Add a generic BackpressureQueue that uses a DropPredicate to proactively
shed load before the queue is completely full.
Two predicate types are provided:
- DropCheckFunc: length-only drop decision (func(queueLen int) bool)
- DropPredicate[T]: item-aware drop decision
RandomEarlyDrop returns a DropCheckFunc since RED only considers queue
depth. The AsDropPredicate helper adapts it to DropPredicate[T] for use
with BackpressureQueue.
In addition to the blocking Enqueue/Dequeue methods, the queue exposes
TryEnqueue (non-blocking send with drop check), Len, ReceiveChan, and
Close. These are needed by the actor package's BackpressureMailbox which
uses BackpressureQueue as its core buffer while implementing the Mailbox
interface's select-based iteration and lifecycle methods.
Property-based tests using pgregory.net/rapid verify queue invariants
(capacity bounds, FIFO ordering, model consistency) across randomized
enqueue/dequeue sequences with RED enabled.
With Go 1.26 now released, this bumps the minimum required Go version
from 1.24.11 to 1.25.5 across all go.mod files and updates the
installation documentation with the correct download links and SHA256
hashes for Go 1.25.5 binaries.
The build system (Dockerfiles, Makefile, CI) was already using Go 1.25.5,
so this change aligns the go.mod minimum version to match.
Bump all build go versions to v1.21.0
Bump the minimum build package version to v1.19.0
Debian "buster" is not longer supported. Security updates have been
discontinued since June 30th 2022. We will build using the latest
version, "bookworm".
