Merge pull request #12165 from vespa-engine/balder/add-support-for-trace-in-accesslog

Balder/add support for trace in accesslog

8 files changed, 272 insertions, 161 deletions

diff --git a/container-accesslogging/src/main/java/com/yahoo/container/logging/AccessLogEntry.java b/container-accesslogging/src/main/java/com/yahoo/container/logging/AccessLogEntry.java
index b943c03f48f..d8085cc808b 100644
--- a/container-accesslogging/src/main/java/com/yahoo/container/logging/AccessLogEntry.java
+++ b/container-accesslogging/src/main/java/com/yahoo/container/logging/AccessLogEntry.java
@@ -2,6 +2,7 @@
 package com.yahoo.container.logging;
 
 import com.yahoo.collections.ListMap;
+import com.yahoo.yolean.trace.TraceNode;
 
 import javax.security.auth.x500.X500Principal;
 import java.net.InetAddress;
@@ -69,6 +70,7 @@ public class AccessLogEntry {
     private X500Principal sslPrincipal;
     private String rawPath;
     private String rawQuery;
+    private TraceNode traceNode;
 
     private ListMap<String,String> keyValues=null;
 
@@ -452,6 +454,18 @@ public class AccessLogEntry {
         }
     }
 
+    public void setTrace(TraceNode traceNode) {
+        synchronized (monitor) {
+            requireNull(this.traceNode);
+            this.traceNode = traceNode;
+        }
+    }
+    public TraceNode getTrace() {
+        synchronized (monitor) {
+            return traceNode;
+        }
+    }
+
     @Override
     public String toString() {
         synchronized (monitor) {
@@ -481,6 +495,7 @@ public class AccessLogEntry {
                     ", sslPrincipal=" + sslPrincipal +
                     ", rawPath='" + rawPath + '\'' +
                     ", rawQuery='" + rawQuery + '\'' +
+                    ", trace='" + traceNode + '\'' +
                     ", keyValues=" + keyValues +
                     '}';
         }
diff --git a/container-accesslogging/src/main/java/com/yahoo/container/logging/JSONFormatter.java b/container-accesslogging/src/main/java/com/yahoo/container/logging/JSONFormatter.java
index 556b97ced62..ae794e5b60a 100644
--- a/container-accesslogging/src/main/java/com/yahoo/container/logging/JSONFormatter.java
+++ b/container-accesslogging/src/main/java/com/yahoo/container/logging/JSONFormatter.java
@@ -5,6 +5,7 @@ import com.fasterxml.jackson.core.JsonEncoding;
 import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.yahoo.yolean.trace.TraceNode;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -55,8 +56,7 @@ public class JSONFormatter {
             generator.writeStartObject();
             generator.writeStringField("ip", accessLogEntry.getIpV4Address());
             generator.writeNumberField("time", toTimestampInSeconds(accessLogEntry.getTimeStampMillis()));
-            generator.writeNumberField("duration",
-                                       durationAsSeconds(accessLogEntry.getDurationBetweenRequestResponseMillis()));
+            generator.writeNumberField("duration", durationAsSeconds(accessLogEntry.getDurationBetweenRequestResponseMillis()));
             generator.writeNumberField("responsesize", accessLogEntry.getReturnedContentSize());
             generator.writeNumberField("code", accessLogEntry.getStatusCode());
             generator.writeStringField("method", accessLogEntry.getHttpMethod());
@@ -95,6 +95,15 @@ public class JSONFormatter {
                 }
             }
 
