Balancing

Balancers

The Balancer is a TarantoolClient component designed to distribute requests between Tarantool nodes.

Concept

The balancer abstraction in Tarantool Java EE is represented by the TarantoolBalancer interface. Let's look at how balancing works in the Java client:

1. The programmer executes a request through the API of high-level clients (TarantoolClient, TarantoolCrudClient or TarantoolBoxClient)
2. The high-level client requests a connection to execute the request from TarantoolBalancer
3. The balancer, using its logic, requests an available node from the connection pool (IProtoClientPool) Node availability is determined using the heartbeat mechanism
4. The connection pool returns an available connection to the balancer
5. The balancer provides the high-level client with a connection
6. The high-level client executes the request through the provided connection
7. The high-level client returns a CompletableFuture<?> with the result to the calling code

Available Default Implementations

By default, the following types of balancers are available:

TarantoolRoundRobinBalancer

This implementation of the TarantoolBalancer interface performs connection selection according to the following algorithm:

1. Selection of the group of connections with which the balancing starts (the order is not deterministic).
2. Connection selection within the group is performed in order from first to last.
3. After the last connection in the current group, the balancer moves to connections belonging to another group.

TarantoolDistributingRoundRobinBalancer

This implementation of the TarantoolBalancer interface performs connection selection according to the following algorithm:

1. Selection of the group of connections with which the balancing starts (the order is not deterministic).
2. Selection of the first connection in the first group.
3. Moving to the next group and selecting the first connection.
4. Repeat step 3, selecting the next connection in the group.

Client Balancing Configuration

To configure balancing in the client, use the TarantoolFactory API, for example:

final TarantoolCrudClient crudClient = TarantoolFactory.crud()
    .withBalancerClass(TarantoolRoundRobinBalancer.class)
    //... other settings
    .build();

Custom Balancers

To use your own balancer, create a class that implements the TarantoolBalancer interface.