Use protobuf to encode data instead of JSON

14 files changed, 164 insertions, 157 deletions

diff --git a/spark-common/src/main/java/me/lucko/spark/common/CommandSender.java b/spark-common/src/main/java/me/lucko/spark/common/CommandSender.java
index aca5fba..198bd79 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/CommandSender.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/CommandSender.java
@@ -23,6 +23,7 @@ package me.lucko.spark.common;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonPrimitive;
+import me.lucko.spark.proto.SparkProtos.CommandSenderData;
 import net.kyori.text.Component;
 
 import java.util.UUID;
@@ -72,6 +73,18 @@ public interface CommandSender {
             return user;
         }
 
+        public CommandSenderData toProto() {
+            CommandSenderData.Builder proto = CommandSenderData.newBuilder()
+                    .setType(isPlayer() ? CommandSenderData.Type.PLAYER : CommandSenderData.Type.OTHER)
+                    .setName(this.name);
+
+            if (this.uniqueId != null) {
+                proto.setUniqueId(this.uniqueId.toString());
+            }
+
+            return proto.build();
+        }
+
         public static CommandSender.Data deserialize(JsonElement element) {
             JsonObject userObject = element.getAsJsonObject();
             String user = userObject.get("name").getAsJsonPrimitive().getAsString();
diff --git a/spark-common/src/main/java/me/lucko/spark/common/command/modules/MemoryModule.java b/spark-common/src/main/java/me/lucko/spark/common/command/modules/MemoryModule.java
index a52bf8c..0033716 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/command/modules/MemoryModule.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/command/modules/MemoryModule.java
@@ -54,7 +54,7 @@ import java.util.function.LongConsumer;
 import java.util.zip.GZIPOutputStream;
 
 public class MemoryModule implements CommandModule {
-    private static final MediaType JSON_TYPE = MediaType.parse("application/json; charset=utf-8");
+    private static final MediaType SPARK_HEAP_MEDIA_TYPE = MediaType.parse("application/x-spark-heap");
 
     @Override
     public void registerCommands(Consumer<Command> consumer) {
@@ -81,7 +81,7 @@ public class MemoryModule implements CommandModule {
 
                         byte[] output = heapDump.formCompressedDataPayload(sender);
                         try {
-                            String key = SparkPlatform.BYTEBIN_CLIENT.postContent(output, JSON_TYPE, false).key();
+                            String key = SparkPlatform.BYTEBIN_CLIENT.postContent(output, SPARK_HEAP_MEDIA_TYPE, false).key();
                             String url = SparkPlatform.VIEWER_URL + key;
 
                             resp.broadcastPrefixed(TextComponent.of("Heap dump summmary output:", TextColor.GOLD));
diff --git a/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java b/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java
index 4b7baae..ee16830 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/command/modules/SamplerModule.java
@@ -48,7 +48,7 @@ import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 
 public class SamplerModule implements CommandModule {
-    private static final MediaType JSON_TYPE = MediaType.parse("application/json; charset=utf-8");
+    private static final MediaType SPARK_SAMPLER_MEDIA_TYPE = MediaType.parse("application/x-spark-sampler");
 
     /** The WarmRoast instance currently running, if any */
     private Sampler activeSampler = null;
@@ -246,7 +246,7 @@ public class SamplerModule implements CommandModule {
         platform.getPlugin().runAsync(() -> {
             byte[] output = sampler.formCompressedDataPayload(resp.sender());
             try {
-                String key = SparkPlatform.BYTEBIN_CLIENT.postContent(output, JSON_TYPE, false).key();
+                String key = SparkPlatform.BYTEBIN_CLIENT.postContent(output, SPARK_SAMPLER_MEDIA_TYPE, false).key();
                 String url = SparkPlatform.VIEWER_URL + key;
 
                 resp.broadcastPrefixed(TextComponent.of("Sampling results:", TextColor.GOLD));
diff --git a/spark-common/src/main/java/me/lucko/spark/common/heapdump/HeapDumpSummary.java b/spark-common/src/main/java/me/lucko/spark/common/heapdump/HeapDumpSummary.java
index 867dcc6..c949fc8 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/heapdump/HeapDumpSummary.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/heapdump/HeapDumpSummary.java
@@ -20,20 +20,19 @@
 
 package me.lucko.spark.common.heapdump;
 
