Fluent Bit: Official Manual
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3.0
3.0
  • Fluent Bit v3.0 Documentation
  • About
    • What is Fluent Bit?
    • A Brief History of Fluent Bit
    • Fluentd & Fluent Bit
    • License
  • Concepts
    • Key Concepts
    • Buffering
    • Data Pipeline
      • Input
      • Parser
      • Filter
      • Buffer
      • Router
      • Output
  • Installation
    • Getting Started with Fluent Bit
    • Upgrade Notes
    • Supported Platforms
    • Requirements
    • Sources
      • Download Source Code
      • Build and Install
      • Build with Static Configuration
    • Linux Packages
      • Amazon Linux
      • Redhat / CentOS
      • Debian
      • Ubuntu
      • Raspbian / Raspberry Pi
    • Docker
    • Containers on AWS
    • Amazon EC2
    • Kubernetes
    • macOS
    • Windows
    • Yocto / Embedded Linux
    • Buildroot / Embedded Linux
  • Administration
    • Configuring Fluent Bit
      • Classic mode
        • Format and Schema
        • Configuration File
        • Variables
        • Commands
        • Upstream Servers
        • Record Accessor
      • YAML Configuration
        • Configuration File
      • Unit Sizes
      • Multiline Parsing
    • Transport Security
    • Buffering & Storage
    • Backpressure
    • Scheduling and Retries
    • Networking
    • Memory Management
    • Monitoring
    • HTTP Proxy
    • Hot Reload
    • Troubleshooting
  • Local Testing
    • Validating your Data and Structure
    • Running a Logging Pipeline Locally
  • Data Pipeline
    • Pipeline Monitoring
    • Inputs
      • Collectd
      • CPU Log Based Metrics
      • Disk I/O Log Based Metrics
      • Docker Log Based Metrics
      • Docker Events
      • Dummy
      • Elasticsearch
      • Exec
      • Exec Wasi
      • Fluent Bit Metrics
      • Forward
      • Head
      • HTTP
      • Health
      • Kafka
      • Kernel Logs
      • Kubernetes Events
      • Memory Metrics
      • MQTT
      • Network I/O Log Based Metrics
      • NGINX Exporter Metrics
      • Node Exporter Metrics
      • Podman Metrics
      • Process Log Based Metrics
      • Process Exporter Metrics
      • Prometheus Scrape Metrics
      • Prometheus Remote Write
      • Random
      • Serial Interface
      • Splunk
      • Standard Input
      • StatsD
      • Syslog
      • Systemd
      • Tail
      • TCP
      • Thermal
      • UDP
      • OpenTelemetry
      • Windows Event Log
      • Windows Event Log (winevtlog)
      • Windows Exporter Metrics
    • Parsers
      • Configuring Parser
      • JSON
      • Regular Expression
      • LTSV
      • Logfmt
      • Decoders
    • Processors
      • Content Modifier
      • Metrics Selector
      • SQL
    • Filters
      • AWS Metadata
      • CheckList
      • ECS Metadata
      • Expect
      • GeoIP2 Filter
      • Grep
      • Kubernetes
      • Log to Metrics
      • Lua
      • Parser
      • Record Modifier
      • Modify
      • Multiline
      • Nest
      • Nightfall
      • Rewrite Tag
      • Standard Output
      • Sysinfo
      • Throttle
      • Type Converter
      • Tensorflow
      • Wasm
    • Outputs
      • Amazon CloudWatch
      • Amazon Kinesis Data Firehose
      • Amazon Kinesis Data Streams
      • Amazon S3
      • Azure Blob
      • Azure Data Explorer
      • Azure Log Analytics
      • Azure Logs Ingestion API
      • Counter
      • Datadog
      • Elasticsearch
      • File
      • FlowCounter
      • Forward
      • GELF
      • Google Chronicle
      • Google Cloud BigQuery
      • HTTP
      • InfluxDB
      • Kafka
      • Kafka REST Proxy
      • LogDNA
      • Loki
      • Microsoft Fabric
      • NATS
      • New Relic
      • NULL
      • Observe
      • Oracle Log Analytics
      • OpenSearch
      • OpenTelemetry
      • PostgreSQL
      • Prometheus Exporter
      • Prometheus Remote Write
      • SkyWalking
      • Slack
      • Splunk
      • Stackdriver
      • Standard Output
      • Syslog
      • TCP & TLS
      • Treasure Data
      • Vivo Exporter
      • WebSocket
  • Stream Processing
    • Introduction to Stream Processing
    • Overview
    • Changelog
    • Getting Started
      • Fluent Bit + SQL
      • Check Keys and NULL values
      • Hands On! 101
  • Fluent Bit for Developers
    • C Library API
    • Ingest Records Manually
    • Golang Output Plugins
    • WASM Filter Plugins
    • WASM Input Plugins
    • Developer guide for beginners on contributing to Fluent Bit
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  • Sections
  • Entries: Key/Value
  • Indented Configuration Mode

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  1. Administration
  2. Configuring Fluent Bit
  3. Classic mode

Format and Schema

Fluent Bit might optionally use a configuration file to define how the service will behave.

Before proceeding we need to understand how the configuration schema works.

The schema is defined by three concepts:

  • Sections

  • Entries: Key/Value

  • Indented Configuration Mode

A simple example of a configuration file is as follows:

[SERVICE]
    # This is a commented line
    Daemon    off
    log_level debug

Sections

A section is defined by a name or title inside brackets. Looking at the example above, a Service section has been set using [SERVICE] definition. Section rules:

  • All section content must be indented (4 spaces ideally).

  • Multiple sections can exist on the same file.

  • A section is expected to have comments and entries, it cannot be empty.

  • Any commented line under a section, must be indented too.

  • End-of-line comments are not supported, only full-line comments.

Entries: Key/Value

A section may contain Entries, an entry is defined by a line of text that contains a Key and a Value, using the above example, the [SERVICE] section contains two entries, one is the key Daemon with value off and the other is the key Log_Level with the value debug. Entries rules:

  • An entry is defined by a key and a value.

  • A key must be indented.

  • A key must contain a value which ends in the breakline.

  • Multiple keys with the same name can exist.

Also commented lines are set prefixing the # character, those lines are not processed but they must be indented too.

Indented Configuration Mode

Fluent Bit configuration files are based in a strict Indented Mode, that means that each configuration file must follow the same pattern of alignment from left to right when writing text. By default an indentation level of four spaces from left to right is suggested. Example:

[FIRST_SECTION]
    # This is a commented line
    Key1  some value
    Key2  another value
    # more comments

[SECOND_SECTION]
    KeyN  3.14

As you can see there are two sections with multiple entries and comments, note also that empty lines are allowed and they do not need to be indented.

Last updated 1 year ago

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