Add util contrib package for AppEngine standard. (#1214)

12 files changed, 403 insertions, 20 deletions

diff --git a/.gitignore b/.gitignore
index 685c85a3..a6064114 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,9 @@ gradle.properties
 local.properties
 out/
 
+# Protobuf
+gen_gradle
+
 # Bazel
 bazel-*
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9bccb10f..9b4f4c52 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@
 - Remove namespace and help message prefix for Prometheus exporter. This could be
   a breaking change if you have Prometheus metrics from OpenCensus Prometheus exporter
   of previous versions, please point to the new metrics with no namespace instead.
+- Add an util artifact `opencensus-contrib-appengine-standard-util` to interact with the AppEngine
+  CloudTraceContext.
 
 ## 0.13.2 - 2018-05-08
 - Map http attributes to Stackdriver format (fix [#1153](https://github.com/census-instrumentation/opencensus-java/issues/1153)).
diff --git a/all/build.gradle b/all/build.gradle
index 044dc13f..f4255f39 100644
--- a/all/build.gradle
+++ b/all/build.gradle
@@ -13,6 +13,7 @@ def subprojects = [
         project(':opencensus-impl-lite'),
         project(':opencensus-testing'),
         project(':opencensus-contrib-agent'),
+        project(':opencensus-contrib-appengine-standard-util'),
         project(':opencensus-contrib-grpc-util'),
         project(':opencensus-contrib-grpc-metrics'),
         project(':opencensus-contrib-http-util'),
@@ -32,6 +33,7 @@ def subprojects_javadoc = [
         project(':opencensus-api'),
         project(':opencensus-testing'),
         project(':opencensus-contrib-agent'),
+        project(':opencensus-contrib-appengine-standard-util'),
         project(':opencensus-contrib-grpc-util'),
         project(':opencensus-contrib-grpc-metrics'),
         project(':opencensus-contrib-http-util'),
diff --git a/build.gradle b/build.gradle
index 28900f0a..3927cdda 100644
--- a/build.gradle
+++ b/build.gradle
@@ -74,6 +74,8 @@ subprojects {
         if (useErrorProne) {
             if (JavaVersion.current().isJava8Compatible()) {
                 it.options.compilerArgs += ["-XepDisableWarningsInGeneratedCode"]
+                // Exclude generated protobuf from error-prone checks.
+                it.options.compilerArgs += ["-XepExcludedPaths:.*/gen_gradle/.*"]
                 // TODO(bdrutu): Read files directly instead of reading from properties.
                 if (rootProject.hasProperty("errorProneWarnings")) {
                     it.options.compilerArgs += rootProject.properties["errorProneWarnings"].split(',').collect {
@@ -105,6 +107,9 @@ subprojects {
             ]
         }
         it.options.encoding = "UTF-8"
+        // Protobuf-generated code produces some warnings.
+        // https://github.com/google/protobuf/issues/2718
+        it.options.compilerArgs += ["-Xlint:-cast"]
         if (!JavaVersion.current().isJava9()) {
             // TODO(sebright): Enable -Werror for Java 9 once we upgrade AutoValue (issue #1017).
             it.options.compilerArgs += ["-Werror"]
@@ -151,6 +156,7 @@ subprojects {
     }
 
     ext {
+        appengineVersion = '1.9.63'
         autoValueVersion = '1.4'
         findBugsVersion = '3.0.1'
         errorProneVersion = '2.2.0'
@@ -160,10 +166,12 @@ subprojects {
         googleCloudVersion = '0.47.0-beta'
         signalfxVersion = '0.0.39'
         prometheusVersion = '0.4.0'
+        protobufVersion = '3.5.1'
         zipkinReporterVersion = '2.3.2'
         jaegerReporterVersion = '0.24.0'
 
         libraries = [
+                appengine_api: "com.google.appengine:appengine-api-1.0-sdk:${appengineVersion}",
                 auto_value: "com.google.auto.value:auto-value:${autoValueVersion}",
                 auto_service: 'com.google.auto.service:auto-service:1.0-rc3',
                 byte_buddy: 'net.bytebuddy:byte-buddy:1.7.11',
@@ -183,6 +191,7 @@ subprojects {
                 jsr305: "com.google.code.findbugs:jsr305:${findBugsVersion}",
                 signalfx_java: "com.signalfx.public:signalfx-java:${signalfxVersion}",
                 prometheus_simpleclient: "io.prometheus:simpleclient:${prometheusVersion}",
+                protobuf: "com.google.protobuf:protobuf-java:${protobufVersion}",
 
                 // Test dependencies.
