FastAPI: Capture exception detail on 5xx (#286)

* FastAPI: Capture exception detail on 5xx

* Version limit urllib3 to sidestep bug

The following seems to be occurring with 1.26.0:
> ImportError: cannot import name 'HTTPHeaderDict' from 'urllib3.connection'

Author: Peter Giacomo Lombardo

instana/instrumentation/fastapi_inst.py

@@ -13,10 +13,31 @@
     from ..util import running_in_gunicorn
     from .asgi import InstanaASGIMiddleware
     from starlette.middleware import Middleware
+    from fastapi import HTTPException
+    from fastapi.exception_handlers import http_exception_handler
+
+    from instana.singletons import async_tracer
 
     if hasattr(fastapi, '__version__') and \
         (LooseVersion(fastapi.__version__) >= LooseVersion('0.51.0')):
 
+        async def instana_exception_handler(request, exc):
+            """
+            We capture FastAPI HTTPException, log the error and pass it on
+            to the default exception handler.
+            """
+            try:
+                span = async_tracer.active_span
+
+                if span is not None:
+                    if hasattr(exc, 'detail'):
+                        span.set_tag('http.error', exc.detail)
+                    span.set_tag('http.status_code', exc.status_code)
+            except Exception:
+                logger.debug("FastAPI instana_exception_handler: ", exc_info=True)
+
+            return await http_exception_handler(request, exc)
+
         @wrapt.patch_function_wrapper('fastapi.applications', 'FastAPI.__init__')
         def init_with_instana(wrapped, instance, args, kwargs):
             middleware = kwargs.get('middleware')
@@ -25,6 +46,13 @@ def init_with_instana(wrapped, instance, args, kwargs):
             elif isinstance(middleware, list):
                 middleware.append(Middleware(InstanaASGIMiddleware))
 
+            exception_handlers = kwargs.get('exception_handlers')
+            if exception_handlers is None:
+                kwargs['exception_handlers'] = dict()
+
+            if isinstance(kwargs['exception_handlers'], dict):
+                kwargs['exception_handlers'][HTTPException] = instana_exception_handler
+
             return wrapped(*args, **kwargs)
 
         logger.debug("Instrumenting FastAPI")

setup.py

@@ -79,14 +79,14 @@ def check_setuptools():
               'nose>=1.0',
               'pyramid>=1.2',
               'pytest>=4.6',
-              'urllib3[secure]>=1.15'
+              'urllib3[secure]>=1.15,<=1.25.11'
           ],
           'test-cassandra': [
               'cassandra-driver==3.20.2',
               'mock>=2.0.0',
               'nose>=1.0',
               'pytest>=4.6',
-              'urllib3[secure]>=1.15'
+              'urllib3[secure]>=1.15<=1.25.11'
           ],
           'test-couchbase': [
               'couchbase==2.5.9',
@@ -122,7 +122,7 @@ def check_setuptools():
               'suds-jurko>=0.6',
               'tornado>=4.5.3,<6.0',
               'uvicorn>=0.12.2;python_version>="3.6"',
-              'urllib3[secure]>=1.15'
+              'urllib3[secure]>=1.15,<=1.25.11'
           ],
       },
       test_suite='nose.collector',