skywalking和sleuth採集率的問題

3、探針配置

 

 這裏的採樣率是這個意思：

例如100次請求，skywalking agent都會攔截到這100次請求，產生100條tracesegement，可是是否將這100條tracement上報給collect，讓頁面顯示出來

就是上面設置的採用率的問題，若是上面採樣率設置爲70%，那麼100條tracement中只會上報其中的70條

咱們看源碼就知道了

/*
 * 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.skywalking.apm.agent.core.sampling;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.skywalking.apm.agent.core.boot.BootService;
import org.apache.skywalking.apm.agent.core.boot.DefaultImplementor;
import org.apache.skywalking.apm.agent.core.boot.DefaultNamedThreadFactory;
import org.apache.skywalking.apm.agent.core.conf.Config;
import org.apache.skywalking.apm.agent.core.context.trace.TraceSegment;
import org.apache.skywalking.apm.agent.core.logging.api.ILog;
import org.apache.skywalking.apm.agent.core.logging.api.LogManager;
import org.apache.skywalking.apm.util.RunnableWithExceptionProtection;

/** * The <code>SamplingService</code> take charge of how to sample the {@link TraceSegment}. Every {@link TraceSegment}s * have been traced, but, considering CPU cost of serialization/deserialization, and network bandwidth, the agent do NOT * send all of them to collector, if SAMPLING is on. * <p> * By default, SAMPLING is on, and {@link Config.Agent#SAMPLE_N_PER_3_SECS } * * @author wusheng */
@DefaultImplementor
public class SamplingService implements BootService {
    private static final ILog logger = LogManager.getLogger(SamplingService.class);

    private volatile boolean on = false;
    private volatile AtomicInteger samplingFactorHolder;
    private volatile ScheduledFuture<?> scheduledFuture;

    @Override
    public void prepare() throws Throwable {

    }

    @Override
    public void boot() throws Throwable {
        if (scheduledFuture != null) {
            /**
             * If {@link #boot()} invokes twice, mostly in test cases,
             * cancel the old one.
             */
            scheduledFuture.cancel(true);
        }
        if (Config.Agent.SAMPLE_N_PER_3_SECS > 0) {
            on = true;
            this.resetSamplingFactor();
            ScheduledExecutorService service = Executors
                .newSingleThreadScheduledExecutor(new DefaultNamedThreadFactory("SamplingService"));
            scheduledFuture = service.scheduleAtFixedRate(new RunnableWithExceptionProtection(new Runnable() {
                @Override
                public void run() {
                    resetSamplingFactor();
                }
            }, new RunnableWithExceptionProtection.CallbackWhenException() {
                @Override public void handle(Throwable t) {
                    logger.error("unexpected exception.", t);
                }
            }), 0, 3, TimeUnit.SECONDS);
            logger.debug("Agent sampling mechanism started. Sample {} traces in 3 seconds.", Config.Agent.SAMPLE_N_PER_3_SECS);
        }
    }

    @Override
    public void onComplete() throws Throwable {

    }

    @Override
    public void shutdown() throws Throwable {
        if (scheduledFuture != null) {
            scheduledFuture.cancel(true);
        }
    }

    /**
     * @return true, if sampling mechanism is on, and getDefault the sampling factor successfully.
     */
    public boolean trySampling() {
        if (on) {
            int factor = samplingFactorHolder.get();
            if (factor < Config.Agent.SAMPLE_N_PER_3_SECS) {
                boolean success = samplingFactorHolder.compareAndSet(factor, factor + 1);
                return success;
            } else {
                return false;
            }
        }
        return true;
    }

    /**
     * Increase the sampling factor by force,
     * to avoid sampling too many traces.
     * If many distributed traces require sampled,
     * the trace beginning at local, has less chance to be sampled.
     */
    public void forceSampled() {
        if (on) {
            samplingFactorHolder.incrementAndGet();
        }
    }

    private void resetSamplingFactor() {
        samplingFactorHolder = new AtomicInteger(0);
    }
}

agent上傳tracement到collect，會將tracement進行序列化和反序列化，這樣會消耗cpu，因此採樣率指的是是否將所有的tracesegeent上傳給collect，agent會對全部的請求都攔截產生對於的tracesegment，可是是否所有上傳segment由採樣率來決定

 

 

同理sleuth中的採樣率，原理和skwalking的同樣，也是指產生的tracesegment是否所有上傳給zipkin進行展現，sleuth會攔截所有的http請求

spring:
  application:
    name: microservice-consumer-order
  zipkin:
    base-url: http://localhost:9411
  sleuth:
    sampler:
      percentage: 1.0