Introduce GsonGrpcJsonMarshaller and catch JsonMarshaller initializat…

…ion failure (#4033)

Motivation:

Currently, armeria server fails to start up while trying to create a `MessageMarshaller` for `proto2` files containing `Enum` definitions.

It seems like [protobuf-jackson](curioswitch/protobuf-jackson#8) doesn't support `proto2`.
However, it seems like upstream at least partially supports `proto2`.

https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/util/JsonFormat

> The JSON format follows Proto3 JSON specification and only proto3 features are supported. Proto2 only features (e.g., extensions and unknown fields) will be discarded in the conversion. That is, when converting proto2 messages to JSON format, extensions and unknown fields will be treated as if they do not exist. This applies to proto2 messages embedded in proto3 messages as well.

Modifications:

- Introduce a `GsonGrpcJsonMarshaller` which performs JSON marshalling using Gson.
  - Also introduce a corresponding builder class `GrpcJsonMarshallerBuilder`
- Add `GrpcJsonMarshaller#ofJackson`, `GrpcJsonMarshaller#builderForJackson`, `GrpcJsonMarshaller#ofGson`, `GrpcJsonMarshaller#builderForGson`

Result:

- Closes #4020
- Armeria now provides an easy way to fall back to the upstream `gson` implementation

grpc/src/main/java/com/linecorp/armeria/common/grpc/GrpcJsonMarshaller.java

@@ -39,19 +39,54 @@ public interface GrpcJsonMarshaller {
 
     /**
      * Returns a newly-created {@link GrpcJsonMarshaller} which serializes and deserializes a {@link Message}
-     * served by the {@linkplain ServiceDescriptor service}.
+     * served by the {@linkplain ServiceDescriptor service}. This implementation internally uses
+     * <a href="https://github.com/curioswitch/protobuf-jackson">protobuf-jackson</a>
+     * to serialize and deserialize messages.
      */
     static GrpcJsonMarshaller of(ServiceDescriptor serviceDescriptor) {
         return builder().build(serviceDescriptor);
     }
 
     /**
-     * Returns a new {@link GrpcJsonMarshallerBuilder}.
+     * Returns a new {@link GrpcJsonMarshallerBuilder}. This implementation internally uses
+     * <a href="https://github.com/curioswitch/protobuf-jackson">protobuf-jackson</a>
+     * to serialize and deserialize messages.
      */
     static GrpcJsonMarshallerBuilder builder() {
         return new GrpcJsonMarshallerBuilder();
     }
 
+    /**
+     * Returns a newly-created {@link GrpcJsonMarshaller} which serializes and deserializes a {@link Message}.
+     * This implementation internally uses
+     * <a href="https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/util/JsonFormat">JsonFormat</a>
+     * and {@code Gson} to serialize and deserialize messages.
+     * Note:
+     * <a href="https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/util/JsonFormat">JsonFormat</a>
+     * has a known <a href="https://github.com/curioswitch/protobuf-jackson#benchmarks">performance issue</a>.
+     * Use this method only when
+     * 1) you're using Protobuf 2 or 2) you have an issue with
+     * <a href="https://github.com/curioswitch/protobuf-jackson">protobuf-jackson</a>.
+     */
+    static GrpcJsonMarshaller ofGson() {
+        return builderForGson().build();
+    }
+
+    /**
+     * Returns a new {@link GsonGrpcJsonMarshallerBuilder}. This implementation internally uses
+     * <a href="https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/util/JsonFormat">JsonFormat</a>
+     * and {@code Gson} to serialize and deserialize messages.
+     * Note:
+     * <a href="https://developers.google.com/protocol-buffers/docs/reference/java/com/google/protobuf/util/JsonFormat">JsonFormat</a>
+     * has a known <a href="https://github.com/curioswitch/protobuf-jackson#benchmarks">performance issue</a>.
+     * Use this method only when
+     * 1) you're using Protobuf 2 or 2) you have an issue with
+     * <a href="https://github.com/curioswitch/protobuf-jackson">protobuf-jackson</a>.
+     */
+    static GsonGrpcJsonMarshallerBuilder builderForGson() {
+        return new GsonGrpcJsonMarshallerBuilder();
+    }
+
     /**
      * Serializes a gRPC message into JSON.
      */

