Revert "Merge pull request #19686 from vespa-engine/jonmv/revert-streamed-visits"

This reverts commit 56c3fc7c2a3b7e317e79593aa56ed2d03472cbde, reversing
changes made to 367dae08c390833a54c1bae11282df5a7e056d16.

6 files changed, 275 insertions, 141 deletions

diff --git a/container-core/abi-spec.json b/container-core/abi-spec.json
index 02d43104a3f..8c0f3e5fd80 100644
--- a/container-core/abi-spec.json
+++ b/container-core/abi-spec.json
@@ -762,6 +762,19 @@
     ],
     "fields": []
   },
+  "com.yahoo.container.jdisc.MaxPendingContentChannelOutputStream": {
+    "superClass": "com.yahoo.container.jdisc.ContentChannelOutputStream",
+    "interfaces": [],
+    "attributes": [
+      "public"
+    ],
+    "methods": [
+      "public void <init>(com.yahoo.jdisc.handler.ContentChannel, long)",
+      "public void send(java.nio.ByteBuffer)",
+      "public void flush()"
+    ],
+    "fields": []
+  },
   "com.yahoo.container.jdisc.MetricConsumerFactory": {
     "superClass": "java.lang.Object",
     "interfaces": [],
diff --git a/container-core/src/main/java/com/yahoo/container/jdisc/MaxPendingContentChannelOutputStream.java b/container-core/src/main/java/com/yahoo/container/jdisc/MaxPendingContentChannelOutputStream.java
new file mode 100644
index 00000000000..aec4eeecd7b
--- /dev/null
+++ b/container-core/src/main/java/com/yahoo/container/jdisc/MaxPendingContentChannelOutputStream.java
@@ -0,0 +1,92 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.container.jdisc;
+
+import com.yahoo.jdisc.handler.CompletionHandler;
+import com.yahoo.jdisc.handler.ContentChannel;
+
+import java.io.IOException;
+import java.io.InterruptedIOException;
+import java.nio.ByteBuffer;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * @author baldersheim
+ */
+public class MaxPendingContentChannelOutputStream extends ContentChannelOutputStream {
+
+    private final long maxPending;
+    private final AtomicLong sent = new AtomicLong(0);
+    private final AtomicLong acked = new AtomicLong(0);
+
+    public MaxPendingContentChannelOutputStream(ContentChannel endpoint, long maxPending) {
+        super(endpoint);
+        this.maxPending = maxPending;
+    }
+
+    private long pendingBytes() {
+        return sent.get() - acked.get();
+    }
+
+    private class TrackCompletion implements CompletionHandler {
+
+        private final long written;
+        private final AtomicBoolean replied = new AtomicBoolean(false);
+
+        TrackCompletion(long written) {
+            this.written = written;
+            sent.addAndGet(written);
+        }
+
+        @Override
+        public void completed() {
+            if (!replied.getAndSet(true)) {
+                acked.addAndGet(written);
+            }
+        }
+
+        @Override
+        public void failed(Throwable t) {
+            if (!replied.getAndSet(true)) {
+                acked.addAndGet(written);
+            }
+        }
+
+    }
+
+    @Override
+    public void send(ByteBuffer src) throws IOException {
+        try {
+            stallWhilePendingAbove(maxPending);
+        }
+        catch (InterruptedException ignored) {
+            throw new InterruptedIOException("Interrupted waiting for IO");
+        }
+        CompletionHandler pendingTracker = new TrackCompletion(src.remaining());
+        try {
+            send(src, pendingTracker);
+        }
+        catch (Throwable throwable) {
+            pendingTracker.failed(throwable);
+            throw throwable;
+        }
+    }
+
+    private void stallWhilePendingAbove(long pending) throws InterruptedException {
+        while (pendingBytes() > pending) {
+            Thread.sleep(1);
+        }
+    }
+
+    @Override
+    public void flush() throws IOException {
+        super.flush();
+        try {
+            stallWhilePendingAbove(0);
+        }
+        catch (InterruptedException e) {
+            throw new InterruptedIOException("Interrupted waiting for IO");
+        }
+    }
+
+}
diff --git a/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedHttpRequestHandler.java b/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedHttpRequestHandler.java
index 0bfe4afe07d..0c3c1e2120b 100644
--- a/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedHttpRequestHandler.java
+++ b/container-core/src/main/java/com/yahoo/container/jdisc/ThreadedHttpRequestHandler.java
@@ -10,9 +10,6 @@ import com.yahoo.jdisc.handler.ContentChannel;
 import com.yahoo.jdisc.handler.UnsafeContentInputStream;
 import com.yahoo.jdisc.handler.ResponseHandler;
 
