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From afine <...@git.apache.org>
Subject [GitHub] zookeeper pull request #440: ZOOKEEPER-2939 Deal with maxbuffer as it relate...
Date Mon, 08 Jan 2018 20:40:30 GMT
Github user afine commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/440#discussion_r159987502
  
    --- Diff: src/java/main/org/apache/zookeeper/server/quorum/ProposalStats.java ---
    @@ -0,0 +1,70 @@
    +/**
    + * 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.zookeeper.server.quorum;
    +
    +import com.codahale.metrics.ExponentiallyDecayingReservoir;
    +import com.codahale.metrics.Histogram;
    +import com.codahale.metrics.JmxReporter;
    +import com.codahale.metrics.MetricRegistry;
    +import com.codahale.metrics.Reservoir;
    +import com.codahale.metrics.Snapshot;
    +import org.apache.zookeeper.jmx.CommonNames;
    +import org.apache.zookeeper.jmx.MBeanRegistry;
    +
    +import static com.codahale.metrics.MetricRegistry.name;
    +
    +/**
    + * Provides real-time metrics on Leader's proposal size.
    + * The class uses a histogram included in Dropwizard metrics library with ExponentiallyDecayingReservoir.
    + * It provides stats of proposal sizes from the last 5 minutes with acceptable cpu/memory
footprint optimized for streaming data.
    + */
    +public class ProposalStats {
    +    private final Histogram proposalSizes;
    +
    +    ProposalStats() {
    +        final MetricRegistry metrics = new MetricRegistry();
    +        Reservoir reservoir = new ExponentiallyDecayingReservoir();
    --- End diff --
    
    I won't pretend to know much about exponentially decaying reservoirs. I'm curious what
the behavior is with minimum and maximum values. Are these guaranteed to always be exact and
for what time period?


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