                 guava_testlib: "com.google.guava:guava-testlib:${guavaVersion}",
@@ -359,6 +368,7 @@ subprojects {
     uploadArchives.onlyIf {
         name in ['opencensus-api',
                  'opencensus-contrib-agent',
+                 'opencensus-contrib-appengine-standard-util',
                  'opencensus-contrib-grpc-metrics',
                  'opencensus-contrib-grpc-util',
                  'opencensus-contrib-http-util',
@@ -397,7 +407,7 @@ subprojects {
                     compile.options.compilerArgs += [
                         '-Xmaxerrs', '10000',
                         "-Xbootclasspath/p:${configurations.checkerFrameworkAnnotatedJDK.asPath}",
-                        "-AskipDefs=\\.AutoValue_",
+                        "-AskipDefs=[\\.AutoValue_|\\.TraceIdProto]",
                         "-AinvariantArrays"
                     ]
                     options.fork = true
diff --git a/buildscripts/import-control.xml b/buildscripts/import-control.xml
index 38cd747d..845bcc87 100644
--- a/buildscripts/import-control.xml
+++ b/buildscripts/import-control.xml
@@ -73,6 +73,10 @@ General guidelines on imports:
       <allow pkg="io.opencensus.trace"/>
       <allow pkg="net.bytebuddy"/>
     </subpackage>
+    <subpackage name="appengine.standard.util">
+      <allow pkg="com.google.apphosting"/>
+      <allow pkg="io.opencensus.trace"/>
+    </subpackage>
     <subpackage name="grpc.metrics">
       <allow pkg="io.opencensus.contrib.grpc.metrics"/>
       <allow pkg="io.opencensus.stats"/>
diff --git a/contrib/appengine_standard_util/README.md b/contrib/appengine_standard_util/README.md
new file mode 100644
index 00000000..ba1a4871
--- /dev/null
+++ b/contrib/appengine_standard_util/README.md
@@ -0,0 +1,35 @@
+# OpenCensus AppEngine Standard Util
+[![Build Status][travis-image]][travis-url]
+[![Windows Build Status][appveyor-image]][appveyor-url]
+[![Maven Central][maven-image]][maven-url]
+
+The *OpenCensus AppEngine Standard Util for Java* is a collection of utilities for trace
+instrumentation when working with [AppEngine][appengine-url].