-import com.google.gson.Gson;
-import com.google.gson.stream.JsonWriter;
 import me.lucko.spark.common.CommandSender;
 import me.lucko.spark.common.util.TypeDescriptors;
+import me.lucko.spark.proto.SparkProtos;
+import me.lucko.spark.proto.SparkProtos.HeapData;
+import me.lucko.spark.proto.SparkProtos.HeapEntry;
 
 import javax.management.JMX;
 import javax.management.MBeanServer;
 import javax.management.ObjectName;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.OutputStreamWriter;
-import java.io.Writer;
+import java.io.OutputStream;
 import java.lang.management.ManagementFactory;
-import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
@@ -113,34 +112,24 @@ public final class HeapDumpSummary {
         this.entries = entries;
     }
 
-    private void writeOutput(JsonWriter writer, CommandSender creator) throws IOException {
-        writer.beginObject();
-        writer.name("type").value("heap");
+    private HeapData toProto(CommandSender creator) {
+        HeapData.Builder proto = HeapData.newBuilder();
+        proto.setMetadata(SparkProtos.HeapMetadata.newBuilder()
+                .setUser(creator.toData().toProto())
+                .build()
+        );
 
-        writer.name("metadata").beginObject();
-        writer.name("user");
-        new Gson().toJson(creator.toData().serialize(), writer);
-        writer.endObject();
-
-        writer.name("entries").beginArray();
         for (Entry entry : this.entries) {
-            writer.beginObject();
-            writer.name("#").value(entry.getOrder());
-            writer.name("i").value(entry.getInstances());
-            writer.name("s").value(entry.getBytes());
-            writer.name("t").value(entry.getType());
-            writer.endObject();
+            proto.addEntries(entry.toProto());
         }
-        writer.endArray();
-        writer.endObject();
+
+        return proto.build();
     }
 
     public byte[] formCompressedDataPayload(CommandSender creator) {
         ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
-        try (Writer writer = new OutputStreamWriter(new GZIPOutputStream(byteOut), StandardCharsets.UTF_8)) {
-            try (JsonWriter jsonWriter = new JsonWriter(writer)) {
-                writeOutput(jsonWriter, creator);
-            }
+        try (OutputStream out = new GZIPOutputStream(byteOut)) {
+            toProto(creator).writeTo(out);
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
@@ -175,6 +164,15 @@ public final class HeapDumpSummary {
         public String getType() {
             return this.type;
         }
+
+        public HeapEntry toProto() {
+            return HeapEntry.newBuilder()
+                    .setOrder(this.order)
+                    .setInstances(this.instances)
+                    .setSize(this.bytes)
+                    .setType(this.type)
+                    .build();
+        }
     }
 
     public interface DiagnosticCommandMXBean {
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java
index a02eec5..1fb4d2d 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/Sampler.java
@@ -22,22 +22,20 @@
 package me.lucko.spark.common.sampler;
 
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
-import com.google.gson.Gson;
-import com.google.gson.stream.JsonWriter;
 import me.lucko.spark.common.CommandSender;
 import me.lucko.spark.common.sampler.aggregator.DataAggregator;
 import me.lucko.spark.common.sampler.aggregator.SimpleDataAggregator;
 import me.lucko.spark.common.sampler.aggregator.TickedDataAggregator;
 import me.lucko.spark.common.sampler.node.ThreadNode;
+import me.lucko.spark.proto.SparkProtos.SamplerData;
+import me.lucko.spark.proto.SparkProtos.SamplerMetadata;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.OutputStreamWriter;
-import java.io.Writer;
+import java.io.OutputStream;
 import java.lang.management.ManagementFactory;
 import java.lang.management.ThreadInfo;
 import java.lang.management.ThreadMXBean;
-import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -165,56 +163,31 @@ public class Sampler implements Runnable {
         }
     }
 
