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/*
* Copyright 2020 The gRPC Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.grpc.rls;
import javax.annotation.concurrent.ThreadSafe;
/**
* A strategy for deciding when to throttle requests at the client.
*/
@ThreadSafe
interface Throttler {
/**
* Checks if a given request should be throttled by the client. This should be called for every
* request before allowing it to hit the network. If the returned value is true, the request
* should be aborted immediately (as if it had been throttled by the server).
*
* This updates internal state and should be called exactly once for each request.
*/
boolean shouldThrottle();
/**
* Registers a response received from the backend for a request allowed by shouldThrottle. This
* should be called for every response received from the backend (i.e., once for each request for
* which ShouldThrottle returned false). This updates the internal statistics used by
* shouldThrottle.
*
* @param throttled specifies whether the request was throttled by the backend.
*/
void registerBackendResponse(boolean throttled);
/**
* A ThrottledException indicates the call is throttled. This exception is meant to be used by
* caller of {@link Throttler}, the implementation of Throttler should not throw
* this exception when {@link #shouldThrottle()} is called.
*/
final class ThrottledException extends RuntimeException {
static final long serialVersionUID = 1L;
public ThrottledException() {
super();
}
public ThrottledException(String s) {
super(s);
}
@Override
public synchronized Throwable fillInStackTrace() {
return this;
}
}
}