The Ultimate Guide to High Availability with MariaDB

2-Binlog Event Header

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All the binlog events stored into a binary log file have a common structure:

  • an event header
  • event data

Event Header structure, 19 bytes

Note: if CRC32 is in use, the Event Length is 4 bytes bigger in size.
The 4 bytes CRC32 are written at the end of the event (just after the last 'data' byte).

Event Header example of FORMAT_DESCRIPTION_EVENT

This is the first event in the binlog file at pos 4

a4 85 9e 59 0f 8c 27 00  00 f5 00 00 00 f9 00 00  ...Y..'.........
00 00 00 04 00 31 30 2e  31 2e 32 34 2d 4d 61 72  .....10.1.24-Mar
69 61 44 42 00 6c 6f 67  00 00 00 00 00 00 00 00  iaDB.log....
...
...

Interpretation of first 19 bytes of the event (the event header)

  • a4 85 9e 59 [4] Timestamp => 59 9e 85 a4 => 1503561124 = 2017-08-24 09:52:04
  • 0f [1] Event Type = 0x0f = FORMAT_DESCRIPTION_EVENT
  • 8c 27 00 00 [4] Server_id => 00 00 27 8c = 10124
  • f5 00 00 00 [4] Event length => 00 00 00 f5 => 245
  • f9 00 00 00 [4] Next Event pos => 00 00 00 f9 => 249 (pos 4 + event size)
  • 00 00 [2] Event flags = 0

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