-    private void writeMetadata(JsonWriter writer) throws IOException {
-        writer.name("startTime").value(this.startTime);
-        writer.name("interval").value(this.interval);
-
-        writer.name("threadDumper").beginObject();
-        this.threadDumper.writeMetadata(writer);
-        writer.endObject();
-
-        writer.name("dataAggregator").beginObject();
-        this.dataAggregator.writeMetadata(writer);
-        writer.endObject();
-    }
-
-    private void writeOutput(JsonWriter writer, CommandSender creator) throws IOException {
-        writer.beginObject();
-
-        writer.name("type").value("sampler");
-
-        writer.name("metadata").beginObject();
-        writeMetadata(writer);
-
-        writer.name("user");
-        new Gson().toJson(creator.toData().serialize(), writer);
-
-        writer.endObject();
-
-        writer.name("threads").beginArray();
+    private SamplerData toProto(CommandSender creator) {
+        SamplerData.Builder proto = SamplerData.newBuilder();
+        proto.setMetadata(SamplerMetadata.newBuilder()
+                .setUser(creator.toData().toProto())
+                .setStartTime(this.startTime)
+                .setInterval(this.interval)
+                .setThreadDumper(this.threadDumper.getMetadata())
+                .setDataAggregator(this.dataAggregator.getMetadata())
+                .build()
+        );
 
         List<Map.Entry<String, ThreadNode>> data = new ArrayList<>(this.dataAggregator.getData().entrySet());
         data.sort(Map.Entry.comparingByKey());
 
         for (Map.Entry<String, ThreadNode> entry : data) {
-            writer.beginObject();
-            writer.name("threadName").value(entry.getKey());
-            writer.name("totalTime").value(entry.getValue().getTotalTime());
-            writer.name("rootNode");
-            entry.getValue().serializeTo(writer);
-            writer.endObject();
+            proto.addThreads(entry.getValue().toProto());
         }
 
-        writer.endArray();
-        writer.endObject();
+        return proto.build();
     }
 
     public byte[] formCompressedDataPayload(CommandSender creator) {
         ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
-        try (Writer writer = new OutputStreamWriter(new GZIPOutputStream(byteOut), StandardCharsets.UTF_8)) {
-            try (JsonWriter jsonWriter = new JsonWriter(writer)) {
-                writeOutput(jsonWriter, creator);
-            }
+        try (OutputStream out = new GZIPOutputStream(byteOut)) {
+            toProto(creator).writeTo(out);
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadDumper.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadDumper.java
index fee130e..8ae2613 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadDumper.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadDumper.java
@@ -21,12 +21,12 @@
 
 package me.lucko.spark.common.sampler;
 
-import com.google.gson.stream.JsonWriter;
 import me.lucko.spark.common.util.ThreadFinder;
+import me.lucko.spark.proto.SparkProtos.SamplerMetadata;
 
-import java.io.IOException;
 import java.lang.management.ThreadInfo;
 import java.lang.management.ThreadMXBean;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -50,12 +50,9 @@ public interface ThreadDumper {
     ThreadInfo[] dumpThreads(ThreadMXBean threadBean);
 
     /**
-     * Writes metadata about the thread dumper instance to the given {@code writer}.
-     *
-     * @param writer the writer
-     * @throws IOException if thrown by the writer
+     * Gets metadata about the thread dumper instance.
      */
-    void writeMetadata(JsonWriter writer) throws IOException;
+    SamplerMetadata.ThreadDumper getMetadata();
 
