Code-Memo

Using Django Debug Toolbar

Django Debug Toolbar is an essential tool for monitoring and optimizing Django applications. It provides insights into SQL queries, cache usage, template rendering time, and more.

1. Installing Django Debug Toolbar

Install the package using pip:

pip install django-debug-toolbar

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2. Adding to Installed Apps

Modify settings.py to include 'debug_toolbar' in INSTALLED_APPS:

INSTALLED_APPS = [
    ...
    "debug_toolbar",
]

---

3. Adding Middleware

Insert 'debug_toolbar.middleware.DebugToolbarMiddleware' before 'django.middleware.common.CommonMiddleware' in MIDDLEWARE:

MIDDLEWARE = [
    "django.middleware.security.SecurityMiddleware",
    "debug_toolbar.middleware.DebugToolbarMiddleware",
    "django.middleware.common.CommonMiddleware",
    ...
]

---

4. Configuring Internal IPs

Django Debug Toolbar is only available for internal IPs. Add this setting to settings.py:

INTERNAL_IPS = [
    "127.0.0.1",
]

If using Docker, use:

import socket

hostname, _, ips = socket.gethostbyname_ex(socket.gethostname())
INTERNAL_IPS = [ip[:-1] + "1" for ip in ips]

---

5. Adding Debug Toolbar URLs

Modify urls.py to include Debug Toolbar’s URLs:

from django.conf import settings
from django.conf.urls import include
from django.urls import path

urlpatterns = [
    ...
]

if settings.DEBUG:
    import debug_toolbar
    urlpatterns += [path("__debug__/", include(debug_toolbar.urls))]

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6. Running the Server

Start the development server:

python manage.py runserver

Visit your project in the browser, and you should see the Django Debug Toolbar appear on the right side of the screen.

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7. Features of Django Debug Toolbar

The toolbar provides several built-in panels for debugging:

• SQL Queries: View the SQL executed for each request.
• Templates: See which templates were rendered and how long they took.
• Cache: Check cache hits and misses.
• Static Files: Monitor loaded static assets.
• Signals: View Django’s internal signals.
• Logging: Inspect log messages.

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8. Configuring Debug Toolbar Panels

Customize which panels appear in settings.py:

DEBUG_TOOLBAR_PANELS = [
    "debug_toolbar.panels.versions.VersionsPanel",
    "debug_toolbar.panels.timer.TimerPanel",
    "debug_toolbar.panels.settings.SettingsPanel",
    "debug_toolbar.panels.headers.HeadersPanel",
    "debug_toolbar.panels.request.RequestPanel",
    "debug_toolbar.panels.sql.SQLPanel",
    "debug_toolbar.panels.staticfiles.StaticFilesPanel",
    "debug_toolbar.panels.templates.TemplatesPanel",
    "debug_toolbar.panels.cache.CachePanel",
    "debug_toolbar.panels.signals.SignalsPanel",
    "debug_toolbar.panels.logging.LoggingPanel",
]

---

9. Monitoring SQL Queries

To log all SQL queries in real time, enable query logging:

DEBUG_TOOLBAR_CONFIG = {
    "SHOW_TOOLBAR_CALLBACK": lambda request: True,
    "SQL_WARNING_THRESHOLD": 100,  # Highlight queries taking more than 100ms
}

You can also enable detailed query execution plans with:

from django.db import connection

with connection.cursor() as cursor:
    cursor.execute("EXPLAIN ANALYZE SELECT * FROM my_table")
    print(cursor.fetchall())

---

10. Enabling Debug Toolbar Only in Development

Ensure Debug Toolbar is active only in development:

DEBUG_TOOLBAR_CONFIG = {
    "SHOW_TOOLBAR_CALLBACK": lambda request: request.META.get("REMOTE_ADDR") in INTERNAL_IPS,
}

---

11. Checking Cache Performance

If caching is enabled, Debug Toolbar provides insights into cache performance.

from django.core.cache import cache

cache.set("my_key", "my_value", timeout=60)
value = cache.get("my_key")
print(value)  # Output: my_value

---

12. Debugging Template Performance

The toolbar shows:

• Which templates were used.
• How long each template took to render.
• Context variables passed to each template.

{% endraw %}{% for book in books %}
    <p></p>
&#123;% endraw %&#125;&#123;% endfor %&#125;

With Debug Toolbar, you can check if template rendering is slow due to large context data.

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13. Viewing HTTP Headers

Debug Toolbar provides HTTP request and response headers, useful for debugging:

def my_view(request):
    print(request.headers)
    return HttpResponse("Check Debug Toolbar for headers")

---

14. Disabling Debug Toolbar in Production

Never use Django Debug Toolbar in production. Disable it using:

if not DEBUG:
    INSTALLED_APPS.remove("debug_toolbar")
    MIDDLEWARE.remove("debug_toolbar.middleware.DebugToolbarMiddleware")

Or completely disable it with:

SHOW_TOOLBAR_CALLBACK = lambda request: False

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15. Summary of Django Debug Toolbar

Feature	Benefit
SQL Queries Panel	Shows all executed queries and highlights slow ones
Templates Panel	Displays template load times and context variables
Cache Panel	Shows cache hits, misses, and usage
Static Files Panel	Monitors loaded static files
Headers Panel	Displays HTTP request/response headers
Signals Panel	Shows all Django signals being triggered
Logging Panel	Displays log messages in real-time