On 2014, the Fluentd team at Treasure Data was forecasting the need for a lightweight log processor for constraint environments like Embedded Linux and Gateways, the project aimed to be part of the Fluentd Ecosystem; at that moment, Eduardo created Fluent Bit, a new open source solution written from scratch available under the terms of the Apache License v2.0.\

After the project was around for some time, it got more traction for normal Linux systems, also with the new containerized world, the Cloud Native community asked to extend the project scope to support more sources, filters, and destinations. Not so long after, Fluent Bit became one of the preferred solutions to solve the logging challenges in Cloud environments.

Fluent Bit is an open-source telemetry agent specifically designed to efficiently handle the challenges of collecting and processing telemetry data across a wide range of environments, from constrained systems to complex cloud infrastructures. Managing telemetry data from various sources and formats can be a constant challenge, particularly when performance is a critical factor.

Rather than serving as a drop-in replacement, Fluent Bit enhances the observability strategy for your infrastructure by adapting and optimizing your existing logging layer, as well as metrics and traces processing. Furthermore, Fluent Bit supports a vendor-neutral approach, seamlessly integrating with other ecosystems such as Prometheus and OpenTelemetry. Trusted by major cloud providers, banks, and companies in need of a ready-to-use telemetry agent solution, Fluent Bit effectively manages diverse data sources and formats while maintaining optimal performance.

Fluent Bit can be deployed as an edge agent for localized telemetry data handling or utilized as a central aggregator/collector for managing telemetry data across multiple sources and environments.

Fluent Bit has been designed with performance and low resource consumption in mind.

, including it core, plugins and tools are distributed under the terms of the :

When processes data, it uses the system memory (heap) as a primary and temporary place to store the record logs before they get delivered, in this private memory area the records are processed.

Buffering refers to the ability to store the records somewhere, and while they are processed and delivered, still be able to store more. Buffering in memory is the fastest mechanism, but there are certain scenarios where it requires special strategies to deal with , data safety or reduce memory consumption by the service in constrained environments.

Fluent Bit as buffering strategies go, offers a primary buffering mechanism in memory and an optional secondary one using the file system. With this hybrid solution you can accommodate any use case safely and keep a high performance while processing your data.

Both mechanisms are not mutually exclusive and when the data is ready to be processed or delivered it will always be in memory, while other data in the queue might be in the file system until is ready to be processed and moved up to memory.

To learn more about the buffering configuration in Fluent Bit, please jump to the section.

Before diving into it’s good to get acquainted with some of the key concepts of the service. This document provides a gentle introduction to those concepts and common terminology. We’ve provided a list below of all the terms we’ll cover, but we recommend reading this document from start to finish to gain a more general understanding of our log and stream processor.

• Event or Record

• Filtering

• Tag

• Timestamp

• Match

• Structured Message

Event or Record

Every incoming piece of data that belongs to a log or a metric that is retrieved by Fluent Bit is considered an Event or a Record.

As an example consider the following content of a Syslog file:

It contains four lines and all of them represents four independent Events.

Internally, an Event always has two components (in an array form):

Filtering

In some cases it is required to perform modifications on the Events content, the process to alter, enrich or drop Events is called Filtering.

There are many use cases when Filtering is required like:

• Append specific information to the Event like an IP address or metadata.

• Select a specific piece of the Event content.

• Drop Events that matches certain pattern.

Tag

Every Event that gets into Fluent Bit gets assigned a Tag. This tag is an internal string that is used in a later stage by the Router to decide which Filter or Output phase it must go through.

Most of the tags are assigned manually in the configuration. If a tag is not specified, Fluent Bit will assign the name of the Input plugin instance from where that Event was generated from.

Timestamp

The Timestamp represents the time when an Event was created. Every Event contains a Timestamp associated. The Timestamp is a numeric fractional integer in the format:

Seconds

It is the number of seconds that have elapsed since the Unix epoch.

Nanoseconds

Fractional second or one thousand-millionth of a second.

Match

Fluent Bit allows to deliver your collected and processed Events to one or multiple destinations, this is done through a routing phase. A Match represent a simple rule to select Events where it Tags matches a defined rule.

Structured Messages

Source events can have or not have a structure. A structure defines a set of keys and values inside the Event message. As an example consider the following two messages:

No structured message

Structured Message

At a low level both are just an array of bytes, but the Structured message defines keys and values, having a structure helps to implement faster operations on data modifications.

Fluent Bit is a Fast and Lightweight Telemetry Agent for Logs, Metrics, and Traces for Linux, macOS, Windows, and BSD family operating systems. It has been made with a strong focus on performance to allow the collection and processing of telemetry data from different sources without complexity.

Features

• High Performance: High throughput with low resources consumption

• Data Parsing

  • Convert your unstructured messages using our parsers: JSON, Regex, LTSV and Logfmt

• Metrics Support: Prometheus and OpenTelemetry compatible

• Reliability and Data Integrity

  • Backpressure Handling

  • Data Buffering in memory and file system

• Networking

  • Security: built-in TLS/SSL support

  • Asynchronous I/O

• Pluggable Architecture and Extensibility: Inputs, Filters and Outputs

  • More than 100 built-in plugins are available

  • Extensibility

    • Write any input, filter or output plugin in C language

    • WASM: WASM Filter Plugins or WASM Input Plugins

    • Bonus: write Filters in Lua or Output plugins in Golang

• Monitoring: expose internal metrics over HTTP in JSON and Prometheus format

• Stream Processing: Perform data selection and transformation using simple SQL queries

  • Create new streams of data using query results

  • Aggregation Windows

  • Data analysis and prediction: Timeseries forecasting

• Portable: runs on Linux, macOS, Windows and BSD systems

Fluent Bit, Fluentd and CNCF

Fluent Bit is a CNCF graduated sub-project under the umbrella of Fluentd, it's licensed under the terms of the Apache License v2.0.

Fluent Bit was originally created by Eduardo Silva; as a CNCF-hosted project is a fully vendor-neutral and community-driven project.

In production environments we want to have full control of the data we are collecting, filtering is an important feature that allows us to alter the data before delivering it to some destination.

Filtering is implemented through plugins, so each filter available could be used to match, exclude or enrich your logs with some specific metadata.

