Ten years, countless pipelines: Fluent Bit v4.2 still logging strong!

In our previous blog, The Journey: From Embedded Logging to Multi-Signal Observability, Paige Cruz reflected on Fluent Bit’s ten-year journey; from its early days as a lightweight log processor to becoming a cornerstone of cloud-native observability.

Now, as we enter the next chapter, we’re looking forward, exploring how Fluent Bit v4.2 continues to build on that legacy to shape the next decade of open source telemetry.

Fluent Bit’s tenth anniversary marks more than just a decade of code but a decade of collaboration, community, and continuous improvement. With that comes changes to the overall project structuring of both Fluentd and Fluent Bit under a new unified Fluent organization at CNCF. This change will:

• Create a shared governance model while preserving project independence.
• Enable future growth of new observability projects under the Fluent umbrella.
• Maintain vendor neutrality with no changes to licenses, names, or day-to-day contributions.

What began as a small open source subproject built to handle embedded logging has become one of the most deployed telemetry agents in the world; powering observability pipelines across clouds, data centers, and edge environments alike.

This new chapter under the Fluent umbrella formally recognizes that growth, positioning Fluent Bit and Fluentd as equal, collaborative projects driving the next era of open source observability.

We’re excited to see both communities come together, learn from one another, and continue to flourish under a unified name

Fluent Bit v4.2 is more than an update; it’s a reimagining of what a telemetry pipeline can do. Building on years of feedback and innovation, this release introduces new capabilities that simplify complex data processing, strengthen security, and open the door to even broader community contribution.

We are excited to highlight the following key features:

• Flexible Telemetry Routing: The new Telemetry Router enables content-aware routing based on record metadata, attributes, or tags, allowing users to define dynamic data flows without relying on traditional tag-based matching. The new complementary routing metrics provide per-path visibility of record and byte throughput across inputs and outputs.
• Performance Breakthroughs: Pipeline optimizations enable twice the speed of JSON generation through SIMD-accelerated writing, and provide faster and more efficient Trace Sampling with reduced CPU and memory usage.
• Reliability and Security: The new Supervisor Mode continuously monitors and restarts child processes to ensure consistent uptime. The independent Hot Reload Watchdog validates and protects configuration updates at runtime. Lastly, the enhanced TLS session handling with ALPN support strengthens secure connectivity and resilience.
• Expanded Data Outputs and OpenTelemetry Enhancements: The Amazon S3 output plugin now supports Parquet format with Apache Arrow and ZSTD compression, while the OpenTelemetry output plugin introduces updated protocol support and AWS SigV4 authentication.
• Next-Level Observability: The new GPU metrics collector (AMD) and Prometheus textfile collector for .prom files expand system-level introspection and monitoring flexibility.
• Broader Platform Support: Now supporting Debian Trixie, Rocky/AlmaLinux 10, CentOS Stream 10, the latest openSUSE release, and improved Windows Certstore compatibility.

Fluent Bit’s progress has always been fueled by its community, contributors, adopters, and maintainers working together across industries and time zones.

Every feature in v4 reflects real-world feedback, friction logs, and user stories. From Kubernetes operators to observability engineers and platform teams, your input shapes every release.

As Fluent Bit continues to grow, so does the community’s role in driving what’s next, from tracing improvements to new integrations and plugin ecosystems. Thank you for being part of our journey and community!

Fluent Bit v4 sets the foundation for what’s next in open source telemetry: intelligent, efficient, and extensible pipelines that scale across every environment, from cloud to edge.

As observability matures, the focus is shifting from simply collecting data to understanding it and Fluent Bit is evolving to meet that challenge head-on.

The next decade will bring deeper integrations with OpenTelemetry, smarter routing and correlation, and even greater flexibility for contributors to shape Fluent Bit’s future.

Fluent Bit v4 isn’t just a milestone, it’s a starting point. We invite you to:

• Upgrade to v4.2 and experience its new capabilities firsthand
• Join our Slack community to connect with maintainers and contributors
• Join our newsletter to stay up to date with all things observability

Here’s to another decade of open source innovation, community collaboration, and observability without compromise.