Oracle 5.0 Reference Manual page 2641

Mysqlnd replication and load balancing plugin (mysqlnd_ms)
Keyword
session_consistency
Description
considers only slaves for reading for which
MySQL replication reports a slave lag less or
equal to age. The replication lag is measure
using STATUS. If the plugin fails
SHOW SLAVE
to fetch the replication lag, the slave tested
is skipped. Implementation details and tips
are given in the quality of service concepts
section.
Please note, if a filter chain generates an
empty slave list and the PHP configuration
directive
mysqlnd_ms.multi_master=0
used, the plugin may emit a warning.
Example 20.284. Global limit on slave lag
{
"myapp": {
"master": {
"master_0": {
"host": "localhost"
}
},
"slave": {
"slave_0": {
"host": "192.168.2.27",
"port": "3306"
},
"slave_1": {
"host": "192.168.78.136",
"port": "3306"
}
},
"filters": {
"quality_of_service": {
"eventual_consistency": {
"age":123
}
}
}
}
}
Request session consistency (read your
writes). Allows use of all masters and all
slaves which are in sync with the master. If no
further parameters are given slaves are filtered
out as there is no reliable way to test if a slave
has caught up to the master or is lagging
behind. Please note, if a filter chain generates
an empty slave list and the PHP configuration
directive
mysqlnd_ms.multi_master=0
used, the plugin may emit a warning.
Session consistency temporarily requested
using
mysqlnd_ms_set_qos
alternative to using master_on_write.
is likely to send more
master_on_write
statements to the master than needed. The
application may be able to continue operation
2621
Version
is
Since 1.1.0.
is
is a valuable