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    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

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

    # Create the AddDatabaseNodeOperation
# Add a random node to 'Northwind' database-group
add_database_node_op = AddDatabaseNodeOperation("Northwind")

# Execute the operation by passing it to maintenance.server.send
result = store.maintenance.server.send(add_database_node_op)

# Can access the new topology
number_of_replicas = len(result.topology.all_nodes)

    Add database node - specific

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

    # Create the AddDatabaseNodeOperation
# Add node C to 'Northwind
add_database_node_op = AddDatabaseNodeOperation("Northwind", "C")

# Execute the operation by passing it to maintenance.server.send
result = store.maintenance.server.send(add_database_node_op)

    Syntax 

    class AddDatabaseNodeOperation(ServerOperation[DatabasePutResult]):
    def __init__(self, database_name: str, node_tag: str = None): ...
    Parameters Type Description
    database_name str Name of a database for which to add the node.
    node_tag str 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
    raft_command_index int Index of the raft command that was executed
    name str Database name
    topology DatabaseTopology The database topology
    nodes_added_to list<str> New nodes added to the cluster topology.
    Will be 0 for this operation.

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