     /**
      * Implementation of {@link ThreadDumper} that generates data for all threads.
@@ -67,8 +64,10 @@ public interface ThreadDumper {
         }
 
         @Override
-        public void writeMetadata(JsonWriter writer) throws IOException {
-            writer.name("type").value("all");
+        public SamplerMetadata.ThreadDumper getMetadata() {
+            return SamplerMetadata.ThreadDumper.newBuilder()
+                    .setType(SamplerMetadata.ThreadDumper.Type.ALL)
+                    .build();
         }
     };
 
@@ -96,13 +95,11 @@ public interface ThreadDumper {
         }
 
         @Override
-        public void writeMetadata(JsonWriter writer) throws IOException {
-            writer.name("type").value("specific");
-            writer.name("ids").beginArray();
-            for (long id : this.ids) {
-                writer.value(id);
-            }
-            writer.endArray();
+        public SamplerMetadata.ThreadDumper getMetadata() {
+            return SamplerMetadata.ThreadDumper.newBuilder()
+                    .setType(SamplerMetadata.ThreadDumper.Type.SPECIFIC)
+                    .addAllIds(Arrays.stream(this.ids).boxed().collect(Collectors.toList()))
+                    .build();
         }
     }
 
@@ -151,13 +148,11 @@ public interface ThreadDumper {
         }
 
         @Override
-        public void writeMetadata(JsonWriter writer) throws IOException {
-            writer.name("type").value("regex");
-            writer.name("patterns").beginArray();
-            for (Pattern pattern : this.namePatterns) {
-                writer.value(pattern.pattern());
-            }
-            writer.endArray();
+        public SamplerMetadata.ThreadDumper getMetadata() {
+            return SamplerMetadata.ThreadDumper.newBuilder()
+                    .setType(SamplerMetadata.ThreadDumper.Type.REGEX)
+                    .addAllPatterns(this.namePatterns.stream().map(Pattern::pattern).collect(Collectors.toList()))
+                    .build();
         }
     }
 
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadGrouper.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadGrouper.java
index 3023676..d70ba1a 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadGrouper.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/ThreadGrouper.java
@@ -20,6 +20,8 @@
 
 package me.lucko.spark.common.sampler;
 
+import me.lucko.spark.proto.SparkProtos.SamplerMetadata;
+
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.regex.Matcher;
@@ -89,4 +91,17 @@ public enum ThreadGrouper {
      */
     public abstract String getGroup(long threadId, String threadName);
 
+    public static SamplerMetadata.DataAggregator.ThreadGrouper asProto(ThreadGrouper threadGrouper) {
+        switch (threadGrouper) {
+            case BY_NAME:
+                return SamplerMetadata.DataAggregator.ThreadGrouper.BY_NAME;
+            case BY_POOL:
+                return SamplerMetadata.DataAggregator.ThreadGrouper.BY_POOL;
+            case AS_ONE:
+                return SamplerMetadata.DataAggregator.ThreadGrouper.AS_ONE;
+            default:
+                throw new AssertionError();
+        }
+    }
+
 }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/DataAggregator.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/DataAggregator.java
index 6fc62d4..2024f97 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/DataAggregator.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/DataAggregator.java
@@ -20,10 +20,9 @@
 
 package me.lucko.spark.common.sampler.aggregator;
 
-import com.google.gson.stream.JsonWriter;
 import me.lucko.spark.common.sampler.node.ThreadNode;
+import me.lucko.spark.proto.SparkProtos.SamplerMetadata;
 
-import java.io.IOException;
 import java.util.Map;
 
 /**
@@ -47,11 +46,8 @@ public interface DataAggregator {
     void insertData(long threadId, String threadName, StackTraceElement[] stack);
 
     /**
-     * Writes metadata about the data aggregator instance to the given {@code writer}.
-     *
-     * @param writer the writer
-     * @throws IOException if thrown by the writer
+     * Gets metadata about the data aggregator instance.
      */
-    void writeMetadata(JsonWriter writer) throws IOException;
+    SamplerMetadata.DataAggregator getMetadata();
 