+
+## Quickstart
+
+### Add the dependencies to your project
+
+For Maven add to your `pom.xml`:
+```xml
+<dependencies>
+  <dependency>
+    <groupId>io.opencensus</groupId>
+    <artifactId>opencensus-appengine-standard-util</artifactId>
+    <version>0.14.0</version>
+  </dependency>
+</dependencies>
+```
+
+For Gradle add to your dependencies:
+```gradle
+compile 'io.opencensus:opencensus-contrib-appengine-standard-util:0.14.0'
+```
+
+[travis-image]: https://travis-ci.org/census-instrumentation/opencensus-java.svg?branch=master
+[travis-url]: https://travis-ci.org/census-instrumentation/opencensus-java
+[appveyor-image]: https://ci.appveyor.com/api/projects/status/hxthmpkxar4jq4be/branch/master?svg=true
+[appveyor-url]: https://ci.appveyor.com/project/opencensusjavateam/opencensus-java/branch/master
+[maven-image]: https://maven-badges.herokuapp.com/maven-central/io.opencensus/opencensus-contrib-appengine-standard-util/badge.svg
+[maven-url]: https://maven-badges.herokuapp.com/maven-central/io.opencensus/opencensus-contrib-appengine-standard-util
+[appengine-url]: https://appengine.google.com/
diff --git a/contrib/appengine_standard_util/build.gradle b/contrib/appengine_standard_util/build.gradle
new file mode 100644
index 00000000..a5c122a6
--- /dev/null
+++ b/contrib/appengine_standard_util/build.gradle
@@ -0,0 +1,52 @@
+description = 'OpenCensus AppEngine Standard Util'
+
+apply plugin: 'java'
+apply plugin: 'com.google.protobuf'
+
+def protocVersion = '3.5.1-1'
+
+buildscript {
+    repositories {
+        maven { url "https://plugins.gradle.org/m2/" }
+    }
+    dependencies {
+        classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.5"
+    }
+}
+
+[compileJava, compileTestJava].each() {
+    it.sourceCompatibility = 1.7
+    it.targetCompatibility = 1.7
+}
+
+dependencies {
+    compile project(':opencensus-api'),
+            libraries.appengine_api,
+            libraries.guava,
+            libraries.protobuf
+
+    signature "org.codehaus.mojo.signature:java18:+@signature"
+}
+
+protobuf {
+    protoc {
+        // The artifact spec for the Protobuf Compiler
+        artifact = "com.google.protobuf:protoc:${protocVersion}"
+    }
+
+    generatedFilesBaseDir = "$projectDir/gen_gradle/src"
+
+    generateProtoTasks {
+        all().each { task ->
+            task.builtins {
+                java {
+                    option 'annotate_code'
+                }
+            }
+        }
+    }
+}
+
+clean {
+    delete protobuf.generatedFilesBaseDir
+}
diff --git a/contrib/appengine_standard_util/src/main/java/io/opencensus/contrib/appengine/standard/util/AppEngineCloudTraceContextUtils.java b/contrib/appengine_standard_util/src/main/java/io/opencensus/contrib/appengine/standard/util/AppEngineCloudTraceContextUtils.java
new file mode 100644
index 00000000..aff2ee3e
--- /dev/null
+++ b/contrib/appengine_standard_util/src/main/java/io/opencensus/contrib/appengine/standard/util/AppEngineCloudTraceContextUtils.java
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2018, OpenCensus Authors
+ *
+ * Licensed 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 io.opencensus.contrib.appengine.standard.util;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.apphosting.api.CloudTraceContext;
+import com.google.common.annotations.VisibleForTesting;
+import io.opencensus.trace.SpanContext;
+import io.opencensus.trace.SpanId;
+import io.opencensus.trace.TraceId;
+import io.opencensus.trace.TraceOptions;
+import java.nio.ByteBuffer;
+
+/**
+ * Utility class to convert between {@link io.opencensus.trace.SpanContext} and {@link
+ * CloudTraceContext}.
+ *
+ * @since 0.14
+ */
+public final class AppEngineCloudTraceContextUtils {
+  private static final byte[] INVALID_TRACE_ID =
+      TraceIdProto.newBuilder().setHi(0).setLo(0).build().toByteArray();
+  private static final long INVALID_SPAN_ID = 0L;
+  private static final long INVALID_TRACE_MASK = 0L;
+
+  @VisibleForTesting
+  static final CloudTraceContext INVALID_CLOUD_TRACE_CONTEXT =
+      new CloudTraceContext(INVALID_TRACE_ID, INVALID_SPAN_ID, INVALID_TRACE_MASK);
+
+  /**
+   * Converts AppEngine {@code CloudTraceContext} to {@code SpanContext}.
+   *
+   * @param cloudTraceContext the AppEngine {@code CloudTraceContext}.
+   * @return the converted {@code SpanContext}.
+   * @since 0.14
+   */
+  public static SpanContext fromCloudTraceContext(CloudTraceContext cloudTraceContext) {
+    checkNotNull(cloudTraceContext, "cloudTraceContext");
+
+    try {
+      // Extract the trace ID from the binary protobuf CloudTraceContext#traceId.
