def _decode_message(cls, data, offset):
"""
Decode a single Message
The only caller of this method is decode_message_set_iter.
They are decoupled to support nested messages (compressed MessageSets).
The offset is actually read from decode_message_set_iter (it is part
of the MessageSet payload).
"""
((crc, magic, att), cur) = relative_unpack('>IBB', data, 0)
if crc != crc32(data[4:]):
raise ChecksumError("Message checksum failed")
(key, cur) = read_int_string(data, cur)
(value, cur) = read_int_string(data, cur)
codec = att & ATTRIBUTE_CODEC_MASK
if codec == CODEC_NONE:
yield (offset, Message(magic, att, key, value))
elif codec == CODEC_GZIP:
gz = gzip_decode(value)
for (offset, msg) in KafkaProtocol._decode_message_set_iter(gz):
yield (offset, msg)
elif codec == CODEC_SNAPPY:
snp = snappy_decode(value)
for (offset, msg) in KafkaProtocol._decode_message_set_iter(snp):
yield (offset, msg)
def _decode_message(cls, data, offset):
"""
Decode a single Message
The only caller of this method is decode_message_set_iter.
They are decoupled to support nested messages (compressed MessageSets).
The offset is actually read from decode_message_set_iter (it is part
of the MessageSet payload).
"""
((crc, magic, att), cur) = relative_unpack('>IBB', data, 0)
if crc != crc32(data[4:]):
raise ChecksumError("Message checksum failed")
(key, cur) = read_int_string(data, cur)
(value, cur) = read_int_string(data, cur)
codec = att & ATTRIBUTE_CODEC_MASK
if codec == CODEC_NONE:
yield (offset, Message(magic, att, key, value))
elif codec == CODEC_GZIP:
gz = gzip_decode(value)
for (offset, msg) in KafkaProtocol._decode_message_set_iter(gz):
yield (offset, msg)
elif codec == CODEC_SNAPPY:
snp = snappy_decode(value)
for (offset, msg) in KafkaProtocol._decode_message_set_iter(snp):
yield (offset, msg)
def _decode_message_set_iter(cls, data):
"""
Iteratively decode a MessageSet
Reads repeated elements of (offset, message), calling decode_message
to decode a single message. Since compressed messages contain futher
MessageSets, these two methods have been decoupled so that they may
recurse easily.
"""
cur = 0
read_message = False
while cur < len(data):
try:
((offset, ), cur) = relative_unpack('>q', data, cur)
(msg, cur) = read_int_string(data, cur)
for (offset, message) in KafkaProtocol._decode_message(msg, offset):
read_message = True
yield OffsetAndMessage(offset, message)
except BufferUnderflowError:
# NOTE: Not sure this is correct error handling:
# Is it possible to get a BUE if the message set is somewhere
# in the middle of the fetch response? If so, we probably have
# an issue that's not fetch size too small.
# Aren't we ignoring errors if we fail to unpack data by
# raising StopIteration()?
# If _decode_message() raises a ChecksumError, couldn't that
# also be due to the fetch size being too small?
if read_message is False:
# If we get a partial read of a message, but haven't
# yielded anything there's a problem
raise ConsumerFetchSizeTooSmall()
else:
raise StopIteration()
def _decode_message_set_iter(cls, data):
"""
Iteratively decode a MessageSet
Reads repeated elements of (offset, message), calling decode_message
to decode a single message. Since compressed messages contain futher
MessageSets, these two methods have been decoupled so that they may
recurse easily.
"""
cur = 0
read_message = False
while cur < len(data):
try:
((offset, ), cur) = relative_unpack('>q', data, cur)
(msg, cur) = read_int_string(data, cur)
for (offset, message) in KafkaProtocol._decode_message(msg, offset):
read_message = True
yield OffsetAndMessage(offset, message)
except BufferUnderflowError:
# NOTE: Not sure this is correct error handling:
# Is it possible to get a BUE if the message set is somewhere
# in the middle of the fetch response? If so, we probably have
# an issue that's not fetch size too small.
# Aren't we ignoring errors if we fail to unpack data by
# raising StopIteration()?
# If _decode_message() raises a ChecksumError, couldn't that
# also be due to the fetch size being too small?
if read_message is False:
# If we get a partial read of a message, but haven't
# yielded anything there's a problem
raise ConsumerFetchSizeTooSmall()
else:
raise StopIteration()
def decode_fetch_response(cls, data):
"""
Decode bytes to a FetchResponse
Arguments:
data: bytes to decode
"""
((correlation_id, num_topics), cur) = relative_unpack('>ii', data, 0)
for _ in range(num_topics):
(topic, cur) = read_short_string(data, cur)
((num_partitions, ), cur) = relative_unpack('>i', data, cur)
for j in range(num_partitions):
((partition, error, highwater_mark_offset), cur) = \
relative_unpack('>ihq', data, cur)
(message_set, cur) = read_int_string(data, cur)
yield FetchResponse(
topic, partition, error, highwater_mark_offset,
KafkaProtocol._decode_message_set_iter(message_set))
def decode_fetch_response(cls, data):
"""
Decode bytes to a FetchResponse
Arguments:
data: bytes to decode
"""
((correlation_id, num_topics), cur) = relative_unpack('>ii', data, 0)
for _ in range(num_topics):
(topic, cur) = read_short_string(data, cur)
((num_partitions,), cur) = relative_unpack('>i', data, cur)
for j in range(num_partitions):
((partition, error, highwater_mark_offset), cur) = \
relative_unpack('>ihq', data, cur)
(message_set, cur) = read_int_string(data, cur)
yield FetchResponse(
topic, partition, error,
highwater_mark_offset,
KafkaProtocol._decode_message_set_iter(message_set))