ZongJi

A MySQL binlog listener running on Node.js.

ZongJi (踪迹) is pronounced as zōng jì in Chinese.

This package is a "pure JS" implementation based on node-mysql. Since v0.2.0, The native part (which was written in C++) has been dropped.

This package has been tested to work in MySQL 5.5, 5.6, and 5.7.

Quick Start

var zongji = new ZongJi({ /* ... MySQL Connection Settings ... */ });

// Each change to the replication log results in an event
zongji.on('binlog', function(evt) {
  evt.dump();
});

// Binlog must be started, optionally pass in filters
zongji.start({
  includeEvents: ['tablemap', 'writerows', 'updaterows', 'deleterows']
});

For a complete implementation see example.js...

Installation

• Requires Node.js v4+

  $ npm install zongji

• Enable MySQL binlog in my.cnf, restart MySQL server after making the changes.

  From MySQL 5.6, binlog checksum is enabled by default. Zongji can work with it, but it doesn't really verify it.

  # Must be unique integer from 1-2^32
  server-id        = 1
  # Row format required for ZongJi
  binlog_format    = row
  # Directory must exist. This path works for Linux. Other OS may require
  #   different path.
  log_bin          = /var/log/mysql/mysql-bin.log
  
  binlog_do_db     = employees   # Optional, limit which databases to log
  expire_logs_days = 10          # Optional, purge old logs
  max_binlog_size  = 100M        # Optional, limit log size
  

• Create an account with replication privileges, e.g. given privileges to account zongji (or any account that you use to read binary logs)

  GRANT REPLICATION SLAVE, REPLICATION CLIENT, SELECT ON *.* TO 'zongji'@'localhost'

ZongJi Class

The ZongJi constructor accepts one argument of either:

• An object containing MySQL connection details in the same format as used by node-mysql
• Or, a node-mysql Connection or Pool object that will be used for querying column information.

If a Connection or Pool object is passed to the constructor, it will not be destroyed/ended by Zongji's stop() method.

If there is a dateStrings node-mysql configuration option in the connection details or connection, ZongJi will follow it.

Each instance includes the following methods:

Method Name	Arguments	Description
start	options	Start receiving replication events, see options listed below
stop	None	Disconnect from MySQL server, stop receiving events
set	options	Change options after start()
on	eventName, handler	Add a listener to the binlog or error event. Each handler function accepts one argument.

Options available:

Option Name	Type	Description
serverId	integer	Unique number (1 - 232) to identify this replication slave instance. Must be specified if running more than one instance of ZongJi. Must be used in start() method for effect. Default: 1
startAtEnd	boolean	Pass true to only emit binlog events that occur after ZongJi's instantiation. Must be used in start() method for effect. Default: false
binlogName	string	Begin reading events from this binlog file. If specified together with binlogNextPos, will take precedence over startAtEnd.
binlogNextPos	integer	Begin reading events from this position. Must be included with binlogName.
includeEvents	[string]	Array of event names to include Example: ['writerows', 'updaterows', 'deleterows']
excludeEvents	[string]	Array of event names to exclude Example: ['rotate', 'tablemap']
includeSchema	object	Object describing which databases and tables to include (Only for row events). Use database names as the key and pass an array of table names or true (for the entire database). Example: { 'my_database': ['allow_table', 'another_table'], 'another_db': true }
excludeSchema	object	Object describing which databases and tables to exclude (Same format as includeSchema) Example: { 'other_db': ['disallowed_table'], 'ex_db': true }

• By default, all events and schema are emitted.
• excludeSchema and excludeEvents take precedence over includeSchema and includeEvents, respectively.

Supported Binlog Events:

Event name	Description
unknown	Catch any other events
query	Insert/Update/Delete Query
intvar	Autoincrement and LAST_INSERT_ID
rotate	New Binlog file Not required to be included to rotate to new files, but it is required to be included in order to keep the binlogName and binlogNextPos properties updated with current values for graceful restarting on errors.
format	Format Description
xid	Transaction ID
tablemap	Before any row event (must be included for any other row events)
writerows	Rows inserted, row data array available as rows property on event object
updaterows	Rows changed, row data array available as rows property on event object
deleterows	Rows deleted, row data array available as rows property on event object

Event Methods

Neither method requires any arguments.

Name	Description
dump	Log a description of the event to the console
getEventName	Return the name of the event

Important Notes

• 🌟 All types allowed by node-mysql are supported by this package.
• 🙊 While 64-bit integers in MySQL (BIGINT type) allow values in the range of 2⁶⁴ (± ½ × 2⁶⁴ for signed values), Javascript's internal storage of numbers limits values to 2⁵³, making the allowed range of BIGINT fields only -9007199254740992 to 9007199254740992. Unsigned 64-bit integers must also not exceed 9007199254740992.
• 👉 TRUNCATE statement does not cause corresponding DeleteRows event. Use unqualified DELETE FROM for same effect.
• When using fractional seconds with DATETIME and TIMESTAMP data types in MySQL > 5.6.4, only millisecond precision is available due to the limit of Javascript's Date object.

Run Tests

• install Docker
• run docker-compose up and then ./docker-test.sh

Reference

I learnt many things from following resources while making ZongJi.

• https://github.com/felixge/node-mysql
• https://github.com/felixge/faster-than-c/
• http://intuitive-search.blogspot.co.uk/2011/07/binary-log-api-and-replication-listener.html
• https://github.com/Sannis/node-mysql-libmysqlclient
• https://kkaefer.com/node-cpp-modules/
• http://dev.mysql.com/doc/internals/en/replication-protocol.html
• http://www.cs.wichita.edu/~chang/lecture/cs742/program/how-mysql-c-api.html
• https://github.com/jeremycole/mysql_binlog (Ruby implemenation of MySQL binlog parser)
• http://dev.mysql.com/doc/internals/en/date-and-time-data-type-representation.html

License

MIT