v5.0.3

Next generation Telemetry Agent for Logs, Metrics and Traces.

April 14, 2026

KNOWLEDGE BASE

Release Notes v5.0.3

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 v5.0.3.

Below is a detailed list of changes included in this release…

For the new deferred ingress queue configuration and metrics introduced for HTTP-based inputs, see:

What’s new ?


Core


  • config: add extended environment variable support in YAML, including structured env entries with file-backed values and refresh intervals
  • http_server: add ingress queue limit settings plus deferred ingress queue metrics for better backpressure visibility
  • http_client: harden timeout handling, chunked response parsing, and connection teardown across shared HTTP paths
  • tests: Fluent Bit now ships an in-tree integration test suite covering end-to-end scenarios across HTTP, OTLP, Kafka, S3, Syslog, Tail, and more
  • network: handle bracketed IPv6 addresses correctly
  • parser: fix timestamp parsing around DST changes just after local midnight
  • cmetrics: upgrade to v2.1.2

Plugins


  • eBPF (Input)
    • add TCP trace support and clean up eBPF programs more reliably on shutdown and exception paths
  • OpenTelemetry (Input)
    • honor explicit tag configuration over URI-derived tags
  • Tail (Input)
    • harden restart restore and aged-out file recovery to avoid resuming from stale offsets after copytruncate, inode reuse, or partial-line restarts
  • Dummy (Input)
    • add support for dynamic environment values in body and metadata
  • S3 (Output)
    • fix retry_limit semantics and multiple multipart upload memory-management issues
  • Azure Logs Ingestion (Output)
    • validate auth_url overrides for safer OAuth2-based testing and setup
  • Syslog (Output)
    • reject unsupported proto and TLS combinations more cleanly
  • HTTP-based plugins
    • inputs and outputs using the shared HTTP client received timeout, chunked-response, and cleanup fixes across in_http, in_calyptia_fleet, filter_ecs, out_azure_blob, out_calyptia, out_http, out_opentelemetry, out_slack, out_td, and out_websocket

Contributors

On every release, there are many people involved doing contributions to different areas like bug reporting, troubleshooting, documentation and coding, without these contributions from the community, the project won’t be the same and won’t be in the good shape that it is now. So THANK YOU! to everyone who takes part of this journey!

Join us

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