-import java.io.InterruptedIOException;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Level;
 
 import java.io.IOException;
@@ -253,81 +250,4 @@ public abstract class ThreadedHttpRequestHandler extends ThreadedRequestHandler
     }
 
 
-    /**
-     * @author baldersheim
-     */
-    static class MaxPendingContentChannelOutputStream extends ContentChannelOutputStream {
-        private final long maxPending;
-        private final AtomicLong sent = new AtomicLong(0);
-        private final AtomicLong acked = new AtomicLong(0);
-
-        public MaxPendingContentChannelOutputStream(ContentChannel endpoint, long maxPending) {
-            super(endpoint);
-            this.maxPending = maxPending;
-        }
-
-        private long pendingBytes() {
-            return sent.get() - acked.get();
-        }
-
-        private class TrackCompletion implements CompletionHandler {
-
-            private final long written;
-            private final AtomicBoolean replied = new AtomicBoolean(false);
-
-            TrackCompletion(long written) {
-                this.written = written;
-                sent.addAndGet(written);
-            }
-
-            @Override
-            public void completed() {
-                if ( ! replied.getAndSet(true)) {
-                    acked.addAndGet(written);
-                }
-            }
-
-            @Override
-            public void failed(Throwable t) {
-                if ( ! replied.getAndSet(true)) {
-                    acked.addAndGet(written);
-                }
-            }
-        }
-
-        @Override
-        public void send(ByteBuffer src) throws IOException {
-            try {
-                stallWhilePendingAbove(maxPending);
-            } catch (InterruptedException ignored) {
-                throw new InterruptedIOException("Interrupted waiting for IO");
-            }
-            CompletionHandler pendingTracker = new TrackCompletion(src.remaining());
-            try {
-                send(src, pendingTracker);
-            } catch (Throwable throwable) {
-                pendingTracker.failed(throwable);
-                throw throwable;
-            }
-        }
-
-        private void stallWhilePendingAbove(long pending) throws InterruptedException {
-            while (pendingBytes() > pending) {
-                Thread.sleep(1);
-            }
-        }
-
-        @Override
-        public void flush() throws IOException {
-            super.flush();
-            try {
-                stallWhilePendingAbove(0);
-            }
-            catch (InterruptedException e) {
-                throw new InterruptedIOException("Interrupted waiting for IO");
-            }
-        }
-
-    }
-
 }
diff --git a/container-core/src/test/java/com/yahoo/container/jdisc/ThreadedRequestHandlerTestCase.java b/container-core/src/test/java/com/yahoo/container/jdisc/ThreadedRequestHandlerTestCase.java
index d1036ce0e45..a9b16799aea 100644
--- a/container-core/src/test/java/com/yahoo/container/jdisc/ThreadedRequestHandlerTestCase.java
+++ b/container-core/src/test/java/com/yahoo/container/jdisc/ThreadedRequestHandlerTestCase.java
@@ -1,7 +1,6 @@
 // Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.container.jdisc;
 