We support many filters, A common use case for filtering is Kubernetes deployments. Every Pod log needs to get the proper metadata associated

Very similar to the input plugins, Filters run in an instance context, which has its own independent configuration. Configuration keys are often called properties.

For more details about the Filters available and their usage, please refer to the Filters section.

Previously defined in the Buffering concept section, the buffer phase in the pipeline aims to provide a unified and persistent mechanism to store your data, either using the primary in-memory model or using the filesystem based mode.

The buffer phase already contains the data in an immutable state, meaning, no other filter can be applied.

Fluent Bit offers a buffering mechanism in the file system that acts as a backup system to avoid data loss in case of system failures.

Telemetry data processing in general can be complex, and at scale a bit more, that's why Fluentd was born. Fluentd has become more than a simple tool, it has grown into a fullscale ecosystem that contains SDKs for different languages and sub-projects like Fluent Bit.

On this page, we will describe the relationship between the Fluentd and Fluent Bit open source projects, as a summary we can say both are:

• Licensed under the terms of Apache License v2.0

• Graduated Hosted projects by the Cloud Native Computing Foundation (CNCF)

• Production Grade solutions: deployed million of times every single day.

• Vendor neutral and community driven projects

• Widely Adopted by the Industry: trusted by all major companies like AWS, Microsoft, Google Cloud and hundreds of others.

Both projects share a lot of similarities, Fluent Bit is fully designed and built on top of the best ideas of Fluentd architecture and general design. Choosing which one to use depends on the end-user needs.

The following table describes a comparison of different areas of the projects:

Both Fluentd and Fluent Bit can work as Aggregators or Forwarders, they both can complement each other or use them as standalone solutions. In the recent years, Cloud Providers switched from Fluentd to Fluent Bit for performance and compatibility reasons. Fluent Bit is now considered the next generation solution.

Fluent Bit provides different Input Plugins to gather information from different sources, some of them just collect data from log files while others can gather metrics information from the operating system. There are many plugins for different needs.

When an input plugin is loaded, an internal instance is created. Every instance has its own and independent configuration. Configuration keys are often called properties.

Every input plugin has its own documentation section where it's specified how it can be used and what properties are available.

For more details, please refer to the Input Plugins section.

Routing is a core feature that allows to route your data through Filters and finally to one or multiple destinations. The router relies on the concept of Tags and Matching rules

There are two important concepts in Routing:

• Tag

• Match

When the data is generated by the input plugins, it comes with a Tag (most of the time the Tag is configured manually), the Tag is a human-readable indicator that helps to identify the data source.

In order to define where the data should be routed, a Match rule must be specified in the output configuration.

Consider the following configuration example that aims to deliver CPU metrics to an Elasticsearch database and Memory metrics to the standard output interface:

[INPUT]
    Name cpu
    Tag  my_cpu

[INPUT]
    Name mem
    Tag  my_mem

[OUTPUT]
    Name   es
    Match  my_cpu

[OUTPUT]
    Name   stdout
    Match  my_mem

Note: the above is a simple example demonstrating how Routing is configured.

Routing works automatically reading the Input Tags and the Output Match rules. If some data has a Tag that doesn't match upon routing time, the data is deleted.

Routing with Wildcard

Routing is flexible enough to support wildcard in the Match pattern. The below example defines a common destination for both sources of data:

[INPUT]
    Name cpu
    Tag  my_cpu

[INPUT]
    Name mem
    Tag  my_mem

[OUTPUT]
    Name   stdout
    Match  my_*

The match rule is set to my_* which means it will match any Tag that starts with my_.

Dealing with raw strings or unstructured messages is a constant pain; having a structure is highly desired. Ideally we want to set a structure to the incoming data by the Input Plugins as soon as they are collected:

The Parser allows you to convert from unstructured to structured data. As a demonstrative example consider the following Apache (HTTP Server) log entry:

192.168.2.20 - - [28/Jul/2006:10:27:10 -0300] "GET /cgi-bin/try/ HTTP/1.0" 200 3395

The above log line is a raw string without format, ideally we would like to give it a structure that can be processed later easily. If the proper configuration is used, the log entry could be converted to:

{
  "host":    "192.168.2.20",
  "user":    "-",
  "method":  "GET",
  "path":    "/cgi-bin/try/",
  "code":    "200",
  "size":    "3395",
  "referer": "",
  "agent":   ""
 }

Parsers are fully configurable and are independently and optionally handled by each input plugin, for more details please refer to the Parsers section.

The following operating systems and architectures are supported in Fluent Bit.

From an architecture support perspective, Fluent Bit is fully functional on x86_64, Arm64v8 and Arm32v7 based processors.

uses very low CPU and Memory consumption, it's compatible with most of x86, x86_64, arm32v7 and arm64v8 based platforms. In order to build it you need the following components in your system for the build process:

• Compiler: GCC or clang

• CMake

• Flex & Bison: only if you enable the Stream Processor or Record Accessor feature (both enabled by default)

• Libyaml development headers and libraries

In the core there are not other dependencies, For certain features that depends on third party components like output plugins with special backend libraries (e.g: kafka), those are included in the main source code repository.

Container Deployment

Install on Linux (Packages)

Install on Windows (Packages)

Install on macOS (Packages)

Compile from Source (Linux, Windows, FreeBSD, macOS)

Sandbox Environment

If you are interested in learning about Fluent Bit you can try out the sandbox environment

Enterprise Packages

The following article cover the relevant notes for users upgrading from previous Fluent Bit versions. We aim to cover compatibility changes that you must be aware of.

For more details about changes on each release please refer to the .

Note: release notes will be prepared in advance of a Git tag for a release so an official release should provide both a tag and a release note together to allow users to verify and understand the release contents.

The tag drives the overall binary release process so release binaries (containers/packages) will appear after a tag and its associated release note. This allows users to expect the new release binary to appear and allow/deny/update it as appropriate in their infrastructure.

Fluent Bit v1.9.9

The td-agent-bit package is no longer provided after this release. Users should switch to the fluent-bit package.

Fluent Bit v1.6

If you are migrating from previous version of Fluent Bit please review the following important changes:

Tail Input Plugin

Now by default the plugin follows a file from the end once the service starts (old behavior was always read from the beginning). For every file found at start, its followed from it last position, for new files discovered at runtime or rotated, they are read from the beginning.

If you desire to keep the old behavior you can set the option read_from_head to true.

