What changed in Fluent Bit from 4 to 5

8 releases numbered after v4.2.8 up to and including v5.1.1, stable releases only. v4.2.8 and v5.1.1 are the newest stable releases of 4 and 5 we track; this page follows them as new ones ship.

140 changes across 8 releases

Added 30

v5.0.10

  • Add a capability to adjust log level with error paths in in_node_exporter_metrics
  • Enrich EventData key-value map if enabled in in_winevtlog

v5.1.1

  • Support timestamp placeholder in out_file
  • Add auto_extract_timestamp parameter in out_splunk
  • Add hostname as primary field and runtime tests in out_logdna
  • Add config map to the plugin registration in plugin_proxy

v5.1.0

  • Extract skills from memory
  • Add in_gpu_metrics input plugin to handle NVIDIA GPU metrics via NVML
  • Implement in_etw event tracing for Windows input plugin
  • Add capability to adjust log level with error paths in in_node_exporter_metrics
  • Add format=parquet,arrow with selectable page compression codecs to out_s3
  • Handle input, output, filter, and processor plugin aliases
  • Implement adaptive flushing in config engine
  • Implement out_gcs Google Cloud Storage plugin
  • Implement additional metrics (filesystem, EXT_* metrics, powersupplyclass) on node exporter metrics
  • Support RA placeholders for dynamic creation of files in out_file
  • Add per-container disk I/O metrics to in_podman_metrics
  • Initial implementation to enable FIPS compliance

v5.0.9

  • Implement user-defined performance counters with PDH in in_windows_exporter_metrics
  • Implement openssl trace in in_ebpf

v5.0.8

  • Implement sched trace in in_ebpf

v5.0.7

  • Support label and namespace mapping in out_chronicle
  • Add IANA time_zone support for native timestamps in parser
  • Support stdin plugin on windows in in_stdin
  • Implement dns trace in in_ebpf
  • Provide options for inactive chunks behavior in out_s3

v5.0.6

  • Add bash-style default value operator :- for environment variables
  • Add support for Ubuntu 26.04 in packaging
  • Add total limit size configuration for DLQ in storage

v5.0.5

  • in_ebpf: implement exec trace
Changed 29

v5.1.1

  • Display evicted logs on dropping chunks in input_chunk in_storage_backlog

v5.1.0

  • Enrich EventData key-value map if enabled in in_winevtlog
  • Upgrade cmetrics library to v2.2.0
  • Upgrade cfl library to v1.0.0
  • Reduce protobuf log allocation churn in opentelemetry
  • Re-architect workers support in downstream
  • Reduce protobuf decode allocation churn in in_opentelemetry
  • Handle DTLS protocol on out_syslog
  • Add coroutine-based event dispatch to downstream
  • Reload and watch certificates on Linux in OpenSSL TLS

v5.0.9

  • Upgrade librdkafka to v2.15.0
  • Generate mostly monotonic event id for increasing traceability in in_ebpf
  • Align secure forward handshake and chunk ack with protocol spec in out_forward
  • Attach k8s metadata for internal logs in filter_kubernetes
  • Use semver and timestamp suffixes to distinguish branches in workflows
  • Return Splunk HEC auth status codes in in_splunk

v5.0.8

  • Upgrade cmetrics to v2.1.5

v5.0.7

  • Add 100 MB decompression size limit to zstd
  • Handle conversion rules of windows and IANA tzinfo in time_tz
  • Increase PUT_RECORDS_PAYLOAD_SIZE to 10MB in out_kinesis_streams

v5.0.6

  • Upgrade cfl library to v0.7.1
  • Partition OTLP logs by resource in out_kafka
  • Harden listener and architecture for http_server
  • Spawn internal server in threaded mode for http_server
  • Omit SNI for IP literal hosts in TLS

v5.0.5

  • in_node_exporter_metrics: skip IPv6 metrics collection when disabled
  • aws: update support for additional regions
  • out_s3: handle otlp JSON format
  • lib: cmetrics: upgrade to v2.1.3
Fixed 75

v5.0.10

  • Yield downstream read retries to the event loop in TLS
  • Handle empty map even if avro schema defines map type in out_kafka
  • Preserve syscall error details in TLS OpenSSL

v5.1.1

  • Fix persistent chunks issues without matching routes on hot reloading in in_storage_backlog
  • Address underflow of buffer size on startup in out_s3
  • Ensure alignment of reading dword width in compat
  • Address stale failed tasks on dispatch in engine_dispatch
  • Fix incorrect pointer arithmetic in diskstats metric cache in in_node_exporter_metrics
  • Fix SIMD boundary for JSON string encoding in utils
  • Plug unfreed allocated memories on exceptions in stream_processor sp_stream
  • Invalidate TLS session before socket close in downstream
  • Fix storage limit eviction with 32 or more outputs in input_chunk

v5.1.0

  • Return not found for invalid endpoint in in_opentelemetry
  • Do not recycle a connection after peer close_notify in OpenSSL TLS
  • Fix incorrectly detected C TLS existence in thread_storage
  • Fix stale byte accounting when multiple frames share a buffer in in_forward
  • Plug 2038 problem on timestamp in log_event_decoder time
  • Plug unsupported shared port issue on Windows in http_server
  • Handle byte order mark for non-ASCII environment of Windows correctly in tests
  • Plug uninitialized member in network
  • Avoid unbounded recursion in chunk cobj record iteration in mp
  • Plug SEGV occurrence on enabling Use_Pod_Association in filter_kubernetes
  • Fix the reported RSS ram in in_process_exporter_metrics
  • Adjust consuming mechanism to improve throughput in in_lib