+      TraceIdProto traceIdProto = TraceIdProto.parseFrom(cloudTraceContext.getTraceId());
+      ByteBuffer traceIdBuf = ByteBuffer.allocate(TraceId.SIZE);
+      traceIdBuf.putLong(traceIdProto.getHi());
+      traceIdBuf.putLong(traceIdProto.getLo());
+      ByteBuffer spanIdBuf = ByteBuffer.allocate(SpanId.SIZE);
+      spanIdBuf.putLong(cloudTraceContext.getSpanId());
+
+      return SpanContext.create(
+          TraceId.fromBytes(traceIdBuf.array()),
+          SpanId.fromBytes(spanIdBuf.array()),
+          TraceOptions.builder().setIsSampled(cloudTraceContext.isTraceEnabled()).build());
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  /**
+   * Converts {@code SpanContext} to AppEngine {@code CloudTraceContext}.
+   *
+   * @param spanContext the {@code SpanContext}.
+   * @return the converted AppEngine {@code CloudTraceContext}.
+   * @since 0.14
+   */
+  public static CloudTraceContext toCloudTraceContext(SpanContext spanContext) {
+    checkNotNull(spanContext, "spanContext");
+
+    ByteBuffer traceIdBuf = ByteBuffer.wrap(spanContext.getTraceId().getBytes());
+    TraceIdProto traceIdProto =
+        TraceIdProto.newBuilder().setHi(traceIdBuf.getLong()).setLo(traceIdBuf.getLong()).build();
+    ByteBuffer spanIdBuf = ByteBuffer.wrap(spanContext.getSpanId().getBytes());
+
+    return new CloudTraceContext(
+        traceIdProto.toByteArray(),
+        spanIdBuf.getLong(),
+        spanContext.getTraceOptions().isSampled() ? 1L : 0L);
+  }
+
+  private AppEngineCloudTraceContextUtils() {}
+}
diff --git a/contrib/appengine_standard_util/src/main/proto/trace_id.proto b/contrib/appengine_standard_util/src/main/proto/trace_id.proto
new file mode 100644
index 00000000..35e2e087
--- /dev/null
+++ b/contrib/appengine_standard_util/src/main/proto/trace_id.proto
@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "io.opencensus.contrib.appengine.standard.util";
+option java_outer_classname = "TraceProto";
+
+message TraceIdProto {
+  fixed64 hi = 1;
+  fixed64 lo = 2;
+}
diff --git a/contrib/appengine_standard_util/src/test/java/io/opencensus/contrib/appengine/standard/util/AppEngineCloudTraceContextUtilsTest.java b/contrib/appengine_standard_util/src/test/java/io/opencensus/contrib/appengine/standard/util/AppEngineCloudTraceContextUtilsTest.java
new file mode 100644
index 00000000..dc53d8f3
--- /dev/null
+++ b/contrib/appengine_standard_util/src/test/java/io/opencensus/contrib/appengine/standard/util/AppEngineCloudTraceContextUtilsTest.java
@@ -0,0 +1,161 @@
+/*
+ * Copyright 2018, OpenCensus Authors
+ *
+ * Licensed 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 io.opencensus.contrib.appengine.standard.util;
+
+import static com.google.common.truth.Truth.assertThat;
+import static io.opencensus.contrib.appengine.standard.util.AppEngineCloudTraceContextUtils.INVALID_CLOUD_TRACE_CONTEXT;
+
+import com.google.apphosting.api.CloudTraceContext;
+import io.opencensus.trace.SpanContext;
+import io.opencensus.trace.SpanId;
+import io.opencensus.trace.TraceId;
+import io.opencensus.trace.TraceOptions;
+import java.util.Arrays;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link AppEngineCloudTraceContextUtils}. */
+@RunWith(JUnit4.class)
+public class AppEngineCloudTraceContextUtilsTest {
+  @Test
+  public void toFromSampledCloudTraceContext() {
+    CloudTraceContext cloudTraceContext =
+        new CloudTraceContext(
+            // Protobuf-encoded upper and lower 64 bits of the example trace ID
+            // fae1c6346b9cf9a272cb6504b5a10dcc/123456789.
