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OpenCensus Agent

Introduction

The OpenCensus Agent exporter aka “ocagent-exporter” enables Java applications to send the observability signals that they’ve collected using OpenCensus to the OpenCensus Agent

This exporter connects and sends observability signals via a single HTTP/2 stream and gRPC with Protocol Buffers to the OpenCensus Agent. If unspecified, this exporter tries to connect to the OpenCensus Agent on port 55678.

Purpose

It converts OpenCensus Stats and Traces into OpenCensus Proto Metrics and Traces which are then sent to the OpenCensus Agent. Therefore programs no longer have to enable the traditional backends’ exporters for every single application.

For example, some backends like Prometheus require opening a unique port per application. This port is what they’ll pull stats from. If you have 10,000 microservices that all each export to Prometheus, you already have to manually and uniquely create at least 10,000 unique ports. Uniquely creating a port will not only exhaust your file descriptors but it also becomes cumbersome and error prone to do.

With the ocagent-exporter, instead the stats are uploaded to the OpenCensus Agent and from there, the agent is singly scraped by Prometheus.

As you can see from above, this not only scales your application’s resource allocation but also scales your development speed and liberates you from complex batching deployments. It also ensures that your applications can be kept light, that the agent’s deployment can safely be restarted flexibly.

The same thing happens for traces.

Add the dependencies to your project

For Maven add to your pom.xml:

<dependencies>
  <dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-exporter-metrics-ocagent</artifactId>
    <version>0.20.0</version>
  </dependency>
  <dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-exporter-trace-ocagent</artifactId>
    <version>0.20.0</version>
  </dependency>
</dependencies>

For Gradle add to your dependencies:

compile 'io.opencensus:opencensus-exporter-metrics-ocagent:0.20.0'
compile 'io.opencensus:opencensus-exporter-trace-ocagent:0.20.0'

Register the exporter

An exporter can be started by invoking createAndRegister(), whose signature is:

OcAgentMetricsExporter.createAndRegister(OcAgentMetricsExporterConfiguration.builder().build());
OcAgentTraceExporter.createAndRegister(OcAgentTraceExporterConfiguration.builder().build());

Options

Options allow you to customize the exporter. Options use a builder pattern which allows optional functional options.

OcAgentTraceExporterConfiguration.builder().setEndPoint("localhost:55678").setUseInsecure(true).build();

Custom address

This option allows one to talk to an OpenCensus Agent running on a customized address. The customized address could be anything that is resolvable by io.grpc.NameResolver.

OcAgentMetricsExporterConfiguration.builder().setEndPoint("zookeeper://zk.example.com:9900/ocagent").build();
OcAgentTraceExporterConfiguration.builder().setEndPoint("zookeeper://zk.example.com:9900/ocagent").build();

Insecure

This option allows one to talk to the OpenCensus Agent without mutual TLS.

This option is mutually exclusive to SSL Context. If both are set, an IllegalArgumentException will be thrown.

It can be enabled like this

OcAgentMetricsExporterConfiguration.builder().setUseInsecure(true).build();
OcAgentTraceExporterConfiguration.builder().setUseInsecure(true).build();

SSL Context

Alternatively you can configure the exporter to talk to the OpenCensus Agent with TLS.

This option is mutually exclusive to Insecure. If both are set, an IllegalArgumentException will be thrown.

It can be enabled like this

OcAgentMetricsExporterConfiguration.builder().setSslContext(SslContext.defaultClientProvider()).build();
OcAgentTraceExporterConfiguration.builder().setSslContext(SslContext.defaultClientProvider()).build();

Service name

This option allows one to set the service name of the caller by using setServiceName.

It can be enabled like this

OcAgentMetricsExporterConfiguration.builder().setServiceName("my own service").build();
OcAgentTraceExporterConfiguration.builder().setServiceName("my own service").build();

Reconnection period

This option defines the amount of time for a failed connection, that the exporter takes before a reconnection attempt to the agent.

The option’s name is setRetryInterval.

Here is an example for how to tell it to attempt reconnecting on fail, after 10 seconds.

OcAgentMetricsExporterConfiguration.builder().setRetryInterval(Duration.create(10, 0)).build();
OcAgentTraceExporterConfiguration.builder().setRetryInterval(Duration.create(10, 0)).build();

End to end Example

This end to end example exports stats and traces to the agent. It will require you to deploy the OpenCensus-Agent in order to examine the stats and traces.

