def __handle_state_change(data, stat):
if self.__stop_requested.is_set():
return False # we're exiting anyway, don't do anything
if data is None:
# TODO: it would probably make sense for this to have an exit code
logger.warning(
'Received no replication set configuration data! Requesting exit...'
)
self.__stop_requested.set()
return False
logger.debug(
'Recieved an update to replication set configuration.')
configuration = BinaryCodec(
ReplicationSetConfiguration).decode(data)
with self.__worker_state_lock:
# TODO: this is annoying and repetative and should be cleaned up
if self.__worker_state is None:
self.__worker_state = start_worker(
configuration.database.dsn)
elif self.__worker_state.worker.database.dsn != configuration.database.dsn:
self.__worker_state.worker.stop_async()
stopping.append(
WorkerState(self.__worker_state.worker,
time.time()))
self.__worker_state = start_worker(
configuration.database.dsn)
def __init__(self, cluster, set, hosts, topic, prime_threshold):
self.cluster = cluster
self.set = set
self.hosts = hosts
self.topic = topic
self.codec = BinaryCodec(Message)
self.prime_threshold = prime_threshold
def upgrade_cluster(cluster, force=False):
zookeeper = cluster.zookeeper
codec = BinaryCodec(ClusterConfiguration)
data, stat = zookeeper.get(cluster.path)
configuration = codec.decode(data)
# if the configuration is newer or equal, require manual intervention
assert parse_version(__version__) > parse_version(
configuration.version) or force, 'cannot downgrade %s to %s' % (
configuration.version, __version__)
logger.info('Upgrading cluster from %s to %s...', configuration.version,
__version__)
configuration.version = __version__
ztransaction = zookeeper.transaction()
ztransaction.set_data(cluster.path,
codec.encode(configuration),
version=stat.version)
# collect databases
databases = set()
for s, (configuration, stat) in fetch_sets(cluster):
databases.add(configuration.database.dsn)
# TODO: not entirely sure that this is necessary, but can't hurt
ztransaction.check(cluster.get_set_path(s), version=stat.version)
transactions = []
# get_managed_databases prevents duplicates, so this is safe to perform
# without doing any advisory locking (although it will error if two sets
# refer to the same database using different DSNs.) get_managed_databases
# should provide some capacity for doing deduplication to make this more
# convenient, probably, but this at least keeps it from inadvertently
# breaking for now.
for connection in get_managed_databases(cluster,
databases,
configure=False,
same_version=False).values():
transaction = Transaction(connection, 'update-cluster')
transactions.append(transaction)
with connection.cursor() as cursor:
setup_database(cluster, cursor)
with managed(transactions):
commit(ztransaction)
def initialize_cluster(cluster):
"""
Initialize a pgshovel cluster in ZooKeeper.
"""
logger.info('Creating a new cluster for %s...', cluster)
configuration = ClusterConfiguration(version=__version__)
ztransaction = cluster.zookeeper.transaction()
ztransaction.create(
cluster.path,
BinaryCodec(ClusterConfiguration).encode(configuration))
ztransaction.create(cluster.get_set_path())
commit(ztransaction)
def upgrade_cluster(cluster, force=False):
zookeeper = cluster.zookeeper
codec = BinaryCodec(ClusterConfiguration)
data, stat = zookeeper.get(cluster.path)
configuration = codec.decode(data)
# if the configuration is newer or equal, require manual intervention
assert parse_version(__version__) > parse_version(configuration.version) or force, 'cannot downgrade %s to %s' % (configuration.version, __version__)
logger.info('Upgrading cluster from %s to %s...', configuration.version, __version__)
configuration.version = __version__
ztransaction = zookeeper.transaction()
ztransaction.set_data(cluster.path, codec.encode(configuration), version=stat.version)
# collect databases
databases = set()
for s, (configuration, stat) in fetch_sets(cluster):
databases.add(configuration.database.dsn)
# TODO: not entirely sure that this is necessary, but can't hurt
ztransaction.check(cluster.get_set_path(s), version=stat.version)
transactions = []
# get_managed_databases prevents duplicates, so this is safe to perform
# without doing any advisory locking (although it will error if two sets
# refer to the same database using different DSNs.) get_managed_databases
# should provide some capacity for doing deduplication to make this more
# convenient, probably, but this at least keeps it from inadvertently
# breaking for now.
for connection in get_managed_databases(cluster, databases, configure=False, same_version=False).values():
transaction = Transaction(connection, 'update-cluster')
transactions.append(transaction)
with connection.cursor() as cursor:
setup_database(cluster, cursor)
with managed(transactions):
commit(ztransaction)
def check_version(cluster):
zookeeper = cluster.zookeeper
logger.debug('Checking cluster version...')
