Hi users!
We have released fluent-package v6.0.4 on 2026-06-26. Fluent Package is a stable distribution package of Fluentd. (successor of td-agent)
This is a maintenance release of v6.0.x LTS series.
Fluent Package v6.0.4 includes the following improvements:
This article explains the changes in Fluent Package v6.0.4.
In this release, some critical vulnerabilities were fixed.
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shared_key for authentication, filter incoming untrusted tags.in_monitor_agent, allow connection from only localhost.in_http and in_forward
in_forward or in_http, use shared_key for authentication which allow trusted incoming source.in_opentelemetry
in_opentelemetry, use a robust reverse proxy in front of Fluentd to mitigate GZIP decompression bomb.in_s3
in_s3 is strictly limited to trusted services and administrators.The above vulnerabilities affects to older than v1.19.3, thus the following packages also will be affected.
We recommend upgrading fluent-package to v6.0.4.
If you can't upgrade it immediately, there is a case that mitigation method is explained in above advisory. Please check each advisory and take care of it.
Please visit the download page.
We plan to release the next LTS version of fluent-package v6.0.5 at Sep 2026. The content of updates are still TBD.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
Hi users!
We have released fluent-package v6.0.3 on 2026-03-27. Fluent Package is a stable distribution package of Fluentd. (successor of td-agent)
This is a maintenance release of v6.0.x LTS series.
Fluent Package v6.0.3 includes the following improvements:
cool.io v1.9.3 under specific conditionsThis article explains the changes in Fluent Package v6.0.3.
In fluent-package v6.0.2, a critical issue was discovered where memory usage continuously increases over time. This release completely resolves this problem.
out_forward plugin with the keepalive false setting (which is the default value).cool.io (v1.9.2 and v1.9.3) bundled in fluent-package v6.0.2 had a bug in its detachment process.cool.io v1.9.4 which fixes this bug, and it is now bundled by default in fluent-package v6.0.3. If operated for a long period, this memory leak will exhaust system memory resources, eventually causing the Fluentd process to be terminated unexpectedly by the OOM (Out of Memory) Killer. We strongly recommend users who are using out_forward on v6.0.2 to update to this version immediately.
Note: Users on fluent-package v6.0.1 or earlier are not affected by this specific issue.
Ruby 3.4.9 includes multiple bug and security fixes. Specifically, it addresses the following vulnerability:
For details, please see the Ruby 3.4.9 release notes.
We have updated the bundled Nokogiri from v1.18.10 to v1.19.2 for the Windows version to address the following vulnerability:
Please visit the download page.
We plan to release the next LTS version of fluent-package v6.0.4 at June 2026. The content of updates are still TBD.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
Hi users!
We have released fluent-package v6.0.2 on 2026-02-27. Fluent Package is a stable distribution package of Fluentd. (successor of td-agent)
This is a maintenance release of v6.0.x LTS series.
Fluent Package v6.0.2 includes the following improvements:
This article explains the changes in Fluent Package v6.0.2.
Ruby 3.4.8 includes multiple bug and security fixes. For details, please see the Ruby 3.4.8 release notes.
Fluentd v1.19.2 includes the following fixes:
config_include_dirFor details, please see the Fluentd v1.19.2 has been released.
In this release, it was fixed update error if temporary working directory was removed.
In the previous versions, if temporary working directory was removed by tmpfiles.d, there was a case that updating to v6 (up to v6.0.1) causes fatal error while rpm processes transaction.
Now, with changing temporary working directory handling, it was fixed in v6.0.2.
Since v6.0.0, installation maintenance script (powershell) was partially introduced for Windows. But in some environments, there is a case that the execution of powershell was prohibited in your policy. In such a case, installation process will be failed unexpectedly.
In this release, added fallback not to terminate installation process accidentally.
Please visit the download page.
We plan to release the next LTS version of fluent-package v6.0.3 at June 2026. The content of updates are still TBD.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
Hi users!
We have released fluent-package v5.0.9 on December 19, 2025. Fluent Package is a stable distribution package of Fluentd. (successor of td-agent v4)
This is a maintenance release of v5.0.x LTS series.
Fluent Package v5 LTS series is scheduled to be supported until the end of 2025. This release (v5.0.9) is planned to be the final version of the v5 LTS series.
