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mahadirz/read_event_descriptor.py

Last active January 22, 2022 15:46
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mysql_binlog_tutorial
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read_event_descriptor.py
import struct
bin_log_file = "mysql-bin-changelog.000050.bin"
file_pointer = 0
with open(bin_log_file, 'rb') as f:
magic = f.read(4)
# 0xfe, 0x62, 0x69, 0x6e
assert magic == b"\xfe\x62\x69\x6e"
# or
assert magic == b"\xfebin"
# update the file pointer to 4
file_pointer += len(magic)
# At 4
# read the header
# https://dev.mysql.com/doc/internals/en/event-classes-and-types.html
header_length = 19
header = f.read(header_length)
file_pointer += header_length
unpacked = struct.unpack('<IBIIIH', header)
timestamp = unpacked[0]
event_type = unpacked[1]
server_id = unpacked[2]
event_size = unpacked[3]
log_pos = unpacked[4]
print(f"timestamp:{timestamp}\n"
f"event_type:{event_type}\n"
f"server_id: {server_id}\n"
f"event_size: {event_size}\n"
f"next_log_pos: {log_pos}")
# body = f.read(event_size - header_length)
print("body size", event_size - header_length)
version = f.read(2)
file_pointer += 2
print("binlog version", struct.unpack('<H', version)[0])
server_version = f.read(50)
file_pointer += 50
# s is chart[] in bytes
print("server version", struct.unpack('<50s', server_version)[0].decode())
timestamp = f.read(4)
file_pointer += 4
# is empty and follow the timestamp of header
print("timestamp", struct.unpack('<i', timestamp)[0])
# the remaining has no use as for v4
# 2 + 50 + 4 = 56
_ = f.read(event_size - 19 - 56)
file_pointer += (event_size - 19 - 56)
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