race that causes unnecessary wake.
  • v0.1.2 - Implement Future
  • v0.1.1 - Make revoke return &Self
  • v0.1.0 - Initial version

Happy Contributors 🙂

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  • Always respond within 24 hours
  • Provide clear & concrete feedback
  • Immediately make a new release for your accepted change



A struct for cancelling operations.