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Diffstat (limited to 'nova/api/openstack/limits.py')
| -rw-r--r-- | nova/api/openstack/limits.py | 358 |
1 files changed, 358 insertions, 0 deletions
diff --git a/nova/api/openstack/limits.py b/nova/api/openstack/limits.py new file mode 100644 index 000000000..efc7d193d --- /dev/null +++ b/nova/api/openstack/limits.py @@ -0,0 +1,358 @@ +# Copyright 2011 OpenStack LLC. +# All Rights Reserved. +# +# 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 datetime + +""" +Module dedicated functions/classes dealing with rate limiting requests. +""" + +import copy +import httplib +import json +import math +import re +import time +import urllib +import webob.exc + +from collections import defaultdict + +from webob.dec import wsgify + +from nova import wsgi +from nova.api.openstack import faults +from nova.wsgi import Controller +from nova.wsgi import Middleware + + +# Convenience constants for the limits dictionary passed to Limiter(). +PER_SECOND = 1 +PER_MINUTE = 60 +PER_HOUR = 60 * 60 +PER_DAY = 60 * 60 * 24 + + +class LimitsController(Controller): + """ + Controller for accessing limits in the OpenStack API. + """ + + _serialization_metadata = { + "application/xml": { + "attributes": { + "limit": ["verb", "URI", "regex", "value", "unit", + "resetTime", "remaining", "name"], + }, + "plurals": { + "rate": "limit", + }, + }, + } + + def index(self, req): + """ + Return all global and rate limit information. + """ + abs_limits = {} + rate_limits = req.environ.get("nova.limits", []) + + return { + "limits": { + "rate": rate_limits, + "absolute": abs_limits, + }, + } + + +class Limit(object): + """ + Stores information about a limit for HTTP requets. + """ + + UNITS = { + 1: "SECOND", + 60: "MINUTE", + 60 * 60: "HOUR", + 60 * 60 * 24: "DAY", + } + + def __init__(self, verb, uri, regex, value, unit): + """ + Initialize a new `Limit`. + + @param verb: HTTP verb (POST, PUT, etc.) + @param uri: Human-readable URI + @param regex: Regular expression format for this limit + @param value: Integer number of requests which can be made + @param unit: Unit of measure for the value parameter + """ + self.verb = verb + self.uri = uri + self.regex = regex + self.value = int(value) + self.unit = unit + self.unit_string = self.display_unit().lower() + self.remaining = int(value) + + if value <= 0: + raise ValueError("Limit value must be > 0") + + self.last_request = None + self.next_request = None + + self.water_level = 0 + self.capacity = self.unit + self.request_value = float(self.capacity) / float(self.value) + self.error_message = _("Only %(value)s %(verb)s request(s) can be "\ + "made to %(uri)s every %(unit_string)s." % self.__dict__) + + def __call__(self, verb, url): + """ + Represents a call to this limit from a relevant request. + + @param verb: string http verb (POST, GET, etc.) + @param url: string URL + """ + if self.verb != verb or not re.match(self.regex, url): + return + + now = self._get_time() + + if self.last_request is None: + self.last_request = now + + leak_value = now - self.last_request + + self.water_level -= leak_value + self.water_level = max(self.water_level, 0) + self.water_level += self.request_value + + difference = self.water_level - self.capacity + + self.last_request = now + + if difference > 0: + self.water_level -= self.request_value + self.next_request = now + difference + return difference + + cap = self.capacity + water = self.water_level + val = self.value + + self.remaining = math.floor(((cap - water) / cap) * val) + self.next_request = now + + def _get_time(self): + """Retrieve the current time. Broken out for testability.""" + return time.time() + + def display_unit(self): + """Display the string name of the unit.""" + return self.UNITS.get(self.unit, "UNKNOWN") + + def display(self): + """Return a useful representation of this class.""" + return { + "verb": self.verb, + "URI": self.uri, + "regex": self.regex, + "value": self.value, + "remaining": int(self.remaining), + "unit": self.display_unit(), + "resetTime": int(self.next_request or self._get_time()), + } + +# "Limit" format is a dictionary with the HTTP verb, human-readable URI, +# a regular-expression to match, value and unit of measure (PER_DAY, etc.) + +DEFAULT_LIMITS = [ + Limit("POST", "*", ".*", 10, PER_MINUTE), + Limit("POST", "*/servers", "^/servers", 50, PER_DAY), + Limit("PUT", "*", ".*", 10, PER_MINUTE), + Limit("GET", "*changes-since*", ".*changes-since.