-import com.yahoo.container.jdisc.ThreadedHttpRequestHandler.MaxPendingContentChannelOutputStream;
 import com.yahoo.jdisc.Request;
 import com.yahoo.jdisc.Response;
 import com.yahoo.jdisc.application.ContainerBuilder;
@@ -20,11 +19,9 @@ import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
-import java.util.concurrent.Phaser;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.junit.Assert.*;
 
diff --git a/vespaclient-container-plugin/src/main/java/com/yahoo/document/restapi/resource/DocumentV1ApiHandler.java b/vespaclient-container-plugin/src/main/java/com/yahoo/document/restapi/resource/DocumentV1ApiHandler.java
index aa96b0932c3..a3e3c512dcd 100644
--- a/vespaclient-container-plugin/src/main/java/com/yahoo/document/restapi/resource/DocumentV1ApiHandler.java
+++ b/vespaclient-container-plugin/src/main/java/com/yahoo/document/restapi/resource/DocumentV1ApiHandler.java
@@ -8,7 +8,9 @@ import com.yahoo.cloud.config.ClusterListConfig;
 import com.yahoo.concurrent.DaemonThreadFactory;
 import com.yahoo.container.core.HandlerMetricContextUtil;
 import com.yahoo.container.core.documentapi.VespaDocumentAccess;
+import com.yahoo.container.handler.threadpool.ContainerThreadPool;
 import com.yahoo.container.jdisc.ContentChannelOutputStream;
+import com.yahoo.container.jdisc.MaxPendingContentChannelOutputStream;
 import com.yahoo.document.Document;
 import com.yahoo.document.DocumentId;
 import com.yahoo.document.DocumentOperation;
@@ -86,10 +88,12 @@ import java.util.Optional;
 import java.util.StringJoiner;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Phaser;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.Lock;
@@ -158,6 +162,7 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
     private static final String TIME_CHUNK = "timeChunk";
     private static final String TIMEOUT = "timeout";
     private static final String TRACELEVEL = "tracelevel";
+    private static final String STREAM = "stream";
 
     private final Clock clock;
     private final Duration handlerTimeout;
@@ -175,10 +180,12 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
     private final Map<VisitorControlHandler, VisitorSession> visits = new ConcurrentHashMap<>();
     private final ScheduledExecutorService dispatcher = Executors.newSingleThreadScheduledExecutor(new DaemonThreadFactory("document-api-handler-"));
     private final ScheduledExecutorService visitDispatcher = Executors.newSingleThreadScheduledExecutor(new DaemonThreadFactory("document-api-handler-visit-"));
+    private final Executor defaultExecutor;
     private final Map<String, Map<Method, Handler>> handlers = defineApi();
 
     @Inject
-    public DocumentV1ApiHandler(Metric metric,
+    public DocumentV1ApiHandler(ContainerThreadPool threadPool,
+                                Metric metric,
                                 MetricReceiver metricReceiver,
                                 VespaDocumentAccess documentAccess,
                                 DocumentmanagerConfig documentManagerConfig,
@@ -186,12 +193,12 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
                                 AllClustersBucketSpacesConfig bucketSpacesConfig,
                                 DocumentOperationExecutorConfig executorConfig) {
         this(Clock.systemUTC(), Duration.ofSeconds(5), metric, metricReceiver, documentAccess,
-             documentManagerConfig, executorConfig, clusterListConfig, bucketSpacesConfig);
+             documentManagerConfig, executorConfig, clusterListConfig, bucketSpacesConfig, threadPool.executor());
     }
 
     DocumentV1ApiHandler(Clock clock, Duration handlerTimeout, Metric metric, MetricReceiver metricReceiver, DocumentAccess access,
                          DocumentmanagerConfig documentmanagerConfig, DocumentOperationExecutorConfig executorConfig,
-                         ClusterListConfig clusterListConfig, AllClustersBucketSpacesConfig bucketSpacesConfig) {
+                         ClusterListConfig clusterListConfig, AllClustersBucketSpacesConfig bucketSpacesConfig, Executor defaultExecutor) {
         this.clock = clock;
         this.handlerTimeout = handlerTimeout;
         this.parser = new DocumentOperationParser(documentmanagerConfig);
@@ -210,6 +217,7 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
                                                     executorConfig.resendDelayMillis(),
                                                     executorConfig.resendDelayMillis(),
                                                     TimeUnit.MILLISECONDS);
+        this.defaultExecutor = defaultExecutor;
     }
 
