Adding a Database Node

• When creating a database, you can specify the number of replicas for that database.
  This determines the number of database instances in the database-group.

• The number of replicas can be dynamically increased even after the database is up and running,
  by adding more nodes to the database-group.

• The nodes added must already exist in the cluster topology.

• Once a new node is added to the database-group,
  the cluster assigns a mentor node (from the existing database-group nodes) to update the new node.

• In this page:

  • Add database node - random
  • Add database node - specific
  • Syntax

Add database node - random

• Use AddDatabaseNodeOperation to add another database-instance to the database-group.
• The node added will be a random node from the existing cluster nodes.

• Sync
• Async

// Create the AddDatabaseNodeOperation
// Add a random node to 'Northwind' database-group
var addDatabaseNodeOp = new AddDatabaseNodeOperation("Northwind");

// Execute the operation by passing it to Maintenance.Server.Send
DatabasePutResult result = store.Maintenance.Server.Send(addDatabaseNodeOp);

// Can access the new topology
var numberOfReplicas = result.Topology.AllNodes.Count();

// Create the AddDatabaseNodeOperation
// Add a random node to 'Northwind' database-group
var addDatabaseNodeOp = new AddDatabaseNodeOperation("Northwind");

// Execute the operation by passing it to Maintenance.Server.SendAsync
DatabasePutResult result = await store.Maintenance.Server.SendAsync(addDatabaseNodeOp);

// Can access the new topology
var numberOfReplicas = result.Topology.AllNodes.Count();

Add database node - specific

• You can specify the node tag to add.
• This node must already exist in the cluster topology.

• Sync
• Async

// Create the AddDatabaseNodeOperation
// Add node C to 'Northwind' database-group
var addDatabaseNodeOp = new AddDatabaseNodeOperation("Northwind", "C");

// Execute the operation by passing it to Maintenance.Server.Send
DatabasePutResult result = store.Maintenance.Server.Send(addDatabaseNodeOp);

// Create the AddDatabaseNodeOperation
// Add node C to 'Northwind' database-group
var addDatabaseNodeOp = new AddDatabaseNodeOperation("Northwind", "C");

// Execute the operation by passing it to Maintenance.Server.SendAsync
DatabasePutResult result = await store.Maintenance.Server.SendAsync(addDatabaseNodeOp);

Syntax

public AddDatabaseNodeOperation(string databaseName, string nodeTag = null)

Parameters	Type	Description
databaseName	string	Name of a database for which to add the node.
nodeTag	string	Tag of node to add. Default: a random node from the existing cluster topology will be added.

Object returned by Send operation: DatabasePutResult	Type	Description
RaftCommandIndex	long	Index of the raft command that was executed
Name	string	Database name
Topology	DatabaseTopology	The database topology
NodesAddedTo	List<string>	New nodes added to the cluster topology. Will be 0 for this operation.