| /* |
| * Copyright 2015, Google Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package io.grpc; |
| |
| import java.util.List; |
| |
| import javax.annotation.concurrent.ThreadSafe; |
| |
| /** |
| * A pluggable component that receives resolved addresses from {@link NameResolver} and provides the |
| * channel a usable transport when asked. |
| * |
| * <p>Note to implementations: all methods are expected to return quickly. Any work that may block |
| * should be done asynchronously. |
| * |
| * @param <T> the transport type to balance |
| */ |
| // TODO(zhangkun83): since it's also used for non-loadbalancing cases like pick-first, |
| // "RequestRouter" might be a better name. |
| @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771") |
| @ThreadSafe |
| public abstract class LoadBalancer<T> { |
| /** |
| * Pick a transport that Channel will use for next RPC. |
| * |
| * <p>If called after {@link #shutdown} has been called, this method will return |
| * a transport that would fail all requests. |
| * |
| * @param affinity for affinity-based routing |
| */ |
| @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1766") |
| public abstract T pickTransport(Attributes affinity); |
| |
| /** |
| * Shuts down this {@code LoadBalancer}. |
| */ |
| public void shutdown() { } |
| |
| /** |
| * Handles newly resolved server groups and metadata attributes from name resolution system. |
| * {@code servers} contained in {@link ResolvedServerInfoGroup} should be considered equivalent |
| * but may be flattened into a single list if needed. |
| * |
| * <p>Implementations should not modify the given {@code servers}. |
| * |
| * @param servers the resolved server addresses, never empty. |
| * @param attributes extra metadata from naming system. |
| */ |
| public void handleResolvedAddresses(List<ResolvedServerInfoGroup> servers, |
| Attributes attributes) { } |
| |
| /** |
| * Handles an error from the name resolution system. |
| * |
| * @param error a non-OK status |
| */ |
| public void handleNameResolutionError(Status error) { } |
| |
| /** |
| * Called when a transport is fully connected and ready to accept traffic. |
| */ |
| public void handleTransportReady(EquivalentAddressGroup addressGroup) { } |
| |
| /** |
| * Called when a transport is shutting down. |
| */ |
| public void handleTransportShutdown(EquivalentAddressGroup addressGroup, Status s) { } |
| |
| public abstract static class Factory { |
| /** |
| * Creates a {@link LoadBalancer} that will be used inside a channel. |
| * |
| * @param serviceName the DNS-style service name, which is also the authority |
| * @param tm the interface where an {@code LoadBalancer} implementation gets connected |
| * transports from |
| */ |
| public abstract <T> LoadBalancer<T> newLoadBalancer(String serviceName, TransportManager<T> tm); |
| } |
| } |