WIP: tracecontext

brave-bom/pom.xml

@@ -272,6 +272,11 @@
         <artifactId>brave-spring-beans</artifactId>
         <version>${project.version}</version>
       </dependency>
+      <dependency>
+        <groupId>${project.groupId}</groupId>
+        <artifactId>brave-propagation-w3c</artifactId>
+        <version>${project.version}</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>
 </project>

instrumentation/benchmarks/pom.xml

@@ -239,6 +239,12 @@
       <artifactId>grpc-core</artifactId>
       <version>${grpc.version}</version>
     </dependency>
+
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>brave-propagation-w3c</artifactId>
+      <version>${project.version}</version>
+    </dependency>
   </dependencies>
 
   <build>

instrumentation/benchmarks/src/main/java/brave/propagation/B3SinglePropagationBenchmarks.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2019 The OpenZipkin Authors
+ * Copyright 2013-2020 The OpenZipkin 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

instrumentation/benchmarks/src/main/java/brave/propagation/w3c/TraceContextPropagationBenchmarks.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2013-2020 The OpenZipkin 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 brave.propagation.w3c;
+
+import brave.internal.HexCodec;
+import brave.propagation.Propagation;
+import brave.propagation.TraceContext;
+import brave.propagation.TraceContext.Extractor;
+import brave.propagation.TraceContext.Injector;
+import brave.propagation.TraceContextOrSamplingFlags;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@Measurement(iterations = 5, time = 1)
+@Warmup(iterations = 10, time = 1)
+@Fork(3)
+@BenchmarkMode(Mode.SampleTime)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+public class TraceContextPropagationBenchmarks {
+  static final Propagation<String> tc =
+    TraceContextPropagation.FACTORY.create(Propagation.KeyFactory.STRING);
+  static final Injector<Map<String, String>> tcInjector = tc.injector(Map::put);
+  static final Extractor<Map<String, String>> tcExtractor = tc.extractor(Map::get);
+
+  static final TraceContext context = TraceContext.newBuilder()
+    .traceIdHigh(HexCodec.lowerHexToUnsignedLong("67891233abcdef01"))
+    .traceId(HexCodec.lowerHexToUnsignedLong("2345678912345678"))
+    .spanId(HexCodec.lowerHexToUnsignedLong("463ac35c9f6413ad"))
+    .sampled(true)
+    .build();
+
+  // TODO: add tracestate examples which prefer the b3 entry
+  static final Map<String, String> incoming128 = new LinkedHashMap<String, String>() {
+    {
+      put("traceparent", TraceparentFormat.writeTraceparentFormat(context));
+    }
+  };
+
+  static final Map<String, String> incomingPadded = new LinkedHashMap<String, String>() {
+    {
+      put("traceparent",
+        TraceparentFormat.writeTraceparentFormat(context.toBuilder().traceIdHigh(0).build()));
+    }
+  };
+
+  static final Map<String, String> incomingMalformed = new LinkedHashMap<String, String>() {
+    {
+      put("traceparent", "b970dafd-0d95-40aa-95d8-1d8725aebe40"); // not ok
+    }
+  };
+
+  static final Map<String, String> nothingIncoming = Collections.emptyMap();
+
+  @Benchmark public void inject() {
+    Map<String, String> carrier = new LinkedHashMap<>();
+    tcInjector.inject(context, carrier);
+  }
+
+  @Benchmark public TraceContextOrSamplingFlags extract_128() {
+    return tcExtractor.extract(incoming128);
+  }
+
+  @Benchmark public TraceContextOrSamplingFlags extract_padded() {
+    return tcExtractor.extract(incomingPadded);
+  }
+
+  @Benchmark public TraceContextOrSamplingFlags extract_nothing() {
+    return tcExtractor.extract(nothingIncoming);
+  }
+
+  @Benchmark public TraceContextOrSamplingFlags extract_malformed() {
+    return tcExtractor.extract(incomingMalformed);
+  }
+
+  // Convenience main entry-point
+  public static void main(String[] args) throws RunnerException {
+    Options opt = new OptionsBuilder()
+      .addProfiler("gc")
+      .include(".*" + TraceContextPropagationBenchmarks.class.getSimpleName())
+      .build();
+
+    new Runner(opt).run();
+  }
+}

pom.xml

@@ -132,6 +132,7 @@
     <module>brave-bom</module>
     <module>brave-tests</module>
     <module>context</module>
+    <module>propagation</module>
     <module>instrumentation</module>
     <module>spring-beans</module>
   </modules>

propagation/pom.xml

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright 2013-2020 The OpenZipkin 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.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>io.zipkin.brave</groupId>
+    <artifactId>brave-parent</artifactId>
+    <version>5.10.2-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>brave-propagation-parent</artifactId>
+  <name>Brave: Trace Propagation Formats</name>
+  <packaging>pom</packaging>
+
+  <properties>
+    <main.basedir>${project.basedir}/..</main.basedir>
+  </properties>
+
+  <modules>
+    <module>w3c</module>
+  </modules>
+
+  <dependencies>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>brave</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>brave-tests</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

