Registry Center

Motivation

  • As config center manage configuration data, registry center hold all ephemeral status data dynamically generated in runtime(such as available proxy instances, disabled datasource instances etc).

  • Registry center can disable the access to slave database and the access of application. Governance still has many functions(such as flow control) to be developed.

Data Structure in Registry Center

The registry center can create running node of database access object under states in defined namespace, to distinguish different database access instances, including proxynodes and datanodes nodes.

namespace
   ├──states
   ├    ├──proxynodes
   ├    ├     ├──${your_instance_ip_a}@${your_instance_pid_x}@${UUID}
   ├    ├     ├──${your_instance_ip_b}@${your_instance_pid_y}@${UUID}
   ├    ├     ├──....
   ├    ├──datanodes
   ├    ├     ├──${schema_1}
   ├    ├     ├      ├──${ds_0}
   ├    ├     ├      ├──${ds_1}
   ├    ├     ├──${schema_2}
   ├    ├     ├      ├──${ds_0}
   ├    ├     ├      ├──${ds_1}
   ├    ├     ├──....

/states/proxynodes

It includes running instance information of database access object, with sub-nodes as the identifiers of currently running instance, which consist of IP and PID. Those identifiers are temporary nodes, which are registered when instances are on-line and cleared when instances are off-line. The registry center monitors the change of those nodes to govern the database access of running instances and other things.

/states/datanodes

It is able to orchestrate read-write split slave database, delete or disable data dynamically.

Operation Guide

Circuit Breaker

Write DISABLED (case insensitive) to IP@PID@UUID to disable that instance; delete DISABLED to enable the instance.

Zookeeper command is as follows:

[zk: localhost:2181(CONNECTED) 0] set /${your_zk_namespace}/states/proxynodes/${your_instance_ip_a}@${your_instance_pid_x}@${UUID} DISABLED

Disable Slave Database

Under read-write split scenarios, users can write DISABLED (case insensitive) to sub-nodes of data source name to disable slave database sources. Delete DISABLED or the node to enable it.

Zookeeper command is as follows:

[zk: localhost:2181(CONNECTED) 0] set /${your_zk_namespace}/states/datanodes/${your_schema_name}/${your_slave_datasource_name} DISABLED