webapp2: New automatic instrumentation (#194)

* Initial webapp2 automatic instrumentation

* Remove trailing whitespace

Author: pglombardo

instana/__init__.py

@@ -79,6 +79,7 @@ def boot_agent():
         from .instrumentation import sqlalchemy
         from .instrumentation import sudsjurko
         from .instrumentation import urllib3
+        from .instrumentation import webapp2_inst
         from .instrumentation.django import middleware
 
 
@@ -114,7 +115,7 @@ def boot_agent():
 else:
     if "INSTANA_MAGIC" in os.environ:
         # If we're being loaded into an already running process, then delay agent initialization
-        t = Timer(3.0, boot_agent)
+        t = Timer(2.0, boot_agent)
         t.start()
     else:
         boot_agent()

instana/instrumentation/webapp2_inst.py

@@ -0,0 +1,65 @@
+from __future__ import absolute_import
+import wrapt
+
+import opentracing as ot
+import opentracing.ext.tags as tags
+
+from ..log import logger
+from ..singletons import agent, tracer
+from ..util import strip_secrets
+
+
+try:
+    import webapp2
+
+    logger.debug("Instrumenting webapp2")
+
+    @wrapt.patch_function_wrapper('webapp2', 'WSGIApplication.__call__')
+    def call_with_instana(wrapped, instance, argv, kwargs):
+        env = argv[0]
+        start_response = argv[1]
+
+        def new_start_response(status, headers, exc_info=None):
+            """Modified start response with additional headers."""
+            if 'stan_scope' in env:
+                scope = env['stan_scope']
+                tracer.inject(scope.span.context, ot.Format.HTTP_HEADERS, headers)
+                headers.append(('Server-Timing', "intid;desc=%s" % scope.span.context.trace_id))
+
+                res = start_response(status, headers, exc_info)
+
+                sc = status.split(' ')[0]
+                if 500 <= int(sc) <= 511:
+                    scope.span.set_tag("error", True)
+                    ec = scope.span.tags.get('ec', 0)
+                    scope.span.set_tag("ec", ec+1)
+
+                scope.span.set_tag(tags.HTTP_STATUS_CODE, sc)
+                scope.close()
+                return res
+            else:
+                return start_response(status, headers, exc_info)
+
+        ctx = tracer.extract(ot.Format.HTTP_HEADERS, env)
+        scope = env['stan_scope'] = tracer.start_active_span("wsgi", child_of=ctx)
+
+        if agent.extra_headers is not None:
+            for custom_header in agent.extra_headers:
+                # Headers are available in this format: HTTP_X_CAPTURE_THIS
+                wsgi_header = ('HTTP_' + custom_header.upper()).replace('-', '_')
+                if wsgi_header in env:
+                    scope.span.set_tag("http.%s" % custom_header, env[wsgi_header])
+
+        if 'PATH_INFO' in env:
+            scope.span.set_tag('http.path', env['PATH_INFO'])
+        if 'QUERY_STRING' in env and len(env['QUERY_STRING']):
+            scrubbed_params = strip_secrets(env['QUERY_STRING'], agent.secrets_matcher, agent.secrets_list)
+            scope.span.set_tag("http.params", scrubbed_params)
+        if 'REQUEST_METHOD' in env:
+            scope.span.set_tag(tags.HTTP_METHOD, env['REQUEST_METHOD'])
+        if 'HTTP_HOST' in env:
+            scope.span.set_tag("http.host", env['HTTP_HOST'])
+
+        return wrapped(env, new_start_response)
+except ImportError:
+    pass