 }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/SimpleDataAggregator.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/SimpleDataAggregator.java
index 52e4912..7df3b9e 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/SimpleDataAggregator.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/SimpleDataAggregator.java
@@ -20,11 +20,10 @@
 
 package me.lucko.spark.common.sampler.aggregator;
 
-import com.google.gson.stream.JsonWriter;
 import me.lucko.spark.common.sampler.ThreadGrouper;
 import me.lucko.spark.common.sampler.node.ThreadNode;
+import me.lucko.spark.proto.SparkProtos.SamplerMetadata;
 
-import java.io.IOException;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutorService;
@@ -89,8 +88,10 @@ public class SimpleDataAggregator implements DataAggregator {
     }
 
     @Override
-    public void writeMetadata(JsonWriter writer) throws IOException {
-        writer.name("type").value("simple");
-        writer.name("threadGrouper").value(this.threadGrouper.name().toLowerCase());
+    public SamplerMetadata.DataAggregator getMetadata() {
+        return SamplerMetadata.DataAggregator.newBuilder()
+                .setType(SamplerMetadata.DataAggregator.Type.SIMPLE)
+                .setThreadGrouper(ThreadGrouper.asProto(this.threadGrouper))
+                .build();
     }
 }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/TickedDataAggregator.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/TickedDataAggregator.java
index 3b9bcd2..2437de8 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/TickedDataAggregator.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/aggregator/TickedDataAggregator.java
@@ -20,13 +20,12 @@
 
 package me.lucko.spark.common.sampler.aggregator;
 
-import com.google.gson.stream.JsonWriter;
 import me.lucko.spark.common.sampler.ThreadGrouper;
 import me.lucko.spark.common.sampler.TickCounter;
 import me.lucko.spark.common.sampler.node.AbstractNode;
 import me.lucko.spark.common.sampler.node.ThreadNode;
+import me.lucko.spark.proto.SparkProtos.SamplerMetadata;
 
-import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -153,10 +152,12 @@ public class TickedDataAggregator implements DataAggregator {
     }
 
     @Override
-    public void writeMetadata(JsonWriter writer) throws IOException {
-        writer.name("type").value("ticked");
-        writer.name("threadGrouper").value(this.threadGrouper.name().toLowerCase());
-        writer.name("tickLengthThreshold").value(this.tickLengthThreshold);
+    public SamplerMetadata.DataAggregator getMetadata() {
+        return SamplerMetadata.DataAggregator.newBuilder()
+                .setType(SamplerMetadata.DataAggregator.Type.TICKED)
+                .setThreadGrouper(ThreadGrouper.asProto(this.threadGrouper))
+                .setTickLengthThreshold(this.tickLengthThreshold)
+                .build();
     }
 
     private final class TickList implements Runnable {
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/node/AbstractNode.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/node/AbstractNode.java
index 221b9cb..c5dde1c 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/node/AbstractNode.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/node/AbstractNode.java
@@ -21,11 +21,7 @@
 
 package me.lucko.spark.common.sampler.node;
 
-import com.google.gson.stream.JsonWriter;
-
-import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -103,7 +99,7 @@ public abstract class AbstractNode {
         child.log(elements, offset + 1, time, includeLineNumbers);
     }
 
-    private Collection<? extends AbstractNode> getChildren() {
+    protected List<StackTraceNode> getChildren() {
         if (this.children.isEmpty()) {
             return Collections.emptyList();
         }
@@ -113,28 +109,4 @@ public abstract class AbstractNode {
         return list;
     }
 