*", 3, PER_MINUTE), + Limit("DELETE", "*", ".*", 100, PER_MINUTE), +] + + +class RateLimitingMiddleware(Middleware): + """ + Rate-limits requests passing through this middleware. All limit information + is stored in memory for this implementation. + """ + + def __init__(self, application, limits=None): + """ + Initialize new `RateLimitingMiddleware`, which wraps the given WSGI + application and sets up the given limits. + + @param application: WSGI application to wrap + @param limits: List of dictionaries describing limits + """ + Middleware.__init__(self, application) + self._limiter = Limiter(limits or DEFAULT_LIMITS) + + @wsgify(RequestClass=wsgi.Request) + def __call__(self, req): + """ + Represents a single call through this middleware. We should record the + request if we have a limit relevant to it. If no limit is relevant to + the request, ignore it. + + If the request should be rate limited, return a fault telling the user + they are over the limit and need to retry later. + """ + verb = req.method + url = req.url + context = req.environ.get("nova.context") + + if context: + username = context.user_id + else: + username = None + + delay, error = self._limiter.check_for_delay(verb, url, username) + + if delay: + msg = _("This request was rate-limited.") + retry = time.time() + delay + return faults.OverLimitFault(msg, error, retry) + + req.environ["nova.limits"] = self._limiter.get_limits(username) + + return self.application + + +class Limiter(object): + """ + Rate-limit checking class which handles limits in memory. + """ + + def __init__(self, limits): + """ + Initialize the new `Limiter`. + + @param limits: List of `Limit` objects + """ + self.limits = copy.deepcopy(limits) + self.levels = defaultdict(lambda: copy.deepcopy(limits)) + + def get_limits(self, username=None): + """ + Return the limits for a given user. + """ + return [limit.display() for limit in self.levels[username]] + + def check_for_delay(self, verb, url, username=None): + """ + Check the given verb/user/user triplet for limit. + + @return: Tuple of delay (in seconds) and error message (or None, None) + """ + delays = [] + + for limit in self.levels[username]: + delay = limit(verb, url) + if delay: + delays.append((delay, limit.error_message)) + + if delays: + delays.sort() + return delays[0] + + return None, None + + +class WsgiLimiter(object): + """ + Rate-limit checking from a WSGI application. Uses an in-memory `Limiter`. + + To use: + POST /<username> with JSON data such as: + { + "verb" : GET, + "path" : "/servers" + } + + and receive a 204 No Content, or a 403 Forbidden with an X-Wait-Seconds + header containing the number of seconds to wait before the action would + succeed. + """ + + def __init__(self, limits=None): + """ + Initialize the new `WsgiLimiter`. + + @param limits: List of `Limit` objects + """ + self._limiter = Limiter(limits or DEFAULT_LIMITS) + + @wsgify(RequestClass=wsgi.Request) + def __call__(self, request): + """ + Handles a call to this application. Returns 204 if the request is + acceptable to the limiter, else a 403 is returned with a relevant + header indicating when the request *will* succeed. + """ + if request.method != "POST": + raise webob.exc.HTTPMethodNotAllowed() + + try: + info = dict(json.loads(request.body)) + except ValueError: + raise webob.exc.HTTPBadRequest() + + username = request.path_info_pop() + verb = info.get("verb") + path = info.get("path") + + delay, error = self._limiter.check_for_delay(verb, path, username) + + if delay: + headers = {"X-Wait-Seconds": "%.2f" % delay} + return webob.exc.HTTPForbidden(headers=headers, explanation=error) + else: + return webob.exc.HTTPNoContent() + + +class WsgiLimiterProxy(object): + """ + Rate-limit requests based on answers from a remote source. + """ + + def __init__(self, limiter_address): + """ + Initialize the new `WsgiLimiterProxy`. + + @param limiter_address: IP/port combination of where to request limit + """ + self.limiter_address = limiter_address + + def check_for_delay(self, verb, path, username=None): + body = json.dumps({"verb": verb, "path": path}) + headers = {"Content-Type": "application/json"} + + conn = httplib.HTTPConnection(self.limiter_address) + + if username: + conn.request("POST", "/%s" % (username), body, headers) + else: + conn.request("POST", "/", body, headers) + + resp = conn.getresponse() + + if 200 >= resp.status < 300: + return None, None + + return resp.getheader("X-Wait-Seconds"), resp.read() or None |