Stackdriver Output Plugin

The project_id of in sent to Google Cloud Logging would be set to the project ID rather than the project number. To learn the difference between Project ID and project number, see for more details.

If you have any existing queries based on the resource's project_id, please update your query accordingly.

Fluent Bit v1.5

The migration from v1.4 to v1.5 is pretty straightforward.

Fluent Bit v1.4

If you are migrating from Fluent Bit v1.3, there are no breaking changes. Just new exciting features to enjoy :)

Fluent Bit v1.3

If you are migrating from Fluent Bit v1.2 to v1.3, there are no breaking changes. If you are upgrading from an older version please review the incremental changes below.

Fluent Bit v1.2

Docker, JSON, Parsers and Decoders

On Fluent Bit v1.2 we have fixed many issues associated with JSON encoding and decoding, for hence when parsing Docker logs is no longer necessary to use decoders. The new Docker parser looks like this:

Note: again, do not use decoders.

Kubernetes Filter

We have done improvements also on how Kubernetes Filter handle the stringified log message. If the option Merge_Log is enabled, it will try to handle the log content as a JSON map, if so, it will add the keys to the root map.

In addition, we have fixed and improved the option called Merge_Log_Key. If a merge log succeed, all new keys will be packaged under the key specified by this option, a suggested configuration is as follows:

As an example, if the original log content is the following map:

the final record will be composed as follows:

Fluent Bit v1.1

If you are upgrading from Fluent Bit <= 1.0.x you should take in consideration the following relevant changes when switching to Fluent Bit v1.1 series:

Kubernetes Filter

We introduced a new configuration property called Kube_Tag_Prefix to help Tag prefix resolution and address an unexpected behavior that landed in previous versions.

During 1.0.x release cycle, a commit in Tail input plugin changed the default behavior on how the Tag was composed when using the wildcard for expansion generating breaking compatibility with other services. Consider the following configuration example:

The expected behavior is that Tag will be expanded to:

but the change introduced in 1.0 series switched from absolute path to the base file name only:

On Fluent Bit v1.1 release we restored to our default behavior and now the Tag is composed using the absolute path of the monitored file.

Having absolute path in the Tag is relevant for routing and flexible configuration where it also helps to keep compatibility with Fluentd behavior.

This behavior switch in Tail input plugin affects how Filter Kubernetes operates. As you know when the filter is used it needs to perform local metadata lookup that comes from the file names when using Tail as a source. Now with the new Kube_Tag_Prefix option you can specify what's the prefix used in Tail input plugin, for the configuration example above the new configuration will look as follows:

So the proper for Kube_Tag_Prefix value must be composed by Tag prefix set in Tail input plugin plus the converted monitored directory replacing slashes with dots.

The output interface allows us to define destinations for the data. Common destinations are remote services, local file system or standard interface with others. Outputs are implemented as plugins and there are many available.

When an output plugin is loaded, an internal instance is created. Every instance has its own independent configuration. Configuration keys are often called properties.

Every output plugin has its own documentation section specifying how it can be used and what properties are available.

Stable

For production systems, we strongly suggest that you always get the latest stable release of the source code in either zip or tarball format from Github using the following link pattern:

https://github.com/fluent/fluent-bit/archive/refs/tags/v<release version>.tar.gz https://github.com/fluent/fluent-bit/archive/refs/tags/v<release version>.zip

For example for version 1.8.12 the link is the following:

Development

For anyone who aims to contribute to the project by testing or extending the code base, you can get the development version from our GIT repository:

Note that our master branch is where the development of Fluent Bit happens. Since it's a development version, expect issues when compiling or at run time.

We encourage everybody to help us testing every development version, at the end this is what will become stable.

Fluent Bit is distributed as fluent-bit package and is available for the latest (and legacy) stable Debian systems: Bookworm and Bullseye. The following architectures are supported

• x86_64

• aarch64 / arm64v8

Single line install

A simple installation script is provided to be used for most Linux targets. This will always install the most recent version released.

curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh

This is purely a convenience helper and should always be validated prior to use. The recommended secure deployment approach is to follow the instructions below.

Server GPG key

The first step is to add our server GPG key to your keyring, on that way you can get our signed packages. Follow the official Debian wiki guidance: https://wiki.debian.org/DebianRepository/UseThirdParty#OpenPGP\_Key\_distribution

curl https://packages.fluentbit.io/fluentbit.key | gpg --dearmor > /usr/share/keyrings/fluentbit-keyring.gpg

Updated key from March 2022

From the 1.9.0 and 1.8.15 releases please note that the GPG key has been updated at https://packages.fluentbit.io/fluentbit.key so ensure this new one is added.

The GPG Key fingerprint of the new key is:

C3C0 A285 34B9 293E AF51  FABD 9F9D DC08 3888 C1CD
Fluentbit releases (Releases signing key) <releases@fluentbit.io>

The previous key is still available at https://packages.fluentbit.io/fluentbit-legacy.key and may be required to install previous versions.

The GPG Key fingerprint of the old key is:

F209 D876 2A60 CD49 E680 633B 4FF8 368B 6EA0 722A

Refer to the supported platform documentation to see which platforms are supported in each release.

Update your sources lists

On Debian, you need to add our APT server entry to your sources lists, please add the following content at bottom of your /etc/apt/sources.list file - ensure to set CODENAME to your specific Debian release name (e.g. bookworm for Debian 12):

deb [signed-by=/usr/share/keyrings/fluentbit-keyring.gpg] https://packages.fluentbit.io/debian/${CODENAME} ${CODENAME} main

Update your repositories database

Now let your system update the apt database:

sudo apt-get update

Install Fluent Bit

Using the following apt-get command you are able now to install the latest fluent-bit:

sudo apt-get install fluent-bit

Now the following step is to instruct systemd to enable the service:

sudo systemctl start fluent-bit

If you do a status check, you should see a similar output like this:

sudo service fluent-bit status
● fluent-bit.service - Fluent Bit
   Loaded: loaded (/lib/systemd/system/fluent-bit.service; disabled; vendor preset: enabled)
   Active: active (running) since mié 2016-07-06 16:58:25 CST; 2h 45min ago
 Main PID: 6739 (fluent-bit)
    Tasks: 1
   Memory: 656.0K
      CPU: 1.393s
   CGroup: /system.slice/fluent-bit.service
           └─6739 /opt/fluent-bit/bin/fluent-bit -c /etc/fluent-bit/fluent-bit.conf
...