v5.0.9

  • Validate PING is a msgpack array in check_ping in in_forward
  • Plug segmentation violation on in_tail
  • Mitigate data loss on multiline in filter_write_tag and in_emitter
  • Plug segmentation violation on not found error in out_cloudwatch_logs
  • Fix multi-worker resource-metadata data race in out_stackdriver
  • Fix payload parsing over-reads and null safety in out_stackdriver
  • Skip FCOMMENT terminator in streaming decompressor in gzip
  • Fix 100% CPU hang and connection teardown use-after-free in in_forward
  • Fix int64_t line var in out_stackdriver and gzip endian-safe magic check

v5.0.8

  • Plug bitwise glitches on 32bit OSes in in_windows_exporter_metrics
  • Plug a regex literal crash
  • Process type and length of pong strictly in out_forward
  • Use the correct maximum size of Cyrillic in unicode
  • Render unset AnyValue in OTLP JSON in opentelemetry
  • Fix stale chunks handling on limits in storage
  • Plug timer lifecycle glitches on progress check in in_tail
  • Handle structured xml query as separated subscriptions in in_winevtlog
  • Plug SEGV occurrences on cloudwatch logs in aws error_reporter
  • Fix out-of-bounds read in unesc_ends_with_nl in in_tail
  • Fix caller-owned parse failure cleanup in config_format
  • Plug FD leaks on destroy in scheduler
  • Handle loki tenant_id_key properly in out_loki
  • Ensure escaping backslashes on cloudwatch API requests' body in out_cloudwatch_logs
  • Fix ignore_active_older_files to re-check mtime on aged-out files in in_tail
  • Catch auth errors on XML responses in aws
  • Correctly handle successful Delete Blob responses in out_azure_blob
  • Sanitize bulk action metadata in out_es and out_opensearch
  • Fix JSON histogram bounds handling in opentelemetry

v5.0.7

  • Serialize worker teardown in http_server to prevent race conditions
  • Fix libevent crash on connection drop in http_server
  • Fix YAML variant cleanup on parser errors in config_format
  • Handle int64 values correctly in avro
  • Check map size before accessing first entry in in_elasticsearch
  • Fix multiple memory leaks and potential corruption in out_stackdriver
  • Discard checksum corrupt chunks on startup in storage

v5.0.6

  • Fix general issues with sds_cat() usage
  • Handle unpacker allocation failure in in_forward
  • Prevent port binding failures in concurrent OTEL tests
  • Ignore duplicate STOP messages to prevent shutdown spin in engine
  • Plug segmentation fault on termination in out_azure_logs_ingestion
  • Fix file append cleanup on failure in in_tail
  • Reconcile files after missed inotify events in in_tail
  • Fix handling of cfl_sds return buffers after cfl upgrade

v5.0.5

  • filter_kubernetes: destroy TLS session to prevent SSL object leak
  • filter_kubernetes: make memory growth rigidly on filter k8s
  • filter_log_to_metrics: retry timer metric append
  • crypto: fix build with OPENSSL_NO_ENGINE
  • opentelemetry: preserve otlp log resource grouping
  • filter_kubernetes: destroy upstream and TLS context on happy path exit
  • out_forward: fix retain_metadata_in_forward_mode default value
  • input: fix threaded input conditional routing for logs
Removed 1

v5.0.5

  • out_logdna: remove promoted known keys
Security 5

v5.0.7

  • Fix OOB reads in framed data parser in snappy
  • Fix OOB read from hardcoded remaining length overhead in in_mqtt
  • Reject parts with length < 4 and fix null-terminator OOB in in_collectd
  • Validate array size before accessing message mode fields in in_forward
  • Fix integer overflow in octet-counting length parser in in_syslog

Original release notes, newest first

The list above is our reading of these notes; the originals from Fluent are here, one fold per release.

v5.0.10Fluent Bit 5.0.10

https://fluentbit.io/announcements/v5.0.10/

What's Changed

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.9...v5.0.10

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v5.1.1Fluent Bit 5.1.1

https://fluentbit.io/announcements/v5.1.1/

What's Changed
New Contributors

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.1.0...v5.1.1

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v5.1.0Fluent Bit 5.1.0

https://fluentbit.io/announcements/v5.1.0/

What's Changed
New Contributors

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.9...v5.1.0

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v5.0.9Fluent Bit 5.0.9

https://fluentbit.io/announcements/v5.0.9/

What's Changed

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.8...v5.0.9

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v5.0.8Fluent Bit 5.0.8

https://fluentbit.io/announcements/v5.0.8/

What's Changed
New Contributors

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.7...v5.0.8

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v5.0.7Fluent Bit 5.0.7

https://fluentbit.io/announcements/v5.0.7/

What's Changed
New Contributors

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.6...v5.0.7

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v5.0.6Fluent Bit 5.0.6

https://fluentbit.io/announcements/v5.0.6/

What's Changed
New Contributors

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.5...v5.0.6

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v5.0.5Fluent Bit 5.0.5

https://fluentbit.io/announcements/v5.0.5/

What's Changed
New Contributors

Full Changelog: https://github.com/fluent/fluent-bit/compare/v5.0.4...v5.0.5

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