FastAPI: Load only when supported version in use (#284)

Author: Peter Giacomo Lombardo

instana/instrumentation/fastapi_inst.py

@@ -4,30 +4,36 @@
 """
 try:
     import fastapi
+    import os
     import wrapt
     import signal
-    import os
+    from distutils.version import LooseVersion
 
     from ..log import logger
     from ..util import running_in_gunicorn
     from .asgi import InstanaASGIMiddleware
     from starlette.middleware import Middleware
 
-    @wrapt.patch_function_wrapper('fastapi.applications', 'FastAPI.__init__')
-    def init_with_instana(wrapped, instance, args, kwargs):
-        middleware = kwargs.get('middleware')
-        if middleware is None:
-            kwargs['middleware'] = [Middleware(InstanaASGIMiddleware)]
-        elif isinstance(middleware, list):
-            middleware.append(Middleware(InstanaASGIMiddleware))
+    if hasattr(fastapi, '__version__') and \
+        (LooseVersion(fastapi.__version__) >= LooseVersion('0.51.0')):
+
+        @wrapt.patch_function_wrapper('fastapi.applications', 'FastAPI.__init__')
+        def init_with_instana(wrapped, instance, args, kwargs):
+            middleware = kwargs.get('middleware')
+            if middleware is None:
+                kwargs['middleware'] = [Middleware(InstanaASGIMiddleware)]
+            elif isinstance(middleware, list):
+                middleware.append(Middleware(InstanaASGIMiddleware))
 
-        return wrapped(*args, **kwargs)
+            return wrapped(*args, **kwargs)
 
-    logger.debug("Instrumenting FastAPI")
+        logger.debug("Instrumenting FastAPI")
 
-    # Reload GUnicorn when we are instrumenting an already running application
-    if "INSTANA_MAGIC" in os.environ and running_in_gunicorn():
-        os.kill(os.getpid(), signal.SIGHUP)
+        # Reload GUnicorn when we are instrumenting an already running application
+        if "INSTANA_MAGIC" in os.environ and running_in_gunicorn():
+            os.kill(os.getpid(), signal.SIGHUP)
+    else:
+        logger.debug("Instana supports FastAPI package versions 0.51.0 and newer.  Skipping.")
 
 except ImportError:
-    pass
+    pass