def _undo_remove_shard(shard_id, update_only=False):
"""Recreate the shard metadata.
:param shard_id: The ID of the shard that was being removed.
:param update_only: Only update the state store and skip adding range
checks.
"""
if update_only:
return
group_id = Shards.fetch(shard_id).group_id
try:
SHARD_METADATA.create_shard_meta_data(group_id)
except _errors.DatabaseError as error:
#If the create fails, do not insert the metadata.
return
spec_handler = SHARDING_SPECIFICATION_HANDLER[shard_type]
upper_bound = spec_handler.get_upper_bound(
shard.lower_bound,
shard_mapping_id,
shard_type
)
SHARD_METADATA.insert_shard_meta_data(shard.shard_id,
shard.lower_bound,
upper_bound,
group_id)
def _remove_shard(shard_id, update_only=False):
"""Remove the RANGE specification mapping represented by the current
RANGE shard specification object.
:param shard_id: The shard ID of the shard that needs to be removed.
:param update_only: Only update the state store and skip adding range
checks.
:return: True if the remove succeeded
False if the query failed
:raises: ShardingError if the shard id is not found,
: ShardingError if the shard is not disabled.
"""
range_sharding_specification, shard, _, _ = \
verify_and_fetch_shard(shard_id)
if shard.state == "ENABLED":
raise _errors.ShardingError(SHARD_NOT_DISABLED)
#Stop the replication of the shard group with the global
#group. Also clear the references of the master and the
#slave group from the current group.
#NOTE: When we do the stopping of the shard group
#replication in shard remove we are actually just clearing
#the references, since a shard cannot be removed unless
#it is disabled and when it is disabled the replication is
#stopped but the references are not cleared.
if not update_only:
#The Group ID needs to be fetched before the sharding
#information is removed.
group_id = Shards.fetch(shard.shard_id).group_id
_stop_shard_group_replication(shard_id, True)
range_sharding_specification.remove()
shard.remove()
if not update_only:
SHARD_METADATA.drop_shard_meta_data(group_id)
_LOGGER.debug("Removed Shard (%s).", shard_id)
def _remove_shard(shard_id, update_only=False):
"""Remove the RANGE specification mapping represented by the current
RANGE shard specification object.
:param shard_id: The shard ID of the shard that needs to be removed.
:param update_only: Only update the state store and skip adding range
checks.
:return: True if the remove succeeded
False if the query failed
:raises: ShardingError if the shard id is not found,
: ShardingError if the shard is not disabled.
"""
range_sharding_specification, shard, _, _ = \
verify_and_fetch_shard(shard_id)
if shard.state == "ENABLED":
raise _errors.ShardingError(SHARD_NOT_DISABLED)
#Stop the replication of the shard group with the global
#group. Also clear the references of the master and the
#slave group from the current group.
#NOTE: When we do the stopping of the shard group
#replication in shard remove we are actually just clearing
#the references, since a shard cannot be removed unless
#it is disabled and when it is disabled the replication is
#stopped but the references are not cleared.
if not update_only:
#The Group ID needs to be fetched before the sharding
#information is removed.
group_id = Shards.fetch(shard.shard_id).group_id
_stop_shard_group_replication(shard_id, True)
range_sharding_specification.remove()
shard.remove()
if not update_only:
SHARD_METADATA.drop_shard_meta_data(group_id)
_LOGGER.debug("Removed Shard (%s).", shard_id)
def _add_shard_range_check(shard_mapping_id, shard_type):
"""Add the shard ranges in the metadata tables of the shards
:param shard_mapping_id: The shard mapping ID of the shards for which
the metadata needs to be added.
:param shard_type: The datatype of the sharding definition.
"""
shard_list = SHARDING_SPECIFICATION_HANDLER[shard_type].list(shard_mapping_id)
for shard in shard_list:
group_id = Shards.fetch(shard.shard_id).group_id
#The metadata has to be created before adding the ranges because
#the global group might have still not replicated the schema to the
#shard group. If the replication has still not happened, adding
#the bounds will throw an error.