     // ------------------------------------------------ Requests -------------------------------------------------
@@ -355,9 +363,10 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
 
     private ContentChannel getDocuments(HttpRequest request, DocumentPath path, ResponseHandler handler) {
         enqueueAndDispatch(request, handler, () -> {
-            VisitorParameters parameters = parseGetParameters(request, path);
+            boolean streaming = getProperty(request, STREAM, booleanParser).orElse(false);
+            VisitorParameters parameters = parseGetParameters(request, path, streaming);
             return () -> {
-                visitAndWrite(request, parameters, handler);
+                visitAndWrite(request, parameters, handler, streaming);
                 return true; // VisitorSession has its own throttle handling.
             };
         });
@@ -573,19 +582,22 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
     private static class JsonResponse implements AutoCloseable {
 
         private final BufferedContentChannel buffer = new BufferedContentChannel();
-        private final OutputStream out = new ContentChannelOutputStream(buffer);
-        private final JsonGenerator json = jsonFactory.createGenerator(out);
+        private final OutputStream out;
+        private final JsonGenerator json;
         private final ResponseHandler handler;
         private ContentChannel channel;
 
-        private JsonResponse(ResponseHandler handler) throws IOException {
+        private JsonResponse(ResponseHandler handler, boolean streaming) throws IOException {
             this.handler = handler;
+            out = streaming ? new MaxPendingContentChannelOutputStream(buffer, 1 << 24)
+                            : new ContentChannelOutputStream(buffer);
+            json = jsonFactory.createGenerator(out);
             json.writeStartObject();
         }
 
         /** Creates a new JsonResponse with path and id fields written. */
         static JsonResponse create(DocumentPath path, ResponseHandler handler) throws IOException {
-            JsonResponse response = new JsonResponse(handler);
+            JsonResponse response = new JsonResponse(handler, false);
             response.writePathId(path.rawPath());
             response.writeDocId(path.id());
             return response;
@@ -593,15 +605,19 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
 
         /** Creates a new JsonResponse with path field written. */
         static JsonResponse create(HttpRequest request, ResponseHandler handler) throws IOException {
-            JsonResponse response = new JsonResponse(handler);
+            return create(request, handler, false);
+        }
+
+        /** Creates a new JsonResponse with path field written. */
+        static JsonResponse create(HttpRequest request, ResponseHandler handler, boolean streaming) throws IOException {
+            JsonResponse response = new JsonResponse(handler, streaming);
             response.writePathId(request.getUri().getRawPath());
             return response;
         }
 
         /** Creates a new JsonResponse with path and message fields written. */
         static JsonResponse create(HttpRequest request, String message, ResponseHandler handler) throws IOException {
-            JsonResponse response = new JsonResponse(handler);
-            response.writePathId(request.getUri().getRawPath());
+            JsonResponse response = create(request, handler);
             response.writeMessage(message);
             return response;
         }
@@ -955,8 +971,10 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
 
     // ------------------------------------------------- Visits ------------------------------------------------
 
-    private VisitorParameters parseGetParameters(HttpRequest request, DocumentPath path) {
-        int wantedDocumentCount = Math.min(1 << 10, getProperty(request, WANTED_DOCUMENT_COUNT, integerParser).orElse(1));
+    private VisitorParameters parseGetParameters(HttpRequest request, DocumentPath path, boolean streaming) {
+        int wantedDocumentCount = Math.min(streaming ? Integer.MAX_VALUE : 1 << 10,
+                                           getProperty(request, WANTED_DOCUMENT_COUNT, integerParser)
+                                                   .orElse(streaming ? Integer.MAX_VALUE : 1));
         if (wantedDocumentCount <= 0)
             throw new IllegalArgumentException("wantedDocumentCount must be positive");
 
