mirror of
https://github.com/sprockets/sprockets.mixins.correlation.git
synced 2024-11-30 11:19:52 +00:00
126 lines
4.8 KiB
Python
126 lines
4.8 KiB
Python
import uuid
|
|
|
|
import tornado.gen
|
|
import tornado.log
|
|
|
|
if tornado.version_info[0] >= 4:
|
|
from tornado.concurrent import is_future
|
|
else:
|
|
import tornado.concurrent
|
|
|
|
def is_future(maybe_future):
|
|
return isinstance(maybe_future, tornado.concurrent.Future)
|
|
|
|
|
|
class HandlerMixin(object):
|
|
"""
|
|
Mix this in over a ``RequestHandler`` for a correlating header.
|
|
|
|
:keyword str correlation_header: the name of the header to use
|
|
for correlation. If this keyword is omitted, then the header
|
|
is named ``Correlation-ID``.
|
|
|
|
This mix-in ensures that responses include a header that correlates
|
|
requests and responses. If there header is set on the incoming
|
|
request, then it will be copied to the outgoing response. Otherwise,
|
|
a new UUIDv4 will be generated and inserted. The value can be
|
|
examined or modified via the ``correlation_id`` property.
|
|
|
|
The MRO needs to contain something that resembles a standard
|
|
:class:`tornado.web.RequestHandler`. Specifically, we need the
|
|
following things to be available:
|
|
|
|
- :meth:`~tornado.web.RequestHandler.prepare` needs to be called
|
|
appropriately
|
|
- :meth:`~tornado.web.RequestHandler.set_header` needs to exist in
|
|
the MRO and it needs to overwrite the header value
|
|
- :meth:`~tornado.web.RequestHandler.set_default_headers` should be
|
|
called to establish the default header values
|
|
- ``self.request`` is a object that has a ``headers`` property that
|
|
contains the request headers as a ``dict``.
|
|
|
|
"""
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
# correlation_id is used from within set_default_headers
|
|
# which is called from within super().__init__() so we need
|
|
# to make sure that it is set *BEFORE* we call super.
|
|
self.__header_name = kwargs.pop(
|
|
'correlation_header', 'Correlation-ID')
|
|
self.__correlation_id = str(uuid.uuid4())
|
|
super(HandlerMixin, self).__init__(*args, **kwargs)
|
|
|
|
@tornado.gen.coroutine
|
|
def prepare(self):
|
|
# Here we want to copy an incoming Correlation-ID header if
|
|
# one exists. We also want to set it in the outgoing response
|
|
# which the property setter does for us.
|
|
maybe_future = super(HandlerMixin, self).prepare()
|
|
if is_future(maybe_future):
|
|
yield maybe_future
|
|
|
|
correlation_id = self.get_request_header(self.__header_name, None)
|
|
if correlation_id is not None:
|
|
self.correlation_id = correlation_id
|
|
|
|
def set_default_headers(self):
|
|
# This is called during initialization as well as *AFTER*
|
|
# calling clear() when an error occurs so we need to make
|
|
# sure that our header is set again...
|
|
super(HandlerMixin, self).set_default_headers()
|
|
self.set_header(self.__header_name, self.correlation_id)
|
|
|
|
@property
|
|
def correlation_id(self):
|
|
"""Correlation header value."""
|
|
return self.__correlation_id
|
|
|
|
@correlation_id.setter
|
|
def correlation_id(self, value):
|
|
self.__correlation_id = value
|
|
self.set_header(self.__header_name, self.__correlation_id)
|
|
|
|
def get_request_header(self, name, default):
|
|
"""
|
|
Retrieve the value of a request header.
|
|
|
|
:param str name: the name of the header to retrieve
|
|
:param default: the value to return if the header is not set
|
|
|
|
This method abstracts the act of retrieving a header value out
|
|
from the implementation. This makes it possible to implement
|
|
a *RequestHandler* that is something other than a
|
|
:class:`tornado.web.RequestHandler` by simply implementing this
|
|
method and ``set_header`` over the underlying implementation,
|
|
for example, say AMQP message properties.
|
|
|
|
"""
|
|
return self.request.headers.get(name, default)
|
|
|
|
|
|
def correlation_id_logger(handler):
|
|
""" Custom Tornado access log writer that appends correlation-id.
|
|
|
|
This function can be used to append the coorelation-id to the
|
|
Tornado access logs. To use, simply set the value of the
|
|
log_function kwarg of the Tornado Application constructor to this
|
|
function.
|
|
|
|
*Example*
|
|
web.Application([], log_function=correlation_id_logger)
|
|
|
|
:param tornado.web.RequestHandler handler: the request handler that
|
|
is processing the client request.
|
|
"""
|
|
if handler.get_status() < 400:
|
|
log_method = tornado.log.access_log.info
|
|
elif handler.get_status() < 500:
|
|
log_method = tornado.log.access_log.warning
|
|
else:
|
|
log_method = tornado.log.access_log.error
|
|
request_time = 1000.0 * handler.request.request_time()
|
|
correlation_id = getattr(handler, "correlation_id", None)
|
|
if correlation_id is None:
|
|
correlation_id = handler.request.headers.get('Correlation-ID', None)
|
|
log_method("%d %s %.2fms {CID %s}", handler.get_status(),
|
|
handler._request_summary(), request_time, correlation_id)
|