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Date: Wed, 13 Apr 2016 16:23:25 +0000 (UTC)
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Subject: [jira] [Commented] (ACCUMULO-4187) Rate limiting of major
 compactions
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    [ https://issues.apache.org/jira/browse/ACCUMULO-4187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15239533#comment-15239533 ] 

ASF GitHub Bot commented on ACCUMULO-4187:
------------------------------------------

Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/90#discussion_r59579043
  
    --- Diff: server/base/src/main/java/org/apache/accumulo/server/util/ratelimit/SharedRateLimiterFactory.java ---
    @@ -0,0 +1,152 @@
    +/*
    + * 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 org.apache.accumulo.server.util.ratelimit;
    +
    +import com.google.common.collect.ImmutableList;
    +import java.util.List;
    +import java.util.WeakHashMap;
    +import java.util.concurrent.Callable;
    +import java.util.concurrent.atomic.LongAdder;
    +import org.apache.accumulo.core.conf.AccumuloConfiguration;
    +import org.apache.accumulo.core.util.ratelimit.GuavaRateLimiter;
    +import org.apache.accumulo.core.util.ratelimit.RateLimiter;
    +import org.apache.accumulo.server.util.time.SimpleTimer;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +public class SharedRateLimiterFactory {
    +  private static final long REPORT_RATE = 60000;
    +  private static final long UPDATE_RATE = 1000;
    +  private static SharedRateLimiterFactory instance = null;
    +  private final Logger logger = LoggerFactory.getLogger(SharedRateLimiterFactory.class);
    +  private final WeakHashMap<String,SharedRateLimiter> activeLimiters = new WeakHashMap<>();
    +
    +  private SharedRateLimiterFactory() {}
    +
    +  public static SharedRateLimiterFactory getInstance(SimpleTimer timer) {
    +    synchronized (SharedRateLimiterFactory.class) {
    +      if (instance == null) {
    +        instance = new SharedRateLimiterFactory();
    +
    +        // Update periodically
    +        timer.schedule(new Runnable() {
    +          @Override
    +          public void run() {
    +            instance.update();
    +          }
    +        }, UPDATE_RATE, UPDATE_RATE);
    +
    +        // Report periodically
    +        timer.schedule(new Runnable() {
    +          @Override
    +          public void run() {
    +            instance.report();
    +          }
    +        }, REPORT_RATE, REPORT_RATE);
    +      }
    +      return instance;
    +    }
    +  }
    +
    +  public static SharedRateLimiterFactory getInstance(AccumuloConfiguration conf) {
    +    return getInstance(SimpleTimer.getInstance(conf));
    +  }
    +
    +  /**
    +   * Lookup the RateLimiter associated with the specified name, or create a new one for that name. RateLimiters should be closed when no longer needed.
    +   *
    +   * @param name
    +   *          key for the rate limiter
    +   * @param rateGenerator
    +   *          a function which can be called to get what the current rate for the rate limiter should be.
    +   */
    +  public RateLimiter create(String name, Callable<Long> rateGenerator) {
    +    synchronized (activeLimiters) {
    +      if (activeLimiters.containsKey(name)) {
    +        SharedRateLimiter limiter = activeLimiters.get(name);
    +        return limiter;
    +      } else {
    +        long initialRate;
    +        try {
    +          initialRate = rateGenerator.call();
    +        } catch (Exception ex) {
    +          throw new IllegalStateException(ex);
    +        }
    +        SharedRateLimiter limiter = new SharedRateLimiter(name, rateGenerator, initialRate);
    +        activeLimiters.put(name, limiter);
    +        return limiter;
    +      }
    +    }
    +  }
    +
    +  protected void update() {
    +    List<SharedRateLimiter> limiters;
    +    synchronized (activeLimiters) {
    +      limiters = ImmutableList.copyOf(activeLimiters.values());
    +    }
    +    for (SharedRateLimiter limiter : limiters) {
    +      limiter.update();
    +    }
    +  }
    +
    +  protected void report() {
    +    List<SharedRateLimiter> limiters;
    +    synchronized (activeLimiters) {
    +      limiters = ImmutableList.copyOf(activeLimiters.values());
    +    }
    +    for (SharedRateLimiter limiter : limiters) {
    +      limiter.report();
    +    }
    +  }
    +
    +  protected class SharedRateLimiter extends GuavaRateLimiter {
    +    private final LongAdder permitsAcquired = new LongAdder();
    +    private final Callable<Long> rateCallable;
    +    private final String name;
    +
    +    SharedRateLimiter(String name, Callable<Long> rateCallable, long initialRate) {
    +      super(initialRate);
    +      this.name = name;
    +      this.rateCallable = rateCallable;
    +    }
    +
    +    @Override
    +    public void acquire(long permits) {
    +      super.acquire(permits);
    +      permitsAcquired.add(permits);
    +    }
    +
    +    public void update() {
    +      try {
    +        // Reset rate if needed
    +        long rate = rateCallable.call();
    +        if (rate != getRate()) {
    +          setRate(rate);
    +        }
    +      } catch (Exception ex) {
    +        logger.debug("Failed to update rate limiter", ex);
    +      }
    +    }
    +
    +    public void report() {
    +      long sum = permitsAcquired.sumThenReset();
    +      if (sum > 0) {
    +        logger.debug(String.format("RateLimiter '%s': %,d of %,d permits/second", name, sum * 1000L / REPORT_RATE, getRate()));
    --- End diff --
    
    The timer will not always call report at the requested frequency.   Could track the last report time and use that to calculate the rate.


> Rate limiting of major compactions
> ----------------------------------
>
>                 Key: ACCUMULO-4187
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4187
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: core, tserver
>    Affects Versions: 1.8.0
>            Reporter: Shawn Walker
>            Assignee: Shawn Walker
>            Priority: Minor
>             Fix For: 1.8.0
>
>
> In discussing [ACCUMULO-4166] with Keith Turner, we decided that the underlying issue is that major compactions can overwhelm a tablet server, rendering it nearly unresponsive.
> To address this, we should take a cue from Apache Cassandra and restrict how quickly we perform major compactions.  Rate limiting reads and writes involved in major compactions will directly affect the IO load caused by major compactions, and should also indirectly affect the CPU load.


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