@@ -1015,10 +1033,10 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
         /** Called at the start of response rendering. */
         default void onStart(JsonResponse response) throws IOException { }
 
-        /** Called for every document received from backend visitors — must call the ack for these to proceed. */
+        /** Called for every document received from backend visitors—must call the ack for these to proceed. */
         default void onDocument(JsonResponse response, Document document, Runnable ack, Consumer<String> onError) { }
 
-        /** Called at the end of response rendering, before generic status data is written. */
+        /** Called at the end of response rendering, before generic status data is written. Called from a dedicated thread pool. */
         default void onEnd(JsonResponse response) throws IOException { }
     }
 
@@ -1042,7 +1060,7 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
 
     private void visitAndProcess(HttpRequest request, VisitorParameters parameters, ResponseHandler handler,
                                  String route, BiFunction<DocumentId, DocumentOperationParameters, Result> operation) {
-        visit(request, parameters, handler, new VisitCallback() {
+        visit(request, parameters, false, handler, new VisitCallback() {
             @Override public void onDocument(JsonResponse response, Document document, Runnable ack, Consumer<String> onError) {
                 DocumentOperationParameters operationParameters = parameters().withRoute(route)
                         .withResponseHandler(operationResponse -> {
@@ -1079,66 +1097,92 @@ public class DocumentV1ApiHandler extends AbstractRequestHandler {
         });
     }
 
-    private void visitAndWrite(HttpRequest request, VisitorParameters parameters, ResponseHandler handler) {
-        visit(request, parameters, handler, new VisitCallback() {
+    private void visitAndWrite(HttpRequest request, VisitorParameters parameters, ResponseHandler handler, boolean streaming) {
+        visit(request, parameters, streaming, handler, new VisitCallback() {
+            final Deque<Runnable> writes = new ConcurrentLinkedDeque<>();
+            final AtomicBoolean writing = new AtomicBoolean();
             @Override public void onStart(JsonResponse response) throws IOException {
+                if (streaming)
+                    response.commit(Response.Status.OK);
+
                 response.writeDocumentsArrayStart();
             }
             @Override public void onDocument(JsonResponse response, Document document, Runnable ack, Consumer<String> onError) {
-                response.writeDocumentValue(document);
-                ack.run();
+                writes.add(() -> {
+                    response.writeDocumentValue(document);
+                    ack.run();
+                });
+                if (writing.compareAndSet(false, true)) // Occupy only a single thread for writing.
+                    defaultExecutor.execute(() -> {
+                        for (Runnable write; (write = writes.poll()) != null; write.run());
+                        writing.set(false);
+                    });
             }
             @Override public void onEnd(JsonResponse response) throws IOException {
+                // Wait for other writers to complete, then write what remains here.
+                while ( ! writing.compareAndSet(false, true)) {
+                    try {
+                        Thread.sleep(1);
+                    }
+                    catch (InterruptedException e) {
+                        log.log(WARNING, "Interrupted waiting for visited documents to be written; this should not happen");
+                        Thread.currentThread().interrupt();
+                    }
+                }
+                for (Runnable write; (write = writes.poll()) != null; write.run());
                 response.writeArrayEnd();
             }
         });
     }
 
     private void visitWithRemote(HttpRequest request, VisitorParameters parameters, ResponseHandler handler) {
-        visit(request, parameters, handler, new VisitCallback() { });
+        visit(request, parameters, false, handler, new VisitCallback() { });
     }
 
