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* Copyright 2015, Google Inc. All rights reserved.
*
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*
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*
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package org.glowroot.agent.shaded.grpc;
import org.glowroot.agent.shaded.google.common.util.concurrent.ListenableFuture;
import java.util.List;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;
/**
* A pluggable component that receives resolved addresses from {@link NameResolver} and provides the
* channel a usable transport when asked.
*
* 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
@ThreadSafe
public abstract class LoadBalancer {
/**
* Pick a transport that Channel will use for next RPC.
*
* If the caller gives up before the futrue is done, it should call either {@code cancel(true)}
* or {@code cancel(false)} (they have the same effect) on the future to avoid leaking of
* resources.
*
* @param requestKey for affinity-based routing
*/
public abstract ListenableFuture pickTransport(@Nullable RequestKey requestKey);
/**
* Shuts down this {@code LoadBalancer}.
*/
public void shutdown() { }
/**
* Handles newly resolved addresses and service config from name resolution system.
*
* Implementations should not modify the given {@code servers}.
*/
public void handleResolvedAddresses(List servers, Attributes config) { }
/**
* 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 transportReady(EquivalentAddressGroup addressGroup, T transport) { }
/**
* Called when a transport is shutting down.
*/
public void transportShutdown(EquivalentAddressGroup addressGroup, T transport, 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 LoadBalancer newLoadBalancer(String serviceName, TransportManager tm);
}
}