+            TraceNode trace = accessLogEntry.getTrace();
+            if (trace != null) {
+                long timestamp = trace.timestamp();
+                if (timestamp == 0L) {
+                    timestamp = accessLogEntry.getTimeStampMillis();
+                }
+                trace.accept(new TraceRenderer(generator, timestamp));
+            }
+
             // Only add search sub block of this is a search request
             if (isSearchRequest(accessLogEntry)) {
                 generator.writeObjectFieldStart("search");
diff --git a/container-accesslogging/src/main/java/com/yahoo/container/logging/TraceRenderer.java b/container-accesslogging/src/main/java/com/yahoo/container/logging/TraceRenderer.java
new file mode 100644
index 00000000000..295786aa15d
--- /dev/null
+++ b/container-accesslogging/src/main/java/com/yahoo/container/logging/TraceRenderer.java
@@ -0,0 +1,185 @@
+package com.yahoo.container.logging;
+
+import com.yahoo.data.access.Inspectable;
+import com.yahoo.data.access.Inspector;
+import com.yahoo.data.access.simple.JsonRender;
+import com.yahoo.yolean.trace.TraceNode;
+import com.yahoo.yolean.trace.TraceVisitor;
+import com.fasterxml.jackson.core.JsonGenerator;
+
+import java.io.IOException;
+
+public class TraceRenderer extends TraceVisitor {
+    private static final String TRACE_CHILDREN = "children";
+    private static final String TRACE_MESSAGE = "message";
+    private static final String TRACE_TIMESTAMP = "timestamp";
+    private static final String TRACE = "trace";
+
+    private final long basetime;
+    private final JsonGenerator generator;
+    private final FieldConsumer fieldConsumer;
+    private boolean hasFieldName = false;
+    int emittedChildNesting = 0;
+    int currentChildNesting = 0;
+    private boolean insideOpenObject = false;
+
+    public interface FieldConsumer {
+        void accept(Object object) throws IOException;
+    }
+
+    private static class Consumer implements FieldConsumer {
+        private final JsonGenerator generator;
+
+        Consumer(JsonGenerator generator) {
+            this.generator = generator;
+        }
+
+        @Override
+        public void accept(Object object) throws IOException {
+            if (object instanceof Inspectable) {
+                renderInspectorDirect(((Inspectable) object).inspect());
+            } else {
+                generator.writeObject(object);
+            }
+        }
+        private void renderInspectorDirect(Inspector data) throws IOException {
+            StringBuilder intermediate = new StringBuilder();
+            JsonRender.render(data, intermediate, true);
+            generator.writeRawValue(intermediate.toString());
+        }
+    }
+
+    TraceRenderer(JsonGenerator generator, long basetime) {
+        this(generator, new Consumer(generator), basetime);
+    }
+    public TraceRenderer(JsonGenerator generator, FieldConsumer consumer, long basetime) {
+        this.generator = generator;
+        this.fieldConsumer = consumer;
+        this.basetime = basetime;
+    }
+
+    @Override
+    public void entering(TraceNode node) {
+        ++currentChildNesting;
+    }
+
+    @Override
+    public void leaving(TraceNode node) {
+        conditionalEndObject();
+        if (currentChildNesting == emittedChildNesting) {
+            try {
+                generator.writeEndArray();
+                generator.writeEndObject();
+            } catch (IOException e) {
+                throw new TraceRenderWrapper(e);
+            }
+            --emittedChildNesting;
+        }
+        --currentChildNesting;
+    }
+
+    @Override
+    public void visit(TraceNode node) {
+        try {
+            doVisit(node.timestamp(), node.payload(), node.children().iterator().hasNext());
+        } catch (IOException e) {
+            throw new TraceRenderWrapper(e);
+        }
+    }
+
+    private void doVisit(long timestamp, Object payload, boolean hasChildren) throws IOException {
+        boolean dirty = false;
+        if (timestamp != 0L) {
+            header();
+            generator.writeStartObject();
+            generator.writeNumberField(TRACE_TIMESTAMP, timestamp - basetime);
+            dirty = true;
+        }
+        if (payload != null) {
+            if (!dirty) {
+                header();
+                generator.writeStartObject();
+            }
+            generator.writeFieldName(TRACE_MESSAGE);
+            fieldConsumer.accept(payload);
+            dirty = true;
+        }
+        if (dirty) {
+            if (!hasChildren) {
+                generator.writeEndObject();
+            } else {
+                setInsideOpenObject(true);
+            }
+        }
+    }
+    private void header() {
+        fieldName();
+        for (int i = 0; i < (currentChildNesting - emittedChildNesting); ++i) {
+            startChildArray();
+        }
+        emittedChildNesting = currentChildNesting;
+    }
+
+    private void startChildArray() {
+        try {
+            conditionalStartObject();
+            generator.writeArrayFieldStart(TRACE_CHILDREN);
+        } catch (IOException e) {
+            throw new TraceRenderWrapper(e);
+        }
+    }
+
+    private void conditionalStartObject() throws IOException {
+        if (!isInsideOpenObject()) {
+            generator.writeStartObject();
+        } else {
+            setInsideOpenObject(false);
+        }
+    }
+
+    private void conditionalEndObject() {
+        if (isInsideOpenObject()) {
+            // This triggers if we were inside a data node with payload and
+            // subnodes, but none of the subnodes contained data
+            try {
+                generator.writeEndObject();
+                setInsideOpenObject(false);
+            } catch (IOException e) {
+                throw new TraceRenderWrapper(e);
+            }
+        }
+    }
+
+    private void fieldName() {
+        if (hasFieldName) {
+            return;
+        }
+
+        try {
+            generator.writeFieldName(TRACE);
+        } catch (IOException e) {
+            throw new TraceRenderWrapper(e);
+        }
+        hasFieldName = true;
+    }
+
+    boolean isInsideOpenObject() {
+        return insideOpenObject;
+    }
+
+    void setInsideOpenObject(boolean insideOpenObject) {
+        this.insideOpenObject = insideOpenObject;
+    }
+    public static final class TraceRenderWrapper extends RuntimeException {
+
+        /**
+         * Should never be serialized, but this is still needed.
+         */
+        private static final long serialVersionUID = 2L;
+
+        TraceRenderWrapper(IOException wrapped) {
+            super(wrapped);
+        }
+
+    }
+}
diff --git a/container-accesslogging/src/test/java/com/yahoo/container/logging/JSONLogTestCase.java b/container-accesslogging/src/test/java/com/yahoo/container/logging/JSONLogTestCase.java
index 8bbb8500cfd..6c7878f99ed 100644
--- a/container-accesslogging/src/test/java/com/yahoo/container/logging/JSONLogTestCase.java
+++ b/container-accesslogging/src/test/java/com/yahoo/container/logging/JSONLogTestCase.java
@@ -1,8 +1,10 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.container.logging;
 
