2-Binlog Event Header
All the binlog events stored in a binary log file have a common structure:
an event header
event data
Event Header Structure, 19 Bytes
uint<4> Timestamp (creation time)
uint<1> Event Type (type_code)
uint<4> Server_id (server which created the event)
uint<4> Event Length (header + data)
uint<4> Next Event position
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).
Encrypted Binlog Events
For encrypted binlog events, only the event length is in plaintext and everything else is encrypted.
To decrypt the binlog event:
Store the event length in memory
Move the timestamp into the event length position
Decrypt the whole payload except the first four bytes
Move the timestamp back to its original position
Copy the original event length back to its position
Regardless of the cipher used to encrypt the binlogs, the encrypted data will be the same size as the original unencrypted event. For events that are encrypted in CBC mode and whose length is not a multiple of the cipher block size, the final partial block is encrypted using a form of residual block termination:
Encrypt the current IV of the binlog file in ECB mode
XOR the remaining bytes with the encrypted IV
Event Type
Hex
Event type description
0x02
0x03
0x04
0x10
0x0d
0x0e
0x13
0xa2
0xa3
0xa9
0xaa
0xab
Fake Events
These are generated on the fly, never written.
Event Flag
Hex
Event flag description
0x0001
LOG_EVENT_BINLOG_IN_USE_FThis flag only makes sense for Format_description_log_event. It is set when the event is written, and reset when a binlog file is closed (yes, it's the only case when MySQL modifies already written part of binlog). Thus it is a reliable indicator that binlog was closed correctly.
0x0002
LOG_EVENT_FORCED_ROTATE_F(unused)
0x0004
LOG_EVENT_THREAD_SPECIFIC_F If the query depends on the thread (for example: TEMPORARY TABLE)
0x0008
LOG_EVENT_SUPPRESS_USE_F Suppress the generation of 'USE' statements before the actual statement. This flag should be set for any events that does not need the current database set to function correctly. Most notable cases are 'CREATE DATABASE' and 'DROP DATABASE'.
0x0010
LOG_EVENT_UPDATE_TABLE_MAP_VERSION_F (unused)
0x0020
LOG_EVENT_ARTIFICIAL_F Artificial events are created arbitarily and not written to binary log.These events should not update the master log position when slave SQL thread executes them.
0x0040
LOG_EVENT_RELAY_LOG_F Events with this flag set are created by slave IO thread and written to relay log
0x0080
LOG_EVENT_IGNORABLE_F For an event, 'e', carrying a type code, that a slave,'s', does not recognize, 's' will check 'e' forLOG_EVENT_IGNORABLE_F, and if the flag is set, then 'e'is ignored. Otherwise, 's' acknowledges that it has found an unknown event in the relay log.
0x0100
LOG_EVENT_NO_FILTER_F (no description yet)
0x0200
LOG_EVENT_MTS_ISOLATE_F (no description yet)
0x8000
LOG_EVENT_SKIP_REPLICATION_F Flag set by application creating the event (with @@skip_replication);the slave will skip replication of such eventsif --replicate-events-marked-for-skip is not set to REPLICATE.This is a MariaDB flag; we allocate it from the end of the available values to reduce risk of conflict with new MySQL flags.
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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