data, stat = zookeeper.get(cluster.path)
configuration = BinaryCodec(ClusterConfiguration).decode(data)
if __version__ != configuration.version:
raise VersionMismatchError(configuration.version)
logger.debug('Remote version: %s', configuration.version)
ztransaction = zookeeper.transaction()
ztransaction.check(cluster.path, version=stat.version)
return ztransaction
def fetch_sets(cluster, names=None):
if names is None:
names = cluster.zookeeper.get_children(cluster.get_set_path())
sets = map(VersionedSet.expand, names)
paths = map(
cluster.get_set_path,
map(operator.attrgetter('name'), sets),
)
futures = map(cluster.zookeeper.get_async, paths)
results = []
decode = BinaryCodec(ReplicationSetConfiguration).decode
for s, future in zip(sets, futures):
data, stat = future.get()
configuration = decode(data)
assert s.version is None or s.version == get_version(configuration), \
'versions do not match (%s and %s)' % (s.version, get_version(configuration))
results.append((s.name, (configuration, stat)))
return results
def test_handler():
topic = '%s-mutations' % (uuid.uuid1().hex,)
codec = BinaryCodec(Message)
client = KafkaClient('kafka')
producer = SimpleProducer(client)
writer = KafkaWriter(producer, topic, codec)
inputs = list(transaction)
writer.push(inputs)
consumer = SimpleConsumer(client, 'test', topic, auto_offset_reset='smallest')
outputs = map(
codec.decode,
map(
operator.attrgetter('message.value'),
list(consumer.get_messages(count=3)),
),
)
assert outputs == inputs
def create_set(cluster, name, configuration):
# TODO: add dry run support
validate_set_configuration(configuration)
databases = get_managed_databases(cluster, (configuration.database.dsn, ))
ztransaction = check_version(cluster)
transactions = []
for connection in databases.values():
transaction = Transaction(connection, 'create-set:%s' % (name, ))
transactions.append(transaction)
with connection.cursor() as cursor:
configure_set(cluster, cursor, name, configuration)
ztransaction.create(
cluster.get_set_path(name),
BinaryCodec(ReplicationSetConfiguration).encode(configuration),
)
with managed(transactions):
commit(ztransaction)
def inspect(cluster, name):
with cluster:
data, stat = cluster.zookeeper.get(cluster.get_set_path(name))
configuration = BinaryCodec(ReplicationSetConfiguration).decode(data)
click.echo(TextCodec(ReplicationSetConfiguration).encode(configuration))
click.echo('version: %s' % (administration.get_version(configuration)), err=True)
def main(cluster, set, kafka_hosts, kafka_topic):
client = KafkaClient(kafka_hosts)
producer = SimpleProducer(client)
topic = kafka_topic.format(cluster=cluster.name, set=set)
return KafkaWriter(producer, topic, BinaryCodec(Message))
class KafkaStream(object):
def __init__(self, cluster, set, hosts, topic, prime_threshold):
self.cluster = cluster
self.set = set
self.hosts = hosts
self.topic = topic
self.codec = BinaryCodec(Message)
self.prime_threshold = prime_threshold
def consume(self, state):
"""
Starts consuming from the configured Kafka topic given a possible
existing ``pgshovel.interfaces.replication_pb2:State``.
If the provided ``state`` does not contain a
``stream_state.consumer_state`` value, the ``KafaStream`` attempts to
start reading from the Kafka topic after first "priming" the stream.
Priming involves consuming messages from the topic looking for a
``BeginOperation``. Any message that is not a ``BeginOperation`` is
dropped, until a ``BeginOperation`` is seen or the ``prime_threshold``
is reached. The latter of which raises a
``pgshovel.streams.utilities:UnableToPrimeError`` error.
