v5.0.9

KNOWLEDGE BASE

Release Notes v5.0.9

Fluent Bit is a Fast and Lightweight Data Processor and Forwarder for Linux, BSD, Windows and macOS. We are proud to announce the availability of Fluent Bit v5.0.9.

This maintenance release improves Forward protocol interoperability and secure-forward validation, hardens Stackdriver and CloudWatch Logs delivery paths, adds OpenSSL TLS visibility to eBPF, introduces user-defined Windows performance counters, and upgrades the bundled Kafka client library.

What’s new ?

Core

• downstream: defer connection destruction while queued events still reference the connection, improving idle TLS connection churn handling
• gzip: handle optional-header field lengths safely and skip streaming FCOMMENT terminators correctly
• emitter: account for queued pending bytes when applying mem_buf_limit and keep records buffered during paused backpressure states
• tests: expand runtime, internal, and integration coverage for Forward secure handshakes, idle TLS connection churn, Stackdriver multi-worker formatting, CloudWatch stream eviction, Splunk authentication responses, eBPF OpenSSL traces, Kubernetes local metadata, Tail threaded inotify handling, emitter backpressure, gzip optional headers, and TCP assertions

Libraries

• librdkafka: upgrade the bundled Kafka client library to v2.15.0

Plugins

• eBPF (Input)
  • add OpenSSL uprobe traces for TLS handshake, read, write, and shutdown events
  • add per-CPU monotonic event IDs and improve libssl shared-object discovery for OpenSSL tracing
• Windows Exporter Metrics (Input)
  • add user-defined Windows Performance Counter collection with PerformanceCounter entries
  • add collector.performancecounter.scrape_interval for independent custom-counter collection timing
• Forward (Input)
  • release connection wrappers when the engine drops idle or timed-out connections
  • validate secure-forward PING messages before processing their fields
• Splunk (Input)
  • return Splunk-compatible 401 and 403 responses for missing, malformed, or invalid HEC authentication
• Tail (Input)
  • pause inotify events correctly when Tail runs in threaded mode
• Kubernetes (Filter)
  • enrich Fluent Bit internal log records from local Kubernetes metadata
  • add kube_namespace_file so deployments can customize the namespace metadata file path
  • improve NULL checks and container-specific annotation handling
• Rewrite Tag (Filter)
  • keep records when emitter backpressure or enqueue errors prevent retagging
• CloudWatch Logs (Output)
  • treat missing log-stream errors as unrecoverable for the current chunk and evict stale stream state
• Forward (Output)
  • verify secure-forward server digests during PONG handling
  • reject username and password configuration without a shared key
  • send chunk acknowledgment tokens as base64-encoded 128-bit identifiers
  • handle formatter transcode failures cleanly before sending chunks
• Stackdriver (Output)
  • make resource metadata extraction safe across output workers
  • reject malformed numeric subfields and harden local resource ID validation
  • improve null-safety while parsing payloads and building requests

Join us

We want to hear about you, our community is growing, and you can be part of it!, you can contact us at:

• Github: http://github.com/fluent/fluent-bit
• Slack: CNCF Slack, channel #fluent-bit (https://communityinviter.com/apps/cloud-native/cncf)
• Twitter: @fluentbit