"Network is unreachable" problem

[VitMosin]

Bug Overview

I'm setting up nginx to cache files from S3 and getting a random error. Simetimes is ok, sometimes no.

2025/10/22 08:03:11 [error] 81#81: *4256 connect() to [ipv6]:443 failed (101: Network is unreachable) while connecting to upstream, client: 10.200.186.53, server: , request: "GET /a14feca0-274e-4265-a1c0-c541e50c3b99 HTTP/1.1", upstream: "https://[ipv6]:443/a14feca0-274e-4265-a1c0-c541e50c3b99", host: "nginx-s3-gateway.development"

2025/10/22 08:03:11 [warn] 81#81: *4256 upstream server temporarily disabled while Connecting to upstream, client: 10.200.186.53, server: , request: "GET /a14feca0-274e-4265-a1c0-c541e50c3b99 HTTP/1.1", upstream: "https://[ipv6]:443/a14feca0-274e-4265-a1c0-c541e50c3b99", host: "nginx-s3-gateway.development"

Everything is fine without errors locally in Docker. This error appears only in Cloud provider - and in the k8s pod, and on a separate Docker node.
S3 address is the same locally and in cloud provider.

Expected Behavior

conrainer has no error log

Steps to Reproduce the Bug

When I use the gateway using docker in Cloud provider, gateway fails with "Network unreachable" error. If I use it locally everything is ok.

Environment Details

• nginxinc/nginx-s3-gateway:latest-20251020
• Target deployment platforms [e.g. AWS/GCP/local cluster/etc...]: Yandex cloud
• S3 backend implementation: [e.g. AWS, Ceph, NetApp StorageGrid, etc...]: AWS
• Authentication method: [e.g. IAM, IAM with Fargate, IAM with K8S, AWS Credentials, etc...]: AWS Credentials

Additional Context

No response

[VitMosin]

Solved by setting
resolver ${DNS_RESOLVERS} ipv6=off;