Kepiye cara kerja request lifecycle ing Django?

Question

IT Interview Practice · Accepted Answer

Ing Django, sawijining request ditangani dening **WSGI/ASGI handler**, dibungkus dening tumpukan **middleware**, dirutekake dening **URL resolver** menyang sawijining **view**, lan diowahi dadi sawijining `HttpResponse` sing mili bali metu liwat middleware sing padha kanthi urutan kuwalik.

## Tahap-tahape

```
Web server ──▶ WSGI/ASGI handler  (nggawe HttpRequest)
   ▼
Middleware — fase request          (ndhuwur → ngisor: __call__ sadurunge get_response)
   ▼
URL resolver (urls.py)  ── cocogake path → view + kwargs
   ▼
Middleware — hook process_view
   ▼
View (function / class-based)  ── logika sampeyan, mbalekake HttpResponse
   ▼
Middleware — fase response         (ngisor → ndhuwur: sawise get_response)
   ▼
HttpResponse ──▶ client
```

1. **Handler** — handler WSGI (sync) utawa ASGI (async) mbangun sawijining `HttpRequest` saka environ/scope.
2. **Middleware, fase request** — kode saben middleware *sadurunge* `get_response()` mlaku saka ndhuwur menyang ngisor (`SecurityMiddleware`, `SessionMiddleware`, `AuthenticationMiddleware`, CSRF, …). Salah sawijine bisa medhot dalan lan mbalekake response luwih dhisik.
3. **Resolusi URL** — pola-pola `ROOT_URLCONF` dicocogake karo path kanggo milih sawijining view lan njupuk kwargs.
4. **`process_view`** — sawijining hook middleware sing mlaku pas sadurunge view diundang.
5. **View** — view basis fungsi utawa kelas sampeyan mlaku, biasane query model lan render template, banjur mbalekake sawijining `HttpResponse`. Exception micu `process_exception`.
6. **Middleware, fase response** — kode *sawise* `get_response()` mlaku saka ngisor menyang ndhuwur, ngidini middleware ngowahi response sing metu (header, kompresi).
7. `HttpResponse` di-stream bali menyang server lan client.

```python
# middleware.py
class TimingMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

def __call__(self, request):          # 2. fase request (sadurunge)
        request.started = time.monotonic()
        response = self.get_response(request)  # ngundang lapisan sabanjure / view
        response["X-Time"] = "..."         # 6. fase response (sawise)
        return response

# urls.py  → 3. routing
urlpatterns = [path("items/<int:pk>/", views.item_detail)]

# views.py → 5. view
def item_detail(request, pk):
    return render(request, "item.html", {"item": Item.objects.get(pk=pk)})
```

## Kenapa iki penting

Siklus request/response Django dipuseraké ing middleware, dadi umume prilaku lintas-potong — auth, session, CSRF, security header, caching — diimplementasi minangka middleware sing urut. Ngerti yen kode fase-request mlaku saka ndhuwur menyang ngisor lan kode fase-response mlaku saka ngisor menyang ndhuwur (lan yen urutan ing `MIDDLEWARE` iku penting) iku wigati banget kanggo nyelehake middleware sampeyan dhewe kanthi bener, ndebug kenapa sawijining `403`/redirect kedadeyan sadurunge view sampeyan, lan ngerti ing ngendi kudu nyanthol logika tanpa ndemek saben view.

Tahap-tahape

Kenapa iki penting

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