Greedily load the handler module. (#1)

It turns out that at cold start time, the CPU isn't so throttled. So that's
the time to do big jobs like instrumenting crazy dependencies. So we should
try to load all our user's deps up front, before their first invocation.

Plus, the lazy-load strategy would have them paying for DB connection setup
and stuff on first invoke, which is bad.

Author: Matt Whelan

python/newrelic_lambda_wrapper.py

@@ -18,8 +18,6 @@
 
 newrelic.agent.initialize()
 
-wrapped_handler = None
-
 
 class IOpipeNoOp(object):
     def __call__(self, *args, **kwargs):
@@ -33,12 +31,6 @@ def __getattr__(self, name):
         return IOpipeNoOp()
 
 
-@newrelic.agent.lambda_handler()
-def handler(event, context):
-    context.iopipe = IOpipeNoOp()
-    return get_wrapped_handler()(event, context)
-
-
 def get_handler():
     if (
         "NEW_RELIC_LAMBDA_HANDLER" not in os.environ
@@ -89,10 +81,12 @@ def get_handler():
     return handler
 
 
-def get_wrapped_handler():
-    global wrapped_handler
+# Greedily load the handler during cold start, so we don't pay for it on first invoke
+wrapped_handler = get_handler()
+
 
-    if not wrapped_handler:
-        wrapped_handler = get_handler()
+@newrelic.agent.lambda_handler()
+def handler(event, context):
+    context.iopipe = IOpipeNoOp()
+    return wrapped_handler(event, context)
 
-    return wrapped_handler