[WIP] Sentry improvements (#108)

Stator clears scope during the main loop to behave more like
transactions. Transaction names are set.

Sentry tags:
* 'takahe.version'
* 'takahe.app' values 'web' or 'stator'

Added settings:
* TAKAHE_SENTRY_SAMPLE_RATE
* TAKAHE_SENTRY_TRACES_SAMPLE_RATE

2 files changed, 68 insertions, 0 deletions

diff --git a/core/middleware.py b/core/middleware.py
index fca5dd8..08c28fa 100644
--- a/core/middleware.py
+++ b/core/middleware.py
@@ -1,3 +1,6 @@
+from django.core.exceptions import MiddlewareNotUsed
+
+from core import sentry
 from core.models import Config
 
 
@@ -13,3 +16,19 @@ class ConfigLoadingMiddleware:
         Config.system = Config.load_system()
         response = self.get_response(request)
         return response
+
+
+class SentryTaggingMiddleware:
+    """
+    Sets Sentry tags at the start of the request if Sentry is configured.
+    """
+
+    def __init__(self, get_response):
+        if not sentry.SENTRY_ENABLED:
+            raise MiddlewareNotUsed()
+        self.get_response = get_response
+
+    def __call__(self, request):
+        sentry.set_takahe_app("web")
+        response = self.get_response(request)
+        return response
diff --git a/core/sentry.py b/core/sentry.py
new file mode 100644
index 0000000..9a7b100
--- /dev/null
+++ b/core/sentry.py
@@ -0,0 +1,49 @@
+from contextlib import contextmanager
+
+from django.conf import settings
+
+SENTRY_ENABLED = False
+try:
+    if settings.SETUP.SENTRY_DSN:
+        import sentry_sdk
+
+        SENTRY_ENABLED = True
+except ImportError:
+    pass
+
+
+def noop(*args, **kwargs):
+    pass
+
+
+@contextmanager
+def noop_context(*args, **kwargs):
+    yield
+
+
+if SENTRY_ENABLED:
+    configure_scope = sentry_sdk.configure_scope
+    push_scope = sentry_sdk.push_scope
+    set_context = sentry_sdk.set_context
+    set_tag = sentry_sdk.set_tag
+    start_transaction = sentry_sdk.start_transaction
+else:
+    configure_scope = noop_context
+    push_scope = noop_context
+    set_context = noop
+    set_tag = noop
+    start_transaction = noop_context
+
+
+def set_takahe_app(name: str):
+    set_tag("takahe.app", name)
+
+
+def scope_clear(scope):
+    if scope:
+        scope.clear()
+
+
+def set_transaction_name(scope, name: str):
+    if scope:
+        scope.set_transaction_name(name)