The full code snippet can also be found on the OpenCensus-Java repo.

package io.opencensus.examples.ocagent;

import io.opencensus.common.Duration;
import io.opencensus.common.Scope;
import io.opencensus.exporter.metrics.ocagent.OcAgentMetricsExporter;
import io.opencensus.exporter.metrics.ocagent.OcAgentMetricsExporterConfiguration;
import io.opencensus.exporter.trace.ocagent.OcAgentTraceExporter;
import io.opencensus.exporter.trace.ocagent.OcAgentTraceExporterConfiguration;
import io.opencensus.metrics.LabelKey;
import io.opencensus.metrics.LabelValue;
import io.opencensus.metrics.LongGauge;
import io.opencensus.metrics.LongGauge.LongPoint;
import io.opencensus.metrics.MetricRegistry;
import io.opencensus.metrics.Metrics;
import io.opencensus.stats.Aggregation;
import io.opencensus.stats.Aggregation.Distribution;
import io.opencensus.stats.BucketBoundaries;
import io.opencensus.stats.Measure.MeasureDouble;
import io.opencensus.stats.Measure.MeasureLong;
import io.opencensus.stats.Stats;
import io.opencensus.stats.StatsRecorder;
import io.opencensus.stats.View;
import io.opencensus.stats.View.Name;
import io.opencensus.stats.ViewManager;
import io.opencensus.tags.TagContext;
import io.opencensus.tags.TagKey;
import io.opencensus.tags.TagValue;
import io.opencensus.tags.Tagger;
import io.opencensus.tags.Tags;
import io.opencensus.trace.Status;
import io.opencensus.trace.Tracer;
import io.opencensus.trace.Tracing;
import io.opencensus.trace.config.TraceConfig;
import io.opencensus.trace.config.TraceParams;
import io.opencensus.trace.samplers.Samplers;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Random;
import java.util.logging.Logger;

/** Sample application that shows how to export traces and metrics to OC-Agent. */
public class OcAgentExportersQuickStart {

  private static final Logger logger = Logger.getLogger(OcAgentExportersQuickStart.class.getName());
  private static final Random random = new Random();

  private static final Tracer tracer = Tracing.getTracer();
  private static final Tagger tagger = Tags.getTagger();
  private static final StatsRecorder statsRecorder = Stats.getStatsRecorder();
  private static final ViewManager viewManager = Stats.getViewManager();
  private static final MetricRegistry metricRegistry = Metrics.getMetricRegistry();

  private static final String SERVICE_NAME = "ocagent-java-exporter-quickstart";
  private static final String DEFAULT_ENDPOINT = "localhost:55678";
  private static final Duration RETRY_INTERVAL = Duration.create(10, 0);
  private static final Duration EXPORT_INTERVAL = Duration.create(5, 0);

  // The latency in milliseconds
  private static final MeasureDouble M_LATENCY_MS =
      MeasureDouble.create("repl/latency", "The latency in milliseconds per REPL loop", "ms");

  // Counts the number of lines read.
  private static final MeasureLong M_LINES_IN =
      MeasureLong.create("repl/lines_in", "The number of lines read in", "1");

  // Counts the number of non EOF(end-of-file) errors.
  private static final MeasureLong M_ERRORS =
      MeasureLong.create("repl/errors", "The number of errors encountered", "1");

  // Counts/groups the lengths of lines read in.
  private static final MeasureLong M_LINE_LENGTHS =
      MeasureLong.create("repl/line_lengths", "The distribution of line lengths", "By");

  // The tag "method"
  private static final TagKey KEY_METHOD = TagKey.create("method");

  // Defining the distribution aggregations
  private static final Aggregation LATENCY_DISTRIBUTION =
      Distribution.create(
          BucketBoundaries.create(
              Arrays.asList(
                  // [>=0ms, >=25ms, >=50ms, >=75ms, >=100ms, >=200ms, >=400ms, >=600ms, >=800ms,
                  // >=1s, >=2s, >=4s, >=6s]
                  0.0,
                  25.0,
                  50.0,
                  75.0,
                  100.0,
                  200.0,
                  400.0,
                  600.0,
                  800.0,
                  1000.0,
                  2000.0,
                  4000.0,
                  6000.0)));

  private static final Aggregation LENGTH_DISTRIBUTION =
      Distribution.create(
          BucketBoundaries.create(
              Arrays.asList(
                  // [>=0B, >=5B, >=10B, >=20B, >=40B, >=60B, >=80B, >=100B, >=200B, >=400B,
                  // >=600B,
                  // >=800B, >=1000B]
                  0.0,
                  5.0,
                  10.0,
                  20.0,
                  40.0,
                  60.0,
                  80.0,
                  100.0,
                  200.0,
                  400.0,
                  600.0,
                  800.0,
                  1000.0)));

  // Define the count aggregation
  private static final Aggregation COUNT = Aggregation.Count.create();

  // Empty column
  private static final List<TagKey> NO_KEYS = Collections.emptyList();

  // Define the views
  private static final List<View> VIEWS =
      Arrays.asList(
          View.create(
              Name.create("ocjavametrics/latency"),
              "The distribution of latencies",
              M_LATENCY_MS,
              LATENCY_DISTRIBUTION,
              Collections.singletonList(KEY_METHOD)),
          View.create(
              Name.create("ocjavametrics/lines_in"),
              "The number of lines read in from standard input",
              M_LINES_IN,
              COUNT,
              NO_KEYS),
          View.create(
              Name.create("ocjavametrics/errors"),
              "The number of errors encountered",
              M_ERRORS,
              COUNT,
              Collections.singletonList(KEY_METHOD)),
          View.create(
              Name.create("ocjavametrics/line_lengths"),
              "The distribution of line lengths",
              M_LINE_LENGTHS,
              LENGTH_DISTRIBUTION,
              NO_KEYS));