+            new byte[] {
+              (byte) 0x09,
+              (byte) 0xa2,
+              (byte) 0xf9,
+              (byte) 0x9c,
+              (byte) 0x6b,
+              (byte) 0x34,
+              (byte) 0xc6,
+              (byte) 0xe1,
+              (byte) 0xfa,
+              (byte) 0x11,
+              (byte) 0xcc,
+              (byte) 0x0d,
+              (byte) 0xa1,
+              (byte) 0xb5,
+              (byte) 0x04,
+              (byte) 0x65,
+              (byte) 0xcb,
+              (byte) 0x72
+            },
+            Long.MIN_VALUE,
+            // Trace enabled.
+            1L);
+
+    SpanContext spanContext =
+        AppEngineCloudTraceContextUtils.fromCloudTraceContext(cloudTraceContext);
+
+    assertThat(spanContext)
+        .isEqualTo(
+            SpanContext.create(
+                TraceId.fromLowerBase16("fae1c6346b9cf9a272cb6504b5a10dcc"),
+                SpanId.fromLowerBase16("8000000000000000"),
+                TraceOptions.builder().setIsSampled(true).build()));
+
+    // CloudTraceContext does not implement equals, so need to check every argument.
+    CloudTraceContext newCloudTraceContext =
+        AppEngineCloudTraceContextUtils.toCloudTraceContext(spanContext);
+    assertThat(newCloudTraceContext.getTraceId()).isEqualTo(cloudTraceContext.getTraceId());
+    assertThat(newCloudTraceContext.getSpanId()).isEqualTo(cloudTraceContext.getSpanId());
+    assertThat(newCloudTraceContext.getTraceMask()).isEqualTo(cloudTraceContext.getTraceMask());
+  }
+
+  @Test
+  public void toFromNotSampledCloudTraceContext() {
+    CloudTraceContext cloudTraceContext =
+        new CloudTraceContext(
+            // Protobuf-encoded upper and lower 64 bits of the example trace ID
+            // fae1c6346b9cf9a272cb6504b5a10dcc/123456789.
+            new byte[] {
+              (byte) 0x09,
+              (byte) 0xa2,
+              (byte) 0xf9,
+              (byte) 0x9c,
+              (byte) 0x6b,
+              (byte) 0x34,
+              (byte) 0xc6,
+              (byte) 0xe1,
+              (byte) 0xfa,
+              (byte) 0x11,
+              (byte) 0xcc,
+              (byte) 0x0d,
+              (byte) 0xa1,
+              (byte) 0xb5,
+              (byte) 0x04,
+              (byte) 0x65,
+              (byte) 0xcb,
+              (byte) 0x72
+            },
+            Long.MIN_VALUE,
+            // Trace disabled.
+            0L);
+
+    SpanContext spanContext =
+        AppEngineCloudTraceContextUtils.fromCloudTraceContext(cloudTraceContext);
+
+    assertThat(spanContext)
+        .isEqualTo(
+            SpanContext.create(
+                TraceId.fromLowerBase16("fae1c6346b9cf9a272cb6504b5a10dcc"),
+                SpanId.fromLowerBase16("8000000000000000"),
+                TraceOptions.builder().setIsSampled(false).build()));
+
+    // CloudTraceContext does not implement equals, so need to check every argument.
