Version 0.4.0

Changes:
- put ObservabilityMiddleware before ExceptionHandlerMiddleware to avoid repetative code
- add application startup and last metrics update metrics along with CPU usage metric and threads count
- move host and port to new uvicorn section at config along with new reload and forwarded_allow_ips
- add request_id and remove trace_id/span_id generation if tracing is disabled
- move logging logic from utils to observability
- pass trace_id/span_id in HEX form

{{project_slug}}/observability/utils.py

@@ -0,0 +1,64 @@
+"""Observability-related utility functions and classes are located here."""
+
+import re
+from collections import defaultdict
+
+import fastapi
+import structlog
+from opentelemetry import trace
+
+
+class URLsMapper:
+    """Helper to change URL from given regex pattern to the given static value.
+
+    For example, with map {"GET": {"/api/debug/.*": "/api/debug/*"}} all GET-requests with URL
+    starting with "/api/debug/" will be placed in path "/api/debug/*" in metrics.
+    """
+
+    def __init__(self, urls_map: dict[str, dict[str, str]] | None = None):
+        self._map: dict[str, dict[re.Pattern, str]] = defaultdict(dict)
+        """[method -> [pattern -> mapped_to]]"""
+
+        if urls_map is not None:
+            for method, patterns in urls_map.items():
+                for pattern, value in patterns.items():
+                    self.add(method, pattern, value)
+
+    def add(self, method: str, pattern: str, mapped_to: str) -> None:
+        """Add entry to the map. If pattern compilation is failed, ValueError is raised."""
+        regexp = re.compile(pattern)
+        self._map[method.upper()][regexp] = mapped_to
+
+    def add_routes(self, routes: list[fastapi.routing.APIRoute]) -> None:
+        """Add full route regexes to the map."""
+        logger: structlog.stdlib.BoundLogger = structlog.get_logger(__name__)
+        for route in routes:
+            if not hasattr(route, "path_regex") or not hasattr(route, "path"):
+                logger.warning("route has no 'path_regex' or 'path' attribute", route=route)
+                continue
+            if "{" not in route.path:  # ignore simple routes
+                continue
+            route_path = route.path
+            while "{" in route_path:
+                lbrace = route_path.index("{")
+                rbrace = route_path.index("}", lbrace + 1)
+                route_path = route_path[:lbrace] + "*" + route_path[rbrace + 1 :]
+            for method in route.methods:
+                self._map[method.upper()][route.path_regex] = route_path
+
+    def map(self, method: str, url: str) -> str:
+        """Check every map entry with `re.match` and return matched value. If not found, return original string."""
+        for regexp, mapped_to in self._map[method.upper()].items():
+            if regexp.match(url) is not None:
+                return mapped_to
+        return url
+
+
+def get_tracing_headers() -> dict[str, str]:
+    ctx = trace.get_current_span().get_span_context()
+    if ctx.trace_id == 0:
+        return {}
+    return {
+        "X-Span-Id": format(ctx.span_id, "016x"),
+        "X-Trace-Id": format(ctx.trace_id, "032x"),
+    }