-    private void visit(HttpRequest request, VisitorParameters parameters, ResponseHandler handler, VisitCallback callback) {
+    private void visit(HttpRequest request, VisitorParameters parameters, boolean streaming, ResponseHandler handler, VisitCallback callback) {
         try {
-            JsonResponse response = JsonResponse.create(request, handler);
+            JsonResponse response = JsonResponse.create(request, handler, streaming);
             Phaser phaser = new Phaser(2); // Synchronize this thread (dispatch) with the visitor callback thread.
             AtomicReference<String> error = new AtomicReference<>(); // Set if error occurs during processing of visited documents.
             callback.onStart(response);
             VisitorControlHandler controller = new VisitorControlHandler() {
                 @Override public void onDone(CompletionCode code, String message) {
-                    super.onDone(code, message);
-                    loggingException(() -> {
-                        callback.onEnd(response);
-                        switch (code) {
-                            case TIMEOUT:
-                                if ( ! hasVisitedAnyBuckets() && parameters.getVisitInconsistentBuckets()) {
-                                    response.writeMessage("No buckets visited within timeout of " +
-                                                          parameters.getSessionTimeoutMs() + "ms (request timeout -5s)");
-                                    response.respond(Response.Status.GATEWAY_TIMEOUT);
-                                    break;
-                                }
-                            case SUCCESS: // Intentional fallthrough.
-                            case ABORTED: // Intentional fallthrough.
-                                if (error.get() == null) {
-                                    ProgressToken progress = getProgress() != null ? getProgress() : parameters.getResumeToken();
-                                    if (progress != null && ! progress.isFinished())
-                                        response.writeContinuation(progress.serializeToString());
+                    defaultExecutor.execute(() -> {
+                        super.onDone(code, message);
+                        loggingException(() -> {
+                            try (response) {
+                                callback.onEnd(response);
 
-                                    if (getVisitorStatistics() != null)
-                                        response.writeDocumentCount(getVisitorStatistics().getDocumentsVisited());
-
-                                    response.respond(Response.Status.OK);
-                                    break;
-                                }
-                            default:
-                                response.writeMessage(error.get() != null ? error.get() : message != null ? message : "Visiting failed");
                                 if (getVisitorStatistics() != null)
                                     response.writeDocumentCount(getVisitorStatistics().getDocumentsVisited());
 
-                                response.respond(Response.Status.BAD_GATEWAY);
-                        }
-                    });
-                    visitDispatcher.execute(() -> {
+                                int status = Response.Status.BAD_GATEWAY;
+                                switch (code) {
+                                    case TIMEOUT:
+                                        if ( ! hasVisitedAnyBuckets() && parameters.getVisitInconsistentBuckets()) {
+                                            response.writeMessage("No buckets visited within timeout of " +
+                                                                  parameters.getSessionTimeoutMs() + "ms (request timeout -5s)");
+                                            status = Response.Status.GATEWAY_TIMEOUT;
+                                            break;
+                                        }
+                                        // TODO jonmv: always supply and document continuation?
+                                    case SUCCESS: // Intentional fallthrough.
+                                    case ABORTED: // Intentional fallthrough.
+                                        if (error.get() == null) {
+                                            ProgressToken progress = getProgress() != null ? getProgress() : parameters.getResumeToken();
+                                            if (progress != null && ! progress.isFinished())
+                                                response.writeContinuation(progress.serializeToString());
+
+                                            status = Response.Status.OK;
+                                            break;
+                                        }
+                                    default:
+                                        response.writeMessage(error.get() != null ? error.get() : message != null ? message : "Visiting failed");
+                                }
+                                if ( ! streaming)
+                                    response.commit(status);
+                            }
+                        });
                         phaser.arriveAndAwaitAdvance(); // We may get here while dispatching thread is still putting us in the map.
                         visits.remove(this).destroy();
                     });
diff --git a/vespaclient-container-plugin/src/test/java/com/yahoo/document/restapi/resource/DocumentV1ApiTest.java b/vespaclient-container-plugin/src/test/java/com/yahoo/document/restapi/resource/DocumentV1ApiTest.java
index 96700f08823..b23533a720e 100644
--- a/vespaclient-container-plugin/src/test/java/com/yahoo/document/restapi/resource/DocumentV1ApiTest.java
+++ b/vespaclient-container-plugin/src/test/java/com/yahoo/document/restapi/resource/DocumentV1ApiTest.java
@@ -4,6 +4,7 @@ package com.yahoo.document.restapi.resource;
 import com.yahoo.cloud.config.ClusterListConfig;
 import com.yahoo.container.jdisc.RequestHandlerTestDriver;
 import com.yahoo.docproc.jdisc.metric.NullMetric;
+import com.yahoo.document.BucketId;
 import com.yahoo.document.Document;
 import com.yahoo.document.DocumentId;
 import com.yahoo.document.DocumentPut;
@@ -37,6 +38,7 @@ import com.yahoo.documentapi.UpdateResponse;
 import com.yahoo.documentapi.VisitorControlHandler;
 import com.yahoo.documentapi.VisitorDestinationParameters;
 import com.yahoo.documentapi.VisitorDestinationSession;
+import com.yahoo.documentapi.VisitorIterator;
 import com.yahoo.documentapi.VisitorParameters;
 import com.yahoo.documentapi.VisitorResponse;
 import com.yahoo.documentapi.VisitorSession;
@@ -134,7 +136,8 @@ public class DocumentV1ApiTest {
         access = new MockDocumentAccess(docConfig);
         metric = new NullMetric();
         metrics = new MetricReceiver.MockReceiver();
-        handler = new DocumentV1ApiHandler(clock, Duration.ofMillis(1), metric, metrics, access, docConfig, executorConfig, clusterConfig, bucketConfig);
+        handler = new DocumentV1ApiHandler(clock, Duration.ofMillis(1), metric, metrics, access, docConfig,
+                                           executorConfig, clusterConfig, bucketConfig, Executors.newFixedThreadPool(2));
     }
 