SHARD_METADATA.create_shard_meta_data(group_id)
spec_handler = SHARDING_SPECIFICATION_HANDLER[shard_type]
upper_bound = spec_handler.get_upper_bound(
shard.lower_bound,
shard_mapping_id,
shard_type
)
SHARD_METADATA.insert_shard_meta_data(shard.shard_id,
shard.lower_bound,
upper_bound,
group_id)
def _lookup(lookup_arg, key, hint):
"""Given a table name and a key return the servers of the Group where the
shard of this table can be found
:param lookup_arg: table name for "LOCAL" lookups
Shard Mapping ID for "GLOBAL" lookups.
:param key: The key value that needs to be looked up
:param hint: A hint indicates if the query is LOCAL or GLOBAL
:return: The servers of the Group that contains the range in which the
key belongs.
"""
VALID_HINTS = ('LOCAL', 'GLOBAL')
hint = hint.upper()
if hint not in VALID_HINTS:
raise _errors.ShardingError(INVALID_SHARDING_HINT)
group = None
#Perform the lookup for the group contaning the lookup data.
if hint == "GLOBAL":
#Fetch the shard mapping object. In the case of GLOBAL lookups
#the shard mapping ID is passed directly. In the case of "LOCAL"
#lookups it is the table name that is passed.
shard_mapping = ShardMapping.fetch_by_id(lookup_arg)
if shard_mapping is None:
raise _errors.ShardingError(
SHARD_MAPPING_NOT_FOUND % (lookup_arg, )
)
#GLOBAL lookups. There can be only one global group, hence using
#shard_mapping[0] is safe.
group = Group.fetch(shard_mapping[0].global_group)
else:
shard_mapping = ShardMapping.fetch(lookup_arg)
if shard_mapping is None:
raise _errors.ShardingError(TABLE_NAME_NOT_FOUND % (lookup_arg, ))
sharding_specification =\
SHARDING_SPECIFICATION_HANDLER[shard_mapping.type_name].\
lookup(key, shard_mapping.shard_mapping_id, shard_mapping.type_name)
if sharding_specification is None:
raise _errors.ShardingError(INVALID_SHARDING_KEY % (key, ))
shard = Shards.fetch(str(sharding_specification.shard_id))
if shard.state == "DISABLED":
raise _errors.ShardingError(SHARD_NOT_ENABLED)
#group cannot be None since there is a foreign key on the group_id.
#An exception will be thrown nevertheless.
group = Group.fetch(shard.group_id)
if group is None:
raise _errors.ShardingError(SHARD_LOCATION_NOT_FOUND)
ret = []
#An empty list will be returned if the registered group has not
#servers.
for server in group.servers():
ret.append([str(server.uuid), server.address,
group.master == server.uuid])
return ret
def verify_and_fetch_shard(shard_id):
"""Find out if the shard_id exists and return the sharding specification for
it. If it does not exist throw an exception.
:param shard_id: The ID for the shard whose specification needs to be
fetched.
:return: The sharding specification class representing the shard ID.
:raises: ShardingError if the shard ID is not found.
"""
#Here the underlying sharding specification might be a RANGE
#or a HASH. The type of sharding specification is obtained from the
#shard mapping.
range_sharding_spec = RangeShardingSpecification.fetch(shard_id)
if range_sharding_spec is None:
raise _errors.ShardingError(SHARD_NOT_FOUND % (shard_id, ))
#Fetch the shard mappings and use them to find the type of sharding
#scheme.
shard_mappings = ShardMapping.fetch_by_id(
range_sharding_spec.shard_mapping_id
)
if shard_mappings is None:
raise _errors.ShardingError(
SHARD_MAPPING_NOT_FOUND % (
range_sharding_spec.shard_mapping_id,
)
)
#Fetch the shard mapping definition. There is only one shard mapping
#definition associated with all of the shard mappings.