propagation/w3c/RATIONALE.md

@@ -0,0 +1,62 @@
+# brave-propagation-w3c rationale
+
+## Trace Context Specification
+
+### Why do we write a tracestate entry?
+We write both "traceparent" and a "tracestate" entry for two reasons. The first is due to
+incompatibility between the "traceparent" format and our trace context. This is described in another
+section.
+
+The other reason is durability across hops. When your direct upstream is not the same tracing
+system, its span ID (which they call parentId in section 3.2.2.4) will not be valid: using it will
+break the trace. Instead, we look at our "tracestate" entry, which represents the last known place
+in the same system.
+
+### What is supported by Brave, but not by traceparent format?
+
+#### `SamplingFlags` can precede a trace
+B3 has always had the ability to influence the start of a trace with a sampling decision. For
+example, you can propagate `b3=0` to force the next hop to not trace the request. This is used for
+things like not sampling health checks. Conversely, you can force sampling by propagating `b3=d`
+(the debug flag). `traceparent` requires a trace ID and a span ID, so cannot propagate this.
+
+#### `TraceIdContext` (trace ID only)
+Amazon trace format can propagate a trace ID prior to starting a trace, for correlation purposes.
+`traceparent` requires a trace ID and a span ID, so cannot a trace ID standalone.
+
+#### Not yet sampled/ deferred decision
+B3 and Amazon formats support assigning a span ID prior to a sampling decision. `traceparent` has no
+way to tell the difference between an explicit no and lack of a decision, as it only has one bit
+flag.
+
+#### Debug flag
+B3 has always had a debug flag, which is a way to force a trace even if normal sampling says no.
+`traceparent` cannot distinguish between this and a normal decision, as it only has one bit flag.
+
+#### Trace-scoped sampling decision
+`traceparent` does not distinguish between a hop-level or a trace scoped decision in the format.
+This means that traces can be broken as it is valid to change the decision at every step (which
+breaks the hierarchy). This is the main reason why we need a separate `tracestate` entry.
+
+### Why serialize the trace context in two formats?
+
+The "traceparent" header is only portable to get the `TraceContext.traceId()` and
+`TraceContext.spanId()`. Section 3.2.2.5.1, the sampled flag, is incompatible with B3 sampling. The
+format also lacks fields for `TraceContext.parentId()` and `TraceContext.debug()`. This requires us
+to re-serialize the same context in two formats: one for compliance ("traceparent") and one that
+actually stores the context (B3 single format).
+
+The impact on users will be higher overhead and confusion when comparing the sampled value of
+"traceparent" which may be different than "b3".
+
+### Why is traceparent incompatible with B3?
+
+It may seem like incompatibility between "traceparent" and B3 were accidental, but that was not the
+case. The Zipkin community held the first meetings leading to this specification, and were directly
+involved in the initial design. Use cases of B3 were well known by working group members. Choices to
+become incompatible with B3 (and Amazon X-Ray format) sampling were conscious, as were decisions to
+omit other fields we use. These decisions were made in spite of protest from Zipkin community
+members and others. There is a rationale document for the specification, but the working group has
+so far not explained these decisions, or even mention B3 at all.
+
+https://github.com/w3c/trace-context/blob/d2ed8084780efcedab7e60c48b06ca3c00bea55c/http_header_format_rationale.md

propagation/w3c/README.md

@@ -0,0 +1,14 @@
+# brave-propagation-w3c
+
+This project includes propagation handlers for W3C defined headers.
+
+## Trace Context
+The [Trace Context][https://w3c.github.io/trace-context/] specification defines two headers:
+
+ * `traceparent` - almost the same as our [B3-single format](https://github.com/openzipkin/b3-propagation#single-header)
+ * `tracestate` - vendor-specific (or format-specific): may impact how to interpret `traceparent`
+
+This implementation can survive mixed systems who follow the specification and forward the
+`tracestate` header. When writing the `traceparent` header, this also overwrites the `tracestate`
+entry named 'b3' (in B3 single format). When reading headers, this entry is favored over the
+`traceparent`, allowing the the next span to re-attach to the last known 'b3' header.

propagation/w3c/pom.xml

@@ -0,0 +1,64 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright 2013-2020 The OpenZipkin 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.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <groupId>io.zipkin.brave</groupId>
+    <artifactId>brave-propagation-parent</artifactId>
+    <version>5.10.2-SNAPSHOT</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+
+  <artifactId>brave-propagation-w3c</artifactId>
+  <name>Brave Propagation: W3C Tracing headers (traceparent, tracestate, etc.)</name>
+
+  <properties>
+    <main.basedir>${project.basedir}/../..</main.basedir>
+    <main.java.version>1.6</main.java.version>
+    <main.signature.artifact>java16</main.signature.artifact>
+  </properties>
+
+  <dependencies>
+    <!-- to mock Platform calls -->
+    <dependency>
+      <groupId>org.powermock</groupId>
+      <artifactId>powermock-module-junit4</artifactId>
+      <version>${powermock.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.powermock</groupId>
+      <artifactId>powermock-api-mockito2</artifactId>
+      <version>${powermock.version}</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <artifactId>maven-jar-plugin</artifactId>
+        <configuration>
+          <archive>
+            <manifestEntries>
+              <Automatic-Module-Name>brave.propagation.w3c</Automatic-Module-Name>
+            </manifestEntries>
+          </archive>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>