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#The MIT License (MIT)
#Copyright (c) 2018 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 azure.cosmos.errors as errors
import azure.cosmos.base as base
from azure.cosmos.http_constants import StatusCodes
class VectorSessionToken(object):
segment_separator = '#'
region_progress_separator = "="
def __init__(self, version, global_lsn, local_lsn_by_region, session_token=None):
self.version = version
self.global_lsn = global_lsn
self.local_lsn_by_region = local_lsn_by_region
self.session_token = session_token
if self.session_token == None:
region_and_local_lsn = []
for key in self.local_lsn_by_region:
region_and_local_lsn.append(str(key) + self.region_progress_separator + str(self.local_lsn_by_region[key]))
region_progress = self.segment_separator.join(region_and_local_lsn)
if not region_progress:
self.session_token = "%s%s%s" % (self.version, self.segment_separator, self.global_lsn)
else:
self.session_token = "%s%s%s%s%s" % (self.version, self.segment_separator, self.global_lsn, self.segment_separator, region_progress)
@classmethod
def create(cls, session_token):
""" Parses session token and creates the vector session token
:param str session_token:
:return:
A Vector session Token
:rtype: VectorSessionToken
"""
version = None
global_lsn = None
local_lsn_by_region = {}
if not session_token:
return None
segments = session_token.split(cls.segment_separator)
if len(segments) < 2:
return None
try:
version = int(segments[0])
except ValueError as _:
return None
try:
global_lsn = int(segments[1])
except ValueError as _:
return None
for i in range(2, len(segments)):
region_segment = segments[i]
region_id_with_lsn = region_segment.split(cls.region_progress_separator)
if len(region_id_with_lsn) != 2:
return None
try:
region_id = int(region_id_with_lsn[0])
local_lsn = int(region_id_with_lsn[1])
except ValueError as _:
return None
local_lsn_by_region[region_id] = local_lsn
return VectorSessionToken(version, global_lsn, local_lsn_by_region, session_token)
def equals(self, other):
if other is None:
return False
else:
return self.version == other.version and self.global_lsn == other.global_lsn and self.are_region_progress_equal(other.local_lsn_by_region)
def merge(self, other):
if other is None:
raise ValueError("Invalid Session Token (should not be None)")
if self.version == other.version and len(self.local_lsn_by_region) != len(other.local_lsn_by_region):
raise errors.CosmosError(Exception("Status Code: %s. Compared session tokens '%s' and '%s' have unexpected regions."
% (StatusCodes.INTERNAL_SERVER_ERROR, self.session_token, other.session_token)))
if self.version < other.version:
session_token_with_lower_version = self
session_token_with_higher_version = other
else:
session_token_with_lower_version = other
session_token_with_higher_version = self
highest_local_lsn_by_region = {}
for key in session_token_with_higher_version.local_lsn_by_region:
region_id = key
local_lsn1 = session_token_with_higher_version.local_lsn_by_region[key]
local_lsn2 = session_token_with_lower_version.local_lsn_by_region[region_id] if region_id in session_token_with_lower_version.local_lsn_by_region else None
if local_lsn2 is not None:
highest_local_lsn_by_region[region_id] = max(local_lsn1, local_lsn2)
elif self.version == other.version:
raise errors.CosmosError(Exception("Status Code: %s. Compared session tokens '%s' and '%s' have unexpected regions."
% (StatusCodes.INTERNAL_SERVER_ERROR, self.session_token, other.session_token)))
else:
highest_local_lsn_by_region[region_id] = local_lsn1
return VectorSessionToken(max(self.version, other.version), max(self.global_lsn, other.global_lsn), highest_local_lsn_by_region)
def convert_to_string(self):
return self.session_token
def are_region_progress_equal(self, other):
if len(self.local_lsn_by_region) != len(other):
return False
for key in self.local_lsn_by_region:
region_id = key
local_lsn1 = self.local_lsn_by_region[region_id]
local_lsn2 = other[region_id] if region_id in other else None
if local_lsn2 is not None:
if local_lsn1 != local_lsn2:
return False
return True
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