DSE Graph systemReplication

How to set the replication factor for the graph_system keyspace of a new graph.

Synopsis

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

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 single nodes or NetworkTopologyStrategy for multiple nodes or multiple datacenters.

The default replication strategy for a multi-node or multi-datacenter graph is NetworkTopologyStrategy, whereas for a single node, 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 single datacenter of 3 nodes:
system.graph('food').
  replication("{'class' : 'NetworkTopologyStrategy', 'dc1' : 3 }").  
  systemReplication("{'class' : 'NetworkTopologyStrategy', 'dc1' : 3 }").
  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'}  AND durable_writes = true;
CREATE KEYSPACE food_system WITH replication = {'class': 'NetworkTopologyStrategy', 'dc1: '3'}  AND durable_writes = true;