Binlog Filter

This filter was introduced in MariaDB MaxScale 2.3.0.

Overview

The binlogfilter can be combined with a binlogrouter service to selectively replicate the binary log events to replica servers.

The filter uses two parameters, match and exclude, to decide which events are replicated. If a binlog event does not match or is excluded, the event is replaced with an empty data event. The empty event is always 35 bytes which translates to a space reduction in most cases.

When statement-based replication is used, any query events that are filtered out are replaced with a SQL comment. This causes the query event to do nothing and thus the event will not modify the contents of the database. The GTID position of the replicating database will still advance which means that downstream servers replicating from it keep functioning correctly.

The filter works with both row based and statement based replication but we recommend using row based replication with the binlogfilter. This guarantees that there are no ambiguities in the event filtering.

Configuration

match and exclude

Both the match and exclude parameters are optional and work mostly as other typical regular expression parameters. If neither of them is defined, the filter does nothing and all events are replicated. This filter does not accept regular expression options as a separate parameter, such settings must be defined in the patterns themselves. See the PCRE2 api documentation for more information.

The two parameters are matched against the database and table name concatenated with a period. For example, the string the patterns are matched against for the database test and table t1 is test.t1.

For statement based replication, the pattern is matched against all the tables in the statements. If any of the tables matches the match pattern, the event is replicated. If any of the tables matches the exclude pattern, the event is not replicated.

rewrite_src and rewrite_dest

These two parameters control the statement rewriting of the binlogfilter. The rewrite_src parameter is a PCRE2 regular expression that is matched against the default database and the SQL of statement based replication events (query events). rewrite_dest is the replacement string which supports the normal PCRE2 backreferences (e.g the first capture group is $1, the second is $2, etc.).

Both rewrite_src and rewrite_dest must be defined to enable statement rewriting.

When statement rewriting is enabled GTID-based replication must be used. The filter will disallow replication for all replicas that attempt to replicate with traditional file-and-position based replication.

The replacement is done both on the default database as well as the SQL statement in the query event. This means that great care must be taken when defining the rewriting rules. To prevent accidental modification of the SQL into a form that is no longer valid, use database and table names that never occur in the inserted data and is never used as a constant value.

Example Configuration

With the following configuration, only events belonging to database customers are replicated. In addition to this, events for the table orders are excluded and thus are not replicated.

[BinlogFilter]
type=filter
module=binlogfilter
match=/customers[.]/
exclude=/[.]orders/

[BinlogServer]
type=service
router=binlogrouter
server_id=33
filters=BinlogFilter

[BinlogListener]
type=listener
service=BinlogServer
protocol=MySQLClient
port=4000

For more information about the binlogrouter and how to use it, refer to the binlogrouter documentation.