     @After
@@ -245,19 +248,83 @@ public class DocumentV1ApiTest {
                        "}", response.readAll());
         assertEquals(200, response.getStatus());
 
+        // GET at root is a visit. Streaming mode can be specified with &stream=true
+        access.expect(tokens);
+        access.expect(parameters -> {
+            assertEquals("content", parameters.getRoute().toString());
+            assertEquals("default", parameters.getBucketSpace());
+            assertEquals(1025, parameters.getMaxTotalHits()); // Not bounded likewise for streamed responses.
+            assertEquals(100, ((StaticThrottlePolicy) parameters.getThrottlePolicy()).getMaxPendingCount());
+            assertEquals("[id]", parameters.getFieldSet());
+            assertEquals("(all the things)", parameters.getDocumentSelection());
+            assertEquals(6000, parameters.getSessionTimeoutMs());
+            // Put some documents in the response
+            parameters.getLocalDataHandler().onMessage(new PutDocumentMessage(new DocumentPut(doc1)), tokens.get(0));
+            parameters.getLocalDataHandler().onMessage(new PutDocumentMessage(new DocumentPut(doc2)), tokens.get(1));
+            parameters.getLocalDataHandler().onMessage(new PutDocumentMessage(new DocumentPut(doc3)), tokens.get(2));
+            VisitorStatistics statistics = new VisitorStatistics();
+            statistics.setBucketsVisited(1);
+            statistics.setDocumentsVisited(3);
+            parameters.getControlHandler().onVisitorStatistics(statistics);
+            parameters.getControlHandler().onDone(VisitorControlHandler.CompletionCode.TIMEOUT, "timeout is OK");
+        });
+        response = driver.sendRequest("http://localhost/document/v1?cluster=content&bucketSpace=default&wantedDocumentCount=1025&concurrency=123" +
+                                      "&selection=all%20the%20things&fieldSet=[id]&timeout=6&stream=true");
+        assertSameJson("{" +
+                       "  \"pathId\": \"/document/v1\"," +
+                       "  \"documents\": [" +
+                       "    {" +
+                       "      \"id\": \"id:space:music::one\"," +
+                       "      \"fields\": {" +
+                       "        \"artist\": \"Tom Waits\"" +
+                       "      }" +
+                       "    }," +
+                       "    {" +
+                       "      \"id\": \"id:space:music:n=1:two\"," +
+                       "      \"fields\": {" +
+                       "        \"artist\": \"Asa-Chan & Jun-Ray\"" +
+                       "      }" +
+                       "    }," +
+                       "    {" +
+                       "     \"id\": \"id:space:music:g=a:three\"," +
+                       "     \"fields\": {}" +
+                       "    }" +
+                       "  ]," +
+                       "  \"documentCount\": 3" +
+                       "}", response.readAll());
+        assertEquals(200, response.getStatus());
+
         // GET with namespace and document type is a restricted visit.
+        ProgressToken progress = new ProgressToken();
+        VisitorIterator.createFromExplicitBucketSet(Set.of(new BucketId(1), new BucketId(2)), 8, progress)
+                       .update(new BucketId(1), new BucketId(1));
         access.expect(parameters -> {
             assertEquals("(music) and (id.namespace=='space')", parameters.getDocumentSelection());
-            assertEquals(new ProgressToken().serializeToString(), parameters.getResumeToken().serializeToString());
+            assertEquals(progress.serializeToString(), parameters.getResumeToken().serializeToString());
             throw new IllegalArgumentException("parse failure");
         });
-        response = driver.sendRequest("http://localhost/document/v1/space/music/docid?continuation=" + new ProgressToken().serializeToString());
+        response = driver.sendRequest("http://localhost/document/v1/space/music/docid?continuation=" + progress.serializeToString());
         assertSameJson("{" +
                        "  \"pathId\": \"/document/v1/space/music/docid\"," +
                        "  \"message\": \"parse failure\"" +
                        "}", response.readAll());
         assertEquals(400, response.getStatus());
 