+import com.yahoo.yolean.trace.TraceNode;
 import org.junit.Test;
 
+import java.io.IOException;
 import java.net.URI;
 
 import static org.junit.Assert.assertEquals;
@@ -70,6 +72,36 @@ public class JSONLogTestCase {
     }
 
     @Test
+    public void test_json_of_trace() throws IOException {
+        TraceNode root = new TraceNode("root", 7);
+        AccessLogEntry entry = newAccessLogEntry("test");
+        entry.setTrace(root);
+
+        String expectedOutput =
+                "{\"ip\":\"152.200.54.243\"," +
+                "\"time\":920880005.023," +
+                "\"duration\":0.122," +
+                "\"responsesize\":9875," +
+                "\"code\":200," +
+                "\"method\":\"GET\"," +
+                "\"uri\":\"?query=test\"," +
+                "\"version\":\"HTTP/1.1\"," +
+                "\"agent\":\"Mozilla/4.05 [en] (Win95; I)\"," +
+                "\"host\":\"localhost\"," +
+                "\"scheme\":null," +
+                "\"localport\":0," +
+                "\"trace\":{\"timestamp\":0,\"message\":\"root\"}," +
+                "\"search\":{" +
+                "\"totalhits\":1234," +
+                "\"hits\":0," +
+                "\"coverage\":{\"coverage\":100,\"documents\":100}" +
+                "}" +
+                "}";
+
+        assertEquals(expectedOutput, new JSONFormatter(entry).format());
+    }
+
+    @Test
     public void test_with_keyvalues() {
         AccessLogEntry entry = newAccessLogEntry("test");
         entry.addKeyValue("singlevalue", "value1");
diff --git a/container-search/abi-spec.json b/container-search/abi-spec.json
index 437db99c45b..78d6dcc9670 100644
--- a/container-search/abi-spec.json
+++ b/container-search/abi-spec.json
@@ -6937,7 +6937,8 @@
   "com.yahoo.search.rendering.JsonRenderer$FieldConsumer": {
     "superClass": "java.lang.Object",
     "interfaces": [
-      "com.yahoo.search.result.Hit$RawUtf8Consumer"
+      "com.yahoo.search.result.Hit$RawUtf8Consumer",
+      "com.yahoo.container.logging.TraceRenderer$FieldConsumer"
     ],
     "attributes": [
       "public"
@@ -6949,6 +6950,7 @@
       "protected boolean shouldRender(java.lang.String, java.lang.Object)",
       "protected boolean shouldRenderUtf8Value(java.lang.String, int)",
       "protected void renderFieldContents(java.lang.Object)",
+      "public void accept(java.lang.Object)",
       "public bridge synthetic void accept(java.lang.Object, java.lang.Object)"
     ],
     "fields": []
diff --git a/container-search/src/main/java/com/yahoo/search/handler/HttpSearchResponse.java b/container-search/src/main/java/com/yahoo/search/handler/HttpSearchResponse.java
index 3602d21f7d8..d636d3bc925 100644
--- a/container-search/src/main/java/com/yahoo/search/handler/HttpSearchResponse.java
+++ b/container-search/src/main/java/com/yahoo/search/handler/HttpSearchResponse.java
@@ -23,6 +23,7 @@ import com.yahoo.processing.rendering.Renderer;
 import com.yahoo.search.Query;
 import com.yahoo.search.Result;
 import com.yahoo.search.query.context.QueryContext;
+import com.yahoo.yolean.trace.TraceNode;
 
