mirror of
https://github.com/sprockets/sprockets.mixins.correlation.git
synced 2024-11-23 19:29:55 +00:00
84 lines
3.4 KiB
Python
84 lines
3.4 KiB
Python
|
import uuid
|
||
|
|
|
||
|
|
|
||
|
|
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)
|
||
|
|
|
||
|
|
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.
|
||
|
|
super(HandlerMixin, self).prepare()
|
||
|
|
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)
|