[CURATOR-695] Open Telemetry tracing

.gitignore

@@ -41,11 +41,9 @@ Thumbs.db
 .gradle
 
 # Build output directies
-/target
-*/target
-/build
-*/build
-*/bin
+target/
+build/
+bin/
 
 # IntelliJ specific files/directories
 out

curator-client/pom.xml

@@ -26,11 +26,11 @@
     <parent>
         <groupId>org.apache.curator</groupId>
         <artifactId>apache-curator</artifactId>
-        <version>5.5.1-SNAPSHOT</version>
+        <version>5.6.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>curator-client</artifactId>
-    <version>5.5.1-SNAPSHOT</version>
+    <version>5.6.1-SNAPSHOT</version>
     <packaging>bundle</packaging>
 
     <name>Curator Client</name>

curator-client/src/main/java/org/apache/curator/drivers/AdvancedTracerDriver.java

@@ -26,17 +26,43 @@
  */
 public abstract class AdvancedTracerDriver implements TracerDriver {
     /**
-     * Record the given trace event
+     * Records the start of a new operation that will later complete successfully or erroneously via a call to
+     * {@link #endTrace(OperationTrace)}. The call may optionally return driver specific state which can be
+     * accessed in {@link #endTrace(OperationTrace) endTrace} via {@link OperationTrace#getDriverTrace()}. The
+     * driver implementation is responsible for checking that any state returned is valid. Additionally, while it is
+     * expected that all calls to {@code startTrace} will have a corresponding call to
+     * {@link #endTrace(OperationTrace) endTrace}, it is the responsibility of the driver implementation to manage any
+     * leaking of non-terminal {@link OperationTrace OperationTraces}.
      *
      * @param trace the metrics of the operation
+     * @return The internal trace representation of the driver implementation. Driver dependent, may be {@code null}.
      */
-    public abstract void addTrace(OperationTrace trace);
+    public abstract Object startTrace(OperationTrace trace);
 
     /**
-     * Add to a named counter
+     * Signals the completion, successful or otherwise, of the specified {@link OperationTrace}.
+     *
+     * @param trace the metrics of the operation
+     */
+    public abstract void endTrace(OperationTrace trace);
+
+    /**
+     * Record the given trace event after the completion of the event. This is equivalent to calling
+     * {@link #startTrace(OperationTrace) startTrace} followed by {@link #endTrace(OperationTrace) endTrace}.
+     *
+     * @param trace the metrics of the operation
+     * @deprecated Prefer the use of {@link #startTrace(OperationTrace)} followed by {@link #endTrace(OperationTrace)}
+     */
+    @Deprecated
+    public void addTrace(OperationTrace trace) {
+        startTrace(trace);
+        endTrace(trace);
+    }
+
+    /**
+     * Record the given trace event
      *
-     * @param name name of the counter
-     * @param increment amount to increment
+     * @param trace name of the counter
      */
     public abstract void addEvent(EventTrace trace);
 

curator-client/src/main/java/org/apache/curator/drivers/OperationTrace.java

@@ -19,28 +19,33 @@
 
 package org.apache.curator.drivers;
 
-import java.io.UnsupportedEncodingException;
+import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.data.Stat;
+
 import java.util.concurrent.TimeUnit;
 import org.apache.zookeeper.KeeperException;
 import org.apache.zookeeper.data.Stat;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
+
 /**
  * Used to trace the metrics of a certain Zookeeper operation.
  */
 public class OperationTrace {
     private final String name;
     private final TracerDriver driver;
-
+    private final long startTimeNanos = System.nanoTime();
+    private final long sessionId;
+    private long endTimeNanos = -1L;
     private int returnCode = KeeperException.Code.OK.intValue();
     private long latencyMs;
     private long requestBytesLength;
     private long responseBytesLength;
     private String path;
     private boolean withWatcher;
-    private long sessionId;
     private Stat stat;
-
-    private final long startTimeNanos = System.nanoTime();
+    // This would ideally be a parameterised type, but we do not wish to break the existing API at this time.
+    private Object driverTrace;
 
