def patch():
"""
Tracing function that patches the Tornado web application so that it will be
traced using the given ``tracer``.
"""
# patch only once
if getattr(tornado, '__datadog_patch', False):
return
setattr(tornado, '__datadog_patch', True)
# patch Application to initialize properly our settings and tracer
_w('tornado.web', 'Application.__init__', application.tracer_config)
# patch RequestHandler to trace all Tornado handlers
_w('tornado.web', 'RequestHandler._execute', handlers.execute)
_w('tornado.web', 'RequestHandler.on_finish', handlers.on_finish)
_w('tornado.web', 'RequestHandler.log_exception', handlers.log_exception)
# patch Tornado decorators
_w('tornado.concurrent', 'run_on_executor', decorators._run_on_executor)
# patch Template system
_w('tornado.template', 'Template.generate', template.generate)
# configure the global tracer
ddtrace.tracer.configure(
context_provider=TracerStackContext,
wrap_executor=decorators.wrap_executor,
)