Technical features that support Kokolink PostgreSpread

Master/slave replication

Binary replication

When the master notices a database change to the slave, a binary format data called write-set will be transferred just before writing to storage. Different from the simple query replication method, this guarantees exact duplication of irreproducible runtime transaction like time or random number or serial number between master and slave.

Synchronous replication

Similarly, synchronous copy is made when the master notices a change in database. In other words, the master sends a write-set to the slave, and after confirming that the slave has received it properly, it ends the transaction. By this way, it guarantees that all data that successfully committed to the master properly exists on the slave as well.

Easy administration

By using IP multi-cast method to reach for the other and acquires information, master/slave node then configures its own role. Even when just one node is running, no configuration need to be changed, and the working node continues its service. Because the two nodes observe each other, when troubles occur on the master and make it stop working, the slave will take over the service automatically. And because the virtual IP address that clients use to access to master will also be handed over, clients then just reconnect to the same address to continue working.

Remote replication

In case data copies need to be saved in a distant place as a protection from large-scale disaster, WAN is used to replicate data. On this remote replication mode, multi-cast transfer enable network is not need. Besides, in most case of remote replication, because the master and slave network environment are fairly different from each others, manual operation is enabled.

Mirror nodes

Multi-level of replication

As shown in the figure above, Kokolink PostgreSpread can be considered as multiple level constructed tree that has the master as its root. Database changes committed to the master are spread down the mirror nodes. Multiple mirrors can be used at the same time because in theory, there is no limit of the tree depth.

Integrity preservation

The transaction committed to the master can be referenced instantly on mirror nodes. When copying data to multiple mirrors, it takes time to transmit the changes from the master to mirrors (there are differences in time). However, because Kokolink PostgreSpread has the contrivance to avoid this kind of data disagreement, integrity (to master) preservation search results from all mirror nodes are retrievable.

Easy administration

Every mirror node can communicate with other existing mirror nodes (by using IP multi-cast), then configures their own roles, and their position in tree structure. Even when mirror suspended due to operator's manipulation or system failure, or newly added mirrors, neither configuration modification on working nodes nor operation switch instruction are needed.