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feat: Add an OpenCensus stats implementation. (#665)
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‎build.gradle‎

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@@ -54,6 +54,7 @@ dependencies {
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compileOnly 'com.google.appengine:appengine-api-1.0-sdk:1.9.76'
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api 'com.squareup.okhttp3:okhttp:3.14.4'
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api 'com.google.code.gson:gson:2.8.5'
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api 'io.opencensus:opencensus-api:0.25.0'
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implementation 'org.slf4j:slf4j-api:1.7.26'
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testImplementation 'junit:junit:4.12'
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testImplementation 'org.mockito:mockito-core:3.0.0'
@@ -62,6 +63,7 @@ dependencies {
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testImplementation 'org.slf4j:slf4j-simple:1.7.26'
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testImplementation 'org.apache.commons:commons-lang3:3.9'
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testImplementation 'org.json:json:20180813'
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testImplementation 'io.opencensus:opencensus-impl:0.25.0'
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}
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task updateVersion(type: Copy) {

‎src/main/java/com/google/maps/metrics/OpenCensusMetrics.java‎

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package com.google.maps.metrics;
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import io.opencensus.stats.Aggregation;
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import io.opencensus.stats.Aggregation.Count;
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import io.opencensus.stats.Aggregation.Distribution;
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import io.opencensus.stats.BucketBoundaries;
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import io.opencensus.stats.Measure.MeasureLong;
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import io.opencensus.stats.Stats;
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import io.opencensus.stats.View;
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import io.opencensus.stats.ViewManager;
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import io.opencensus.tags.TagKey;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.List;
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/*
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* OpenCensus metrics which are measured for every request.
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*/
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public final class OpenCensusMetrics {
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private OpenCensusMetrics() {}
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public static final class Tags {
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private Tags() {}
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public static final TagKey REQUEST_NAME = TagKey.create("request_name");
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public static final TagKey HTTP_CODE = TagKey.create("http_code");
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public static final TagKey API_STATUS = TagKey.create("api_status");
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}
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public static final class Measures {
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private Measures() {}
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public static final MeasureLong LATENCY =
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MeasureLong.create(
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"maps.googleapis.com/measure/client/latency",
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"Total time between library method called and results returned",
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"ms");
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public static final MeasureLong NETWORK_LATENCY =
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MeasureLong.create(
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"maps.googleapis.com/measure/client/network_latency",
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"Network time inside the library",
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"ms");
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public static final MeasureLong RETRY_COUNT =
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MeasureLong.create(
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"maps.googleapis.com/measure/client/retry_count",
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"How many times any request was retried",
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"1");
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}
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private static final class Aggregations {
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private Aggregations() {}
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private static final Aggregation COUNT = Count.create();
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private static final Aggregation DISTRIBUTION_INTEGERS_10 =
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Distribution.create(
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BucketBoundaries.create(
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Arrays.asList(0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0)));
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// every bucket is ~25% bigger = 20 * 2^(N/3)
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private static final Aggregation DISTRIBUTION_LATENCY =
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Distribution.create(
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BucketBoundaries.create(
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Arrays.asList(
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0.0, 20.0, 25.2, 31.7, 40.0, 50.4, 63.5, 80.0, 100.8, 127.0, 160.0, 201.6,
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254.0, 320.0, 403.2, 508.0, 640.0, 806.3, 1015.9, 1280.0, 1612.7, 2031.9,
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2560.0, 3225.4, 4063.7)));
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}
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public static final class Views {
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private Views() {}
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private static final List<TagKey> fields =
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tags(Tags.REQUEST_NAME, Tags.HTTP_CODE, Tags.API_STATUS);
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public static final View REQUEST_COUNT =
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View.create(
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View.Name.create("maps.googleapis.com/client/request_count"),
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"Request counts",
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Measures.LATENCY,
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Aggregations.COUNT,
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fields);
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public static final View REQUEST_LATENCY =
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View.create(
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View.Name.create("maps.googleapis.com/client/request_latency"),
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"Latency in msecs",
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Measures.LATENCY,
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Aggregations.DISTRIBUTION_LATENCY,
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fields);
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public static final View NETWORK_LATENCY =
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View.create(
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View.Name.create("maps.googleapis.com/client/network_latency"),
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"Network latency in msecs (internal)",
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Measures.NETWORK_LATENCY,
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Aggregations.DISTRIBUTION_LATENCY,
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fields);
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public static final View RETRY_COUNT =
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View.create(
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View.Name.create("maps.googleapis.com/client/retry_count"),
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"Retries per request",
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Measures.RETRY_COUNT,
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Aggregations.DISTRIBUTION_INTEGERS_10,
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fields);
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}
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public static void registerAllViews() {
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registerAllViews(Stats.getViewManager());
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}
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public static void registerAllViews(ViewManager viewManager) {
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View[] views_to_register =
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new View[] {
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Views.REQUEST_COUNT, Views.REQUEST_LATENCY, Views.NETWORK_LATENCY, Views.RETRY_COUNT
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};
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for (View view : views_to_register) {
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viewManager.registerView(view);
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}
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}
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private static List<TagKey> tags(TagKey... items) {
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return Collections.unmodifiableList(Arrays.asList(items));
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}
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}

