Hi users!
We have released v1.16.10 on 2025-09-12. ChangeLog is here.
This release is a maintenance release of v1.16 series.
This release will be bundled for upcoming fluent-package LTS version v5.0.8!
This issue has existed since this helper was first introduced and has affected at least Fluentd v0.14 and td-agent v3 and later.
The official plugins mainly affected are:
This bug causes the following two problems:
Fluentd normally shuts down each plugin in a safe sequence, but this bug causes it to continue receiving data unexpectedly during a phase when new data should no longer be accepted.
Even if buffer files remain, they will be restored on the next start, so this is not an issue. On the other hand, when using a memory buffer, the risk of log loss becomes much higher.
Please note that this bug is unlikely to be a major problem when using a file buffer. In the first place, server-type input plugins generally cannot receive data while Fluentd is down, so unless the client has a resend mechanism, there is always a risk of log loss during Fluentd's restart. With the zero-downtime restart feature introduced in Fluentd v1.18 (fluent-package v5.2 or v6), Fluentd can now be restarted without downtime.
Ref: Fluentd#5026
Enjoy logging!
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:
Below 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
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 v1.19.0 on 2025-07-30. ChangeLog is here.
This release is a new release of v1.19 series. This release includes many new features and bug fixes, with a particular focus on reducing operational and running costs and improving overall stability.
In this release, we added some restrictions on dependencies, so updates like bundle update may result in conflicts.
In this case, please adjust the dependencies manually or regenerate the Gemfile.lock as follows, for example:
$ rm Gemfile.lock $ bundle
Please see fluentd#5048 for more details.
In this release, we added a buffer evacuation feature to the buf_file and buf_file_single plugins.
This simplifies recovery after failure.
In previous versions, when an output plugin fails to deliver data by network issue, if the retry limit was exceeded and secondary output was not configured, the data would be discarded.
In this release, buffer files are automatically evacuated when the retry limit is exceeded. Once the issue is resolved, you can restore the evacuated files to the original buffer directory and restart Fluentd to resume sending the data.
You can even restart without causing downtime to input plugins like in_udp by using the zero-downtime restart feature.
Evacuated files are stored at:
${root_dir}/buffer/${plugin_id}/
Ref. Handling Successive Failures
Note: This feature is disabled when secondary outputs or retry_forever are used. To enable buffer evacuation, remove those settings.
Buffer files may become corrupted due to events like system crashes or sudden power down. In previous versions, Fluentd could fail to handle corrupted files properly, triggering errors on every restart. You had to manually identify and delete the corrupted files.
This release improves buffer corruption detection. When corruption is detected, the file is automatically moved to a backup directory, and startup errors are suppressed.
We have improved Fluentd's observability by enhancing its metrics capabilities:
Input plugin metrics are now enabled by default.
enable_input_metrics to true. From this release, it's collected by default. To disable, set enable_input_metrics false.in_tail:
tracked_file_count: Number of files currently being tailed.output plugin:
write_secondary_count: Cumulative count of records written to secondary output.drop_oldest_chunk_count: Cumulative count of chunks dropped when drop_oldest_chunk is used for overflow_action.yajl-ruby to json gemPreviously, we used yajl-ruby for high-performance JSON processing, such as writing buffer chunks and parsing with parser_json.
However, in recent years, the standard Ruby json library has improved performance significantly. So we changed to use the json gem as the default JSON processor.
We have added support for the Zstandard (zstd) compression format, which offers both high compression ratios and faster processing compared to gzip.
Note: To use zstd with out_forward, the destination server should support it. You cannot use it with Fluent Bit or Fluentd versions older than v1.19.0.
The out_http plugin now supports TLS 1.3, offering enhanced security.
By default, TLS 1.2 is used. To enable TLS 1.3, set the tls_version parameter as follows:
<match tag>
@type http
...
tls_version TLSv1_3
...
</match>
in_forward plugin:
out_stdout plugin:
use_logger false forces output to STDOUT regardless of Fluentd's own logging configuration. This is especially useful in container environments like Kubernetes.out_file plugin:
symlink_path_use_relative to allow relative paths in symlink_path.formatter_csv pluginTo improve performance, it introduced a caching mechanism in formatter_csv, but incorrectly cached threads.
This caused memory leaks when used with in_exec, which spawns a new thread per log entry.
This fix is backported to Fluentd v1.16.8.
in_tail plugin: fixed incorrect behavior with encoding optionThe in_tail plugin provides encoding and from_encoding options.
encoding: Specifying encoding information.encoding and from_encoding: Converting encoding.Due to a bug since Fluentd v0.14.12 (at least from td-agent v3),
when only encoding was set, unintended encoding conversion occurred, it might corrupt log data.
In previous versions, you need to specify the same encoding for both encoding and from_encoding as workaround.
