statefun-flink/statefun-flink-datastream/src/main/java/org/apache/flink/statefun/flink/datastream/SerializableHttpFunctionProvider.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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
 *
 *     http://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 org.apache.flink.statefun.flink.datastream;

import java.util.Collections;
import java.util.Map;
import java.util.Objects;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
import org.apache.flink.annotation.Internal;
import org.apache.flink.statefun.flink.core.httpfn.DefaultHttpRequestReplyClientFactory;
import org.apache.flink.statefun.flink.core.httpfn.HttpFunctionEndpointSpec;
import org.apache.flink.statefun.flink.core.httpfn.HttpFunctionProvider;
import org.apache.flink.statefun.flink.core.httpfn.TransportClientConstants;
import org.apache.flink.statefun.flink.core.reqreply.RequestReplyClientFactory;
import org.apache.flink.statefun.flink.core.spi.ExtensionResolver;
import org.apache.flink.statefun.sdk.FunctionType;
import org.apache.flink.statefun.sdk.StatefulFunction;
import org.apache.flink.statefun.sdk.TypeName;

@NotThreadSafe
@Internal
final class SerializableHttpFunctionProvider implements SerializableStatefulFunctionProvider {

  private static final long serialVersionUID = 1;

  private final Map<FunctionType, HttpFunctionEndpointSpec> supportedTypes;
  private transient @Nullable HttpFunctionProvider delegate;

  SerializableHttpFunctionProvider(Map<FunctionType, HttpFunctionEndpointSpec> supportedTypes) {
    this.supportedTypes = Objects.requireNonNull(supportedTypes);
  }

  @Override
  public StatefulFunction functionOfType(FunctionType type) {
    if (delegate == null) {
      delegate =
          new HttpFunctionProvider(
              supportedTypes, Collections.emptyMap(), new OkHttpTransportClientExtensionResolver());
    }
    return delegate.functionOfType(type);
  }

  private static class OkHttpTransportClientExtensionResolver implements ExtensionResolver {

    private final DefaultHttpRequestReplyClientFactory defaultTransportClientFactory =
        new DefaultHttpRequestReplyClientFactory();

    @Override
    public <T> T resolveExtension(TypeName typeName, Class<T> extensionClass) {
      // the DataStream bridge SDK only supports using the default OkHttp request-reply client
      if (!typeName.equals(TransportClientConstants.OKHTTP_CLIENT_FACTORY_TYPE)
          || extensionClass != RequestReplyClientFactory.class) {
        throw new IllegalStateException("The DataStream SDK does not support extensions.");
      }
      return (T) defaultTransportClientFactory;
    }
  }
}