Load Balance Algorithm

Background

ShardingSphere built-in provides a variety of load balancer algorithms, including polling algorithm, random access algorithm and weight access algorithm, which can meet users’ needs in most business scenarios.

Moreover, considering the complexity of the business scenario, the built-in algorithm also provides an extension mode. Users can implement the load balancer algorithm they need based on SPI interface.

Parameters

Round-robin Load Balance Algorithm

Type: ROUND_ROBIN

Description: Within the transaction, read query are routed according to the configuration of the transaction-read-query-strategy property, and outside the transaction, the round-robin strategy is used to route to the replica.

Attributes:

NameDataTypeDescription
transaction-read-query-strategyStringRouting strategy for read query within a transaction, optional values: FIXED_PRIMARY (route to primary), FIXED_REPLICA (select a fixed replica according to the round-robin strategy), DYNAMIC_REPLICA (route to different replicas according to the round-robin strategy), default value: FIXED_PRIMARY.

Random Load Balance Algorithm

Type: RANDOM

Description: Within the transaction, read query are routed according to the configuration of the transaction-read-query-strategy property, and outside the transaction, the random strategy is used to route to the replica.

Attributes:

NameDataTypeDescription
transaction-read-query-strategyStringRouting strategy for read query within a transaction, optional values: FIXED_PRIMARY (route to primary), FIXED_REPLICA (select a fixed replica according to the random strategy), DYNAMIC_REPLICA (route to different replicas according to the random strategy), default value: FIXED_PRIMARY.

Weight Load Balance Algorithm

Type: WEIGHT

Description: Within the transaction, read query are routed according to the configuration of the transaction-read-query-strategy property, and outside the transaction, the weight strategy is used to route to the replica.

Attributes:

NameDataTypeDescription
${replica-name}doubleAttribute name uses the name of the replica, and the parameter fills in the weight value corresponding to the replica. Weight parameter range min > 0, total <= Double.MAX_VALUE.
transaction-read-query-strategyStringRouting strategy for read query within a transaction, optional values: FIXED_PRIMARY (route to primary), FIXED_REPLICA (select a fixed replica according to the weight strategy), DYNAMIC_REPLICA (route to different replicas according to the weight strategy), default value: FIXED_PRIMARY.

Procedure

  1. Configure a load balancer algorithm for the loadBalancers attribute to use read/write splitting.

Sample

  1. rules:
  2. - !READWRITE_SPLITTING
  3.   dataSources:
  4.     readwrite_ds:
  5.       staticStrategy:
  6.         writeDataSourceName: write_ds
  7.         readDataSourceNames:
  8.           - read_ds_0
  9.           - read_ds_1
  10.       loadBalancerName: random
  11.   loadBalancers:
  12.     random:
  13.       type: RANDOM
  14.       props:
  15.         transaction-read-query-strategy: FIXED_PRIMARY