DNS lookup requests through the DNS server for a docker network slows down over time

[Jubk-private]

Description

When doing many DNS requests through the DNS server that is created for a docker network (127.0.0.11) some responses will start to take multiple seconds. The effect seems to be more frequent the more requests are made.

Reproduce

Create a script, test-reverse-dns.py with the following content:

import socket
import time

def timemillis():
    return round(time.time() * 1000)

last = timemillis()

for x in range(10000):
    socket.getnameinfo(('104.16.30.34', 0), 0)
    now = timemillis()
    print('%d: %d' % (x, now - last))
    last = now

And then run it in a docker container connected to a network

docker network create mynetwork
docker run --rm -it -v .\test-reverse-dns.py:/test-reverse-dns.py --network mynetwork --dns 8.8.8.8 python python test-reverse-dns.py

Observe that after many calls (2000+ on one machine, 5000+ on another) some response times will start to be 2000+ milliseconds.

Expected behavior

DNS responses should not slow down over time or perhaps even be cached so quick responses are provided if the same query is run twice.

docker version

Client:
Version: 27.2.0
API version: 1.47
Go version: go1.21.13
Git commit: 3ab4256
Built: Tue Aug 27 14:17:17 2024
OS/Arch: windows/amd64
Context: desktop-linux

Server: Docker Desktop 4.34.3 (170107)
Engine:
Version: 27.2.0
API version: 1.47 (minimum version 1.24)
Go version: go1.21.13
Git commit: 3ab5c7d
Built: Tue Aug 27 14:15:15 2024
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: 1.7.20
GitCommit: 8fc6bcff51318944179630522a095cc9dbf9f353
runc:
Version: 1.1.13
GitCommit: v1.1.13-0-g58aa920
docker-init:
Version: 0.19.0
GitCommit: de40ad0

docker info

Client:
Version: 27.2.0
Context: desktop-linux
Debug Mode: false
Plugins:
buildx: Docker Buildx (Docker Inc.)
Version: v0.16.2-desktop.1
Path: C:\Program Files\Docker\cli-plugins\docker-buildx.exe
compose: Docker Compose (Docker Inc.)
Version: v2.29.2-desktop.2
Path: C:\Program Files\Docker\cli-plugins\docker-compose.exe
debug: Get a shell into any image or container (Docker Inc.)
Version: 0.0.34
Path: C:\Program Files\Docker\cli-plugins\docker-debug.exe
desktop: Docker Desktop commands (Alpha) (Docker Inc.)
Version: v0.0.15
Path: C:\Program Files\Docker\cli-plugins\docker-desktop.exe
dev: Docker Dev Environments (Docker Inc.)
Version: v0.1.2
Path: C:\Program Files\Docker\cli-plugins\docker-dev.exe
extension: Manages Docker extensions (Docker Inc.)
Version: v0.2.25
Path: C:\Program Files\Docker\cli-plugins\docker-extension.exe
feedback: Provide feedback, right in your terminal! (Docker Inc.)
Version: v1.0.5
Path: C:\Program Files\Docker\cli-plugins\docker-feedback.exe
init: Creates Docker-related starter files for your project (Docker Inc.)
Version: v1.3.0
Path: C:\Program Files\Docker\cli-plugins\docker-init.exe
sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc.)
Version: 0.6.0
Path: C:\Program Files\Docker\cli-plugins\docker-sbom.exe
scout: Docker Scout (Docker Inc.)
Version: v1.13.0
Path: C:\Program Files\Docker\cli-plugins\docker-scout.exe

Server:
Containers: 12
Running: 0
Paused: 0
Stopped: 12
Images: 10
Server Version: 27.2.0
Storage Driver: overlayfs
driver-type: io.containerd.snapshotter.v1
Logging Driver: json-file
Cgroup Driver: cgroupfs
Cgroup Version: 1
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
Swarm: inactive
Runtimes: io.containerd.runc.v2 nvidia runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 8fc6bcff51318944179630522a095cc9dbf9f353
runc version: v1.1.13-0-g58aa920
init version: de40ad0
Security Options:
seccomp
Profile: unconfined
Kernel Version: 5.15.153.1-microsoft-standard-WSL2
Operating System: Docker Desktop
OSType: linux
Architecture: x86_64
CPUs: 16
Total Memory: 15.26GiB
Name: docker-desktop
ID: 6e771f03-b9b8-420a-b7eb-6f0e1557af5d
Docker Root Dir: /var/lib/docker
Debug Mode: false
HTTP Proxy: http.docker.internal:3128
HTTPS Proxy: http.docker.internal:3128
No Proxy: hubproxy.docker.internal
Labels:
com.docker.desktop.address=npipe://\.\pipe\docker_cli
Experimental: false
Insecure Registries:
hubproxy.docker.internal:5555
127.0.0.0/8
Live Restore Enabled: false

WARNING: No blkio throttle.read_bps_device support
WARNING: No blkio throttle.write_bps_device support
WARNING: No blkio throttle.read_iops_device support
WARNING: No blkio throttle.write_iops_device support
WARNING: daemon is not using the default seccomp profile

Diagnostics ID

25194D3D-AE23-454A-A54A-E1F56AA672B5/20241025090124

Additional Info

No response