Please refer to Scheduled support lifecycle announcement about Fluent Package v6.
This article explains the changes in Fluent Package v5.0.9.
Fluentd v1.16.11 includes the following fixes:
<security> and TLS setting together under unstable network environments
Please see the download page.
This release (v5.0.9) is planned to be the final version of the v5 LTS series. We strongly recommend upgrading to Fluent Package v6 LTS series for next long term support.
Please refer to Scheduled support lifecycle announcement about Fluent Package v6.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
Hi users!
We have released fluent-package v6.0.1 on 2025-11-11. Fluent Package is a stable distribution package of Fluentd. (successor of td-agent v4)
This is a maintenance release of v6.0.x LTS series.
Fluent Package v6.0.1 includes the following improvements:
This article explains the changes in Fluent Package v6.0.1.
Ruby 3.4.7 includes multiple bug and security fixes. For details, please see the Ruby 3.4.7 release notes.
Fluentd v1.19.1 includes the following fixes:
Previously, when specifying multiple values, you had to use a comma-separated list such as: retryable_response_codes: 503, 504.
With this update, you can now use more YAML-style array notations:
retryable_response_codes: [503, 504]
or
retryable_response_codes:
- 503
- 504
Note: The special element $arg has supported array notation from earlier versions.
Note: There is still a known YAML syntax issue where specifying a single int value for an Array option causes a config error. For details, please refer to #5149.
This issue, which was previously fixed in Fluent Package v5.0.8, has now been included in Fluent Package v6.0.1.
On some Linux distributions, tmpfiles.d is configured as follows, and files or directories in /tmp that remain unused for more than 10 days are deleted:
q /tmp 1777 root root 10d
When using the out_file or out_secondary_file plugins, Fluentd uses temporary directory like /tmp/fluentd-lock-{...}/, depending on the config.
If there is no output with out_file or out_secondary_file for an extended period, the temporary directory could be deleted by tmpfiles.d.
If the temporary directory is deleted while Fluentd is running, the following error occurs continuously in out_file and out_secondary_file output:
2025-09-11 14:33:29 +0900 [warn]: #2 failed to flush the buffer. retry_times=0 next_retry_time=2025-09-11 14:33:30 +0900 chunk="63e7fdca888e679a6fcdefb0c120bf58" error_class=Errno::ENOENT error="No such file or directory @ rb_sysopen - /tmp/fluentd-lock-20250911-1545462-74fvkh/fluentd-foo.lock"
Normally, some output is written periodically, so this issue is rare. If it occurs, you can restore normal operation by restarting Fluentd before reaching the retry limit.
In this release, we added a rule to /usr/lib/tmpfiles.d/fluentd.conf to exclude /tmp/fluentd-lock-{...}/ from automatic deletion.
This fixes an issue in the Windows installer of Fluent Package v6.0.0.
When installing Fluent Package to a path containing spaces (e.g., C:\Program Files\fluentd), an error could occur during installation.
This issue has been fixed in v6.0.1.
Please visit the download page.
We plan to release the next LTS version of fluent-package v6.0.2 at February 2026. The content of updates are still TBD.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
Hi users!
We have released fluent-package v5.0.8 on October 8, 2025. Fluent Package is a stable distribution package of Fluentd. (successor of td-agent v4)
This is a maintenance release of v5.0.x LTS series. Bundled Fluentd was updated to 1.16.10.
This article explains the changes in Fluent Package v5.0.8.
Ruby 3.2.9 includes multiple security and bug fixes. For details, please see the Ruby 3.2.9 release notes.
Fluentd v1.16.10 includes the following fixes:
On some Linux distributions, tmpfiles.d is configured as follows, and files or directories in /tmp that remain unused for more than 10 days are deleted:
q /tmp 1777 root root 10d
When using the out_file or out_secondary_file plugins, Fluentd uses temporary directory like /tmp/fluentd-lock-{...}/, depending on the config.
If there is no output with out_file or out_secondary_file for an extended period, the temporary directory could be deleted by tmpfiles.d.