On Windows, if the supervisor process exited due to configuration errors, the service could continue running incorrectly. This has been fixed so the service now stops as expected, improving error detection.
This fix is backported to Fluentd v1.16.8.
--umask BugFixed a bug where the --umask setting was ignored when used together with --daemon, leading to unexpected file permissions.
Enjoy logging!
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 v1.16.9 on 2025-05-14. ChangeLog is here.
This release is a maintenance release of v1.16 series. In this release, we have fixed a critical bug of the previous version, v1.16.8. Please do not use v1.16.8.
This release will be bundled for upcoming fluent-package LTS version v5.0.7!
In the previous version v1.16.8, the Windows service (fluentdwinsvc) accidentally stops after starting without stopping the supervisor and worker processes. This is a critical bug of v1.16.8 for users who use Fluentd as a Windows service.
In this release, we have fixed this bug.
See #4954 for more information.
Enjoy logging!
Hi users!
We have released v1.16.8 on 2025-05-01. ChangeLog is here.
This release is a maintenance release of v1.16 series.
This release will be bundled for upcoming fluent-package LTS version v5.0.7!
In this release, we have fixed a bug that Windows service process will continue running even if the supervisor process is dead due to config error or etc.
With fluentd#4942 fixed, it becomes easier to notice config errors and other issues.
formatter_csv: Fixed memory leakThe caching mechanism introduced for performance optimization was caching threads inappropriately in formatter_csv.
The in_exec plugin creates a thread each time to emit an event.
Then all threads were cached in formatter_csv, causing a memory leak.
With fluentd#4920 fixed, it becomes stable.
For comming Ruby 3.5, we have added a fiddle gem as dependency.
We are enforcing stabilizing CI of Fluentd. It has nothing to do with Fluentd's functionality directly, but it is very important to provide stable version of Fluentd continuously.
Enjoy logging!
Hi users!
We have planned to change what docker image provides.
Currently, we ship Fluentd docker image for Alpine and Debian (armhf, arm64, amd64). But, Alpine image in Fluentd was already marked as deprecated, so we will make things forward.
In the near future, we will drop Alpine image. This decision affects existing Alpine image users.
fluent/fluentd:edge will be changed from Alpine to Debian image
If you still want to use Alpine, keep v1.16 series or v1.18 series. (not recommended though)
It was well known that Alpine has possibility of incompatibility and performance issues in contrast to Debian images. It was a historical reason to provide Alpine images - "In the previous versions, we provided them", so there is no positive reason to continue it.
Not only just dropping Alpine image, we will improve tagging rules:
In previous versions, there was no version-specific tag which would follow internal version bump.
For example, if you want to stick to Fluentd v1.18.0, you can select v1.18.0-1.0, but if internal version was bumped to v1.18.0-1.1 or something, need to update it.
There is edge-debian tag, but it does not stick to a specific Fluentd version because it will automatically update when the next major/minor version is released.
For such a purpose, shorter v1.19 or v1.19.x tag will be available in the future release.
Happy logging!
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
Hi users!
We have released v1.16.7 on 2025-01-29. ChangeLog is here.
This release is a maintenance release of v1.16 series. In this release, some bugs which are related on Windows were fixed with backporting from v1.18.x.
This release will be bundled for upcoming fluent-package LTS version v5.0.6!
In this release, we have fixed a bug that it will fail when --daemon option is used on Windows.
It was a regression bug since v1.16.0 on Windows, but usually running as a service is recommended way on Windows, so most of Fluentd users were not affected.
In this release, we have fixed the following bugs which are related to start/stop the Fluentd service.
These bug were caused because stop event was not handled correctly in the previous releases.
Typically, this bug will happen if you stop the Fluentd service immediately after startup. Then it could leave the processes or stopping service sometimes can not be completed forever.
We also enforcing stabilizing CI of Fluentd. It has nothing to do with Fluentd's functionality directly, but it is very important to provide stable version of Fluentd continuously.
Not only Windows: Add workaround for unexpected exception #4747, many CI improvements was merged into master, then backported to v1.16 branch, too.
Enjoy logging!
Fluentd is an open source data collector to simplify log management.
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
2025-09-12: Fluentd v1.16.10 has been released
2025-09-04: Upgrade Guide for fluent-package v6
2025-08-29: fluent-package v6.0.0 has been released
2025-08-06: Fluentd v1.19.0 has been released
2025-05-16: fluent-package v5.0.7 has been released
2025-05-14: Fluentd v1.16.9 has been released
2025-05-01: Fluentd v1.16.8 has been released
2025-03-14: Drop Alpine and switch default to Debian for Fluentd docker image
2025-02-14: fluent-package v5.0.6 has been released
2025-01-29: Fluentd v1.16.7 has been released
Want to learn the basics of Fluentd? Check out these pages.
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Fluentd is a hosted project under the Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.