 /**
  * Wrap the result of a query as an HTTP response.
@@ -36,8 +37,13 @@ public class HttpSearchResponse extends ExtendedResponse {
     private final Renderer<Result> rendererCopy;
     private final Timing timing;
     private final HitCounts hitCounts;
+    private final TraceNode trace;
 
     public HttpSearchResponse(int status, Result result, Query query, Renderer renderer) {
+        this(status, result, query, renderer, null);
+    }
+
+    HttpSearchResponse(int status, Result result, Query query, Renderer renderer, TraceNode trace) {
         super(status);
         this.query = query;
         this.result = result;
@@ -45,6 +51,7 @@ public class HttpSearchResponse extends ExtendedResponse {
 
         this.timing = SearchResponse.createTiming(query, result);
         this.hitCounts = SearchResponse.createHitCounts(query, result);
+        this.trace = trace;
         populateHeaders(headers(), result.getHeaders(false));
     }
 
@@ -107,6 +114,9 @@ public class HttpSearchResponse extends ExtendedResponse {
     @Override
     public void populateAccessLogEntry(final AccessLogEntry accessLogEntry) {
         super.populateAccessLogEntry(accessLogEntry);
+        if (trace != null) {
+            accessLogEntry.setTrace(trace);
+        }
         populateAccessLogEntry(accessLogEntry, getHitCounts());
     }
 
diff --git a/container-search/src/main/java/com/yahoo/search/handler/SearchHandler.java b/container-search/src/main/java/com/yahoo/search/handler/SearchHandler.java
index 0f0df3aa93e..dad106570ab 100644
--- a/container-search/src/main/java/com/yahoo/search/handler/SearchHandler.java
+++ b/container-search/src/main/java/com/yahoo/search/handler/SearchHandler.java
@@ -296,7 +296,10 @@ public class SearchHandler extends LoggingRequestHandler {
         // Transform result to response
         Renderer renderer = toRendererCopy(query.getPresentation().getRenderer());
         HttpSearchResponse response = new HttpSearchResponse(getHttpResponseStatus(request, result),
-                                                             result, query, renderer);
+                                                             result, query, renderer,
+                                                             log.isLoggable(Level.FINE)
+                                                                     ? query.getContext(false).getTrace().traceNode()
+                                                                     : null);
         if (hostResponseHeaderKey.isPresent())
             response.headers().add(hostResponseHeaderKey.get(), selfHostname);
 