In general, it makes sense to set the ``prime_threshold`` to high enough
value that exceeds the max transaction size you expect to see in your
data. Generally speaking a ``prime_threshold`` can effectively be
infinite (and you could construct the stream with ``float('inf')``,
however the lack of a ``BeginOperation`` in the stream would cause the
stream to hang, possibly forever, so the ``prime_threshold`` config
parameter is provided to raise an exception if this unexpected behavior
occurs.
"""
consumer = SimpleConsumer(KafkaClient(self.hosts), None, self.topic)
# You can only update one offset at a time with kafka-python, plus
# dealing with reconstituting global order from a partitioned stream is
# hard we don't really need to deal with it right now.
assert len(consumer.offsets) is 1
decoded = imap(
lambda (offset, msg): (offset, self.codec.decode(msg.value)),
consumer
)
if state.stream_state.HasField('consumer_state'):
# Seeking to a direct offset was not in the PyPI release of
# kafka-python when this was implemented:
# https://github.com/mumrah/kafka-python/pull/412
current = consumer.offsets[0]
offset = state.stream_state.consumer_state.offset + 1
delta = offset - current
logger.debug('Moving to previous replication log offset: %s (current position: %s)...', offset, current)
consumer.seek(delta, 1)
assert consumer.offsets[0] == offset
else:
logger.info('No consumer state provided, will attempt to prime to begin BeginOperation')
# The call to ``prime_for_batch_start`` "primes" the stream by
# dropping messages until it sees a message that is an intance of
# one of the types in
# ``pgshovel.replication.validation.TRANSACTION_START_EVENT_TYPES``
decoded = prime_for_batch_start(
max_messages=self.prime_threshold,
stream=decoded
)
for offset, message in decoded:
state = validate_state(state, offset, message)
# XXX: This is necessary because of a bug in protocol buffer oneof.
state = type(state).FromString(state.SerializeToString())
yield state, offset, message
@classmethod
def configure(cls, configuration, cluster, set):
topic = '{cluster}.{set}.mutations'.format(cluster=cluster.name, set=set)
return cls(
cluster,
set,
configuration['hosts'],
topic,
configuration.get('prime_threshold', 1000)
)
def update_set(cluster,
name,
updated_configuration,
allow_forced_removal=False):
# TODO: add dry run support
validate_set_configuration(updated_configuration)
(name, (current_configuration, stat)) = fetch_sets(cluster, (name, ))[0]
# TODO: It probably makes sense to normalize the database URIs here.
current_databases = set((current_configuration.database.dsn, ))
updated_databases = set((updated_configuration.database.dsn, ))
additions = get_managed_databases(cluster,
updated_databases - current_databases)
mutations = get_managed_databases(cluster,
updated_databases & current_databases)
deletions = get_managed_databases(
cluster,
current_databases - updated_databases,
skip_inaccessible=allow_forced_removal,
)
# ensure no items show up multiple times, since that causes incorrect behavior
# TODO: this is a very naive approach to avoid shooting ourselves in the
# foot and could be improved for valid cases (updating a dsn for an
# existing set should be treated as a mutation, not an addition and
# deletion) but this would require a more intelligent implementation
occurrences = collections.Counter()
for nodes in map(operator.methodcaller('keys'),
(additions, mutations, deletions)):
occurrences.update(nodes)
duplicates = list(
itertools.takewhile(lambda (node, count): count > 1,
occurrences.most_common()))
assert not duplicates, 'found duplicates: %s' % (duplicates, )
ztransaction = check_version(cluster)
transactions = []
for connection in additions.values():
transaction = Transaction(connection,
'update-set:create:%s' % (name, ))
transactions.append(transaction)
with connection.cursor() as cursor:
configure_set(cluster, cursor, name, updated_configuration, None)
for connection in mutations.values():
transaction = Transaction(connection,
'update-set:update:%s' % (name, ))
transactions.append(transaction)
with connection.cursor() as cursor:
configure_set(cluster, cursor, name, updated_configuration,
current_configuration)
# TODO: add help to inform user of the possiblity of retry
for connection in deletions.values():
transaction = Transaction(connection,
'update-set:delete:%s' % (name, ))
transactions.append(transaction)
with connection.cursor() as cursor:
unconfigure_set(cluster, cursor, name, current_configuration)
ztransaction.set_data(
cluster.get_set_path(name),
BinaryCodec(ReplicationSetConfiguration).encode(updated_configuration),
version=stat.version,
)
with managed(transactions):
commit(ztransaction)
