zuul/zuul/webapp.py
Timo Tijhof 0ebd29371a web: Allow clients (browsers, proxies) to cache status.json
Follows-up aa4f2e7. While we're sending Last-Modified already,
that's purely informational and doesn't do much.

In theory proxies could figure it out by observing or polling
the backend (with rate limiting) but afaik that isn't generally
implemented.

Web browsers typically send If-Modified-Since. So for requests
coming from the users directly, Response.conditional_response_app
handles the If-Modified-Since header and returns early with
HTTPNotModified if needed (and no body content).

In addition Cache-Control/Expires headers allow clients/proxies
to handle it themselves (without even a 304 rountrip). This is
preferred and informs the client of the actual expiry instead of
having it ask us every time whether or not a timestamp is too old.

Response:
 200 OK
 Cache-Control: public, must-revalidate, max-age=(seconds)
 Expires: (RFC 2822 timestamp + seconds)
 Last-Modified: (RFC 2822 timestamp)

Request:
 GET
 If-Modified-Since: (RFC 2822 timestamp)

Response:
 304 Not Modified
 Expires: (RFC 2822 timestamp + seconds)

http://docs.webob.org/en/1.1/modules/webob.html

Change-Id: I51f31f9d7965d805e147fda4070feead528601ac
2015-04-04 00:44:34 +01:00

131 lines
4.5 KiB
Python

# Copyright 2012 Hewlett-Packard Development Company, L.P.
# Copyright 2013 OpenStack Foundation
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import copy
import json
import logging
import re
import threading
import time
from paste import httpserver
import webob
from webob import dec
"""Zuul main web app.
Zuul supports HTTP requests directly against it for determining the
change status. These responses are provided as json data structures.
The supported urls are:
- /status: return a complex data structure that represents the entire
queue / pipeline structure of the system
- /status.json (backwards compatibility): same as /status
- /status/change/X,Y: return status just for gerrit change X,Y
When returning status for a single gerrit change you will get an
array of changes, they will not include the queue structure.
"""
class WebApp(threading.Thread):
log = logging.getLogger("zuul.WebApp")
def __init__(self, scheduler, port=8001, cache_expiry=1):
threading.Thread.__init__(self)
self.scheduler = scheduler
self.port = port
self.cache_expiry = cache_expiry
self.cache_time = 0
self.cache = None
self.daemon = True
self.server = httpserver.serve(dec.wsgify(self.app), host='0.0.0.0',
port=self.port, start_loop=False)
def run(self):
self.server.serve_forever()
def stop(self):
self.server.server_close()
def _changes_by_func(self, func):
"""Filter changes by a user provided function.
In order to support arbitrary collection of subsets of changes
we provide a low level filtering mechanism that takes a
function which applies to changes. The output of this function
is a flattened list of those collected changes.
"""
status = []
jsonstruct = json.loads(self.cache)
for pipeline in jsonstruct['pipelines']:
for change_queue in pipeline['change_queues']:
for head in change_queue['heads']:
for change in head:
if func(change):
status.append(copy.deepcopy(change))
return json.dumps(status)
def _status_for_change(self, rev):
"""Return the statuses for a particular change id X,Y."""
def func(change):
return change['id'] == rev
return self._changes_by_func(func)
def _normalize_path(self, path):
# support legacy status.json as well as new /status
if path == '/status.json' or path == '/status':
return "status"
m = re.match('/status/change/(\d+,\d+)$', path)
if m:
return m.group(1)
return None
def app(self, request):
path = self._normalize_path(request.path)
if path is None:
raise webob.exc.HTTPNotFound()
if (not self.cache or
(time.time() - self.cache_time) > self.cache_expiry):
try:
self.cache = self.scheduler.formatStatusJSON()
# Call time.time() again because formatting above may take
# longer than the cache timeout.
self.cache_time = time.time()
except:
self.log.exception("Exception formatting status:")
raise
if path == 'status':
response = webob.Response(body=self.cache,
content_type='application/json')
else:
status = self._status_for_change(path)
if status:
response = webob.Response(body=status,
content_type='application/json')
else:
raise webob.exc.HTTPNotFound()
response.headers['Access-Control-Allow-Origin'] = '*'
response.cache_control.public = True
response.cache_control.max_age = self.cache_expiry
response.last_modified = self.cache_time
response.expires = self.cache_time + self.cache_expiry
return response.conditional_response_app