grpc/src/main/java/com/linecorp/armeria/common/grpc/GsonGrpcJsonMarshaller.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2022 LINE Corporation
+ *
+ * LINE Corporation licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.linecorp.armeria.common.grpc;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
+
+import com.google.protobuf.Message;
+import com.google.protobuf.MessageOrBuilder;
+import com.google.protobuf.util.JsonFormat;
+
+import io.grpc.MethodDescriptor.Marshaller;
+import io.grpc.MethodDescriptor.PrototypeMarshaller;
+
+final class GsonGrpcJsonMarshaller implements GrpcJsonMarshaller {
+
+    final JsonFormat.Printer printer;
+    final JsonFormat.Parser parser;
+
+    GsonGrpcJsonMarshaller(JsonFormat.Printer printer, JsonFormat.Parser parser) {
+        this.printer = printer;
+        this.parser = parser;
+    }
+
+    @Override
+    public <T> void serializeMessage(Marshaller<T> marshaller, T message, OutputStream os) throws IOException {
+        os.write(printer.print((MessageOrBuilder) message).getBytes(StandardCharsets.UTF_8));
+    }
+
+    @Override
+    public <T> T deserializeMessage(Marshaller<T> marshaller, InputStream is) throws IOException {
+        final PrototypeMarshaller<T> prototypeMarshaller = (PrototypeMarshaller<T>) marshaller;
+        final Message prototype = (Message) prototypeMarshaller.getMessagePrototype();
+        assert prototype != null;
+        final Message.Builder builder = prototype.newBuilderForType();
+        parser.merge(new InputStreamReader(is, StandardCharsets.UTF_8), builder);
+        @SuppressWarnings("unchecked")
+        final T cast = (T) builder.build();
+        return cast;
+    }
+}

grpc/src/main/java/com/linecorp/armeria/common/grpc/GsonGrpcJsonMarshallerBuilder.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2020 LINE Corporation
+ *
+ * LINE Corporation licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.linecorp.armeria.common.grpc;
+
+import static java.util.Objects.requireNonNull;
+
+import java.util.function.Consumer;
+
+import com.google.protobuf.Message;
+import com.google.protobuf.util.JsonFormat;
+
+import com.linecorp.armeria.common.annotation.Nullable;
+
+/**
+ * A builder for creating a new {@link GrpcJsonMarshaller} that serializes and deserializes a {@link Message}
+ * to and from JSON.
+ */
+public final class GsonGrpcJsonMarshallerBuilder {
+
+    @Nullable
+    private Consumer<JsonFormat.Parser> jsonParserCustomizer;
+
+    @Nullable
+    private Consumer<JsonFormat.Printer> jsonPrinterCustomizer;
+
+    GsonGrpcJsonMarshallerBuilder() {}
+
+    /**
+     * Adds a {@link Consumer} that can customize the {@link JsonFormat.Parser}
+     * used when deserializing a JSON payload into a {@link Message}.
+     */
+    public GsonGrpcJsonMarshallerBuilder jsonParserCustomizer(
+            Consumer<? super JsonFormat.Parser> jsonParserCustomizer) {
+        requireNonNull(jsonParserCustomizer, "jsonParserCustomizer");
+        if (this.jsonParserCustomizer == null) {
+            @SuppressWarnings("unchecked")
+            final Consumer<JsonFormat.Parser> cast = (Consumer<JsonFormat.Parser>) jsonParserCustomizer;
+            this.jsonParserCustomizer = cast;
+        } else {
+            this.jsonParserCustomizer = this.jsonParserCustomizer.andThen(jsonParserCustomizer);
+        }
+        return this;
+    }
+
+    /**
+     * Adds a {@link Consumer} that can customize the {@link JsonFormat.Printer}
+     * used when serializing a {@link Message} into a JSON payload.
+     */
+    public GsonGrpcJsonMarshallerBuilder jsonPrinterCustomizer(
+            Consumer<? super JsonFormat.Printer> jsonPrinterCustomizer) {
+        requireNonNull(jsonPrinterCustomizer, "jsonPrinterCustomizer");
+        if (this.jsonPrinterCustomizer == null) {
+            @SuppressWarnings("unchecked")
+            final Consumer<JsonFormat.Printer> cast = (Consumer<JsonFormat.Printer>) jsonPrinterCustomizer;
+            this.jsonPrinterCustomizer = cast;
+        } else {
+            this.jsonPrinterCustomizer = this.jsonPrinterCustomizer.andThen(jsonPrinterCustomizer);
+        }
+        return this;
+    }
+
+    /**
+     * Returns a newly-created {@link GrpcJsonMarshaller}.
+     */
+    public GrpcJsonMarshaller build() {
+        final JsonFormat.Printer printer = JsonFormat.printer().omittingInsignificantWhitespace();
+        if (jsonPrinterCustomizer != null) {
+            jsonPrinterCustomizer.accept(printer);
+        }
+
+        final JsonFormat.Parser parser = JsonFormat.parser().ignoringUnknownFields();
+        if (jsonParserCustomizer != null) {
+            jsonParserCustomizer.accept(parser);
+        }
+        return new GsonGrpcJsonMarshaller(printer, parser);
+    }
+}

grpc/src/main/java/com/linecorp/armeria/internal/client/grpc/GrpcClientFactory.java

