Module zksync_concurrency::ctx

Implementation of the golang Context (https://pkg.go.dev/context). You can think of context as a runtime equivalent of the rust lifetime: As soon as its context is canceled the function should return ASAP, without doing any further blocking calls.

It is NOT possible to extend the context provided by the caller, who defines how long it allows the function call to execute.

Context is essentially a cancellation token which should be passed down the call stack, so that it can be awaited together with every blocking call: Instead of “awaiting for new data on the channel”, you “await for new data on the channel OR for context to get canceled”. This way you can implement graceful shutdown in a very uniform way.

Modules

• channel
  Implementation of a context-aware bounded and unbounded mpsc async channel. Build on top of tokio::sync::mpsc::(un)bounded_channel. Note that channel disconnection is not observable by default:

Structs

• AffineClock
  Clock which is running speedup times faster than the realtime. (if speedup is <1, then it is actually slower).
• Canceled
  Error returned when the blocking operation was interrupted due to context getting canceled.
• Ctx
  Contexts are composed into a tree via _parent link. We maintain an invariant _parent.deadline <= deadline. If a parent gets canceled, the child also gets canceled immediately afterwards, although not atomically. If deadline passes the context also gets canceled.
• CtxAware
  Context-aware future, that an async task can await and sync task can block on.
• ManualClock
  Fake clock which supports manually advancing the time.
• NoCopy
  No-copy wrapper allowing to carry a Copy type into a closure or an async block.
• RealClock
  Realtime clock.

Enums

• Clock
  An abstract clock. We use a concrete enum rather than a trait to avoid abstract method call in runtime.
• Error
  anyhow::Error + “canceled” variant. Useful for working with concurrent code which doesn’t need structured errors, but needs to handle cancelation explicitly.

Functions

• Ok
  Equivalent to Ok::<_, ctx::Error>(value).
• root
  Constructs a top-level context. Should be called only at the start of the main() function of the binary.
• test_root
  Returns a root context with the given clock and a deterministic RNG provider.
• test_with_clock
  Returns a child context with the given clock. Useful for simulating entities with independent clocks.

Type Aliases

• OrCanceled
  Wraps result with ErrCancel as an error.
• Result
  Alias for Result with ctx::Error.