The default configuration of fluent-bit is collecting metrics of CPU usage and sending the records to the standard output, you can see the outgoing data in your /var/log/syslog file.

The most secure option is to create the repositories acccording to the instructions for your specific OS.

A simple installation script is provided to be used for most Linux targets. This will by default install the most recent version released.

curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh

This is purely a convenience helper and should always be validated prior to use.

GPG key updates

From the 1.9.0 and 1.8.15 releases please note that the GPG key has been updated at https://packages.fluentbit.io/fluentbit.key so ensure this new one is added.

The GPG Key fingerprint of the new key is:

C3C0 A285 34B9 293E AF51  FABD 9F9D DC08 3888 C1CD
Fluentbit releases (Releases signing key) <releases@fluentbit.io>

The previous key is still available at https://packages.fluentbit.io/fluentbit-legacy.key and may be required to install previous versions.

The GPG Key fingerprint of the old key is:

F209 D876 2A60 CD49 E680 633B 4FF8 368B 6EA0 722A

Refer to the supported platform documentation to see which platforms are supported in each release.

Migration to Fluent Bit

From version 1.9, td-agent-bit is a deprecated package and is removed after 1.9.9. The correct package name to use now is fluent-bit.

Fluent Bit in normal operation mode allows to be configurable through text files or using specific arguments in the command line, while this is the ideal deployment case, there are scenarios where a more restricted configuration is required: static configuration mode.

Static configuration mode aims to include a built-in configuration in the final binary of Fluent Bit, disabling the usage of external files or flags at runtime.

Getting Started

Requirements

The following steps assumes you are familiar with configuring Fluent Bit using text files and you have experience building it from scratch as described in the Build and Install section.

Configuration Directory

In your file system prepare a specific directory that will be used as an entry point for the build system to lookup and parse the configuration files. It is mandatory that this directory contain as a minimum one configuration file called fluent-bit.conf containing the required SERVICE, INPUT and OUTPUT sections. As an example create a new fluent-bit.conf file with the following content:

[SERVICE]
    Flush     1
    Daemon    off
    Log_Level info

[INPUT]
    Name      cpu

[OUTPUT]
    Name      stdout
    Match     *

the configuration provided above will calculate CPU metrics from the running system and print them to the standard output interface.

Build with Custom Configuration

Inside Fluent Bit source code, get into the build/ directory and run CMake appending the FLB_STATIC_CONF option pointing the configuration directory recently created, e.g:

$ cd fluent-bit/build/
$ cmake -DFLB_STATIC_CONF=/path/to/my/confdir/

then build it:

$ make

At this point the fluent-bit binary generated is ready to run without necessity of further configuration:

$ bin/fluent-bit 
Fluent-Bit v0.15.0
Copyright (C) Treasure Data

[2018/10/19 15:32:31] [ info] [engine] started (pid=15186)
[0] cpu.local: [1539984752.000347547, {"cpu_p"=>0.750000, "user_p"=>0.500000, "system_p"=>0.250000, "cpu0.p_cpu"=>1.000000, "cpu0.p_user"=>1.000000, "cpu0.p_system"=>0.000000, "cpu1.p_cpu"=>0.000000, "cpu1.p_user"=>0.000000, "cpu1.p_system"=>0.000000, "cpu2.p_cpu"=>0.000000, "cpu2.p_user"=>0.000000, "cpu2.p_system"=>0.000000, "cpu3.p_cpu"=>1.000000, "cpu3.p_user"=>1.000000, "cpu3.p_system"=>0.000000}]

Install on Amazon Linux

Fluent Bit is distributed as fluent-bit package and is available for the latest Amazon Linux 2 and Amazon Linux 2022. The following architectures are supported

• x86_64

• aarch64 / arm64v8

Single line install

A simple installation script is provided to be used for most Linux targets. This will always install the most recent version released.

curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh

This is purely a convenience helper and should always be validated prior to use. The recommended secure deployment approach is to follow the instructions below.

Amazon Linux 2022

For Amazon Linux 2022, until it is GA, we need to force it to use the 2022 releasever in Yum but only for the Fluent Bit repository.

export FLUENT_BIT_INSTALL_COMMAND_PREFIX="sed -i 's|\$releasever/|2022/|g' /etc/yum.repos.d/fluent-bit.repo"
curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh

Configure Yum

We provide fluent-bit through a Yum repository. In order to add the repository reference to your system, please add a new file called fluent-bit.repo in /etc/yum.repos.d/ with the following content:

Amazon Linux 2

[fluent-bit]
name = Fluent Bit
baseurl = https://packages.fluentbit.io/amazonlinux/2/$basearch/
gpgcheck=1
gpgkey=https://packages.fluentbit.io/fluentbit.key
enabled=1

Amazon Linux 2022

[fluent-bit]
name = Fluent Bit
baseurl = https://packages.fluentbit.io/amazonlinux/2022/$basearch/
gpgcheck=1
gpgkey=https://packages.fluentbit.io/fluentbit.key
enabled=1

Note: we encourage you always enable the gpgcheck for security reasons. All our packages are signed.

Updated key from March 2022

From the 1.9.0 and 1.8.15 releases please note that the GPG key has been updated at https://packages.fluentbit.io/fluentbit.key so ensure this new one is added.

The GPG Key fingerprint of the new key is:

C3C0 A285 34B9 293E AF51  FABD 9F9D DC08 3888 C1CD
Fluentbit releases (Releases signing key) <releases@fluentbit.io>

The previous key is still available at https://packages.fluentbit.io/fluentbit-legacy.key and may be required to install previous versions.

The GPG Key fingerprint of the old key is:

F209 D876 2A60 CD49 E680 633B 4FF8 368B 6EA0 722A

Refer to the supported platform documentation to see which platforms are supported in each release.

Install

Once your repository is configured, run the following command to install it:

yum install fluent-bit

Now the following step is to instruct systemd to enable the service:

sudo service fluent-bit start

If you do a status check, you should see a similar output like this:

$ service fluent-bit status
Redirecting to /bin/systemctl status  fluent-bit.service
● fluent-bit.service - Fluent Bit
   Loaded: loaded (/usr/lib/systemd/system/fluent-bit.service; disabled; vendor preset: disabled)
   Active: active (running) since Thu 2016-07-07 02:08:01 BST; 9s ago
 Main PID: 3820 (fluent-bit)
   CGroup: /system.slice/fluent-bit.service
           └─3820 /opt/fluent-bit/bin/fluent-bit -c etc/fluent-bit/fluent-bit.conf
...