@@ -410,7 +413,7 @@ public class SearchHandler extends LoggingRequestHandler {
         } catch (ParseException e) {
             ErrorMessage error = ErrorMessage.createIllegalQuery("Could not parse query [" + request + "]: "
                                                                  + Exceptions.toMessageString(e));
-            log.log(LogLevel.DEBUG, () -> error.getDetailedMessage());
+            log.log(LogLevel.DEBUG, error::getDetailedMessage);
             return new Result(query, error);
         } catch (IllegalArgumentException e) {
             if ("Comparison method violates its general contract!".equals(e.getMessage())) {
@@ -422,7 +425,7 @@ public class SearchHandler extends LoggingRequestHandler {
             else {
                 ErrorMessage error = ErrorMessage.createBadRequest("Invalid search request [" + request + "]: "
                                                                    + Exceptions.toMessageString(e));
-                log.log(LogLevel.DEBUG, () -> error.getDetailedMessage());
+                log.log(LogLevel.DEBUG, error::getDetailedMessage);
                 return new Result(query, error);
             }
         } catch (LinkageError | StackOverflowError e) {
diff --git a/container-search/src/main/java/com/yahoo/search/rendering/JsonRenderer.java b/container-search/src/main/java/com/yahoo/search/rendering/JsonRenderer.java
index af453983f89..31f8194b3b7 100644
--- a/container-search/src/main/java/com/yahoo/search/rendering/JsonRenderer.java
+++ b/container-search/src/main/java/com/yahoo/search/rendering/JsonRenderer.java
@@ -7,6 +7,7 @@ import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.core.TreeNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Preconditions;
+import com.yahoo.container.logging.TraceRenderer;
 import com.yahoo.data.JsonProducer;
 import com.yahoo.data.access.Inspectable;
 import com.yahoo.data.access.Inspector;
@@ -44,8 +45,6 @@ import com.yahoo.search.result.Hit;
 import com.yahoo.search.result.HitGroup;
 import com.yahoo.search.result.NanNumber;
 import com.yahoo.tensor.Tensor;
-import com.yahoo.yolean.trace.TraceNode;
-import com.yahoo.yolean.trace.TraceVisitor;
 import org.json.JSONArray;
 import org.json.JSONObject;
 
@@ -111,10 +110,6 @@ public class JsonRenderer extends AsynchronousSectionedRenderer<Result> {
     private static final String ROOT = "root";
     private static final String SOURCE = "source";
     private static final String TOTAL_COUNT = "totalCount";
-    private static final String TRACE = "trace";
-    private static final String TRACE_CHILDREN = "children";
-    private static final String TRACE_MESSAGE = "message";
-    private static final String TRACE_TIMESTAMP = "timestamp";
     private static final String TIMING = "timing";
     private static final String QUERY_TIME = "querytime";
     private static final String SUMMARY_FETCH_TIME = "summaryfetchtime";
@@ -132,145 +127,6 @@ public class JsonRenderer extends AsynchronousSectionedRenderer<Result> {
     private LongSupplier timeSource;
     private OutputStream stream;
 