‎src/main/java/com/google/maps/metrics/OpenCensusRequestMetrics.java‎

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package com.google.maps.metrics;
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import io.opencensus.stats.StatsRecorder;
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import io.opencensus.tags.TagContext;
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import io.opencensus.tags.TagValue;
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import io.opencensus.tags.Tagger;
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/** An OpenCensus logger that generates success and latency metrics. */
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final class OpenCensusRequestMetrics implements RequestMetrics {
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private final String requestName;
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private final Tagger tagger;
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private final StatsRecorder statsRecorder;
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private long requestStart;
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private long networkStart;
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private long networkTime;
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private boolean finished;
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OpenCensusRequestMetrics(String requestName, Tagger tagger, StatsRecorder statsRecorder) {
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this.requestName = requestName;
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this.tagger = tagger;
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this.statsRecorder = statsRecorder;
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this.requestStart = milliTime();
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this.networkStart = milliTime();
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this.networkTime = 0;
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this.finished = false;
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}
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@Override
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public void startNetwork() {
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this.networkStart = milliTime();
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}
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@Override
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public void endNetwork() {
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this.networkTime += milliTime() - this.networkStart;
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}
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@Override
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public void endRequest(Exception exception, int httpStatusCode, long retryCount) {
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// multiple endRequest are ignored
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if (this.finished) {
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return;
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}
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this.finished = true;
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long requestTime = milliTime() - this.requestStart;
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TagContext tagContext =
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tagger
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.currentBuilder()
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.putLocal(OpenCensusMetrics.Tags.REQUEST_NAME, TagValue.create(requestName))
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.putLocal(
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OpenCensusMetrics.Tags.HTTP_CODE, TagValue.create(Integer.toString(httpStatusCode)))
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.putLocal(OpenCensusMetrics.Tags.API_STATUS, TagValue.create(exceptionName(exception)))
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.build();
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statsRecorder
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.newMeasureMap()
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.put(OpenCensusMetrics.Measures.LATENCY, requestTime)
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.put(OpenCensusMetrics.Measures.NETWORK_LATENCY, this.networkTime)
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.put(OpenCensusMetrics.Measures.RETRY_COUNT, retryCount)
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.record(tagContext);
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}
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private String exceptionName(Exception exception) {
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if (exception == null) {
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return "";
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} else {
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return exception.getClass().getName();
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}
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}
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private long milliTime() {
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return System.currentTimeMillis();
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}
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}

‎src/main/java/com/google/maps/metrics/OpenCensusRequestMetricsReporter.java‎

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package com.google.maps.metrics;
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import io.opencensus.stats.Stats;
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import io.opencensus.stats.StatsRecorder;
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import io.opencensus.tags.Tagger;
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import io.opencensus.tags.Tags;
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/** An OpenCensus logger that generates success and latency metrics. */
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public final class OpenCensusRequestMetricsReporter implements RequestMetricsReporter {
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private static final Tagger tagger = Tags.getTagger();
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private static final StatsRecorder statsRecorder = Stats.getStatsRecorder();
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public OpenCensusRequestMetricsReporter() {}
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@Override
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public RequestMetrics newRequest(String requestName) {
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return new OpenCensusRequestMetrics(requestName, tagger, statsRecorder);
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}
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}