If the temporary directory is deleted while Fluentd is running, the following error occurs continuously in out_file and out_secondary_file output:
2025-09-11 14:33:29 +0900 [warn]: #2 failed to flush the buffer. retry_times=0 next_retry_time=2025-09-11 14:33:30 +0900 chunk="63e7fdca888e679a6fcdefb0c120bf58" error_class=Errno::ENOENT error="No such file or directory @ rb_sysopen - /tmp/fluentd-lock-20250911-1545462-74fvkh/fluentd-foo.lock"
Normally, some output is written periodically, so this issue is rare. If it occurs, you can restore normal operation by restarting Fluentd before reaching the retry limit.
In this release, we added a rule to /usr/lib/tmpfiles.d/fluentd.conf to exclude /tmp/fluentd-lock-{...}/ from automatic deletion.
The bundled Nokogiri (for Windows only) has been updated from v1.16.8 to v1.18.10 to address the following vulnerabilities:
The bundled rexml has been updated from v3.3.9 to v3.4.4 to address the following vulnerabilities:
Please see the download page.
We plan to release the next LTS version of fluent-package v5.0.9 by the end of 2025. The content of updates are still TBD.
We strongly recommend upgrading to fluent-package v6 LTS.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
On August 29, 2025, we released fluent-package v6 as a new series of stable packages.
Fluent Package v6 LTS is a long-term support (LTS), stable package of Fluentd.
Fluent Package v5 LTS will reach end of support at the end of 2025. As its successor, Fluent Package v6 LTS will be supported until at least the end of 2027.
For more details, see the following article:
As an example, you can upgrade with the following steps:
/etc/fluent/conf.d/ directory on the user sideBelow are details for each step.
If your current version (before upgrade) is Fluent Package v5.0.2 or later (v5.0.3 for Windows), you can use the bundled fluent-diagtool to list manually installed plugins.
Run the following command:
$ /opt/fluent/bin/fluent-diagtool -t fluentd -o /tmp
-t fluentd: required-o /tmp: specifies the output directory for results (you can choose any directory)The tool outputs various information to standard output. The following section shows the list of manually installed plugins:
(...)
2025-07-17 08:13:31 +0000: [Diagtool] [INFO] [Collect] fluent-package manually installed gem information is stored in /tmp/20250717081331/output/gem_local_list.output
2025-07-17 08:13:31 +0000: [Diagtool] [INFO] [Collect] fluent-package manually installed gems:
2025-07-17 08:13:31 +0000: [Diagtool] [INFO] [Collect] * fluent-plugin-remote_syslog
(...)
In this example, the only manually installed plugin is fluent-plugin-remote_syslog.
The list is also saved to a file:
/{output_directory}/{execution_timestamp}/output/gem_local_list.outputFor the above case, the list was saved to /tmp/20250717081331/output/gem_local_list.output.
If you are using a version earlier than v5.0.2, the bundled fluent-diagtool is outdated.
Please update it in advance:
$ sudo fluent-gem install fluent-diagtool
If you cannot update fluent-diagtool, obtain the list of plugins with:
$ fluent-gem list fluent-plugin
Note:
On fluent-package v5.0.2 for Windows or earlier, fluent-diagtool is not available due to a known issue.
Use fluent-gem list fluent-plugin instead.
Stop any running Fluentd service(s). If multiple Fluentd services are running, stop them in the order: forwarders first, then aggregators.
On Windows, back up registry settings needed for rollback. Run the following command in PowerShell or Command Prompt as an administrator:
> reg export HKLM\System\CurrentControlSet\Services\fluentdwinsvc C:\fluent-package-5_fluentdwinsvc.reg
Install Fluent Package v6 LTS.
Example for RPM Package (Red Hat Linux):
$ curl -fsSL https://fluentd.cdn.cncf.io/sh/install-redhat-fluent-package6-lts.sh | sh
Please refer to the official documentation for each environment:
The manually installed plugins need to be reinstalled. Reinstall the plugins identified in step 1.
Example:
$ sudo fluent-gem install fluent-plugin-remote_syslog
/etc/fluent/conf.d/ directory on the user sideStarting from Fluent Package v6, config files in /etc/fluent/conf.d/ are automatically loaded by default.
If you have manually created and used this directory in a previous version, the config files in that directory will be loaded twice.
In v6.0.0, the Linux packages (RPM and DEB) include the following config files by default:
/etc/fluent/conf.d/obsolete_plugins.conf/etc/fluent/conf.d/update_notifier.confAny other config files in this directory are considered to have been placed manually by the user side.
