DSE Graph systemReplication

Synopsis

system.graph('graph_name').systemReplication("{'class' : 'NetworkTopologyStrategy', 'dc1' : 3, 'dc2' : 2 }")

Description

Create a new graph and set the graph_name replication configuration using replication()as well as the graph_name_system configuration using systemReplication().

Restriction: Both must be set at the time of graph creation, because replication factor and system replication factor cannot be altered once set for the graph_name and graph_name_system keyspaces.

DSE database settings for replication factor are used, either SimpleStrategy for a single datacenter or NetworkTopologyStrategy for multiple datacenters.

The default replication strategy for a multi-datacenter graph is NetworkTopologyStrategy, whereas for a single datacenter, the replication strategy will default to SimpleStrategy. The number of nodes will determine the default replication factors:


number of nodes per datacenter	graph_name replication factor	graph_name_system replication factor
1-3	number of nodes per datacenter	number of nodes per datacenter
4	3	4
5 or greater	3	5

Examples

An example that creates a graph on a cluster with a two datacenters:

system.graph('food').
  replication("{'class' : 'NetworkTopologyStrategy', 'dc1' : 3, 'dc2' : 2 }").  
  systemReplication("{'class' : 'NetworkTopologyStrategy', 'dc1' : 3, 'dc2' : 2 }").
  ifNotExists().create();

The result:

==>null

shows that the graph was successfully created.

The replication settings can be verified using the cqlsh tool, running the CQL DESCRIBE KEYSPACE command:

DESCRIBE KEYSPACE food;

DESCRIBE KEYSPACE food_system;

with a result:

CREATE KEYSPACE food WITH replication = {'class': 'NetworkTopologyStrategy', 'dc1: '3', 'dc2' : 2 }  AND durable_writes = true;
CREATE KEYSPACE food_system WITH replication = {'class': 'NetworkTopologyStrategy', 'dc1: '3', 'dc2' : 2 }  AND durable_writes = true;