io.grpc

Class LoadBalancerProvider

java.lang.Object

io.grpc.LoadBalancer.Factory

io.grpc.LoadBalancerProvider

@ExperimentalApi(value="https://github.com/grpc/grpc-java/issues/1771")
public abstract class LoadBalancerProvider
extends LoadBalancer.Factory

Provider of LoadBalancers. Each provider is bounded to a load-balancing policy name.

Implementations can be automatically discovered by gRPC via Java's SPI mechanism. For automatic discovery, the implementation must have a zero-argument constructor and include a resource named META-INF/services/io.grpc.LoadBalancerProvider in their JAR. The file's contents should be the implementation's class name. Implementations that need arguments in their constructor can be manually registered by LoadBalancerRegistry.register(io.grpc.LoadBalancerProvider).

Implementations should not throw. If they do, it may interrupt class loading. If exceptions may reasonably occur for implementation-specific reasons, implementations should generally handle the exception gracefully and return false from isAvailable().

Since:

1.17.0

Constructor Summary

Constructors

Constructor and Description
LoadBalancerProvider()

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object other) Uses identity equality.
abstract String	getPolicyName() Returns the load-balancing policy name associated with this provider, which makes it selectable via LoadBalancerRegistry.getProvider(java.lang.String).
abstract int	getPriority() A priority, from 0 to 10 that this provider should be used, taking the current environment into consideration.
int	hashCode()
abstract boolean	isAvailable() Whether this provider is available for use, taking the current environment into consideration.
NameResolver.ConfigOrError	parseLoadBalancingPolicyConfig(Map<String,?> rawLoadBalancingPolicyConfig) Parses the config for the Load Balancing policy unpacked from the service config.
String	toString()

Methods inherited from class io.grpc.LoadBalancer.Factory

newLoadBalancer

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

LoadBalancerProvider

public LoadBalancerProvider()

Method Detail

isAvailable

public abstract boolean isAvailable()

Whether this provider is available for use, taking the current environment into consideration. If false, LoadBalancer.Factory.newLoadBalancer(io.grpc.LoadBalancer.Helper) is not safe to be called.

getPriority

public abstract int getPriority()

A priority, from 0 to 10 that this provider should be used, taking the current environment into consideration. 5 should be considered the default, and then tweaked based on environment detection. A priority of 0 does not imply that the provider wouldn't work; just that it should be last in line.

getPolicyName

public abstract String getPolicyName()

Returns the load-balancing policy name associated with this provider, which makes it selectable via LoadBalancerRegistry.getProvider(java.lang.String). This is called only when the class is loaded. It shouldn't change, and there is no point doing so.

The policy name should consist of only lower case letters letters, underscore and digits, and can only start with letters.

parseLoadBalancingPolicyConfig

public NameResolver.ConfigOrError parseLoadBalancingPolicyConfig(Map<String,?> rawLoadBalancingPolicyConfig)

Parses the config for the Load Balancing policy unpacked from the service config. This will return a NameResolver.ConfigOrError which contains either the successfully parsed config, or the Status representing the failure to parse. Implementations are expected to not throw exceptions but return a Status representing the failure. If successful, the load balancing policy config should be immutable.

Parameters:

rawLoadBalancingPolicyConfig - The Map representation of the load balancing policy choice.

Returns:

a tuple of the fully parsed and validated balancer configuration, else the Status.

Since:

1.20.0

See Also:

A24-lb-policy-config.md

toString

public final String toString()

Overrides:

toString in class Object

equals

public final boolean equals(Object other)

Uses identity equality.

Overrides:

equals in class Object

hashCode

public final int hashCode()

Overrides:

hashCode in class Object