java - grpc v1.34.1 的客户端负载均衡，不推荐使用 nameResolverFactory

Question

我在 Java 中使用 grpc v1.34.1 并且很难配置客户端负载平衡，因为一些方法在这个版本中被弃用了。通过以下方式在早期版本中配置客户端负载平衡非常简单:

final ManagedChannel channel = ManagedChannelBuilder.forTarget(target)
        .nameResolverFactory(new DnsNameResolverProvider())  // this is on by default
        .loadBalancerFactory(RoundRobinLoadBalancerFactory.getInstance())
        .usePlaintext(true)
        .build();

或者通过这个https://sultanov.dev/blog/grpc-client-side-load-balancing/

但是，对于已弃用 nameResolverFactory 并删除方法 loadBalancerFactory 的较新版本，没有任何可用的引用。

NameResolver.Factory nameResolverFactory = new MultiAddressNameResolverFactory(
        new InetSocketAddress("localhost", 50000),
        new InetSocketAddress("localhost", 50001),
        new InetSocketAddress("localhost", 50002)
);

channel = ManagedChannelBuilder.forTarget("localhost")
        .nameResolverFactory(nameResolverFactory)
        .defaultLoadBalancingPolicy("round_robin")
        .usePlaintext()
        .build();

客户端负载平衡有效。但是，较新的 API 已弃用 nameResolverFactory。

任何人都可以指出我在较新版本中使用 nameResolverFactory 的替代方案来实现不同服务器(主机和端口)的客户端负载平衡吗？

Answer 1

通过 grpc-java 内部实现后，我发现新版本接受 NameResolver.Factory 对象的方式略有不同。它被封装到NameResolverProvider，需要注册到默认的NameResolverRegistry。下面分享了在较新版本中执行此操作的示例代码:

NameResolverProvider nameResolverFactory = new MultiAddressNameResolverFactory(
                new InetSocketAddress("localhost", 50000),
                new InetSocketAddress("localhost", 50001),
                new InetSocketAddress("localhost", 50002)
        );

NameResolverRegistry nameResolverRegistry = NameResolverRegistry.getDefaultRegistry();
nameResolverRegistry.register(nameResolverFactory);
channel = ManagedChannelBuilder.forTarget("localhost")
          .defaultLoadBalancingPolicy("round_robin")
          .usePlaintext()
          .build();


public class MultiAddressNameResolverFactory extends NameResolverProvider {
    final List<EquivalentAddressGroup> addresses;

    MultiAddressNameResolverFactory(SocketAddress... addresses) {
        this.addresses = Arrays.stream(addresses)
                .map(EquivalentAddressGroup::new)
                .collect(Collectors.toList());
    }

    public NameResolver newNameResolver(URI notUsedUri, NameResolver.Args args) {
        return new NameResolver() {
            @Override
            public String getServiceAuthority() {
                return "fakeAuthority";
            }
            public void start(Listener2 listener) {
                listener.onResult(ResolutionResult.newBuilder().setAddresses(addresses).setAttributes(Attributes.EMPTY).build());
            }
            public void shutdown() {
            }
        };
    }

    @Override
    public String getDefaultScheme() {
        return "multiaddress";
    }

    @Override
    protected boolean isAvailable() {
        return true;
    }

    @Override
    protected int priority() {
        return 0;
    }
}

默认情况下，您对 NameResolver.Factory 的自定义实现将由 channel 选择以连接到服务器。根据负载平衡策略，将选择一个 SocketAddress 连接到服务器。