@@ -29,6 +29,9 @@
 import java.util.Set;
 import java.util.function.Function;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 
@@ -39,6 +42,7 @@
 import com.linecorp.armeria.client.ClientOptionsBuilder;
 import com.linecorp.armeria.client.DecoratingClientFactory;
 import com.linecorp.armeria.client.HttpClient;
+import com.linecorp.armeria.client.grpc.GrpcClientBuilder;
 import com.linecorp.armeria.client.grpc.GrpcClientOptions;
 import com.linecorp.armeria.client.grpc.GrpcClientStubFactory;
 import com.linecorp.armeria.client.grpc.protocol.UnaryGrpcClient;
@@ -62,6 +66,8 @@
  */
 final class GrpcClientFactory extends DecoratingClientFactory {
 
+    private static final Logger logger = LoggerFactory.getLogger(GrpcClientFactory.class);
+
     private static final Set<Scheme> SUPPORTED_SCHEMES =
             Arrays.stream(SessionProtocol.values())
                   .flatMap(p -> GrpcSerializationFormats.values()
@@ -130,8 +136,16 @@ public Object newClient(ClientBuilderParams params) {
 
         final GrpcJsonMarshaller jsonMarshaller;
         if (GrpcSerializationFormats.isJson(serializationFormat)) {
-            jsonMarshaller = options.get(GrpcClientOptions.GRPC_JSON_MARSHALLER_FACTORY)
-                                    .apply(serviceDescriptor);
+            try {
+                jsonMarshaller = options.get(GrpcClientOptions.GRPC_JSON_MARSHALLER_FACTORY)
+                                        .apply(serviceDescriptor);
+            } catch (Exception e) {
+                logger.warn("Failed to instantiate a JSON marshaller for gRPC-JSON. " +
+                            "Consider using a different serialization format with {}.serializationFormat() " +
+                            "or using {}.ofGson() instead.",
+                            GrpcClientBuilder.class.getName(), GrpcJsonMarshaller.class.getName(), e);
+                throw e;
+            }
         } else {
             jsonMarshaller = null;
         }

grpc/src/main/java/com/linecorp/armeria/server/grpc/FramedGrpcService.java

@@ -84,6 +84,28 @@ final class FramedGrpcService extends AbstractHttpService implements GrpcService
     static final AttributeKey<ServerMethodDefinition<?, ?>> RESOLVED_GRPC_METHOD =
             AttributeKey.valueOf(FramedGrpcService.class, "RESOLVED_GRPC_METHOD");
 
+    private static Map<String, GrpcJsonMarshaller> getJsonMarshallers(
+            HandlerRegistry registry,
+            Set<SerializationFormat> supportedSerializationFormats,
+            Function<? super ServiceDescriptor, ? extends GrpcJsonMarshaller> jsonMarshallerFactory) {
+        if (supportedSerializationFormats.stream().noneMatch(GrpcSerializationFormats::isJson)) {
+            return ImmutableMap.of();
+        } else {
+            try {
+                return registry.services().stream()
+                               .map(ServerServiceDefinition::getServiceDescriptor)
+                               .distinct()
+                               .collect(toImmutableMap(ServiceDescriptor::getName, jsonMarshallerFactory));
+            } catch (Exception e) {
+                logger.warn("Failed to instantiate a JSON marshaller. Consider disabling gRPC-JSON " +
+                            "serialization with {}.supportedSerializationFormats() " +
+                            "or using {}.ofGson() instead.",
+                            GrpcServiceBuilder.class.getName(), GrpcJsonMarshaller.class.getName(), e);
+                return ImmutableMap.of();
+            }
+        }
+    }
+
     private final HandlerRegistry registry;
     private final Set<Route> routes;
     private final DecompressorRegistry decompressorRegistry;
@@ -124,15 +146,7 @@ final class FramedGrpcService extends AbstractHttpService implements GrpcService
         this.compressorRegistry = requireNonNull(compressorRegistry, "compressorRegistry");
         this.supportedSerializationFormats = supportedSerializationFormats;
         this.useClientTimeoutHeader = useClientTimeoutHeader;
-        if (supportedSerializationFormats.stream().noneMatch(GrpcSerializationFormats::isJson)) {
-            jsonMarshallers = ImmutableMap.of();
-        } else {
-            jsonMarshallers =
-                    registry.services().stream()
-                            .map(ServerServiceDefinition::getServiceDescriptor)
-                            .distinct()
-                            .collect(toImmutableMap(ServiceDescriptor::getName, jsonMarshallerFactory));
-        }
+        jsonMarshallers = getJsonMarshallers(registry, supportedSerializationFormats, jsonMarshallerFactory);
         this.protoReflectionServiceInterceptor = protoReflectionServiceInterceptor;
         this.statusFunction = statusFunction;
         this.maxRequestMessageLength = maxRequestMessageLength;