The default configuration of fluent-bit is collecting metrics of CPU usage and sending the records to the standard output, you can see the outgoing data in your /var/log/messages file.

Install on Redhat / CentOS

Fluent Bit is distributed as fluent-bit package and is available for the latest stable CentOS system.

The following architectures are supported

• x86_64

• aarch64 / arm64v8

For CentOS 9+ we use CentOS Stream as the canonical base system.

Single line install

A simple installation script is provided to be used for most Linux targets. This will always install the most recent version released.

curl https://raw.githubusercontent.com/fluent/fluent-bit/master/install.sh | sh

This is purely a convenience helper and should always be validated prior to use. The recommended secure deployment approach is to follow the instructions below.

CentOS 8

CentOS 8 is now EOL so the default Yum repositories are unavailable.

Make sure to configure to use an appropriate mirror, for example:

$ sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-* && \
  sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*

An alternative is to use Rocky or Alma Linux which should be equivalent.

Configure Yum

We provide fluent-bit through a Yum repository. In order to add the repository reference to your system, please add a new file called fluent-bit.repo in /etc/yum.repos.d/ with the following content:

[fluent-bit]
name = Fluent Bit
baseurl = https://packages.fluentbit.io/centos/$releasever/$basearch/
gpgcheck=1
gpgkey=https://packages.fluentbit.io/fluentbit.key
repo_gpgcheck=1
enabled=1

It is best practice to always enable the gpgcheck and repo_gpgcheck for security reasons. We sign our repository metadata as well as all of our packages.

Updated key from March 2022

From the 1.9.0 and 1.8.15 releases please note that the GPG key has been updated at https://packages.fluentbit.io/fluentbit.key so ensure this new one is added.

The GPG Key fingerprint of the new key is:

C3C0 A285 34B9 293E AF51  FABD 9F9D DC08 3888 C1CD
Fluentbit releases (Releases signing key) <releases@fluentbit.io>

The previous key is still available at https://packages.fluentbit.io/fluentbit-legacy.key and may be required to install previous versions.

The GPG Key fingerprint of the old key is:

F209 D876 2A60 CD49 E680 633B 4FF8 368B 6EA0 722A

Refer to the supported platform documentation to see which platforms are supported in each release.

Install

Once your repository is configured, run the following command to install it:

yum install fluent-bit

Now the following step is to instruct Systemd to enable the service:

sudo service fluent-bit start

If you do a status check, you should see a similar output like this:

$ service fluent-bit status
Redirecting to /bin/systemctl status  fluent-bit.service
● fluent-bit.service - Fluent Bit
   Loaded: loaded (/usr/lib/systemd/system/fluent-bit.service; disabled; vendor preset: disabled)
   Active: active (running) since Thu 2016-07-07 02:08:01 BST; 9s ago
 Main PID: 3820 (fluent-bit)
   CGroup: /system.slice/fluent-bit.service
           └─3820 /opt/fluent-bit/bin/fluent-bit -c etc/fluent-bit/fluent-bit.conf
...

The default configuration of fluent-bit is collecting metrics of CPU usage and sending the records to the standard output, you can see the outgoing data in your /var/log/messages file.

FAQ

Yum install fails with a "404 - Page not found" error for the package mirror

The fluent-bit.repo file for the latest installations of Fluent-Bit uses a $releasever variable to determine the correct version of the package to install to your system:

[fluent-bit]
name = Fluent Bit
baseurl = https://packages.fluentbit.io/centos/$releasever/$basearch/
...

Depending on your Red Hat distribution version, this variable may return a value other than the OS major release version (e.g., RHEL7 Server distributions return "7Server" instead of just "7"). The Fluent-Bit package url uses just the major OS release version, so any other value here will cause a 404.

In order to resolve this issue, you can replace the $releasever variable with your system's OS major release version. For example:

[fluent-bit]
name = Fluent Bit
baseurl = https://packages.fluentbit.io/centos/7/$basearch/
gpgcheck=1
gpgkey=https://packages.fluentbit.io/fluentbit.key
repo_gpgcheck=1
enabled=1

Fluent Bit uses CMake as its build system. The suggested procedure to prepare the build system consists of the following steps:

Requirements

• CMake >= 3.0

• Flex

• Bison

• YAML headers

• OpenSSL headers

Prepare environment

In the following steps you can find exact commands to build and install the project with the default options. If you already know how CMake works you can skip this part and look at the build options available. Note that Fluent Bit requires CMake 3.x. You may need to use cmake3 instead of cmake to complete the following steps on your system.

Change to the build/ directory inside the Fluent Bit sources:

$ cd build/

Let CMake configure the project specifying where the root path is located:

$ cmake ../
-- The C compiler identification is GNU 4.9.2
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- The CXX compiler identification is GNU 4.9.2
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
...
-- Could NOT find Doxygen (missing:  DOXYGEN_EXECUTABLE)
-- Looking for accept4
-- Looking for accept4 - not found
-- Configuring done
-- Generating done
-- Build files have been written to: /home/edsiper/coding/fluent-bit/build

Now you are ready to start the compilation process through the simple make command:

$ make
Scanning dependencies of target msgpack
[  2%] Building C object lib/msgpack-1.1.0/CMakeFiles/msgpack.dir/src/unpack.c.o
[  4%] Building C object lib/msgpack-1.1.0/CMakeFiles/msgpack.dir/src/objectc.c.o
[  7%] Building C object lib/msgpack-1.1.0/CMakeFiles/msgpack.dir/src/version.c.o
...
[ 19%] Building C object lib/monkey/mk_core/CMakeFiles/mk_core.dir/mk_file.c.o
[ 21%] Building C object lib/monkey/mk_core/CMakeFiles/mk_core.dir/mk_rconf.c.o
[ 23%] Building C object lib/monkey/mk_core/CMakeFiles/mk_core.dir/mk_string.c.o
...
Scanning dependencies of target fluent-bit-static
[ 66%] Building C object src/CMakeFiles/fluent-bit-static.dir/flb_pack.c.o
[ 69%] Building C object src/CMakeFiles/fluent-bit-static.dir/flb_input.c.o
[ 71%] Building C object src/CMakeFiles/fluent-bit-static.dir/flb_output.c.o
...
Linking C executable ../bin/fluent-bit
[100%] Built target fluent-bit-bin

to continue installing the binary on the system just do:

$ make install

it's likely you may need root privileges so you can try to prefixing the command with sudo.