In this case, you can prevent duplicate loading by disabling the automatic loading feature. This can be done by setting config_include_dir as follows:
<system>
config_include_dir ""
</system>
Disabling this feature will stop the following new features introduced in v6, but it will not affect Fluentd’s core operations:
fluent-plugin-obsolete-plugins
fluent-package-update-notifier
If you want to take advantage of these new features and the auto-loading features, of course you can alternatively relocate your config files to a different directory.
Restart the Fluentd service(s) you stopped in step 2. If multiple services exist, start them in the order from aggregators to forwarders.
Note: Zero-Downtime Update Settings (non-Windows)
From the next update onward, you can perform upgrades without stopping the service using the zero-downtime update feature (not supported on Windows).
You can configure how Fluentd restarts after an update:
This setting can be changed anytime and does not require restarting Fluentd itself.
For details, see:
Stop running Fluentd services, in the order from forwarders to aggregators.
On Linux, simply reinstall Fluent Package v5 LTS on top of v6. No need to uninstall v6 beforehand. On Windows, uninstall Fluent Package v6 LTS first, then install v5 LTS.
Manually installed plugins remain on the system, so after rollback they are still available. No reinstallation is required.
On Windows, restore the registry with the following command (admin PowerShell or Command Prompt):
> reg import C:\fluent-package-5_fluentdwinsvc.reg
This restores Windows service auto-start settings and startup command-line arguments.
Restart the stopped Fluentd services in opposite order: aggregators first, then forwarders.
Please see the download page.
As it was already announced Drop schedule announcement about EOL of Treasure Agent (td-agent) 4, td-agent v4 reached EOL in Dec, 2023.
And fluent-package v5 will reach EOL in end of 2025.
We strongly recommend upgrading to fluent-package v6 LTS.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed our X account.
Hi users!
We're excited to announce the release of fluent-package v6.0.0 !
This is the first release of the v6 LTS series, and it will be supported until the end of 2027.
We strongly recommend upgrading to fluent-package v6 LTS!
Fluent Package v6 LTS is a long-term support (LTS), stable package of Fluentd.
The conventional Fluentd project official package, td-agent, reached its end of support at the end of 2023. Fluent Package has been officially developed and distributed by the Fluentd project since the end of August 2023 as its successor package.
The current LTS version, Fluent Package v5 LTS, will reach end of support at the end of 2025. As the next LTS version, Fluent Package v6 LTS will be supported until at least the end of 2027.
In LTS versions, we only perform bug fixes and security fixes over a pre-announced long-term period (minimum 2 years). Therefore, there are two advantages for long-term stable operations:
For detailed support schedule information, please see Scheduled support lifecycle announcement about Fluent Package v6.
This release includes many improvements for long-term stable operations. The main improvements are as follows:
While Fluent Package v5 LTS bundled Fluentd v1.16, v6 LTS moves to Fluentd v1.19. This makes the following new features available:
For more detailed changes since v1.16, see:
Starting from v6 LTS, zero-downtime updates are available. This feature allows you to safely execute configuration file reloading and Fluentd restarts with zero downtime (Windows not supported).
For more details, see the following articles and try out this feature:
Fluent Package v6 supports the following platforms:
This release supports transferring OpenTelemetry data over HTTP/HTTPS. For configuration methods and other details, please see the plugin README.
We also provide a sample for quick testing.
We've improved the system to preserve auto-start configuration and Windows service (fluentdwinsvc) command line options during updates.
This eliminates the need for reconfiguration that was previously required during updates.
In addition, manually installed plugins still need to be reinstalled when updating an LTS version. Starting from this release, plugins will be automatically reinstalled during future updates when using the zero-downtime update feature (Windows not supported). This will make future updates easier.
fluent-plugin-fluent-package-update-notifier plugin
fluent-plugin-obsolete-plugins plugin
fluent-plugin-systemd plugin
SIGABORT error.Please see the download page.
As it was already announced Drop schedule announcement about EOL of Treasure Agent (td-agent) 4, td-agent v4 reached EOL in Dec, 2023.
And fluent-package v5 will reach EOL in end of 2025.
We strongly recommend upgrading to fluent-package v6 LTS.
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed our X account.
Hi users!
