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Beekeeper changelog

0.3.0

The general theme of this release is performance improvement by eliminating thread contention due to unnecessary locking of shared state. This required making some breaking changes to the API.

  • Breaking
    • beekeeper::hive::Hive type signature has changed
      • Removed the W: Worker parameter as it is redundant (can be obtained from Q::Kind)
      • Added T: TaskQueuesto specify the TaskQueues implementation
    • The Builder interface has been re-written to enable maximum flexibility.
      • Builder is now a trait that must be in scope.
      • ChannelBuilder implements the previous builder functionality.
      • WorkstealingBuilder is identical to ChannelBuilder, except that it uses workstealing-based task queues (see Features below).
      • OpenBuilder has no type parameters and can be specialized to create a Hive with any combination of Queen and TaskQueues.
      • BeeBuilder and FullBuilder are intermediate types that generally should not be instantiated directly.
    • beekeeper::bee::Queen::create now takes &self rather than &mut self. There is a new type, beekeeper::bee::QueenMut, with a create(&mut self) method, and needs to be wrapped in a beekeeper::bee::QueenCell to implement the Queen trait. This enables the Hive to create new workers without locking in the case of a Queen that does not need mutable state.
    • beekeeper::bee::Context now takes a generic parameter that must be input type of the Worker.
    • beekeeper::hive::Hive::try_into_husk now has an urgent parameter to indicate whether queued tasks should be abandoned when shutting down the hive (true) or if they should be allowed to finish processing (false).
    • The type of attempt and max_retries has been changed to u8. This reduces memory usage and should still allow for the majority of use cases.
    • The ::of methods have been removed from stock Workers in favor of implementing From.
  • Features
    • Added the TaskQueues trait, which enables Hive to be specialized for different implementations of global (i.e., sending tasks from the Hive to worker threads) and local (i.e., worker thread-specific) queues.
      • ChannelTaskQueues implements the existing behavior, using a channel for sending tasks.
      • WorkstealingTaskQueues has been added to implement the workstealing pattern, based on crossbeam::dequeue.
    • Added the local-batch feature, which enables worker threads to queue up batches of tasks locally, which can alleviate contention between threads in the pool, especially when there are many short-lived tasks.
      • When this feature is enabled, tasks can be optionally weighted (by wrapping each input in crate::hive::Weighted) to help evenly distribute tasks with variable processing times.
      • Enabling this feature should be transparent (i.e., not break existing code), and the Hive's task submission methods support both weighted and unweighted inputs (due to the blanket implementation of From<T> for Weighted<T>); however, there are some cases where it is now necessary to specify the input type where before it could be elided.
    • Added the Context::submit method, which enables tasks to submit new tasks to the Hive.
  • Other
    • Switched to using thread-local retry queues for the implementation of the retry feature, to reduce thread-contention.
    • Switched to storing Outcomes in the hive using a data structure that does not require locking when inserting, which should reduce thread contention when using *_store operations.
    • Switched to using crossbeam_channel for the task input channel in ChannelTaskQueues. These are multi-produer, multi-consumer channels (mpmc; as opposed to std::mpsc, which is single-consumer), which means it is no longer necessary for worker threads to aquire a Mutex lock on the channel receiver when getting tasks.
    • Added the beekeeper::hive::mock module, which has a MockTaskRunner for applying a worker in a mock context. This is useful for testing your Worker.
    • Updated to 2024 edition and Rust version 1.85

0.2.1

  • Bugfixes
    • Reverted accidental change to default features in Cargo.toml
    • Panics during drop of worker threads
  • Other
    • Added initial performance benchmarks

0.2.0

  • Breaking
    • Builder::build*, Husk::into_hive* now return Hive rather than Result<Hive, SpawnError>
    • beekeeper::hive::SpawnError has been removed
    • Hive::grow and Hive::use_all_cores now return Result<usize, Poisoned> rather than usize
    • Hive::num_threads has been renamed Hive::max_workers
  • Features
    • Hive now keeps track of spawn results
      • Hive::alive_workers reports the number of worker threads that are currently alive (<= max_workers)
      • Hive::has_dead_workers returns true if the Hive has encountered any errors spawing worker threads
      • Hive::revive_workers attempts to re-spawn any dead worker threads
  • Bugfixes
    • Ordered iterators would enter an infinite loop if there were missing indicies

0.1.0

  • Initial release