Build Options

Fluent Bit provides certain options to CMake that can be enabled or disabled when configuring, please refer to the following tables under the General Options, Development Options, Input Plugins and _Output Plugins sections.

General Options

Development Options

Optimization Options

Input Plugins

The input plugins provides certain features to gather information from a specific source type which can be a network interface, some built-in metric or through a specific input device, the following input plugins are available:

Filter Plugins

The filter plugins allows to modify, enrich or drop records. The following table describes the filters available on this version:

Output Plugins

The output plugins gives the capacity to flush the information to some external interface, service or terminal, the following table describes the output plugins available as of this version:

Fluent Bit is distributed as fluent-bit package and is available for the Raspberry, specifically for distribution, the following versions are supported:

• Raspbian Bullseye (11)

• Raspbian Buster (10)

Server GPG key

The first step is to add our server GPG key to your keyring, on that way you can get our signed packages:

Updated key from March 2022

From the 1.9.0 and 1.8.15 releases please note that the GPG key has been updated at so ensure this new one is added.

The GPG Key fingerprint of the new key is:

The previous key is still available at and may be required to install previous versions.

The GPG Key fingerprint of the old key is:

Refer to the to see which platforms are supported in each release.

Update your sources lists

On Debian and derivative systems such as Raspbian, you need to add our APT server entry to your sources lists, please add the following content at bottom of your /etc/apt/sources.list file.

Raspbian 11 (Bullseye)

Raspbian 10 (Buster)

Update your repositories database

Now let your system update the apt database:

Install Fluent Bit

Using the following apt-get command you are able now to install the latest fluent-bit:

Now the following step is to instruct systemd to enable the service:

If you do a status check, you should see a similar output like this:

The default configuration of fluent-bit is collecting metrics of CPU usage and sending the records to the standard output, you can see the outgoing data in your /var/log/syslog file.

AWS maintains a distribution of Fluent Bit combining the latest official release with a set of Go Plugins for sending logs to AWS services. AWS and Fluent Bit are working together to rewrite their plugins for inclusion in the official Fluent Bit distribution.

Plugins

Currently, the image contains Go Plugins for:

Fluent Bit includes Amazon CloudWatch Logs plugin named cloudwatch_logs, Amazon Kinesis Firehose plugin named kinesis_firehose and Amazon Kinesis Data Streams plugin named kinesis_streams which are higher performance than Go plugins.

Also, Fluent Bit includes S3 output plugin named s3.

Versions and Regional Repositories

AWS vends their container image via , and a set of highly available regional Amazon ECR repositories. For more information, see the .

The AWS for Fluent Bit image uses a custom versioning scheme because it contains multiple projects. To see what each release contains, check out the .

SSM Public Parameters

AWS vends SSM Public Parameters with the regional repository link for each image. These parameters can be queried by any AWS account.

To see a list of available version tags in a given region, run the following command:

To see the ECR repository URI for a given image tag in a given region, run the following:

You can use these SSM public parameters as parameters in your CloudFormation templates:

Fluent Bit is distributed as fluent-bit package and is available for the latest stable Ubuntu system: Jammy Jellyfish.

Single line install

A simple installation script is provided to be used for most Linux targets. This will always install the most recent version released.

This is purely a convenience helper and should always be validated prior to use. The recommended secure deployment approach is to follow the instructions below.

Server GPG key

The first step is to add our server GPG key to your keyring to ensure you can get our signed packages. Follow the official Debian wiki guidance:

Updated key from March 2022

From the 1.9.0 and 1.8.15 releases please note that the GPG key has been updated at so ensure this new one is added.

The GPG Key fingerprint of the new key is:

The previous key is still available at and may be required to install previous versions.

The GPG Key fingerprint of the old key is:

Update your sources lists

Update your repositories database

Now let your system update the apt database:

## Install Fluent Bit

Using the following apt-get command you are able now to install the latest fluent-bit:

Now the following step is to instruct systemd to enable the service:

If you do a status check, you should see a similar output like this:

The default configuration of fluent-bit is collecting metrics of CPU usage and sending the records to the standard output, you can see the outgoing data in your /var/log/syslog file.

Fluent Bit container images are available on Docker Hub ready for production usage. Current available images can be deployed in multiple architectures.

Quick Start

Get started by simply typing the following command:

Tags and Versions

The following table describes the Linux container tags that are available on Docker Hub repository:

It is strongly suggested that you always use the latest image of Fluent Bit.

Windows container images are provided from v2.0.6 for Windows Server 2019 and Windows Server 2022. These can be found as tags on the same Docker Hub registry above.

Multi Architecture Images

From a deployment perspective, there is no need to specify an architecture, the container client tool that pulls the image gets the proper layer for the running architecture.

Verify signed container images

Note: replace cosign above with the binary installed if it has a different name (e.g. cosign-linux-amd64).

Keyless signing is also provided but this is still experimental:

Getting Started

Download the last stable image from 2.0 series:

Once the image is in place, now run the following (useless) test which makes Fluent Bit measure CPU usage by the container:

That command will let Fluent Bit measure CPU usage every second and flush the results to the standard output, e.g:

F.A.Q

Why there is no Fluent Bit Docker image based on Alpine Linux ?

Alpine Linux uses Musl C library instead of Glibc. Musl is not fully compatible with Glibc which generated many issues in the following areas when used with Fluent Bit:

• Memory Allocator: to run Fluent Bit properly in high-load environments, we use Jemalloc as a default memory allocator which reduce fragmentation and provides better performance for our needs. Jemalloc cannot run smoothly with Musl and requires extra work.

• Alpine Linux Musl functions bootstrap have a compatibility issue when loading Golang shared libraries, this generate problems when trying to load Golang output plugins in Fluent Bit.

• Alpine Linux Musl Time format parser does not support Glibc extensions

• Maintainers preference in terms of base image due to security and maintenance reasons are Distroless and Debian.

