Fluent Bit 4.0.2 HTTP output to AWS Opensearch triggers SIGSEV

[doraamgui]

Bug Report

Describe the bug

With Fluent Bit 4.0.2 ,follow up this document sends log data from Fluent Bit to an OpenSearch Ingestion pipeline https://docs.aws.amazon.com/opensearch-service/latest/developerguide/configure-client-fluentbit.html. It seems that the flush routine for the log data to AWS pipeline is somehow broken.

To Reproduce

• Rubular link if applicable: https://docs.aws.amazon.com/opensearch-service/latest/developerguide/configure-client-fluentbit.html
• Example log message if applicable:

kubectl logs fluent-bit-6m8ms --previous -n fluent-bit
Fluent Bit v4.0.2
* Copyright (C) 2015-2025 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io/

______ _                  _    ______ _ _             ___  _____ 
|  ___| |                | |   | ___ (_) |           /   ||  _  |
| |_  | |_   _  ___ _ __ | |_  | |_/ /_| |_  __   __/ /| || |/' |
|  _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / / /_| ||  /| |
| |   | | |_| |  __/ | | | |_  | |_/ / | |_   \ V /\___  |\ |_/ /
\_|   |_|\__,_|\___|_| |_|\__| \____/|_|\__|   \_/     |_(_)___/ 


[2025/05/21 03:08:17] [engine] caught signal (SIGSEGV)
#0  0x558b294de720      in  flb_http_do_request() at src/flb_http_client.c:1357
#1  0x558b294df0ec      in  flb_http_do() at src/flb_http_client.c:1526
#2  0x558b295a3803      in  http_post() at plugins/out_http/http.c:284
#3  0x558b295a4ce7      in  cb_http_flush() at plugins/out_http/http.c:641
#4  0x558b29b08026      in  co_init() at lib/monkey/deps/flb_libco/amd64.c:117
#5  0xffffffffffffffff  in  ???() at ???:0

• Steps to reproduce the problem:

Expected behavior

we ever submit bug in V4.0.1(#10257). closed with that fix in V 4.0.2. but it has the same issue in V4.0.2. need help to figure out the root cause and fix it.

Screenshots

Your Environment

• Version used: v4.0.2
• Configuration:
• Environment name and version (e.g. Kubernetes? What version?): EKS V1.32
• Server type and version:
• Operating System and version: Amazon Linux 2
• Filters and plugins:
  [SERVICE]
  Flush 5
  Log_Level trace
  Daemon off
  log_file /var/log/fluent-bit.log
  http_server on
  http_listen 0.0.0.0
  http_port 2020

[INPUT]
Name tail
Tag kube.*
Path /var/log/containers/*.log
DB /var/log/flb_kube.db
multiline.parser docker, cri
Docker_Mode On
Mem_Buf_Limit 100MB
Skip_Long_Lines On
Refresh_Interval 10

[FILTER]
Name kubernetes
Match kube.*
Kube_URL https://kubernetes.default.svc:443
Kube_CA_File /var/run/secrets/kubernetes.io/serviceaccount/ca.crt
Kube_Token_File /var/run/secrets/kubernetes.io/serviceaccount/token
Merge_Log On
Merge_Log_Key log_processed
K8S-Logging.Parser On
K8S-Logging.Exclude Off
Kube_Meta_Cache_TTL 300s
Annotations On
Labels On

[OUTPUT]
Name http
Match *
Host ******.us-east-1.osis.amazonaws.com
Port 443
URI /log/ingest
Format json
aws_auth true
aws_region us-east-1
aws_service osis
Log_Level info
tls On
json_date_key time
json_date_format iso8601
Retry_Limit 5

Additional context

[patrick-stephens]

Weirdly is this my prediction from yesterday? #10353 (comment)

There's an open PR on it: #10365
If it's this same issue we can link it to the PR @tkennedy1-godaddy

[patrick-stephens]

Ah my bad, this says Opensearch but is actually using the HTTP output plugin.

Why don't you use the OpenSearch output @doraamgui?

[doraamgui]

used pipeline HTTP output, there would be a cache tier before sending the data to Opensearch directly. I have test OpenSearch output. it is fine without (SIGSEGV).
From our public document(https://docs.fluentbit.io/manual/pipeline/outputs/http), it should support http output. but looks like not stable

[doraamgui]

may I know the update? whether it is the same issue that index set null in configuration, right?

[cosmo0920]

may I know the update? whether it is the same issue that index set null in configuration, right?

Yes, it's same issue for setting up with index as null in configurations.