[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/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;
     }
@@ -148,13 +154,25 @@ 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);
+          this.driver.addTrace(this.name, elapsed, TimeUnit.NANOSECONDS);
         }
     }
 }

curator-drivers/LICENSE

@@ -0,0 +1,202 @@
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curator-drivers/NOTICE

@@ -0,0 +1,5 @@
+Apache Curator
+Copyright 2013-2023 The Apache Software Foundation
+
+This product includes software developed at
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