Serialize MediaType as an integer to avoid string parsing

libs/core/src/main/java/org/opensearch/core/common/io/stream/StreamInput.java

@@ -55,7 +55,6 @@
 import org.opensearch.core.common.text.Text;
 import org.opensearch.core.concurrency.OpenSearchRejectedExecutionException;
 import org.opensearch.core.xcontent.MediaType;
-import org.opensearch.core.xcontent.MediaTypeRegistry;
 import org.opensearch.semver.SemverRange;
 
 import java.io.ByteArrayInputStream;
@@ -353,7 +352,7 @@
     }
 
     public MediaType readMediaType() throws IOException {
-        return MediaTypeRegistry.fromMediaType(readString());
+        return MediaType.readFrom(this);
     }
 
     @Nullable

libs/core/src/main/java/org/opensearch/core/xcontent/MediaType.java

@@ -32,7 +32,10 @@
 
 package org.opensearch.core.xcontent;
 
+import org.opensearch.Version;
 import org.opensearch.common.annotation.PublicApi;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.common.io.stream.StreamOutput;
 import org.opensearch.core.common.io.stream.Writeable;
 
 import java.io.IOException;
@@ -73,6 +76,13 @@
         return type() + "/" + subtype();
     }
 
+    /**
+     * Unique identifier typically used for binary serialization. Must be distinct
+     * from the unique IDs of all other MediaTypes registered with {@link MediaTypeRegistry}.
+     * See {@link MediaType#readFrom} and {@link MediaType#writeTo}.
+     */
+    int uniqueId();
+
     XContent xContent();
 
     boolean detectedXContent(final byte[] bytes, int offset, int length);
@@ -89,6 +99,29 @@
 
     XContentBuilder contentBuilder(final OutputStream os) throws IOException;
 
+    /**
+     * Serializes this MediaType to the given StreamOutput.
+     */
+    @Override
+    default void writeTo(StreamOutput output) throws IOException {
+        if (output.getVersion().onOrAfter(Version.V_2_10_0) && output.getVersion().before(Version.V_3_0_0)) {
+            output.writeString(this.mediaType());
+        } else {
+            output.writeVInt(uniqueId());
+        }
+    }
+
+    /**
+     * Reads a MediaType instance from the given StreamInput.
+     */
+    static MediaType readFrom(StreamInput in) throws IOException {
+        if (in.getVersion().onOrAfter(Version.V_2_10_0) && in.getVersion().before(Version.V_3_0_0)) {
+            return MediaTypeRegistry.fromMediaType(in.readString());
+        } else {
+            return MediaTypeRegistry.fromUniqueId(in.readVInt());
+        }
+    }
+
     /**
      * Accepts a format string, which is most of the time is equivalent to {@link MediaType#subtype()}
      * and attempts to match the value to an {@link MediaType}.

libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java

@@ -57,6 +57,7 @@
 public final class MediaTypeRegistry {
     private static Map<String, MediaType> formatToMediaType = Map.of();
     private static Map<String, MediaType> typeWithSubtypeToMediaType = Map.of();
+    private static Map<Integer, MediaType> uniqueIdToMediaType = Map.of();
 
     // Default mediaType singleton
     private static MediaType DEFAULT_MEDIA_TYPE;
@@ -84,12 +85,19 @@
         // ensures the map is not overwritten:
         Map<String, MediaType> typeMap = new HashMap<>(typeWithSubtypeToMediaType);
         Map<String, MediaType> formatMap = new HashMap<>(formatToMediaType);
+        Map<Integer, MediaType> uniqueIdMap = new HashMap<>(uniqueIdToMediaType);
         for (MediaType mediaType : acceptedMediaTypes) {
             if (formatMap.containsKey(mediaType.format())) {
                 throw new IllegalArgumentException("unable to register mediaType: [" + mediaType.format() + "]. Type already exists.");
             }
+            if (uniqueIdMap.containsKey(mediaType.uniqueId())) {
+                throw new IllegalArgumentException(
+                    "unable to register mediaType with ID: [" + mediaType.uniqueId() + "]. ID already exists."
+                );
+            }
             typeMap.put(mediaType.typeWithSubtype(), mediaType);
             formatMap.put(mediaType.format(), mediaType);
+            uniqueIdMap.put(mediaType.uniqueId(), mediaType);
         }
         for (Map.Entry<String, MediaType> entry : additionalMediaTypes.entrySet()) {
             String typeWithSubtype = entry.getKey().toLowerCase(Locale.ROOT);
@@ -111,6 +119,11 @@
 
         formatToMediaType = Map.copyOf(formatMap);
         typeWithSubtypeToMediaType = Map.copyOf(typeMap);
+        uniqueIdToMediaType = Map.copyOf(uniqueIdMap);
+    }
+
+    public static MediaType fromUniqueId(int id) {
+        return uniqueIdToMediaType.get(id);
     }
 
     public static MediaType fromMediaType(String mediaType) {

libs/core/src/test/java/org/opensearch/core/xcontent/MediaTypeSerializationTests.java