+    assertThat(
+            cloudTraceContextEquals(
+                AppEngineCloudTraceContextUtils.toCloudTraceContext(spanContext),
+                cloudTraceContext))
+        .isTrue();
+  }
+
+  @Test(expected = NullPointerException.class)
+  public void toCloudTraceContext_Null() {
+    AppEngineCloudTraceContextUtils.fromCloudTraceContext(null);
+  }
+
+  @Test
+  public void toCloudTraceContext_Invalid() {
+    assertThat(AppEngineCloudTraceContextUtils.fromCloudTraceContext(INVALID_CLOUD_TRACE_CONTEXT))
+        .isEqualTo(SpanContext.INVALID);
+  }
+
+  @Test(expected = NullPointerException.class)
+  public void fromCloudTraceContext_Null() {
+    AppEngineCloudTraceContextUtils.toCloudTraceContext(null);
+  }
+
+  @Test
+  public void fromCloudTraceContext_Invalid() {
+    assertThat(
+            cloudTraceContextEquals(
+                AppEngineCloudTraceContextUtils.toCloudTraceContext(SpanContext.INVALID),
+                INVALID_CLOUD_TRACE_CONTEXT))
+        .isTrue();
+  }
+
+  private static boolean cloudTraceContextEquals(CloudTraceContext obj1, CloudTraceContext obj2) {
+    return Arrays.equals(obj1.getTraceId(), obj2.getTraceId())
+        && obj1.getSpanId() == obj2.getSpanId()
+        && obj1.getTraceMask() == obj2.getTraceMask();
+  }
+}
diff --git a/findbugs-exclude.xml b/findbugs-exclude.xml
index 87002bd0..78b915b9 100644
--- a/findbugs-exclude.xml
+++ b/findbugs-exclude.xml
@@ -2,38 +2,44 @@
   <Match>
     <!-- Reason: Null has a different meaning than a zero-length array in this case. -->
     <Bug pattern="PZLA_PREFER_ZERO_LENGTH_ARRAYS"/>
-    <Class name="io.opencensus.stats.MutableDistribution" />
-    <Method name="getInternalBucketCountsArray" />
+    <Class name="io.opencensus.stats.MutableDistribution"/>
+    <Method name="getInternalBucketCountsArray"/>
   </Match>
   <Match>
     <!-- Reason: Equal is implemented in the AutoValue generated class. -->
     <Bug pattern="EQ_COMPARETO_USE_OBJECT_EQUALS"/>
-    <Class name="io.opencensus.common.Timestamp" />
-    <Method name="compareTo" />
+    <Class name="io.opencensus.common.Timestamp"/>
+    <Method name="compareTo"/>
   </Match>
   <Match>
     <!-- Reason: Equal is implemented in the AutoValue generated class. -->
     <Bug pattern="EQ_COMPARETO_USE_OBJECT_EQUALS"/>
-    <Class name="io.opencensus.common.Duration" />
-    <Method name="compareTo" />
+    <Class name="io.opencensus.common.Duration"/>
+    <Method name="compareTo"/>
   </Match>
   <Match>
     <!-- Reason: BaseMessageEvent only has two visible subclasses. -->
     <Bug pattern="BC_UNCONFIRMED_CAST"/>
-    <Class name="io.opencensus.trace.internal.BaseMessageEventUtils" />
+    <Class name="io.opencensus.trace.internal.BaseMessageEventUtils"/>
   </Match>
   <Match>
     <!-- Reason: This test is testing for a NPE. -->
     <Bug pattern="NP_NONNULL_PARAM_VIOLATION"/>
-    <Class name="io.opencensus.internal.UtilsTest" />
-    <Method name="checkNotNull" />
+    <Class name="io.opencensus.internal.UtilsTest"/>
+    <Method name="checkNotNull"/>
   </Match>
   <Match>
     <!-- Reason: It seems like FindBugs incorrectly assumes that all -->
     <!-- Throwables are subclasses of Error or Exception. -->
     <Bug pattern="BC_VACUOUS_INSTANCEOF"/>
-    <Class name="io.opencensus.trace.CurrentSpanUtils$CallableInSpan" />
-    <Method name="call" />
