feat: Switch from wsgi to asgi (attempt 3) (#21579)

* Try switching from wsgi to asgi

By default I don't believe this will change anything (everything runs
sync by default), but it will allow us to wrap e.g. clickhouse calls in
sync_to_async wrappers to stop them blocking for ages

* Trigger e2e tests

* Set env var with ASGI/WSGI info

* Fix sentry tracing sampling in ASGI

This was relying on wsgi_environ which is replaced by asgi_scope

* Remove bad headers typecast

* fix linting errors

.github/workflows/ci-e2e.yml

@@ -59,7 +59,6 @@ jobs:
         timeout-minutes: 5
         outputs:
             chunks: ${{ steps.chunk.outputs.chunks }}
-
         steps:
             - name: Check out
               uses: actions/checkout@v3

posthog/asgi.py

@@ -0,0 +1,8 @@
+import os
+
+from django.core.asgi import get_asgi_application
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "posthog.settings")
+os.environ.setdefault("SERVER_GATEWAY_INTERFACE", "ASGI")
+
+application = get_asgi_application()

posthog/settings/sentry.py

@@ -74,6 +74,12 @@ def traces_sampler(sampling_context: dict) -> float:
     if op == "http.server":
         path = sampling_context.get("wsgi_environ", {}).get("PATH_INFO")
         force_sample = bool(sampling_context.get("wsgi_environ", {}).get("HTTP_FORCE_SAMPLE"))
+        if os.environ.get("SERVER_GATEWAY_INTERFACE") == "ASGI":
+            path = sampling_context.get("asgi_scope", {}).get("path")
+            headers = sampling_context.get("asgi_scope", {}).get("headers", [])
+            for name, value in headers:
+                if name.lower().replace(b"_", b"-") == "force-sample":
+                    force_sample = bool(value)
 
         # HTTP header to force sampling set
         if force_sample:

posthog/wsgi.py

@@ -12,5 +12,6 @@
 from django.core.wsgi import get_wsgi_application
 
 os.environ.setdefault("DJANGO_SETTINGS_MODULE", "posthog.settings")
+os.environ.setdefault("SERVER_GATEWAY_INTERFACE", "WSGI")
 
 application = get_wsgi_application()

unit.json

@@ -43,7 +43,8 @@
             "processes": 4,
             "working_directory": "/code",
             "path": ".",
-            "module": "posthog.wsgi",
+            "module": "posthog.asgi",
+            "protocol": "asgi",
             "user": "nobody",
             "limits": {
                 "requests": 50000