Oracle 5.0 Reference Manual page 2612

filter is multi filter. Needs to be non-multi one. Stopping in %s on line
%d. Furthermore, an appropriate error on the connection handle may be set.
20.7.6.5.9. Service level and consistency
Copyright 1997-2012 the PHP Documentation Group. [2230]
The plugin can be used with different kinds of MySQL database clusters. Different clusters can deliver
different levels of service to applications. The service levels can be grouped by the data consistency
levels that can be achieved. The plugin knows about:
• eventual consistency
• session consistency
• strong consistency
Depending how a cluster is used it may be possible to achieve higher service levels than the default
one. For example, a read from an asynchronous MySQL replication slave is eventual consistent. Thus,
one may say the default consistency level of a MySQL replication cluster is eventual consistency.
However, if the master only is used by a client for reading and writing during a session, session
consistency (read your writes) is given. PECL mysqlnd 1.2.0 abstracts the details of choosing an
appropriate node for any of the above service levels from the user.
Service levels can be set through the qualify-of-service filter in the
runtime using the function mysqlnd_ms_set_qos.
The plugin defines the different service levels as follows.
Eventual consistency is the default service provided by an asynchronous cluster, such as classical
MySQL replication. A read operation executed on an arbitrary node may or may not return stale data.
The applications view of the data is eventual consistent.
Session consistency is given if a client can always read its own writes. An asynchronous MySQL
replication cluster can deliver session consistency if clients always use the master after the first write or
never query a slave which has not yet replicated the clients write operation.
The plugins understanding of strong consistency is that all clients always see the committed writes
of all other clients. This is the default when using MySQL Cluster or any other cluster offering
synchronous data distribution.
Service level parameters
Mysqlnd replication and load balancing plugin (mysqlnd_ms)
Speculation towards the future: MySQL replication filtering
In future versions, there may be additional multi filters. For example, there may
be a filter to support MySQL replication filtering. This would allow you
table
to define rules for which database or table is to be replicated to which node of
a replication cluster. Assume your replication cluster consists of four slaves
(slave_0, slave_1, slave_2, slave_3) two of which replicate a database
named (slave_0, slave_1). If the application queries the database
sales
slaves, the hypothetical
and slave_1. Because the output and list of candidates consists of
slave_0
more than one server, it is necessary and possible to add additional filters to the
candidate list, for example, using a load balancing filter to identify a server for
statement execution.
Version requirement
Service levels have been introduced in mysqlnd_ms version 1.2.0-alpha.
mysqlnd_ms_set_qos
filter reduces the list of possible servers to
table
requires PHP 5.4.0 or newer.
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plugins configuration file and at