Why use distroless containers ?

• Only include what you need, reduce the attack surface available.

• Reduces size so improves perfomance as well.

• Reduces false positives on scans (and reduces resources required for scanning).

• Reduces supply chain security requirements to just what you need.

• Helps prevent unauthorised processes or users interacting with the container.

• Less need to harden the container (and container runtime, K8S, etc.).

• Faster CICD processes.

With any choice of course there are downsides:

• No shell or package manager to update/add things.

  • Generally though dynamic updating is a bad idea in containers as the time it is done affects the outcome: two containers started at different times using the same base image may perform differently or get different dependencies, etc.

  • A better approach is to rebuild a new image version but then you can do this with Distroless, however it is harder requiring multistage builds or similar to provide the new dependencies.

• Debugging can be harder.

  • More specifically you need applications set up to properly expose information for debugging rather than rely on traditional debug approaches of connecting to processes or dumping memory. This can be an upfront cost vs a runtime cost but does shift left in the development process so hopefully is a reduction overall.

• Assumption that Distroless is secure: nothing is secure (just more or less secure) and there are still exploits so it does not remove the need for securing your system.

• Sometimes you need to use a common base image, e.g. with audit/security/health/etc. hooks integrated, or common base tooling (this could still be Distroless though).

One other important thing to note is that exec'ing into a container will potentially impact resource limits.

• This can be a quite different container from the one you want to investigate (e.g. lots of extra tools or even a different base).

• No resource limits applied to this container - can be good or bad.

• Runs in pod namespaces, just another container that can access everything the others can.

• May need architecture of the pod to share volumes, etc.

• Requires more recent versions of K8S and the container runtime plus RBAC allowing it.

Learn how to .

Fluent Bit is compatible with latest Apple macOS system on x86_64 and Apple Silicon M1 architectures. At the moment there is no official supported package but you can build it from sources by following the instructions below.

Requirements

For the next steps, you will need to have Homebrew installed in your system. If is not there, you can install it with the following command:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Installing from Homebrew

The Fluent Bit package on Homebrew is not officially supported, but should work for basic use cases and testing. It can be installed using:

brew install fluent-bit

Compile from Source

Install build dependencies

Run the following brew command in your terminal to retrieve the dependencies:

brew install git cmake openssl bison

Get the source and build it

Grab a fresh copy of the Fluent Bit source code (upstream):

git clone https://github.com/fluent/fluent-bit
cd fluent-bit

Optionally, if you want to use a specific version, just checkout to the proper tag. If you want to use v1.8.13 just do:

git checkout v1.8.13

In order to prepare the build system, we need to expose certain environment variables so Fluent Bit CMake build rules can pick the right libraries:

export OPENSSL_ROOT_DIR=`brew --prefix openssl`
export PATH=`brew --prefix bison`/bin:$PATH

Change to the build/ directory inside the Fluent Bit sources:

cd build/

Build Fluent Bit. Note that we are indicating to the build system "where" the final binaries and config files should be installed:

cmake -DFLB_DEV=on -DCMAKE_INSTALL_PREFIX=/opt/fluent-bit ../
make -j 16

Install Fluent Bit to the directory specified above. Note that this requires root privileges due to the directory we will write information to:

sudo make install

The binaries and configuration examples can be located at /opt/fluent-bit/.

Create macOS installer from source

Grab a fresh copy of the Fluent Bit source code (upstream):

git clone https://github.com/fluent/fluent-bit
cd fluent-bit

Optionally, if you want to use a specific version, just checkout to the proper tag. If you want to use v1.9.2 just do:

git checkout v1.9.2

In order to prepare the build system, we need to expose certain environment variables so Fluent Bit CMake build rules can pick the right libraries:

export OPENSSL_ROOT_DIR=`brew --prefix openssl`
export PATH=`brew --prefix bison`/bin:$PATH

And then, creating the specific macOS SDK target (For example, specifying macOS Big Sur (11.3) SDK environment):

export MACOSX_DEPLOYMENT_TARGET=11.3

Change to the build/ directory inside the Fluent Bit sources:

cd build/

Build the Fluent Bit macOS installer.

cmake -DCPACK_GENERATOR=productbuild -DCMAKE_INSTALL_PREFIX=/opt/fluent-bit ../
make -j 16
cpack -G productbuild

Then, macOS installer will be generated as:

CPack: Create package using productbuild
CPack: Install projects
CPack: - Run preinstall target for: fluent-bit
CPack: - Install project: fluent-bit []
CPack: -   Install component: binary
CPack: -   Install component: library
CPack: -   Install component: headers
CPack: -   Install component: headers-extra
CPack: Create package
CPack: -   Building component package: /Users/fluent-bit-builder/GitHub/fluent-bit/build/_CPack_Packages/Darwin/productbuild//Users/fluent-bit-builder/GitHub/fluent-bit/build/fluent-bit-1.9.2-apple/Contents/Packages/fluent-bit-1.9.2-apple-binary.pkg
CPack: -   Building component package: /Users/fluent-bit-builder/GitHub/fluent-bit/build/_CPack_Packages/Darwin/productbuild//Users/fluent-bit-builder/GitHub/fluent-bit/build/fluent-bit-1.9.2-apple/Contents/Packages/fluent-bit-1.9.2-apple-headers.pkg
CPack: -   Building component package: /Users/fluent-bit-builder/GitHub/fluent-bit/build/_CPack_Packages/Darwin/productbuild//Users/fluent-bit-builder/GitHub/fluent-bit/build/fluent-bit-1.9.2-apple/Contents/Packages/fluent-bit-1.9.2-apple-headers-extra.pkg
CPack: -   Building component package: /Users/fluent-bit-builder/GitHub/fluent-bit/build/_CPack_Packages/Darwin/productbuild//Users/fluent-bit-builder/GitHub/fluent-bit/build/fluent-bit-1.9.2-apple/Contents/Packages/fluent-bit-1.9.2-apple-library.pkg
CPack: - package: /Users/fluent-bit-builder/GitHub/fluent-bit/build/fluent-bit-1.9.2-apple.pkg generated.

Finally, fluent-bit-<fluent-bit version>-(intel or apple).pkg will be generated.

The created installer will put binaries at /opt/fluent-bit/.