We have released fluent-package v5.0.7. fluent-package is a stable distribution package of Fluentd. (successor of td-agent v4)
This is a maintenance release of v5.0.x LTS series. Bundled Fluentd was updated to 1.16.9.
We recommend upgrading to fluent-package v5.0.7!
With an old gem, it caused an exception after FIPS enabled in OpenSSL. We have updated the bundled openssl gem to 3.3.0 to solve the issue.
There were memory leaks under conditions where exceptions frequently occurred during communication between Elasticsearch and fluent-plugin-elasticsearch. The issue was fixed in fluent-plugin-elasticsearch v5.4.4 and bundled into fluent-package v5.0.7.
Please see the download page.
We plan to ship the next LTS version of fluent-package v5.0.8 on September, 2025. The content of updates are still in T.B.D.
As it was already announced Drop schedule announcement about EOL of Treasure Agent (td-agent) 4, td-agent v4 reached EOL in Dec, 2023.
After reached EOL, td-agent v4.5.3 on Windows was released because there was a crash bug during startup on Windows. It was backported fix from fluent-package v5 as it is critical in some case. Even though this was a exceptional maintenance release, but there is no change to the fact that we already stopped maintaining td-agent v4.
We strongly recommend migrating from td-agent v4 to fluent-package v5 (LTS). See Upgrade to fluent-package v5
We have been posting information about Fluentd in Japanese on @fluentd_jp. We would appreciate it if you followed the X account.
Hi users!
We have released fluent-package v5.0.6. fluent-package is a stable distribution package of Fluentd. (successor of td-agent v4)
This is a maintenance release of v5.0.x LTS series. Bundled Fluentd was updated to 1.16.7.
We recommend upgrading to fluent-package v5.0.6!
In this release, known Windows issues were fixed.
In the previous versions, there had been a known issue that fluent-package could not keep some registry values when upgrading.
Thus, if you modify Fluentd service (fluentdwinsvc) related registry,
you need to restore your configuration after upgrading.
Since v5.0.6, fluent-package was fixed to keep some registry values during upgrading package.
Here is the target registry which will be kept during upgrading fluent-package:
StartDelayedAutostartfluentdopt (logging path might be modified by users)In most cases, fluent-package user might want to keep fluentdopt because
it stores additional command line option parameters.
In this release, bundled Fluentd v1.16.7 also contains the fixes for Windows.
NoMethodError of --daemon optionSee Fluentd v1.16.7 has been released blog article in details.
Please see the download page.
We plan to ship the next LTS version of fluent-package v5.0.7 on June, 2025. The content of updates are still in T.B.D.
As it was already announced Drop schedule announcement about EOL of Treasure Agent (td-agent) 4, td-agent v4 reached EOL in Dec, 2023.
After reached EOL, td-agent v4.5.3 on Windows was released because there was a crash bug during startup on Windows. It was backported fix from fluent-package v5 as it is critical in some case. Even though this was a exceptional maintenance release, but there is no change to the fact that we already stopped maintaining td-agent v4.
We strongly recommend migrating from td-agent v4 to fluent-package v5 (LTS). See Upgrade to fluent-package v5
Fluentd is an open source data collector to simplify log management.
2025-12-25: Drop schedule announcement about EOL of Fluent Package (fluent-package) 5
2025-09-04: Upgrade Guide for fluent-package v6
2024-08-29: Scheduled support lifecycle announcement about Fluent Package v6
2023-08-29: Drop schedule announcement about EOL of Treasure Agent (td-agent) 4
2023-08-29: Scheduled support lifecycle announcement about Fluent Package
2023-07-31: Upgrade to fluent-package v5
2026-06-26: fluent-package v6.0.4 has been released
2026-06-25: Fluentd v1.19.3 has been released
2026-03-27: fluent-package v6.0.3 has been released
2026-02-27: fluent-package v6.0.2 has been released
2026-02-13: Fluentd v1.19.2 has been released
2025-12-25: Drop schedule announcement about EOL of Fluent Package (fluent-package) 5
2025-12-19: fluent-package v5.0.9 has been released
2025-12-09: Fluentd v1.16.11 has been released
2025-11-11: fluent-package v6.0.1 has been released
2025-11-06: Fluentd v1.19.1 has been released
Want to learn the basics of Fluentd? Check out these pages.
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