shard_mapping_defn = ShardMapping.fetch_shard_mapping_defn(
range_sharding_spec.shard_mapping_id
)
if shard_mapping_defn is None:
raise _errors.ShardingError(
SHARD_MAPPING_DEFN_NOT_FOUND % (
range_sharding_spec.shard_mapping_id,
)
)
shard = Shards.fetch(shard_id)
if shard is None:
raise _errors.ShardingError(SHARD_NOT_FOUND % (shard_id, ))
#Both of the shard_mappings retrieved will be of the same sharding
#type. Hence it is safe to use one of them to retireve the sharding type.
if shard_mappings[0].type_name == "HASH":
return HashShardingSpecification.fetch(shard_id), \
shard, shard_mappings, shard_mapping_defn
else:
return range_sharding_spec, shard, shard_mappings, shard_mapping_defn
def _undo_add_shard_range_check(shard_mapping_id, shard_type):
"""Remove the shard ranges in the metadata tables of the shards
:param shard_mapping_id: The shard mapping ID of the shards for which
the metadata needs to be added.
:param shard_type: The datatype of the sharding definition.
"""
shard_list = SHARDING_SPECIFICATION_HANDLER[shard_type].list(shard_mapping_id)
for shard in shard_list:
group_id = Shards.fetch(shard.shard_id).group_id
SHARD_METADATA.delete_shard_meta_data(group_id, shard.shard_id)
SHARD_METADATA.drop_shard_meta_data(group_id)
def _undo_add_shard_range_check(shard_mapping_id, shard_type):
"""Remove the shard ranges in the metadata tables of the shards
:param shard_mapping_id: The shard mapping ID of the shards for which
the metadata needs to be added.
:param shard_type: The datatype of the sharding definition.
"""
shard_list = SHARDING_SPECIFICATION_HANDLER[shard_type].list(
shard_mapping_id)
for shard in shard_list:
group_id = Shards.fetch(shard.shard_id).group_id
SHARD_METADATA.delete_shard_meta_data(group_id, shard.shard_id)
SHARD_METADATA.drop_shard_meta_data(group_id)
def _lookup(lookup_arg, key, hint):
"""Given a table name and a key return the servers of the Group where the
shard of this table can be found
:param lookup_arg: table name for "LOCAL" lookups
Shard Mapping ID for "GLOBAL" lookups.
:param key: The key value that needs to be looked up
:param hint: A hint indicates if the query is LOCAL or GLOBAL
:return: The servers of the Group that contains the range in which the
key belongs.
"""
VALID_HINTS = ('LOCAL', 'GLOBAL')
hint = hint.upper()
if hint not in VALID_HINTS:
raise _errors.ShardingError(INVALID_SHARDING_HINT)
group = None
#Perform the lookup for the group contaning the lookup data.
if hint == "GLOBAL":
#Fetch the shard mapping object. In the case of GLOBAL lookups
#the shard mapping ID is passed directly. In the case of "LOCAL"
#lookups it is the table name that is passed.
shard_mapping = ShardMapping.fetch_by_id(lookup_arg)
if shard_mapping is None:
raise _errors.ShardingError(SHARD_MAPPING_NOT_FOUND %
(lookup_arg, ))
#GLOBAL lookups. There can be only one global group, hence using
#shard_mapping[0] is safe.
group_id = shard_mapping[0].global_group
else:
shard_mapping = ShardMapping.fetch(lookup_arg)
if shard_mapping is None:
raise _errors.ShardingError(TABLE_NAME_NOT_FOUND % (lookup_arg, ))
sharding_specification = \
SHARDING_SPECIFICATION_HANDLER[shard_mapping.type_name].\
lookup(key, shard_mapping.shard_mapping_id, shard_mapping.type_name)
if sharding_specification is None:
raise _errors.ShardingError(INVALID_SHARDING_KEY % (key, ))
shard = Shards.fetch(str(sharding_specification.shard_id))
if shard.state == "DISABLED":
raise _errors.ShardingError(SHARD_NOT_ENABLED)
#group cannot be None since there is a foreign key on the group_id.
