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Only try resolving the docker gateway IP once per server startup and add some diagnostics #2118

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Only try resolving the docker gateway IP once per server startup and add some diagnostics #2118

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Only try resolving the docker gateway IP once per server startup and …
matthiask Apr 1, 2025
428c796
Clear the cache when settings change
matthiask Apr 1, 2025
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51 changes: 37 additions & 14 deletions debug_toolbar/middleware.py
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This is working fine for me but I am not confident I have correctly reproduced a proper testing environment. These are the steps I took to test and my findings.

I bootstrapped a Django app using Django Cookiecutter with the Docker option, then installed the debug toolbar from your repo by replacing the pinned version with the following (and modifying the Dockerfile to install git):

git+https://github.com/matthiask/django-debug-toolbar.git@2113-dns-resolving

Then, I successfully built and ran the containers, cut off access to the Internet, and commented out the INTERNAL_IPS setting.

$ docker compose -f docker-compose.local.yml run --rm django python manage.py shell
[+] Creating 3/3
 ✔ Container djdt_docker_local_mailpit   Running                                                                                                                            0.0s 
 ✔ Container djdt_docker_local_redis     Running                                                                                                                            0.0s 
 ✔ Container djdt_docker_local_postgres  Running                                                                                                                            0.0s 
wait-for-it: waiting 30 seconds for postgres:5432
wait-for-it: postgres:5432 is available after 0 seconds
PostgreSQL is available
Python 3.12.9 (main, Mar 18 2025, 01:37:06) [GCC 12.2.0]
Type 'copyright', 'credits' or 'license' for more information
IPython 9.0.2 -- An enhanced Interactive Python. Type '?' for help.
Tip: Use `%timeit` or `%%timeit`, and the  `-r`, `-n`, and `-o` options to easily profile your code.

In [1]: from django.conf import settings

In [2]: settings.INTERNAL_IPS
Out[2]: []

Then, I confirmed the toolbar is showing and I see the following variables in the WSGI environ section of the Headers panel.

REMOTE_ADDR 	192.168.65.1
REMOTE_HOST 	192.168.65.1

I did not see any of the debug statements from this file printed in docker logs.

Honestly, I don't know what else to do to test. Perhaps you can give me some ideas tomorrow when we meet.

Original file line number Diff line number Diff line change
Expand Up @@ -13,12 +13,47 @@
sync_to_async,
)
from django.conf import settings
from django.dispatch import receiver
from django.test.signals import setting_changed
from django.utils.module_loading import import_string

from debug_toolbar import settings as dt_settings
from debug_toolbar.toolbar import DebugToolbar
from debug_toolbar.utils import clear_stack_trace_caches, is_processable_html_response

_resolved_gateway_ip = None


def _gateway_ip():
global _resolved_gateway_ip
if _resolved_gateway_ip is None:
print(
"[django-debug-toolbar] Trying to configure determine the Docker gateay address for autoconfiguration... ",
end="",
)
try:
# This is a hack for docker installations. It attempts to look
# up the IP address of the docker host.
# This is not guaranteed to work.
_resolved_gateway_ip = (
# Convert the last segment of the IP address to be .1
".".join(socket.gethostbyname("host.docker.internal").rsplit(".")[:-1])
+ ".1"
)
print("Success.")
except socket.gaierror:
# It's fine if the lookup errored since they may not be using docker
_resolved_gateway_ip = "unresolvable"
print("Not resolvable.")
return _resolved_gateway_ip


@receiver(setting_changed)
def _clear_gateway_ip_cache(*, setting, **kwargs):
global _resolved_gateway_ip
if setting in {"DEBUG", "INTERNAL_IPS"}:
_resolved_gateway_ip = None


def show_toolbar(request):
"""
Expand All @@ -32,20 +67,8 @@ def show_toolbar(request):
return True

# Test: Docker
try:
# This is a hack for docker installations. It attempts to look
# up the IP address of the docker host.
# This is not guaranteed to work.
docker_ip = (
# Convert the last segment of the IP address to be .1
".".join(socket.gethostbyname("host.docker.internal").rsplit(".")[:-1])
+ ".1"
)
if request.META.get("REMOTE_ADDR") == docker_ip:
return True
except socket.gaierror:
# It's fine if the lookup errored since they may not be using docker
pass
if request.META.get("REMOTE_ADDR") == _gateway_ip():
return True

# No test passed
return False
Expand Down