-    private class TraceRenderer extends TraceVisitor {
-        private final long basetime;
-        private boolean hasFieldName = false;
-        int emittedChildNesting = 0;
-        int currentChildNesting = 0;
-        private boolean insideOpenObject = false;
-
-        TraceRenderer(long basetime) {
-            this.basetime = basetime;
-        }
-
-        @Override
-        public void entering(TraceNode node) {
-            ++currentChildNesting;
-        }
-
-        @Override
-        public void leaving(TraceNode node) {
-            conditionalEndObject();
-            if (currentChildNesting == emittedChildNesting) {
-                try {
-                    generator.writeEndArray();
-                    generator.writeEndObject();
-                } catch (IOException e) {
-                    throw new TraceRenderWrapper(e);
-                }
-                --emittedChildNesting;
-            }
-            --currentChildNesting;
-        }
-
-        @Override
-        public void visit(TraceNode node) {
-            try {
-                doVisit(node.timestamp(), node.payload(), node.children().iterator().hasNext());
-            } catch (IOException e) {
-                throw new TraceRenderWrapper(e);
-            }
-        }
-
-        private void doVisit(long timestamp, Object payload, boolean hasChildren) throws IOException {
-            boolean dirty = false;
-            if (timestamp != 0L) {
-                header();
-                generator.writeStartObject();
-                generator.writeNumberField(TRACE_TIMESTAMP, timestamp - basetime);
-                dirty = true;
-            }
-            if (payload != null) {
-                if (!dirty) {
-                    header();
-                    generator.writeStartObject();
-                }
-                generator.writeFieldName(TRACE_MESSAGE);
-                fieldConsumer.renderFieldContentsDirect(payload);
-                dirty = true;
-            }
-            if (dirty) {
-                if (!hasChildren) {
-                    generator.writeEndObject();
-                } else {
-                    setInsideOpenObject(true);
-                }
-            }
-        }
-
-        private void header() {
-            fieldName();
-            for (int i = 0; i < (currentChildNesting - emittedChildNesting); ++i) {
-                startChildArray();
-            }
-            emittedChildNesting = currentChildNesting;
-        }
-
-        private void startChildArray() {
-            try {
-                conditionalStartObject();
-                generator.writeArrayFieldStart(TRACE_CHILDREN);
-            } catch (IOException e) {
-                throw new TraceRenderWrapper(e);
-            }
-        }
-
-        private void conditionalStartObject() throws IOException {
-            if (!isInsideOpenObject()) {
-                generator.writeStartObject();
-            } else {
-                setInsideOpenObject(false);
-            }
-        }
-
-        private void conditionalEndObject() {
-            if (isInsideOpenObject()) {
-                // This triggers if we were inside a data node with payload and
-                // subnodes, but none of the subnodes contained data
-                try {
-                    generator.writeEndObject();
-                    setInsideOpenObject(false);
-                } catch (IOException e) {
-                    throw new TraceRenderWrapper(e);
-                }
-            }
-        }
-
-        private void fieldName() {
-            if (hasFieldName) {
-                return;
-            }
-
-            try {
-                generator.writeFieldName(TRACE);
-            } catch (IOException e) {
-                throw new TraceRenderWrapper(e);
-            }
-            hasFieldName = true;
-        }
-
-        boolean isInsideOpenObject() {
-            return insideOpenObject;
-        }
-
-        void setInsideOpenObject(boolean insideOpenObject) {
-            this.insideOpenObject = insideOpenObject;
-        }
-    }
-
-    private static final class TraceRenderWrapper extends RuntimeException {
-
-        /**
-         * Should never be serialized, but this is still needed.
-         */
-        private static final long serialVersionUID = 2L;
-
-        TraceRenderWrapper(IOException wrapped) {
-            super(wrapped);
-        }
-
-    }
-
     public JsonRenderer() {
         this(null);
     }
@@ -352,8 +208,8 @@ public class JsonRenderer extends AsynchronousSectionedRenderer<Result> {
             long basetime = trace.traceNode().timestamp();
             if (basetime == 0L)
                 basetime = getResult().getElapsedTime().first();
-            trace.accept(new TraceRenderer(basetime));
-        } catch (TraceRenderWrapper e) {
+            trace.accept(new TraceRenderer(generator, fieldConsumer, basetime));
+        } catch (TraceRenderer.TraceRenderWrapper e) {
             throw new IOException(e);
         }
     }
@@ -641,11 +497,9 @@ public class JsonRenderer extends AsynchronousSectionedRenderer<Result> {
 
     private String getJsonCallback() {
         Result result = getResult();
-        if (result != null) {
-            Query query = result.getQuery();
-            if (query != null) {
-                return query.properties().getString(JSON_CALLBACK, null);
-            }
+        Query query = result.getQuery();
+        if (query != null) {
+            return query.properties().getString(JSON_CALLBACK, null);
         }
         return null;
     }
@@ -671,7 +525,7 @@ public class JsonRenderer extends AsynchronousSectionedRenderer<Result> {
      * This instance is reused for all hits of a Result since we are in a single-threaded context
      * and want to limit object creation.
      */
-    public static class FieldConsumer implements Hit.RawUtf8Consumer {
+    public static class FieldConsumer implements Hit.RawUtf8Consumer, TraceRenderer.FieldConsumer {
 
         private final JsonGenerator generator;
         private final boolean debugRendering;
@@ -788,11 +642,12 @@ public class JsonRenderer extends AsynchronousSectionedRenderer<Result> {
             if (field instanceof Inspectable && ! (field instanceof FeatureData)) {
                 renderInspector(((Inspectable)field).inspect());
             } else {
-                renderFieldContentsDirect(field);
+                accept(field);
             }
         }
 
-        private void renderFieldContentsDirect(Object field) throws IOException {
+        @Override
+        public void accept(Object field) throws IOException {
             if (field == null) {
                 generator.writeNull();
             } else if (field instanceof Boolean) {