#An exception will be thrown nevertheless.
group_id = shard.group_id
return ServerLookups().execute(group_id=group_id)
def verify_and_fetch_shard(shard_id):
"""Find out if the shard_id exists and return the sharding specification for
it. If it does not exist throw an exception.
:param shard_id: The ID for the shard whose specification needs to be
fetched.
:return: The sharding specification class representing the shard ID.
:raises: ShardingError if the shard ID is not found.
"""
#Here the underlying sharding specification might be a RANGE
#or a HASH. The type of sharding specification is obtained from the
#shard mapping.
range_sharding_spec = RangeShardingSpecification.fetch(shard_id)
if range_sharding_spec is None:
raise _errors.ShardingError(SHARD_NOT_FOUND % (shard_id, ))
#Fetch the shard mappings and use them to find the type of sharding
#scheme.
shard_mappings = ShardMapping.fetch_by_id(
range_sharding_spec.shard_mapping_id)
if shard_mappings is None:
raise _errors.ShardingError(SHARD_MAPPING_NOT_FOUND %
(range_sharding_spec.shard_mapping_id, ))
#Fetch the shard mapping definition. There is only one shard mapping
#definition associated with all of the shard mappings.
shard_mapping_defn = ShardMapping.fetch_shard_mapping_defn(
range_sharding_spec.shard_mapping_id)
if shard_mapping_defn is None:
raise _errors.ShardingError(SHARD_MAPPING_DEFN_NOT_FOUND %
(range_sharding_spec.shard_mapping_id, ))
shard = Shards.fetch(shard_id)
if shard is None:
raise _errors.ShardingError(SHARD_NOT_FOUND % (shard_id, ))
#Both of the shard_mappings retrieved will be of the same sharding
#type. Hence it is safe to use one of them to retireve the sharding type.
if shard_mappings[0].type_name == "HASH":
return HashShardingSpecification.fetch(shard_id), \
shard, shard_mappings, shard_mapping_defn
else:
return range_sharding_spec, shard, shard_mappings, shard_mapping_defn
def _undo_remove_shard(shard_id, update_only=False):
"""Recreate the shard metadata.
:param shard_id: The ID of the shard that was being removed.
:param update_only: Only update the state store and skip adding range
checks.
"""
if update_only:
return
group_id = Shards.fetch(shard_id).group_id
try:
SHARD_METADATA.create_shard_meta_data(group_id)
except _errors.DatabaseError as error:
#If the create fails, do not insert the metadata.
return
spec_handler = SHARDING_SPECIFICATION_HANDLER[shard_type]
upper_bound = spec_handler.get_upper_bound(shard.lower_bound,
shard_mapping_id, shard_type)
SHARD_METADATA.insert_shard_meta_data(shard.shard_id, shard.lower_bound,
upper_bound, group_id)
def _add_shard_range_check(shard_mapping_id, shard_type):
"""Add the shard ranges in the metadata tables of the shards
:param shard_mapping_id: The shard mapping ID of the shards for which
the metadata needs to be added.
:param shard_type: The datatype of the sharding definition.
"""
shard_list = SHARDING_SPECIFICATION_HANDLER[shard_type].list(
shard_mapping_id)
for shard in shard_list:
group_id = Shards.fetch(shard.shard_id).group_id
#The metadata has to be created before adding the ranges because
#the global group might have still not replicated the schema to the
#shard group. If the replication has still not happened, adding
#the bounds will throw an error.
SHARD_METADATA.create_shard_meta_data(group_id)
spec_handler = SHARDING_SPECIFICATION_HANDLER[shard_type]
upper_bound = spec_handler.get_upper_bound(shard.lower_bound,
shard_mapping_id,
shard_type)
SHARD_METADATA.insert_shard_meta_data(shard.shard_id,
shard.lower_bound, upper_bound,
group_id)
def _check_shard_information(shard_id, destn_group_id, mysqldump_binary,
mysqlclient_binary, split_value, config_file, prune_limit, cmd,
update_only):
"""Verify the sharding information before starting a re-sharding operation.
:param shard_id: The destination shard ID.