@@ -0,0 +1,84 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.core.xcontent;
+
+import org.opensearch.Version;
+import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.common.xcontent.XContentType;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.test.OpenSearchTestCase;
+
+import java.io.IOException;
+
+public class MediaTypeSerializationTests extends OpenSearchTestCase {
+
+    public void testRoundtrip() throws IOException {
+        try (BytesStreamOutput output = new BytesStreamOutput()) {
+            XContentType.JSON.writeTo(output);
+            XContentType.SMILE.writeTo(output);
+            XContentType.YAML.writeTo(output);
+            XContentType.CBOR.writeTo(output);
+            try (StreamInput in = output.bytes().streamInput()) {
+                assertEquals(XContentType.JSON, MediaType.readFrom(in));
+                assertEquals(XContentType.SMILE, MediaType.readFrom(in));
+                assertEquals(XContentType.YAML, MediaType.readFrom(in));
+                assertEquals(XContentType.CBOR, MediaType.readFrom(in));
+            }
+        }
+    }
+
+    public void testHardcodedOrdinals() throws IOException {
+        try (BytesStreamOutput output = new BytesStreamOutput()) {
+            output.writeVInt(0);
+            output.writeVInt(1);
+            output.writeVInt(2);
+            output.writeVInt(3);
+            try (StreamInput in = output.bytes().streamInput()) {
+                assertEquals(XContentType.JSON, MediaType.readFrom(in));
+                assertEquals(XContentType.SMILE, MediaType.readFrom(in));
+                assertEquals(XContentType.YAML, MediaType.readFrom(in));
+                assertEquals(XContentType.CBOR, MediaType.readFrom(in));
+            }
+        }
+    }
+
+    public void testBackwardsCompatibilityWithSerializedEnums() throws IOException {
+        // Prior to version 2.10, OpenSearch would serialize XContentType as enums, which
+        // writes the ordinal as a VInt. This test ensure the new MediaType.readFrom method is
+        // functionally compatible with this previous approach.
+        try (BytesStreamOutput output = new BytesStreamOutput()) {
+            output.writeEnum(XContentType.JSON);
+            output.writeEnum(XContentType.SMILE);
+            output.writeEnum(XContentType.YAML);
+            output.writeEnum(XContentType.CBOR);
+            try (StreamInput in = output.bytes().streamInput()) {
+                assertEquals(XContentType.JSON, MediaType.readFrom(in));
+                assertEquals(XContentType.SMILE, MediaType.readFrom(in));
+                assertEquals(XContentType.YAML, MediaType.readFrom(in));
+                assertEquals(XContentType.CBOR, MediaType.readFrom(in));
+            }
+        }
+    }
+
+    public void testStringVersion() throws IOException {
+        try (BytesStreamOutput output = new BytesStreamOutput()) {
+            output.writeString(XContentType.JSON.mediaType());
+            output.writeString(XContentType.SMILE.mediaType());
+            output.writeString(XContentType.YAML.mediaType());
+            output.writeString(XContentType.CBOR.mediaType());
+            try (StreamInput in = output.bytes().streamInput()) {
+                in.setVersion(Version.V_2_11_0);
+                assertEquals(XContentType.JSON, MediaType.readFrom(in));
+                assertEquals(XContentType.SMILE, MediaType.readFrom(in));
+                assertEquals(XContentType.YAML, MediaType.readFrom(in));
+                assertEquals(XContentType.CBOR, MediaType.readFrom(in));
+            }
+        }
+    }
+}

libs/x-content/src/main/java/org/opensearch/common/xcontent/XContentType.java

@@ -40,7 +40,6 @@
 import org.opensearch.common.xcontent.json.JsonXContent;
 import org.opensearch.common.xcontent.smile.SmileXContent;
 import org.opensearch.common.xcontent.yaml.YamlXContent;
-import org.opensearch.core.common.io.stream.StreamOutput;
 import org.opensearch.core.xcontent.MediaType;
 import org.opensearch.core.xcontent.XContent;
 import org.opensearch.core.xcontent.XContentBuilder;
@@ -238,7 +237,7 @@ public XContentBuilder contentBuilder(final OutputStream os) throws IOException
         }
     };
 
-    private int index;
+    private final int index;
 
     XContentType(int index) {
         this.index = index;
@@ -259,7 +258,7 @@ public String format() {
     }
 
     @Override
-    public void writeTo(StreamOutput output) throws IOException {
-        output.writeString(this.mediaType());
+    public int uniqueId() {
+        return index;
     }
 }

modules/percolator/src/main/java/org/opensearch/percolator/PercolateQueryBuilder.java