Running Fluent Bit

To make the access path easier to Fluent Bit binary, in your terminal extend the PATH variable:

export PATH=/opt/fluent-bit/bin:$PATH

Now as a simple test, try Fluent Bit by generating a simple dummy message which will be printed to the standard output interface every 1 second:

 fluent-bit -i dummy -o stdout -f 1

You will see an output similar to this:

Fluent Bit v1.9.0
* Copyright (C) 2015-2021 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2022/02/08 17:13:52] [ info] [engine] started (pid=14160)
[2022/02/08 17:13:52] [ info] [storage] version=1.1.6, initializing...
[2022/02/08 17:13:52] [ info] [storage] in-memory
[2022/02/08 17:13:52] [ info] [storage] normal synchronization mode, checksum disabled, max_chunks_up=128
[2022/02/08 17:13:52] [ info] [cmetrics] version=0.2.2
[2022/02/08 17:13:52] [ info] [sp] stream processor started
[0] dummy.0: [1644362033.676766000, {"message"=>"dummy"}]
[0] dummy.0: [1644362034.676914000, {"message"=>"dummy"}]

To halt the process, press ctrl-c in the terminal.

Currently, Fluent Bit supports two configuration formats:

• Classic mode.

• Yaml. (YAML configuration is tech preview so not recommended for production.)

CLI flags

Fluent Bit also supports a CLI interface with various flags matching up to the configuration options available.

$ docker run --rm -it fluent/fluent-bit --help
Usage: /fluent-bit/bin/fluent-bit [OPTION]

Available Options
  -b  --storage_path=PATH specify a storage buffering path
  -c  --config=FILE       specify an optional configuration file
  -d, --daemon            run Fluent Bit in background mode
  -D, --dry-run           dry run
  -f, --flush=SECONDS     flush timeout in seconds (default: 1)
  -C, --custom=CUSTOM     enable a custom plugin
  -i, --input=INPUT       set an input
  -F  --filter=FILTER     set a filter
  -m, --match=MATCH       set plugin match, same as '-p match=abc'
  -o, --output=OUTPUT     set an output
  -p, --prop="A=B"        set plugin configuration property
  -R, --parser=FILE       specify a parser configuration file
  -e, --plugin=FILE       load an external plugin (shared lib)
  -l, --log_file=FILE     write log info to a file
  -t, --tag=TAG           set plugin tag, same as '-p tag=abc'
  -T, --sp-task=SQL       define a stream processor task
  -v, --verbose           increase logging verbosity (default: info)
  -w, --workdir           set the working directory
  -H, --http              enable monitoring HTTP server
  -P, --port              set HTTP server TCP port (default: 2020)
  -s, --coro_stack_size   set coroutines stack size in bytes (default: 24576)
  -q, --quiet             quiet mode
  -S, --sosreport         support report for Enterprise customers
  -V, --version           show version number
  -h, --help              print this help

Inputs
  cpu                     CPU Usage
  mem                     Memory Usage
  thermal                 Thermal
  kmsg                    Kernel Log Buffer
  proc                    Check Process health
  disk                    Diskstats
  systemd                 Systemd (Journal) reader
  netif                   Network Interface Usage
  docker                  Docker containers metrics
  docker_events           Docker events
  node_exporter_metrics   Node Exporter Metrics (Prometheus Compatible)
  fluentbit_metrics       Fluent Bit internal metrics
  prometheus_scrape       Scrape metrics from Prometheus Endpoint
  tail                    Tail files
  dummy                   Generate dummy data
  dummy_thread            Generate dummy data in a separate thread
  head                    Head Input
  health                  Check TCP server health
  http                    HTTP
  collectd                collectd input plugin
  statsd                  StatsD input plugin
  opentelemetry           OpenTelemetry
  nginx_metrics           Nginx status metrics
  serial                  Serial input
  stdin                   Standard Input
  syslog                  Syslog
  tcp                     TCP
  mqtt                    MQTT, listen for Publish messages
  forward                 Fluentd in-forward
  random                  Random

Filters
  alter_size              Alter incoming chunk size
  aws                     Add AWS Metadata
  checklist               Check records and flag them
  record_modifier         modify record
  throttle                Throttle messages using sliding window algorithm
  type_converter          Data type converter
  kubernetes              Filter to append Kubernetes metadata
  modify                  modify records by applying rules
  multiline               Concatenate multiline messages
  nest                    nest events by specified field values
  parser                  Parse events
  expect                  Validate expected keys and values
  grep                    grep events by specified field values
  rewrite_tag             Rewrite records tags
  lua                     Lua Scripting Filter
  stdout                  Filter events to STDOUT
  geoip2                  add geoip information to records
  nightfall               scans records for sensitive content

Outputs
  azure                   Send events to Azure HTTP Event Collector
  azure_blob              Azure Blob Storage
  azure_kusto             Send events to Kusto (Azure Data Explorer)
  bigquery                Send events to BigQuery via streaming insert
  counter                 Records counter
  datadog                 Send events to DataDog HTTP Event Collector
  es                      Elasticsearch
  exit                    Exit after a number of flushes (test purposes)
  file                    Generate log file
  forward                 Forward (Fluentd protocol)
  http                    HTTP Output
  influxdb                InfluxDB Time Series
  logdna                  LogDNA
  loki                    Loki
  kafka                   Kafka
  kafka-rest              Kafka REST Proxy
  nats                    NATS Server
  nrlogs                  New Relic
  null                    Throws away events
  opensearch              OpenSearch
  plot                    Generate data file for GNU Plot
  pgsql                   PostgreSQL
  skywalking              Send logs into log collector on SkyWalking OAP
  slack                   Send events to a Slack channel
  splunk                  Send events to Splunk HTTP Event Collector
  stackdriver             Send events to Google Stackdriver Logging
  stdout                  Prints events to STDOUT
  syslog                  Syslog
  tcp                     TCP Output
  td                      Treasure Data
  flowcounter             FlowCounter
  gelf                    GELF Output
  websocket               Websocket
  cloudwatch_logs         Send logs to Amazon CloudWatch
  kinesis_firehose        Send logs to Amazon Kinesis Firehose
  kinesis_streams         Send logs to Amazon Kinesis Streams
  opentelemetry           OpenTelemetry
  prometheus_exporter     Prometheus Exporter
  prometheus_remote_write Prometheus remote write
  s3                      Send to S3