Fluentd Blog

Fluentd v1.16.10 has been released

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!

Bug Fixes

Server plugin helper: Fix bug where it may not properly close connections on Fluentd's shutdown

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:

• in_tcp
• in_syslog
• in_forward

This bug causes the following two problems:

• Even with flush_at_shutdown enabled, Fluentd may stop with buffer files left behind.
• There is a risk of losing received data during Fluentd's shutdown sequence although the probability is very low.

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!