1 files changed, 186 insertions, 0 deletions
diff --git a/container-core/src/main/java/com/yahoo/container/logging/TraceRenderer.java b/container-core/src/main/java/com/yahoo/container/logging/TraceRenderer.java
new file mode 100644
index 00000000000..41b88e08c19
--- /dev/null
+++ b/container-core/src/main/java/com/yahoo/container/logging/TraceRenderer.java
@@ -0,0 +1,186 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+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);
+        }
+
+    }
+}