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Fluent Bit

ANALYTICS
Velocity5.0

Lightweight telemetry and log processor and forwarder

fluentbit.io ↗

Fluent Bit runs a 4.2 and a 5.0 train side by side, both fed by the same backport pipeline.

log-processingopentelemetrydual-branchbackportsplugin-hardeningobservability-pipeline
◆Current state
Two branches ship in parallel on a roughly two-to-four week rhythm: 5.0.x as the current line and 4.2.x as the maintained one, with most 4.2 entries explicitly labelled backports of 5.0 fixes. The work is overwhelmingly correctness and hardening — memory leaks and over-reads in out_stackdriver, protocol-spec alignment in out_forward's secure handshake, endian-safe gzip magic-number reads, crash fixes in the regex engine and input threads. Feature-shaped changes are narrow: IANA time zone support for native timestamps, label and namespace mapping in out_chronicle, Ubuntu 26.04 packaging.
◆Where it's heading
This is a plugin ecosystem being audited rather than expanded — the recurring shape is a defect found in one output or codec, fixed on 5.0, then backported to 4.2 within days. OpenTelemetry handling keeps getting attention across plugins (OTLP JSON in out_s3, unset AnyValue rendering, OTLP log partitioning in out_kafka), which is the one place new capability is accumulating. Windows and cross-platform builds absorb a steady share of every release.
◆Prediction
Expect the two-branch cadence to hold with 4.2 continuing to receive backports, and OpenTelemetry coverage to keep widening plugin by plugin rather than arriving as one release.

◆Recent moves

  1. 7h ago

    Fluent Bit 4.2.8

    A four-change 4.2 patch, every item a backport: Windows event log enrichment, payload parsing over-reads and null safety in out_stackdriver, and empty-map handling in the Kafka Avro path. Routine maintenance on the older branch.

    View source ↗
  2. 26d ago

    Fluent Bit 4.2.7

    A 4.2 patch of backports covering the secure forward handshake and chunk ack alignment with the protocol spec, PING validation in in_forward, an endian-safe gzip magic number read, and a librdkafka bump. Protocol correctness work, not new capability.

    View source ↗
  3. 1mo ago

    Fluent Bit 5.0.9

    A 5.0 release consisting almost entirely of CI workflow and dependabot bumps. It marks the release cadence rather than any change users would notice.

    View source ↗
  4. 1mo ago

    Fluent Bit 4.2.6

    The most substantive 4.2 patch in the window: IANA time zone support for native timestamps and Windows/IANA conversion rules, plus multiple memory leaks and a potential corruption fixed in out_stackdriver and hardened oauth2 token refresh parsing. Timestamp correctness across platforms is a real operational win for a log shipper.

    View source ↗
  5. 1mo ago

    Fluent Bit 5.0.8

    A 5.0 patch of crash and correctness fixes — a regex literal crash, 32-bit bitwise glitches in the Windows exporter metrics input, strict pong handling in out_forward, unset AnyValue rendering in OTLP JSON. Hardening across the plugin surface.

    View source ↗
  6. 1mo ago

    Fluent Bit 5.0.7

    A 5.0 patch pairing HTTP server stability work — serialized worker teardown, a libevent crash on connection drop — with label and namespace mapping in out_chronicle. The out_chronicle change is one of the few genuinely new options in this window, and it was backported to 4.2 within days.

    View source ↗