:param destn_group_id: The Destination group ID.
:param mysqldump_binary: The path to the mysqldump binary.
:param mysqlclient_binary: The path to the mysqlclient binary.
:param split_value: The point at which the sharding definition
should be split.
:param config_file: The complete path to the fabric configuration
file.
:param prune_limit: The number of DELETEs that should be
done in one batch.
:param cmd: Indicates if it is a split or a move being executed.
:param update_only: If the operation is a update only operation.
"""
if not _services_utils.is_valid_binary(mysqldump_binary):
raise _errors.ShardingError(
_services_sharding.MYSQLDUMP_NOT_FOUND % mysqldump_binary)
if not _services_utils.is_valid_binary(mysqlclient_binary):
raise _errors.ShardingError(
_services_sharding.MYSQLCLIENT_NOT_FOUND % mysqlclient_binary)
if cmd == "SPLIT":
range_sharding_spec, _, shard_mappings, _ = \
_services_sharding.verify_and_fetch_shard(shard_id)
upper_bound = \
SHARDING_SPECIFICATION_HANDLER[shard_mappings[0].type_name].\
get_upper_bound(
range_sharding_spec.lower_bound,
range_sharding_spec.shard_mapping_id,
shard_mappings[0].type_name
)
#If the underlying sharding scheme is a HASH. When a shard is split,
#all the tables that are part of the shard, have the same sharding
#scheme. All the shard mappings associated with this shard_id will be
#of the same sharding type. Hence it is safe to use one of the shard
#mappings.
if shard_mappings[0].type_name == "HASH":
if split_value is not None:
raise _errors.ShardingError(
_services_sharding.NO_LOWER_BOUND_FOR_HASH_SHARDING
)
if upper_bound is None:
#While splitting a range, retrieve the next upper bound and
#find the mid-point, in the case where the next upper_bound
#is unavailable pick the maximum value in the set of values in
#the shard.
upper_bound = HashShardingSpecification.fetch_max_key(shard_id)
#Calculate the split value.
split_value = \
SHARDING_DATATYPE_HANDLER[shard_mappings[0].type_name].\
split_value(
range_sharding_spec.lower_bound,
upper_bound
)
elif split_value is not None:
if not (SHARDING_DATATYPE_HANDLER[shard_mappings[0].type_name].\
is_valid_split_value(
split_value, range_sharding_spec.lower_bound,
upper_bound
)
):
raise _errors.ShardingError(
_services_sharding.INVALID_LOWER_BOUND_VALUE %
(split_value, )
)
elif split_value is None:
raise _errors.ShardingError(
_services_sharding.SPLIT_VALUE_NOT_DEFINED
)
#Ensure that the group does not already contain a shard.
if Shards.lookup_shard_id(destn_group_id) is not None:
raise _errors.ShardingError(
_services_sharding.SHARD_MOVE_DESTINATION_NOT_EMPTY %
(destn_group_id, )
)
#Fetch the group information for the source shard that
#needs to be moved.
source_shard = Shards.fetch(shard_id)
if source_shard is None:
raise _errors.ShardingError(
_services_sharding.SHARD_NOT_FOUND % (shard_id, ))
#Fetch the group_id and the group that hosts the source shard.
source_group_id = source_shard.group_id
destn_group = Group.fetch(destn_group_id)
if destn_group is None:
raise _errors.ShardingError(
_services_sharding.SHARD_GROUP_NOT_FOUND %
(destn_group_id, ))
if not update_only:
_events.trigger_within_procedure(
BACKUP_SOURCE_SHARD, shard_id, source_group_id, destn_group_id,
mysqldump_binary, mysqlclient_binary, split_value, config_file,
prune_limit, cmd, update_only
)
else:
_events.trigger_within_procedure(
SETUP_RESHARDING_SWITCH, shard_id, source_group_id, destn_group_id,
split_value, prune_limit, cmd, update_only
)
def _check_shard_information(shard_id, destn_group_id, mysqldump_binary,
mysqlclient_binary, split_value, config_file,
prune_limit, cmd, update_only):
"""Verify the sharding information before starting a re-sharding operation.