  /** Main launcher of the example. */
  public static void main(String[] args) throws InterruptedException {
    configureAlwaysSample(); // Always sample for demo purpose. DO NOT use in production.
    registerAllViews();
    LongGauge gauge = registerGauge();

    String endPoint = getStringOrDefaultFromArgs(args, 0, DEFAULT_ENDPOINT);
    registerAgentExporters(endPoint);

    try (Scope scope = tracer.spanBuilder("root").startScopedSpan()) {
      int iteration = 1;
      while (true) {
        doWork(iteration, random.nextInt(10), gauge);
        iteration++;
        Thread.sleep(5000);
      }
    } catch (InterruptedException e) {
      logger.info("Thread interrupted, exiting in 5 seconds.");
      Thread.sleep(5000); // Wait 5s so that last batch will be exported.
    }
  }

  private static void configureAlwaysSample() {
    TraceConfig traceConfig = Tracing.getTraceConfig();
    TraceParams activeTraceParams = traceConfig.getActiveTraceParams();
    traceConfig.updateActiveTraceParams(
        activeTraceParams.toBuilder().setSampler(Samplers.alwaysSample()).build());
  }

  private static void registerAgentExporters(String endPoint) {
    OcAgentTraceExporter.createAndRegister(
        OcAgentTraceExporterConfiguration.builder()
            .setEndPoint(endPoint)
            .setServiceName(SERVICE_NAME)
            .setUseInsecure(true)
            .setEnableConfig(false)
            .build());

    OcAgentMetricsExporter.createAndRegister(
        OcAgentMetricsExporterConfiguration.builder()
            .setEndPoint(endPoint)
            .setServiceName(SERVICE_NAME)
            .setUseInsecure(true)
            .setRetryInterval(RETRY_INTERVAL)
            .setExportInterval(EXPORT_INTERVAL)
            .build());
  }

  private static void registerAllViews() {
    for (View view : VIEWS) {
      viewManager.registerView(view);
    }
  }

  private static LongGauge registerGauge() {
    return metricRegistry.addLongGauge(
        "pending_jobs",
        "Pending jobs of current iteration",
        "1",
        Collections.singletonList(LabelKey.create("Name", "desc")));
  }

  private static void doWork(int iteration, int jobs, LongGauge gauge) {
    String childSpanName = "iteration-" + iteration;
    LabelValue value = LabelValue.create(childSpanName);
    LongPoint point = gauge.getOrCreateTimeSeries(Collections.singletonList(value));
    try (Scope scope = tracer.spanBuilder(childSpanName).startScopedSpan()) {
      for (int i = 0; i < jobs; i++) {
        String grandChildSpanName = childSpanName + "-job-" + i;
        try (Scope childScope = tracer.spanBuilder(grandChildSpanName).startScopedSpan()) {
          point.set(jobs - i);
          String line = generateRandom(random.nextInt(128));
          processLine(line);
          recordStat(M_LINES_IN, 1L);
          recordStat(M_LINE_LENGTHS, (long) line.length());
        } catch (Exception e) {
          tracer.getCurrentSpan().setStatus(Status.INTERNAL.withDescription(e.toString()));
        }
      }
    }
  }

  private static String generateRandom(int size) {
    byte[] array = new byte[size];
    random.nextBytes(array);
    return new String(array, Charset.forName("UTF-8"));
  }

  private static String processLine(String line) {
    long startTimeNs = System.nanoTime();

    try {
      Thread.sleep(10L);
      return line.toUpperCase(Locale.US);
    } catch (Exception e) {
      recordTaggedStat(KEY_METHOD, "processLine", M_ERRORS, 1L);
      return "";
    } finally {
      long totalTimeNs = System.nanoTime() - startTimeNs;
      double timespentMs = totalTimeNs / 1e6;
      recordTaggedStat(KEY_METHOD, "processLine", M_LATENCY_MS, timespentMs);
    }
  }

  private static void recordStat(MeasureLong ml, Long n) {
    TagContext empty = tagger.emptyBuilder().build();
    statsRecorder.newMeasureMap().put(ml, n).record(empty);
  }

  private static void recordTaggedStat(TagKey key, String value, MeasureLong ml, long n) {
    TagContext context = tagger.emptyBuilder().put(key, TagValue.create(value)).build();
    statsRecorder.newMeasureMap().put(ml, n).record(context);
  }

  private static void recordTaggedStat(TagKey key, String value, MeasureDouble md, double d) {
    TagContext context = tagger.emptyBuilder().put(key, TagValue.create(value)).build();
    statsRecorder.newMeasureMap().put(md, d).record(context);
  }

  private static String getStringOrDefaultFromArgs(String[] args, int index, String defaultString) {
    String s = defaultString;
    if (index < args.length) {
      s = args[index];
    }
    return s;
  }
}

References

Resource URL
OCAgent Metrics Exporter Javadoc io.opencensus.exporter.metrics.ocagent
OCAgent Trace Exporter Javadoc io.opencensus.exporter.trace.ocagent
Source code Metrics exporter on Github, Trace exporter on Github
OpenCensus Agent Agent homepage
gRPC NameResolver io.grpc.NameResolver