+    <Class name="io.opencensus.trace.CurrentSpanUtils$CallableInSpan"/>
+    <Method name="call"/>
+  </Match>
+  <Match>
+    <!-- Reason: Protobuf auto-generated code. -->
+    <Bug pattern="UCF_USELESS_CONTROL_FLOW"/>
+    <Class name="io.opencensus.contrib.appengine.standard.util.TraceIdProto$Builder"/>
+    <Method name="maybeForceBuilderInitialization"/>
   </Match>
 
   <!-- Suppress some FindBugs warnings related to performance or robustness -->
@@ -41,27 +47,27 @@
   <Match>
     <!-- Reason: Only needed for performance. -->
     <Bug pattern="SIC_INNER_SHOULD_BE_STATIC_ANON"/>
-    <Source name="~.*Test\.java" />
+    <Source name="~.*Test\.java"/>
   </Match>
   <Match>
     <!-- Reason: Only needed for performance. -->
     <Bug pattern="WMI_WRONG_MAP_ITERATOR"/>
-    <Source name="~.*Test\.java" />
+    <Source name="~.*Test\.java"/>
   </Match>
   <Match>
     <!-- Reason: Only needed for performance. -->
     <Bug pattern="UM_UNNECESSARY_MATH"/>
-    <Source name="~.*Test\.java" />
+    <Source name="~.*Test\.java"/>
   </Match>
   <Match>
     <!-- Reason: This is less important in a test environment. -->
     <Bug pattern="DP_CREATE_CLASSLOADER_INSIDE_DO_PRIVILEGED"/>
-    <Source name="~.*Test\.java" />
+    <Source name="~.*Test\.java"/>
   </Match>
   <Match>
     <!-- Reason: Many classes initialize fields in @Before methods. -->
     <Bug pattern="UWF_FIELD_NOT_INITIALIZED_IN_CONSTRUCTOR"/>
-    <Source name="~.*Test\.java" />
+    <Source name="~.*Test\.java"/>
   </Match>
 
   <!-- Suppress all FindBugs warnings about NullPointerExceptions in -->
@@ -71,19 +77,19 @@
   <Match>
     <Bug code="NP"/>
     <Not>
-      <Source name="~.*Test\.java" />
+      <Source name="~.*Test\.java"/>
     </Not>
   </Match>
   <Match>
     <Bug pattern="UR_UNINIT_READ"/>
     <Not>
-      <Source name="~.*Test\.java" />
+      <Source name="~.*Test\.java"/>
     </Not>
   </Match>
   <Match>
     <Bug pattern="UWF_FIELD_NOT_INITIALIZED_IN_CONSTRUCTOR"/>
     <Not>
-      <Source name="~.*Test\.java" />
+      <Source name="~.*Test\.java"/>
     </Not>
   </Match>
 </FindBugsFilter>
diff --git a/settings.gradle b/settings.gradle
index 3d9a0ee0..92c19282 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -14,6 +14,7 @@ include ":opencensus-exporter-stats-signalfx"
 include ":opencensus-exporter-stats-stackdriver"
 include ":opencensus-exporter-stats-prometheus"
 include ":opencensus-contrib-agent"
+include ":opencensus-contrib-appengine-standard-util"
 include ":opencensus-contrib-grpc-metrics"
 include ":opencensus-contrib-grpc-util"
 include ":opencensus-contrib-http-util"
@@ -25,6 +26,8 @@ project(':opencensus-impl-lite').projectDir = "$rootDir/impl_lite" as File
 project(':opencensus-impl').projectDir = "$rootDir/impl" as File
 project(':opencensus-testing').projectDir = "$rootDir/testing" as File
 project(':opencensus-contrib-agent').projectDir = "$rootDir/contrib/agent" as File
+project(':opencensus-contrib-appengine-standard-util').projectDir =
+        "$rootDir/contrib/appengine_standard_util" as File
 project(':opencensus-contrib-grpc-metrics').projectDir = "$rootDir/contrib/grpc_metrics" as File
 project(':opencensus-contrib-grpc-util').projectDir = "$rootDir/contrib/grpc_util" as File
 project(':opencensus-contrib-http-util').projectDir = "$rootDir/contrib/http_util" as File