‎src/test/java/com/google/maps/metrics/OpenCensusTest.java‎

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package com.google.maps;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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import static org.junit.Assert.assertTrue;
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import com.google.maps.internal.ApiConfig;
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import com.google.maps.metrics.OpenCensusMetrics;
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import com.google.maps.metrics.OpenCensusRequestMetricsReporter;
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import com.google.maps.model.GeocodingResult;
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import io.opencensus.stats.AggregationData;
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import io.opencensus.stats.Stats;
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import io.opencensus.stats.View;
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import io.opencensus.stats.ViewData;
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import io.opencensus.tags.TagValue;
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import java.io.IOException;
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import java.util.Arrays;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.TimeUnit;
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import okhttp3.mockwebserver.MockResponse;
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import okhttp3.mockwebserver.MockWebServer;
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import org.junit.After;
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import org.junit.Before;
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import org.junit.Test;
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import org.junit.experimental.categories.Category;
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@Category(MediumTests.class)
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public class OpenCensusTest {
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private MockWebServer server;
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private GeoApiContext context;
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@Before
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public void Setup() {
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server = new MockWebServer();
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context =
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new GeoApiContext.Builder()
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.apiKey("AIza...")
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.requestMetricsReporter(new OpenCensusRequestMetricsReporter())
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.baseUrlOverride("http://127.0.0.1:" + server.getPort())
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.build();
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OpenCensusMetrics.registerAllViews();
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}
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@After
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@SuppressWarnings("CatchAndPrintStackTrace")
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public void Teardown() {
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try {
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server.shutdown();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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private MockResponse mockResponse(int code, String status, int delayMs) {
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MockResponse response = new MockResponse();
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response.setResponseCode(code);
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if (status != null) {
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response.setBody("{\"results\" : [{}], \"status\" : \"" + status + "\" }");
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}
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response.setBodyDelay(delayMs, TimeUnit.MILLISECONDS);
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return response;
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}
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private void sleep(int milliseconds) {
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try {
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TimeUnit.MILLISECONDS.sleep(milliseconds);
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} catch (Exception e) {
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}
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}
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private Map.Entry<List<TagValue>, AggregationData> getMetric(String name) {
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sleep(10);
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ViewData viewData = Stats.getViewManager().getView(View.Name.create(name));
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Map<List<TagValue>, AggregationData> values = viewData.getAggregationMap();
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assertEquals(1, values.size());
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for (Map.Entry<List<TagValue>, AggregationData> entry : values.entrySet()) {
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return entry;
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}
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return null;
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}
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@Test
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public void testSuccess() throws Exception {
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server.enqueue(mockResponse(500, "OK", 100)); // retry 1
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server.enqueue(mockResponse(500, "OK", 100)); // retry 2
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server.enqueue(mockResponse(200, "OK", 300)); // succeed
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GeocodingResult[] result =
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context.get(new ApiConfig("/path"), GeocodingApi.Response.class, "k", "v").await();
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assertEquals(1, result.length);
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List<TagValue> tags =
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Arrays.asList(TagValue.create(""), TagValue.create("200"), TagValue.create("/path"));
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Map.Entry<List<TagValue>, AggregationData> latencyMetric =
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getMetric("maps.googleapis.com/client/request_latency");
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assertNotNull(latencyMetric);
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assertEquals(tags, latencyMetric.getKey());
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AggregationData.DistributionData latencyDist =
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(AggregationData.DistributionData) latencyMetric.getValue();
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assertEquals(1, latencyDist.getCount());
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assertTrue(latencyDist.getMean() > 500);
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Map.Entry<List<TagValue>, AggregationData> retryMetric =
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getMetric("maps.googleapis.com/client/retry_count");
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assertNotNull(retryMetric);
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assertEquals(tags, retryMetric.getKey());
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AggregationData.DistributionData retryDist =
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(AggregationData.DistributionData) retryMetric.getValue();
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assertEquals(1, retryDist.getCount());
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assertEquals(2.0, retryDist.getMean(), 0.1);
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Map.Entry<List<TagValue>, AggregationData> countMetric =
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getMetric("maps.googleapis.com/client/request_count");
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assertNotNull(countMetric);
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assertEquals(tags, countMetric.getKey());
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AggregationData.CountData count = (AggregationData.CountData) countMetric.getValue();
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assertEquals(1, count.getCount());
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}
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}

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