| /* |
| * 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.cassandra.metrics; |
| |
| import java.io.PrintStream; |
| import java.io.Serializable; |
| import java.util.List; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.TimeoutException; |
| import java.util.function.BiFunction; |
| |
| import org.apache.cassandra.concurrent.ExecutorPlus; |
| import org.apache.cassandra.net.MessagingService; |
| import org.apache.cassandra.net.Verb; |
| import org.apache.cassandra.utils.ExecutorUtils; |
| import org.apache.cassandra.utils.MonotonicClock; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| |
| import static org.apache.cassandra.concurrent.ExecutorFactory.Global.executorFactory; |
| |
| public abstract class Sampler<T> |
| { |
| private static long DISABLED = -1L; |
| |
| private static final BiFunction<SamplerType, SamplingManager.ResultBuilder, SamplingManager.ResultBuilder> |
| FrequencySamplerFomatter = (type, resultBuilder) -> |
| resultBuilder.forType(type, type.description) |
| .addColumn("Table", "table") |
| .addColumn("Partition", "value") |
| .addColumn("Count", "count") |
| .addColumn("+/-", "error"); |
| |
| public enum SamplerType |
| { |
| READS("Frequency of reads by partition", FrequencySamplerFomatter), |
| WRITES("Frequency of writes by partition", FrequencySamplerFomatter), |
| LOCAL_READ_TIME("Longest read query times", ((samplerType, resultBuilder) -> |
| resultBuilder.forType(samplerType, samplerType.description) |
| .addColumn("Query", "value") |
| .addColumn("Microseconds", "count"))), |
| READ_ROW_COUNT("Partitions read with the most rows", ((samplerType, resultBuilder) -> |
| resultBuilder.forType(samplerType, samplerType.description) |
| .addColumn("Table", "table") |
| .addColumn("Partition", "value") |
| .addColumn("Rows", "count"))), |
| |
| READ_TOMBSTONE_COUNT("Partitions read with the most tombstones", ((samplerType, resultBuilder) -> |
| resultBuilder.forType(samplerType, samplerType.description) |
| .addColumn("Table", "table") |
| .addColumn("Partition", "value") |
| .addColumn("Tombstones", "count"))), |
| |
| READ_SSTABLE_COUNT("Partitions read with the most sstables", ((samplerType, resultBuilder) -> |
| resultBuilder.forType(samplerType, samplerType.description) |
| .addColumn("Table", "table") |
| .addColumn("Partition", "value") |
| .addColumn("SSTables", "count"))), |
| WRITE_SIZE("Max mutation size by partition", ((samplerType, resultBuilder) -> |
| resultBuilder.forType(samplerType, samplerType.description) |
| .addColumn("Table", "table") |
| .addColumn("Partition", "value") |
| .addColumn("Bytes", "count"))), |
| CAS_CONTENTIONS("Frequency of CAS contention by partition", FrequencySamplerFomatter); |
| |
| private final String description; |
| private final BiFunction<SamplerType, SamplingManager.ResultBuilder, SamplingManager.ResultBuilder> formatter; |
| |
| SamplerType(String description, BiFunction<SamplerType, SamplingManager.ResultBuilder, SamplingManager.ResultBuilder> formatter) |
| { |
| this.description = description; |
| this.formatter = formatter; |
| } |
| |
| void format(SamplingManager.ResultBuilder resultBuilder, PrintStream ps) |
| { |
| formatter.apply(this, resultBuilder).print(ps); |
| } |
| } |
| |
| @VisibleForTesting |
| MonotonicClock clock = MonotonicClock.Global.approxTime; |
| |
| @VisibleForTesting |
| static final ExecutorPlus samplerExecutor = executorFactory() |
| .withJmxInternal() |
| .configureSequential("Sampler") |
| .withQueueLimit(1000) |
| .withRejectedExecutionHandler((runnable, executor) -> MessagingService.instance().metrics.recordSelfDroppedMessage(Verb._SAMPLE)) |
| .build(); |
| |
| private long endTimeNanos = -1; |
| |
| public void addSample(final T item, final int value) |
| { |
| if (isEnabled()) |
| samplerExecutor.submit(() -> insert(item, value)); |
| } |
| |
| protected abstract void insert(T item, long value); |
| |
| /** |
| * A sampler is enabled between {@link this#beginSampling} and {@link this#finishSampling} |
| * @return true if the sampler is enabled. |
| */ |
| public boolean isEnabled() |
| { |
| return endTimeNanos != DISABLED; |
| } |
| |
| public void disable() |
| { |
| endTimeNanos = DISABLED; |
| } |
| |
| /** |
| * @return true if the sampler is active. |
| * A sampler is active only if it is enabled and the current time is within the `durationMillis` when beginning sampling. |
| */ |
| public boolean isActive() |
| { |
| return isEnabled() && clock.now() <= endTimeNanos; |
| } |
| |
| /** |
| * Update the end time for the sampler. Implicitly, calling this method enables the sampler. |
| */ |
| public void updateEndTime(long endTimeMillis) |
| { |
| this.endTimeNanos = endTimeMillis; |
| } |
| |
| /** |
| * Begin sampling with the configured capacity and duration |
| * @param capacity Number of sample items to keep in memory, the lower this is |
| * the less accurate results are. For best results use value |
| * close to cardinality, but understand the memory trade offs. |
| * @param durationMillis Upperbound duration in milliseconds for sampling. The sampler |
| * stops accepting new samples after exceeding the duration |
| * even if {@link #finishSampling(int)}} is not called. |
| */ |
| public abstract void beginSampling(int capacity, long durationMillis); |
| |
| /** |
| * Stop sampling and return the results |
| * @param count The number of the samples requested to retrieve from the sampler |
| * @return a list of samples, the size is the minimum of the total samples and {@param count}. |
| */ |
| public abstract List<Sample<T>> finishSampling(int count); |
| |
| public abstract String toString(T value); |
| |
| /** |
| * Represents the ranked items collected during a sample period |
| */ |
| public static class Sample<S> implements Serializable |
| { |
| public final S value; |
| public final long count; |
| public final long error; |
| |
| public Sample(S value, long count, long error) |
| { |
| this.value = value; |
| this.count = count; |
| this.error = error; |
| } |
| |
| @Override |
| public String toString() |
| { |
| return "Sample [value=" + value + ", count=" + count + ", error=" + error + "]"; |
| } |
| } |
| |
| public static void shutdownNowAndWait(long time, TimeUnit units) throws InterruptedException, TimeoutException |
| { |
| ExecutorUtils.shutdownNowAndWait(time, units, samplerExecutor); |
| } |
| } |