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#The MIT License (MIT)
#Copyright (c) 2014 Microsoft Corporation
#Permission is hereby granted, free of charge, to any person obtaining a copy
#of this software and associated documentation files (the "Software"), to deal
#in the Software without restriction, including without limitation the rights
#to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#copies of the Software, and to permit persons to whom the Software is
#furnished to do so, subject to the following conditions:
#The above copyright notice and this permission notice shall be included in all
#copies or substantial portions of the Software.
#THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
#SOFTWARE.
"""Session Consistency Tracking in the Azure Cosmos database service.
"""
import sys, traceback
import threading
import azure.cosmos.base as base
import azure.cosmos.http_constants as http_constants
from azure.cosmos.vector_session_token import VectorSessionToken
from azure.cosmos.errors import HTTPFailure
class SessionContainer(object):
def __init__(self):
self.collection_name_to_rid = {}
self.rid_to_session_token = {}
self.session_lock = threading.RLock()
def get_session_token(self, resource_path):
"""
Get Session Token for collection_link
:param str resource_path:
Self link / path to the resource
:return:
Session Token dictionary for the collection_id
:rtype:
dict
"""
with self.session_lock:
is_name_based = base.IsNameBased(resource_path)
collection_rid = ''
session_token = ''
try:
if is_name_based:
# get the collection name
collection_name = base.GetItemContainerLink(resource_path)
collection_rid = self.collection_name_to_rid[collection_name]
else:
collection_rid = base.GetItemContainerLink(resource_path)
if collection_rid in self.rid_to_session_token:
token_dict = self.rid_to_session_token[collection_rid]
session_token_list = []
for key in token_dict.keys():
session_token_list.append("{0}:{1}".format(key, token_dict[key].convert_to_string()))
session_token = ','.join(session_token_list)
return session_token
else:
# return empty token if not found
return ''
except:
return ''
def set_session_token(self, response_result, response_headers):
"""
Session token must only be updated from response of requests that successfully mutate resource on the
server side (write, replace, delete etc)
:param dict response_result:
:param dict response_headers:
:return:
- None
"""
''' there are two pieces of information that we need to update session token-
self link which has the rid representation of the resource, and
x-ms-alt-content-path which is the string representation of the resource'''
with self.session_lock:
collection_rid = ''
collection_name = ''
try:
self_link = response_result['_self']
''' extract alternate content path from the response_headers
(only document level resource updates will have this),
and if not present, then we can assume that we don't have to update
session token for this request'''
alt_content_path = ''
alt_content_path_key = http_constants.HttpHeaders.AlternateContentPath
response_result_id_key = u'id'
response_result_id = None
if alt_content_path_key in response_headers:
alt_content_path = response_headers[http_constants.HttpHeaders.AlternateContentPath]
response_result_id = response_result[response_result_id_key]
else:
return
collection_rid, collection_name = base.GetItemContainerInfo(self_link, alt_content_path, response_result_id)
except ValueError:
return
except:
exc_type, exc_value, exc_traceback = sys.exc_info()
traceback.print_exception(exc_type, exc_value, exc_traceback,
limit=2, file=sys.stdout)
return
if collection_name in self.collection_name_to_rid:
''' check if the rid for the collection name has changed
this means that potentially, the collection was deleted
and recreated
'''
existing_rid = self.collection_name_to_rid[collection_name]
if (collection_rid != existing_rid):
''' flush the session tokens for the old rid, and
update the new rid into the collection name to rid map.
'''
self.rid_to_session_token[existing_rid] = {}
self.collection_name_to_rid[collection_name] = collection_rid
# parse session token
parsed_tokens = self.parse_session_token(response_headers)
# update session token in collection rid to session token map
if collection_rid in self.rid_to_session_token:
''' we need to update the session tokens for 'this' collection
'''
for id in parsed_tokens:
old_session_token = self.rid_to_session_token[collection_rid][id] if id in self.rid_to_session_token[collection_rid] else None
if not old_session_token:
self.rid_to_session_token[collection_rid][id] = parsed_tokens[id]
else:
self.rid_to_session_token[collection_rid][id] = parsed_tokens[id].merge(old_session_token)
self.collection_name_to_rid[collection_name] = collection_rid
else:
self.rid_to_session_token[collection_rid] = parsed_tokens
self.collection_name_to_rid[collection_name] = collection_rid
def clear_session_token(self, response_headers):
with self.session_lock:
collection_rid = ''
alt_content_path = ''
alt_content_path_key = http_constants.HttpHeaders.AlternateContentPath
if alt_content_path_key in response_headers:
alt_content_path = response_headers[http_constants.HttpHeaders.AlternateContentPath]
if alt_content_path in self.collection_name_to_rid:
collection_rid = self.collection_name_to_rid[alt_content_path]
del self.collection_name_to_rid[alt_content_path]
del self.rid_to_session_token[collection_rid]
@staticmethod
def parse_session_token(response_headers):
""" Extracts session token from response headers and parses
:param dict response_headers:
:return:
A dictionary of partition id to session lsn
for given collection
:rtype: dict
"""
# extract session token from response header
session_token = ''
if http_constants.HttpHeaders.SessionToken in response_headers:
session_token = response_headers[http_constants.HttpHeaders.SessionToken]
id_to_sessionlsn = {}
if session_token != '':
''' extract id, lsn from the token. For p-collection,
the token will be a concatenation of pairs for each collection'''
token_pairs = session_token.split(',')
for token_pair in token_pairs:
tokens = token_pair.split(':')
if (len(tokens) == 2):
id = tokens[0]
sessionToken = VectorSessionToken.create(tokens[1])
if sessionToken is None:
raise HTTPFailure(http_constants.StatusCodes.INTERNAL_SERVER_ERROR, "Could not parse the received session token: %s" % tokens[1])
id_to_sessionlsn[id] = sessionToken
return id_to_sessionlsn
class Session:
"""
State of a Azure Cosmos session. This session object
can be shared across clients within the same process
"""
def __init__(self, url_connection):
self.url_connection = url_connection
self.session_container = SessionContainer()
#include creation time, and some other stats
def clear_session_token(self, response_headers):
self.session_container.clear_session_token(response_headers)
def update_session(self, response_result, response_headers):
self.session_container.set_session_token(response_result, response_headers)
def get_session_token(self, resource_path):
return self.session_container.get_session_token(resource_path)
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