co.cask.tigon.internal.app.runtime.flow.FlowletProcessEntry.java Source code

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Here is the source code for co.cask.tigon.internal.app.runtime.flow.FlowletProcessEntry.java

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * 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 co.cask.tigon.internal.app.runtime.flow;

import com.google.common.primitives.Longs;

import java.util.concurrent.TimeUnit;

/**
 * Data structure for tracking retry and backing off calls to process method in flowlet.
 */
final class FlowletProcessEntry<T> implements Comparable<FlowletProcessEntry> {

    // Minimum back-off time in nanoseconds, 1ms.
    private static final long BACKOFF_MIN = TimeUnit.MILLISECONDS.toNanos(1);

    // Maximum back-off time in nanoseconds when increasing exponentially, 100ms.
    private static final long BACKOFF_MAX = TimeUnit.MILLISECONDS.toNanos(100);

    // Start time for switching from constant to exponentially increasing back-off time, 20ms.
    private static final long BACKOFF_EXP_START = TimeUnit.MILLISECONDS.toNanos(20);

    // Incrementing back-off time by this until reaching exponential increase range.
    private static final long BACKOFF_CONSTANT_INCREMENT = TimeUnit.MILLISECONDS.toNanos(1);

    // Doubling back-off time during exponential increase, up to maximum back-off time.
    private static final int BACKOFF_EXP = 2;

    private final ProcessSpecification<T> processSpec;
    private final ProcessSpecification<T> retrySpec;
    private final boolean isTick;
    private long nextDeque;
    private long currentBackOff = BACKOFF_MIN;

    static <T> FlowletProcessEntry<T> create(ProcessSpecification<T> processSpec) {
        return new FlowletProcessEntry<T>(processSpec, null, processSpec.getInitialCallDelay());
    }

    static <T> FlowletProcessEntry<T> create(ProcessSpecification<T> processSpec,
            ProcessSpecification<T> retrySpec) {
        return new FlowletProcessEntry<T>(processSpec, retrySpec, 0);
    }

    private FlowletProcessEntry(ProcessSpecification<T> processSpec, ProcessSpecification<T> retrySpec,
            long nextDeque) {
        this.processSpec = processSpec;
        this.retrySpec = retrySpec;
        this.nextDeque = nextDeque;
        this.isTick = processSpec.isTick();
    }

    public boolean isRetry() {
        return retrySpec != null;
    }

    public void await() throws InterruptedException {
        long waitTime = nextDeque - System.nanoTime();
        if (waitTime > 0) {
            TimeUnit.NANOSECONDS.sleep(waitTime);
        }
    }

    public boolean shouldProcess() {
        return nextDeque - System.nanoTime() <= 0;
    }

    @Override
    public int compareTo(FlowletProcessEntry o) {
        return Longs.compare(nextDeque, o.nextDeque);
    }

    public void resetBackOff() {
        nextDeque = System.nanoTime() + processSpec.getCallDelay();
        currentBackOff = BACKOFF_MIN;
    }

    public void backOff() {
        nextDeque = System.nanoTime() + currentBackOff;
        if (currentBackOff < BACKOFF_EXP_START) {
            currentBackOff += BACKOFF_CONSTANT_INCREMENT;
        } else {
            currentBackOff = Math.min(currentBackOff * BACKOFF_EXP, BACKOFF_MAX);
        }
    }

    public ProcessSpecification<T> getProcessSpec() {
        return retrySpec == null ? processSpec : retrySpec;
    }

    public FlowletProcessEntry<T> resetRetry() {
        return retrySpec == null ? this : new FlowletProcessEntry<T>(processSpec, null, processSpec.getCallDelay());
    }

    public boolean isTick() {
        return isTick;
    }
}