:param shard_id: The destination shard ID.
:param destn_group_id: The Destination group ID.
:param mysqldump_binary: The path to the mysqldump binary.
:param mysqlclient_binary: The path to the mysqlclient binary.
:param split_value: The point at which the sharding definition
should be split.
:param config_file: The complete path to the fabric configuration
file.
:param prune_limit: The number of DELETEs that should be
done in one batch.
:param cmd: Indicates if it is a split or a move being executed.
:param update_only: If the operation is a update only operation.
"""
if not _services_utils.is_valid_binary(mysqldump_binary):
raise _errors.ShardingError(_services_sharding.MYSQLDUMP_NOT_FOUND %
mysqldump_binary)
if not _services_utils.is_valid_binary(mysqlclient_binary):
raise _errors.ShardingError(_services_sharding.MYSQLCLIENT_NOT_FOUND %
mysqlclient_binary)
if cmd == "SPLIT":
range_sharding_spec, _, shard_mappings, _ = \
_services_sharding.verify_and_fetch_shard(shard_id)
upper_bound = \
SHARDING_SPECIFICATION_HANDLER[shard_mappings[0].type_name].\
get_upper_bound(
range_sharding_spec.lower_bound,
range_sharding_spec.shard_mapping_id,
shard_mappings[0].type_name
)
#If the underlying sharding scheme is a HASH. When a shard is split,
#all the tables that are part of the shard, have the same sharding
#scheme. All the shard mappings associated with this shard_id will be
#of the same sharding type. Hence it is safe to use one of the shard
#mappings.
if shard_mappings[0].type_name == "HASH":
if split_value is not None:
raise _errors.ShardingError(
_services_sharding.NO_LOWER_BOUND_FOR_HASH_SHARDING)
if upper_bound is None:
#While splitting a range, retrieve the next upper bound and
#find the mid-point, in the case where the next upper_bound
#is unavailable pick the maximum value in the set of values in
#the shard.
upper_bound = HashShardingSpecification.fetch_max_key(shard_id)
#Calculate the split value.
split_value = \
SHARDING_DATATYPE_HANDLER[shard_mappings[0].type_name].\
split_value(
range_sharding_spec.lower_bound,
upper_bound
)
elif split_value is not None:
if not (SHARDING_DATATYPE_HANDLER[shard_mappings[0].type_name].\
is_valid_split_value(
split_value, range_sharding_spec.lower_bound,
upper_bound
)
):
raise _errors.ShardingError(
_services_sharding.INVALID_LOWER_BOUND_VALUE %
(split_value, ))
elif split_value is None:
raise _errors.ShardingError(
_services_sharding.SPLIT_VALUE_NOT_DEFINED)
#Ensure that the group does not already contain a shard.
if Shards.lookup_shard_id(destn_group_id) is not None:
raise _errors.ShardingError(
_services_sharding.SHARD_MOVE_DESTINATION_NOT_EMPTY %
(destn_group_id, ))
#Fetch the group information for the source shard that
#needs to be moved.
source_shard = Shards.fetch(shard_id)
if source_shard is None:
raise _errors.ShardingError(_services_sharding.SHARD_NOT_FOUND %
(shard_id, ))
#Fetch the group_id and the group that hosts the source shard.
source_group_id = source_shard.group_id
destn_group = Group.fetch(destn_group_id)
if destn_group is None:
raise _errors.ShardingError(_services_sharding.SHARD_GROUP_NOT_FOUND %
(destn_group_id, ))
if not update_only:
_events.trigger_within_procedure(BACKUP_SOURCE_SHARD, shard_id,
source_group_id, destn_group_id,
mysqldump_binary, mysqlclient_binary,
split_value, config_file, prune_limit,
cmd, update_only)
else:
_events.trigger_within_procedure(SETUP_RESHARDING_SWITCH, shard_id,
source_group_id, destn_group_id,
split_value, prune_limit, cmd,
update_only)
