Treat document V1 API visiting timeouts with progress as successful (#2401)

Previously, using a visitor with a selection that did not match any buckets
visited during the session's lifetime would trigger a timeout error to the
client and abort the visiting. With this change, we special case timeouts if
they have successfully visited at least 1 bucket and return a successful
response for these. The client can then use the updated continuation token
for its subsequent request and continue from where the timed out session
left off.

The timeout special cased handling is done _outside_ the session and control
handler to avoid increasing session-internal complexity, and since not all
visitor use cases want this behavior (e.g. streaming search).

4 files changed, 103 insertions, 13 deletions

diff --git a/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlHandler.java b/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlHandler.java
index b46308e0daf..4d05125f417 100644
--- a/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlHandler.java
+++ b/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlHandler.java
@@ -3,13 +3,15 @@ package com.yahoo.documentapi;
 
 import com.yahoo.vdslib.VisitorStatistics;
 
+import java.time.Duration;
+
 /**
  * A class for controlling a visitor supplied through visitor parameters when
  * creating the visitor session. The class defines callbacks for reporting
  * progress and that the visitor is done. If you want to reimplement the
  * default behavior of those callbacks, you can write your own subclass.
  *
- * @author <a href="mailto:humbe@yahoo-inc.com">H&aring;kon Humberset</a>
+ * @author Håkon Humberset
  */
 public class VisitorControlHandler {
     /** Possible completion codes for visiting. */
@@ -46,6 +48,14 @@ public class VisitorControlHandler {
 
             return "Unknown error";
         }
+
+        public CompletionCode getCode() {
+            return code;
+        }
+
+        public String getMessage() {
+            return message;
+        }
     };
 
     private VisitorControlSession session;
@@ -94,6 +104,17 @@ public class VisitorControlHandler {
     }
 
     /**
+     * Returns true iff the statistics reported by the visiting session indicates at least one
+     * bucket has been completely visited.
+     *
+     * Not thread safe, so should only be called on a quiescent session after waitUntilDone
+     * has completed successfully.
+     */
+    public boolean hasVisitedAnyBuckets() {
+        return ((currentStatistics != null) && (currentStatistics.getBucketsVisited() > 0));
+    }
+
+    /**
      * Callback called when the visitor is done.
      *
      * @param code the completion code
@@ -130,25 +151,52 @@ public class VisitorControlHandler {
      * Waits until visiting is done, or the given timeout (in ms) expires.
      * Will wait forever if timeout is 0.
      *
-     * @param timeoutMs The maximum amount of milliseconds to wait.
-     * @return True if visiting is done (either by error or success).
-     * @throws InterruptedException  If an interrupt signal was received while waiting.
+     * @param timeout Maximum time duration to wait before returning.
+     * @return True if visiting is done (either by error or success), false if session has timed out.
+     * @throws InterruptedException If an interrupt signal was received while waiting.
      */
-    public boolean waitUntilDone(long timeoutMs) throws InterruptedException {
+    public boolean waitUntilDone(Duration timeout) throws InterruptedException {
         synchronized (this) {
-            if (completed) return true;
-            if (timeoutMs == 0) {
+            if (completed) {
+                return true;
+            }
+            if (timeout.isZero()) {
                 while (!completed) {
                     wait();
                 }
             } else {
-                wait(timeoutMs);
+                wait(timeout.toMillis());
             }
             return completed;
         }
     }
 
     /**
+     * Waits until visiting is done, or the given timeout (in ms) expires.
+     * Will wait forever if timeout is 0.
+     *
+     * @param timeoutMs The maximum amount of milliseconds to wait.
+     * @return True if visiting is done (either by error or success), false if session has timed out.
+     * @throws InterruptedException If an interrupt signal was received while waiting.
+     *
+     * TODO deprecate this in favor of waitUntilDone(Duration)
+     */
+    public boolean waitUntilDone(long timeoutMs) throws InterruptedException {
+        return waitUntilDone(Duration.ofMillis(timeoutMs));
+    }
+
+    /**
+     * Waits until visiting is done. Session timeout implicitly completes
+     * the visitor session, but will set an unsuccessful result code.
+     *
+     * @throws InterruptedException If an interrupt signal was received while waiting.
+     */
+    public void waitUntilDone() throws InterruptedException {
+        final boolean done = waitUntilDone(Duration.ZERO);
+        assert done : "Infinite waitUntilDone timeout should always complete";
+    }
+
+    /**
      * Abort this visitor
      */
     public void abort() { session.abort(); }
diff --git a/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlSession.java b/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlSession.java
index 4296407d633..4218417437c 100644
--- a/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlSession.java
+++ b/documentapi/src/main/java/com/yahoo/documentapi/VisitorControlSession.java
@@ -10,7 +10,7 @@ package com.yahoo.documentapi;
  * kinds of visitor sessions, such as acking visitor data and aborting the
  * session.
  *
- * @author <a href="mailto:humbe@yahoo-inc.com">H&aring;kon Humberset</a>
+ * @author Håkon Humberset
  */
 public interface VisitorControlSession {
     /**
diff --git a/documentapi/src/main/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSession.java b/documentapi/src/main/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSession.java
index 306103f2912..56edc7eb42a 100755
--- a/documentapi/src/main/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSession.java
+++ b/documentapi/src/main/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSession.java
@@ -883,8 +883,7 @@ public class MessageBusVisitorSession implements VisitorSession {
 