     public OperationTrace(String name, TracerDriver driver) {
         this(name, driver, -1);
@@ -50,6 +55,9 @@ public OperationTrace(String name, TracerDriver driver, long sessionId) {
         this.name = name;
         this.driver = driver;
         this.sessionId = sessionId;
+        if (this.driver instanceof AdvancedTracerDriver) {
+            driverTrace = ((AdvancedTracerDriver) this.driver).startTrace(this);
+        }
     }
 
     public OperationTrace setReturnCode(int returnCode) {
@@ -66,13 +74,7 @@ public OperationTrace setRequestBytesLength(String data) {
         if (data == null) {
             return this;
         }
-
-        try {
-            this.setRequestBytesLength(data.getBytes("UTF-8").length);
-        } catch (UnsupportedEncodingException e) {
-            // Ignore the exception.
-        }
-
+        this.setRequestBytesLength(data.getBytes(UTF_8).length);
         return this;
     }
 
@@ -112,6 +114,10 @@ public OperationTrace setStat(Stat stat) {
         return this;
     }
 
+    public Object getDriverTrace() {
+        return driverTrace;
+    }
+
     public String getName() {
         return this.name;
     }
@@ -148,11 +154,23 @@ public Stat getStat() {
         return this.stat;
     }
 
+    public long getStartTimeNanos() {
+        return this.startTimeNanos;
+    }
+
+    public long getEndTimeNanos() {
+        if (endTimeNanos < startTimeNanos) {
+            throw new IllegalStateException("End time requested but trace has not yet ended.");
+        }
+        return this.endTimeNanos;
+    }
+
     public void commit() {
-        long elapsed = System.nanoTime() - startTimeNanos;
+        endTimeNanos = System.nanoTime();
+        long elapsed = endTimeNanos - startTimeNanos;
         this.latencyMs = TimeUnit.MILLISECONDS.convert(elapsed, TimeUnit.NANOSECONDS);
         if (this.driver instanceof AdvancedTracerDriver) {
-            ((AdvancedTracerDriver) this.driver).addTrace(this);
+            ((AdvancedTracerDriver) this.driver).endTrace(this);
         } else {
             this.driver.addTrace(this.name, elapsed, TimeUnit.NANOSECONDS);
         }

curator-client/src/main/java/org/apache/curator/retry/ExponentialBackoffRetry.java

@@ -64,7 +64,7 @@ public int getBaseSleepTimeMs() {
     @Override
     protected long getSleepTimeMs(int retryCount, long elapsedTimeMs) {
         // copied from Hadoop's RetryPolicies.java
-        long sleepMs = baseSleepTimeMs * Math.max(1, random.nextInt(1 << (retryCount + 1)));
+        long sleepMs = (long) baseSleepTimeMs * Math.max(1, random.nextInt(1 << (retryCount + 1)));
         if (sleepMs > maxSleepMs) {
             log.warn(String.format("Sleep extension too large (%d). Pinning to %d", sleepMs, maxSleepMs));
             sleepMs = maxSleepMs;

curator-drivers/open-telemetry/pom.xml

@@ -0,0 +1,79 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    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.
+
+-->
+
+<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>org.apache.curator</groupId>
+        <artifactId>curator-drivers</artifactId>
+        <version>5.6.1-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>curator-drivers-open-telemetry</artifactId>
+    <version>5.6.1-SNAPSHOT</version>
+
+    <name>Curator OpenTelemetry Tracing Driver</name>
+    <description>A tracing driver driver that emits OpenTelemetry spans.</description>
+    <inceptionYear>2023</inceptionYear>
+
+    <properties>
+        <opentelemetry.version>1.31.0</opentelemetry.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.curator</groupId>
+            <artifactId>curator-client</artifactId>
+            <version>${project.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.opentelemetry</groupId>
+            <artifactId>opentelemetry-api</artifactId>
+            <version>${opentelemetry.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.opentelemetry</groupId>
+            <artifactId>opentelemetry-sdk-testing</artifactId>
+            <version>${opentelemetry.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-log4j12</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>