distributedlog-service/src/main/java/com/twitter/distributedlog/service/stream/limiter/RequestLimiterBuilder.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 com.twitter.distributedlog.service.stream.limiter;

import static com.google.common.base.Preconditions.checkNotNull;

import com.twitter.distributedlog.exceptions.OverCapacityException;
import com.twitter.distributedlog.limiter.ComposableRequestLimiter;
import com.twitter.distributedlog.limiter.ComposableRequestLimiter.CostFunction;
import com.twitter.distributedlog.limiter.ComposableRequestLimiter.OverlimitFunction;
import com.twitter.distributedlog.limiter.GuavaRateLimiter;
import com.twitter.distributedlog.limiter.RateLimiter;
import com.twitter.distributedlog.limiter.RequestLimiter;
import com.twitter.distributedlog.service.stream.StreamOp;
import com.twitter.distributedlog.service.stream.WriteOpWithPayload;
import org.apache.bookkeeper.stats.NullStatsLogger;
import org.apache.bookkeeper.stats.StatsLogger;

/**
 * Request limiter builder.
 */
public class RequestLimiterBuilder {
    private OverlimitFunction<StreamOp> overlimitFunction = NOP_OVERLIMIT_FUNCTION;
    private RateLimiter limiter;
    private CostFunction<StreamOp> costFunction;
    private StatsLogger statsLogger = NullStatsLogger.INSTANCE;

    /**
     * Function to calculate the `RPS` (Request per second) cost of a given stream operation.
     */
    public static final CostFunction<StreamOp> RPS_COST_FUNCTION = new CostFunction<StreamOp>() {
        @Override
        public int apply(StreamOp op) {
            if (op instanceof WriteOpWithPayload) {
                return 1;
            } else {
                return 0;
            }
        }
    };

    /**
     * Function to calculate the `BPS` (Bytes per second) cost of a given stream operation.
     */
    public static final CostFunction<StreamOp> BPS_COST_FUNCTION = new CostFunction<StreamOp>() {
        @Override
        public int apply(StreamOp op) {
            if (op instanceof WriteOpWithPayload) {
                WriteOpWithPayload writeOp = (WriteOpWithPayload) op;
                return (int) Math.min(writeOp.getPayloadSize(), Integer.MAX_VALUE);
            } else {
                return 0;
            }
        }
    };

    /**
     * Function to check if a stream operation will cause {@link OverCapacityException}.
     */
    public static final OverlimitFunction<StreamOp> NOP_OVERLIMIT_FUNCTION = new OverlimitFunction<StreamOp>() {
        @Override
        public void apply(StreamOp op) throws OverCapacityException {
            return;
        }
    };

    public RequestLimiterBuilder limit(int limit) {
        this.limiter = GuavaRateLimiter.of(limit);
        return this;
    }

    public RequestLimiterBuilder overlimit(OverlimitFunction<StreamOp> overlimitFunction) {
        this.overlimitFunction = overlimitFunction;
        return this;
    }

    public RequestLimiterBuilder cost(CostFunction<StreamOp> costFunction) {
        this.costFunction = costFunction;
        return this;
    }

    public RequestLimiterBuilder statsLogger(StatsLogger statsLogger) {
        this.statsLogger = statsLogger;
        return this;
    }

    public static RequestLimiterBuilder newRpsLimiterBuilder() {
        return new RequestLimiterBuilder().cost(RPS_COST_FUNCTION);
    }

    public static RequestLimiterBuilder newBpsLimiterBuilder() {
        return new RequestLimiterBuilder().cost(BPS_COST_FUNCTION);
    }

    public RequestLimiter<StreamOp> build() {
        checkNotNull(limiter);
        checkNotNull(overlimitFunction);
        checkNotNull(costFunction);
        return new ComposableRequestLimiter(limiter, overlimitFunction, costFunction, statsLogger);
    }
}