-    public void serializeTo(JsonWriter writer) throws IOException {
-        writer.beginObject();
-
-        // append metadata about this node
-        appendMetadata(writer);
-
-        // include the total time recorded for this node
-        writer.name("t").value(getTotalTime());
-
-        // append child nodes, if any are present
-        Collection<? extends AbstractNode> childNodes = getChildren();
-        if (!childNodes.isEmpty()) {
-            writer.name("c").beginArray();
-            for (AbstractNode child : childNodes) {
-                child.serializeTo(writer);
-            }
-            writer.endArray();
-        }
-
-        writer.endObject();
-    }
-
-    protected abstract void appendMetadata(JsonWriter writer) throws IOException;
-
 }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/node/StackTraceNode.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/node/StackTraceNode.java
index 80338e1..5b83c22 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/node/StackTraceNode.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/node/StackTraceNode.java
@@ -21,9 +21,7 @@
 
 package me.lucko.spark.common.sampler.node;
 
-import com.google.gson.stream.JsonWriter;
-
-import java.io.IOException;
+import me.lucko.spark.proto.SparkProtos;
 
 /**
  * Represents a stack trace element within the {@link AbstractNode node} structure.
@@ -60,13 +58,21 @@ public final class StackTraceNode extends AbstractNode implements Comparable<Sta
         this.lineNumber = lineNumber;
     }
 
-    @Override
-    protected void appendMetadata(JsonWriter writer) throws IOException {
-        writer.name("cl").value(this.className);
-        writer.name("m").value(this.methodName);
+    public SparkProtos.StackTraceNode toProto() {
+        SparkProtos.StackTraceNode.Builder proto = SparkProtos.StackTraceNode.newBuilder()
+                .setTime(getTotalTime())
+                .setClassName(this.className)
+                .setMethodName(this.methodName);
+
         if (this.lineNumber >= 0) {
-            writer.name("ln").value(this.lineNumber);
+            proto.setLineNumber(this.lineNumber);
         }
+
+        for (StackTraceNode child : getChildren()) {
+            proto.addChildren(child.toProto());
+        }
+
+        return proto.build();
     }
 
     private String key() {
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/node/ThreadNode.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/node/ThreadNode.java
index 4e8714c..471d2c1 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/sampler/node/ThreadNode.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/node/ThreadNode.java
@@ -20,9 +20,7 @@
 
 package me.lucko.spark.common.sampler.node;
 
-import com.google.gson.stream.JsonWriter;
-
-import java.io.IOException;
+import me.lucko.spark.proto.SparkProtos;
 
 /**
  * The root of a sampling stack for a given thread / thread group.
@@ -38,7 +36,15 @@ public final class ThreadNode extends AbstractNode {
         this.threadName = threadName;
     }
 
-    protected void appendMetadata(JsonWriter writer) throws IOException {
-        writer.name("name").value(this.threadName);
+    public SparkProtos.ThreadNode toProto() {
+        SparkProtos.ThreadNode.Builder proto = SparkProtos.ThreadNode.newBuilder()
+                .setName(this.threadName)
+                .setTime(getTotalTime());
+
+        for (StackTraceNode child : getChildren()) {
+            proto.addChildren(child.toProto());
+        }
+
+        return proto.build();
     }
 }
diff --git a/spark-common/src/main/java/me/lucko/spark/common/sampler/protocol/ProtocolConstants.java b/spark-common/src/main/java/me/lucko/spark/common/sampler/protocol/ProtocolConstants.java
new file mode 100644
index 0000000..1995a58
--- /dev/null
+++ b/spark-common/src/main/java/me/lucko/spark/common/sampler/protocol/ProtocolConstants.java
@@ -0,0 +1,31 @@
+/*
+ * This file is part of spark.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) contributors
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package me.lucko.spark.common.sampler.protocol;
+
+public interface ProtocolConstants {
+
+    int VERSION = 1;
+    int SAMPLER_TYPE = 0;
+
+    byte THREAD_NODE_TYPE = 0;
+    byte STACK_TRACE_NODE_TYPE = 1;
+
+}