Multiple outputs backpressure behavior – one output blocking others

[razbahri]

Hi,

I’m running Fluent Bit as a FireLens sidecar on ECS, replacing the CloudWatch Agent.

Setup

• tail input (stdout)
• Two outputs:
  • CloudWatch Logs
  • OpenAPM

Issue
When one output becomes unavailable:

• The buffer fills up
• Once limits are reached, Fluent Bit stops ingesting new logs
• This blocks both outputs, including the one that is still healthy

Understanding
From the docs, it seems Fluent Bit has a single shared buffer per input, and backpressure is applied at the input level.
So if one output is blocked and the buffer is full, all outputs are affected.

Is this correct?

Question

Is there any supported way to:

• Isolate buffering per output, or
• Allow healthy outputs to continue even if one output is unavailable?

Thanks.

[patrick-stephens]

Adjusting the retry limits on the output would likely prevent it blocking, I'm guessing at the moment you have defaults of retry forever on both outputs?

[patrick-stephens]

https://docs.fluentbit.io/manual/administration/scheduling-and-retries#configure-retries