v9.21.0: 9.21.0

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This is a minor release adding new features and bug fixes. There are no breaking changes; upgrading from 9.20.x is a drop-in replacement.

🚀 Highlights

Zero-copy GetToBuffer / SetFromBuffer

Two new StringCmdable methods let callers read and write Redis string values directly into and from pre-allocated byte buffers, eliminating the per-call payload allocation that Get/Set incur:

GetToBuffer(ctx, key, buf) *ZeroCopyStringCmd   // reads into buf; ZeroCopyStringCmd { Val() int; Bytes() []byte; Result() (int, error) }
SetFromBuffer(ctx, key, buf) *StatusCmd

GetToBuffer decodes the bulk reply straight into the caller-owned buf (no intermediate allocation); a buffer that is too small returns an error after draining the payload, so the connection stays aligned for the next reply. SetFromBuffer is provided for API symmetry — it dispatches to the same []byte writer path as Set(ctx, key, buf, 0) and produces byte-identical output on the wire. Available on *Client, *ClusterClient, *Ring, *Conn and Pipeliner.

(#​3834) by @​ndyakov

Explicit LIMIT 0 for stream trimming

Redis treats XTRIM/XADD approximate-trim (~) LIMIT 0 as "disable the trimming effort cap entirely", which differs from omitting LIMIT (the implicit 100 * stream-node-max-entries default). The command builders previously only emitted LIMIT when limit > 0, so callers could never send an explicit LIMIT 0. Following the KeepTTL = -1 precedent, the new XTrimLimitDisabled = -1 sentinel now emits an explicit LIMIT 0; limit == 0 keeps the historical no-LIMIT behavior, so existing callers produce byte-identical commands.

(#​3848) by @​TheRealMal

✨ New Features

• Zero-copy buffer string commands: new GetToBuffer / SetFromBuffer on StringCmdable and the ZeroCopyStringCmd result type, reading/writing string values into caller-owned buffers without per-call payload allocation (#​3834) by @​ndyakov
• XTrimLimitDisabled sentinel: XTRIM/XADD approximate trimming can now send an explicit LIMIT 0 to disable the trim effort cap, via the new XTrimLimitDisabled = -1 sentinel (#​3848) by @​TheRealMal
• PubSub health-check timeouts: channel.initHealthCheck now bounds the Ping it issues with a fresh per-check timeout context (the exported pingTimeout / reconnectTimeout) instead of context.TODO(), so a stuck health-check Ping can no longer block indefinitely (#​3819) by @​abdellani
• Skip redundant UNWATCH in Tx.Close: a transaction now tracks whether a WATCH is still active (watchArmed) and only issues UNWATCH on Close when it is, removing an extra round trip on the common WATCH/.../EXEC and no-key Watch paths while never returning a connection to the pool with an active watch (#​3854) by @​fcostaoliveira

🐛 Bug Fixes

• maintnotifications ModeAuto fail-open: ModeAuto now stays fail-open when the server does not support maintenance notifications — connections are retired and tracking is guarded during downgrade so the client keeps working instead of erroring (#​3853) by @​terrorobe

👥 Contributors

We'd like to thank all the contributors who worked on this release!

@​abdellani, @​fcostaoliveira, @​ndyakov, @​terrorobe, @​TheRealMal