         if (isFatalError(reply)) {
             if (params.skipBucketsOnFatalErrors()) {
-                progress.getToken().addFailedBucket(bucket, subProgress, message);
-                progress.getIterator().update(bucket, ProgressToken.FINISHED_BUCKET);
+                markBucketProgressAsFailed(bucket, subProgress, message);
             } else {
                 reportVisitorError(message);
                 transitionTo(new StateDescription(State.FAILED, message));
@@ -903,6 +902,11 @@ public class MessageBusVisitorSession implements VisitorSession {
         }
     }
 
+    private void markBucketProgressAsFailed(BucketId bucket, BucketId subProgress, String message) {
+        progress.getToken().addFailedBucket(bucket, subProgress, message);
+        progress.getIterator().update(bucket, ProgressToken.FINISHED_BUCKET);
+    }
+
     private boolean enoughHitsReceived() {
         if (params.getMaxFirstPassHits() != -1
                 && statistics.getDocumentsReturned() >= params.getMaxFirstPassHits())
@@ -1024,7 +1028,6 @@ public class MessageBusVisitorSession implements VisitorSession {
 
     private void handleWrongDistributionReply(WrongDistributionReply reply) {
         try {
-            // Classnames clash with documentapi classes, so be explicit
             ClusterState newState = new ClusterState(reply.getSystemState());
             int stateBits = newState.getDistributionBitCount();
             if (stateBits != progress.getIterator().getDistributionBitCount()) {
@@ -1123,7 +1126,7 @@ public class MessageBusVisitorSession implements VisitorSession {
                 synchronized (completionMonitor) {
                     // If we are destroying the session before it has completed (e.g. because
                     // waitUntilDone timed out or an interactive visiting was interrupted)
-                    // set us to aborted state so that we'll seize
+                    // set us to aborted state so that we'll seize sending new visitors.
                     if (!done) {
                         transitionTo(new StateDescription(State.ABORTED, "Session explicitly destroyed before completion"));
                     }
diff --git a/documentapi/src/test/java/com/yahoo/documentapi/messagebus/test/VisitorControlHandlerTest.java b/documentapi/src/test/java/com/yahoo/documentapi/messagebus/test/VisitorControlHandlerTest.java
new file mode 100644
index 00000000000..d8340e6a3f6
--- /dev/null
+++ b/documentapi/src/test/java/com/yahoo/documentapi/messagebus/test/VisitorControlHandlerTest.java
@@ -0,0 +1,39 @@
+// Copyright 2017 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.documentapi.messagebus.test;
+
+import com.yahoo.documentapi.VisitorControlHandler;
+import com.yahoo.vdslib.VisitorStatistics;
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class VisitorControlHandlerTest {
+
+    @Test
+    public void has_visited_any_buckets_is_false_if_no_bucket_stats_recorded() {
+        VisitorControlHandler handler = new VisitorControlHandler();
+        assertFalse(handler.hasVisitedAnyBuckets());
+    }
+
+    @Test
+    public void has_visited_any_buckets_is_false_if_zero_buckets_visited() {
+        VisitorControlHandler handler = new VisitorControlHandler();
+        VisitorStatistics stats = new VisitorStatistics();
+        stats.setBucketsVisited(0);
+        handler.onVisitorStatistics(stats);
+
+        assertFalse(handler.hasVisitedAnyBuckets());
+    }
+
+    @Test
+    public void has_visited_any_buckets_is_true_if_more_than_zero_buckets_visited() {
+        VisitorControlHandler handler = new VisitorControlHandler();
+        VisitorStatistics stats = new VisitorStatistics();
+        stats.setBucketsVisited(1);
+        handler.onVisitorStatistics(stats);
+
+        assertTrue(handler.hasVisitedAnyBuckets());
+    }
+
+}