+        // GET when a streamed visit returns status code 200 also when errors occur.
+        access.expect(parameters -> {
+            assertEquals("(music) and (id.namespace=='space')", parameters.getDocumentSelection());
+            parameters.getControlHandler().onProgress(progress);
+            parameters.getControlHandler().onDone(VisitorControlHandler.CompletionCode.FAILURE, "failure?");
+        });
+        response = driver.sendRequest("http://localhost/document/v1/space/music/docid?stream=true");
+        assertSameJson("{" +
+                       "  \"pathId\": \"/document/v1/space/music/docid\"," +
+                       "  \"documents\": []," +
+                       //"  \"continuation\": \"" + progress.serializeToString() + "\"," +
+                       "  \"message\": \"failure?\"" +
+                       "}", response.readAll());
+        assertEquals(200, response.getStatus());
+
         // POST with namespace and document type is a restricted visit with a required destination cluster ("destinationCluster")
         access.expect(parameters -> {
             fail("Not supposed to run");
@@ -686,7 +753,8 @@ public class DocumentV1ApiTest {
     @Test
     public void testThroughput() throws InterruptedException {
         DocumentOperationExecutorConfig executorConfig = new DocumentOperationExecutorConfig.Builder().build();
-        handler = new DocumentV1ApiHandler(clock, Duration.ofMillis(1), metric, metrics, access, docConfig, executorConfig, clusterConfig, bucketConfig);
+        handler = new DocumentV1ApiHandler(clock, Duration.ofMillis(1), metric, metrics, access, docConfig,
+                                           executorConfig, clusterConfig, bucketConfig, Executors.newFixedThreadPool(2));
 
         int writers = 4;
         int queueFill = executorConfig.maxThrottled() - writers;
@@ -737,7 +805,7 @@ public class DocumentV1ApiTest {
             replier.schedule(() -> parameters.responseHandler().get().handleResponse(success), 10, TimeUnit.MILLISECONDS);
             return new Result(0);
         });
-        // Send the rest of the documents. Rely on resender to empty queue of throttled oppperations.
+        // Send the rest of the documents. Rely on resender to empty queue of throttled operations.
         for (int i = queueFill; i < docs; i++) {
             int j = i;
             writer.execute(() -> {