@@ -62,7 +62,6 @@
 import org.opensearch.common.xcontent.LoggingDeprecationHandler;
 import org.opensearch.common.xcontent.XContentFactory;
 import org.opensearch.common.xcontent.XContentHelper;
-import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.core.ParseField;
 import org.opensearch.core.action.ActionListener;
 import org.opensearch.core.common.bytes.BytesReference;
@@ -254,11 +253,7 @@ protected PercolateQueryBuilder(String field, Supplier<BytesReference> documentS
         }
         documents = in.readList(StreamInput::readBytesReference);
         if (documents.isEmpty() == false) {
-            if (in.getVersion().onOrAfter(Version.V_2_10_0)) {
-                documentXContentType = in.readMediaType();
-            } else {
-                documentXContentType = in.readEnum(XContentType.class);
-            }
+            documentXContentType = MediaType.readFrom(in);
         } else {
             documentXContentType = null;
         }
@@ -304,11 +299,7 @@ protected void doWriteTo(StreamOutput out) throws IOException {
             out.writeBytesReference(document);
         }
         if (documents.isEmpty() == false) {
-            if (out.getVersion().onOrAfter(Version.V_2_10_0)) {
-                documentXContentType.writeTo(out);
-            } else {
-                out.writeEnum((XContentType) documentXContentType);
-            }
+            documentXContentType.writeTo(out);
         }
     }
 

server/src/main/java/org/opensearch/action/admin/cluster/storedscripts/PutStoredScriptRequest.java

@@ -32,12 +32,10 @@
 
 package org.opensearch.action.admin.cluster.storedscripts;
 
-import org.opensearch.Version;
 import org.opensearch.action.ActionRequestValidationException;
 import org.opensearch.action.support.master.AcknowledgedRequest;
 import org.opensearch.common.annotation.PublicApi;
 import org.opensearch.common.xcontent.XContentHelper;
-import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.core.common.Strings;
 import org.opensearch.core.common.bytes.BytesReference;
 import org.opensearch.core.common.io.stream.StreamInput;
@@ -70,11 +68,7 @@ public PutStoredScriptRequest(StreamInput in) throws IOException {
         super(in);
         id = in.readOptionalString();
         content = in.readBytesReference();
-        if (in.getVersion().onOrAfter(Version.V_2_10_0)) {
-            mediaType = in.readMediaType();
-        } else {
-            mediaType = in.readEnum(XContentType.class);
-        }
+        mediaType = MediaType.readFrom(in);
         context = in.readOptionalString();
         source = new StoredScriptSource(in);
     }
@@ -154,11 +148,7 @@ public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeOptionalString(id);
         out.writeBytesReference(content);
-        if (out.getVersion().onOrAfter(Version.V_2_10_0)) {
-            mediaType.writeTo(out);
-        } else {
-            out.writeEnum((XContentType) mediaType);
-        }
+        mediaType.writeTo(out);
         out.writeOptionalString(context);
         source.writeTo(out);
     }

server/src/main/java/org/opensearch/action/index/IndexRequest.java

@@ -51,7 +51,6 @@
 import org.opensearch.common.annotation.PublicApi;
 import org.opensearch.common.lucene.uid.Versions;
 import org.opensearch.common.xcontent.XContentHelper;
-import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.core.common.Strings;
 import org.opensearch.core.common.bytes.BytesArray;
 import org.opensearch.core.common.bytes.BytesReference;
@@ -161,11 +160,7 @@ public IndexRequest(@Nullable ShardId shardId, StreamInput in) throws IOExceptio
         isRetry = in.readBoolean();
         autoGeneratedTimestamp = in.readLong();
         if (in.readBoolean()) {
-            if (in.getVersion().onOrAfter(Version.V_2_10_0)) {
-                contentType = in.readMediaType();
-            } else {
-                contentType = in.readEnum(XContentType.class);
-            }
+            contentType = MediaType.readFrom(in);
         } else {
             contentType = null;
         }
@@ -672,11 +667,7 @@ private void writeBody(StreamOutput out) throws IOException {
         out.writeLong(autoGeneratedTimestamp);
         if (contentType != null) {
             out.writeBoolean(true);
-            if (out.getVersion().onOrAfter(Version.V_2_10_0)) {
-                contentType.writeTo(out);
-            } else {
-                out.writeEnum((XContentType) contentType);
-            }
+            contentType.writeTo(out);
         } else {
             out.writeBoolean(false);
         }

server/src/main/java/org/opensearch/action/ingest/PutPipelineRequest.java

@@ -32,11 +32,9 @@
 
 package org.opensearch.action.ingest;
 
-import org.opensearch.Version;
 import org.opensearch.action.ActionRequestValidationException;
 import org.opensearch.action.support.master.AcknowledgedRequest;
 import org.opensearch.common.annotation.PublicApi;
-import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.core.common.bytes.BytesReference;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.common.io.stream.StreamOutput;
@@ -72,11 +70,7 @@ public PutPipelineRequest(StreamInput in) throws IOException {
         super(in);
         id = in.readString();
         source = in.readBytesReference();
-        if (in.getVersion().onOrAfter(Version.V_2_10_0)) {
-            mediaType = in.readMediaType();
-        } else {
-            mediaType = in.readEnum(XContentType.class);
-        }
+        mediaType = MediaType.readFrom(in);
     }
 
     PutPipelineRequest() {}
@@ -103,11 +97,7 @@ public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeString(id);
         out.writeBytesReference(source);
-        if (out.getVersion().onOrAfter(Version.V_2_10_0)) {
-            mediaType.writeTo(out);
-        } else {
-            out.writeEnum((XContentType) mediaType);
-        }
+        mediaType.writeTo(out);
     }
 
     @Override