hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/ha/SCMHAInvocationHandler.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
 * <p>
 * <p>http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * <p>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.hadoop.hdds.scm.ha;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import com.google.common.base.Preconditions;
import org.apache.hadoop.hdds.protocol.proto.SCMRatisProtocol.RequestType;
import org.apache.hadoop.hdds.scm.metadata.Replicate;
import org.apache.hadoop.util.Time;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * InvocationHandler which checks for {@link Replicate} annotation and
 * dispatches the request to Ratis Server.
 */
public class SCMHAInvocationHandler implements InvocationHandler {


  private static final Logger LOG = LoggerFactory
      .getLogger(SCMHAInvocationHandler.class);

  private final RequestType requestType;
  private final Object localHandler;
  private final SCMRatisServer ratisHandler;

  /**
   * TODO.
   */
  public SCMHAInvocationHandler(final RequestType requestType,
                                final Object localHandler,
                                final SCMRatisServer ratisHandler) {
    this.requestType = requestType;
    this.localHandler = localHandler;
    this.ratisHandler = ratisHandler;
    if (ratisHandler != null) {
      ratisHandler.registerStateMachineHandler(requestType, localHandler);
    }
  }

  @Override
  public Object invoke(final Object proxy, final Method method,
                       final Object[] args) throws Throwable {
    try {
      long startTime = Time.monotonicNow();
      final Object result =
          ratisHandler != null && method.isAnnotationPresent(Replicate.class) ?
              invokeRatis(method, args) :
              invokeLocal(method, args);
      LOG.debug("Call: {} took {} ms", method, Time.monotonicNow() - startTime);
      return result;
    } catch(InvocationTargetException iEx) {
      throw iEx.getCause();
    }
  }

  /**
   * TODO.
   */
  private Object invokeLocal(Method method, Object[] args)
      throws InvocationTargetException, IllegalAccessException {
    LOG.trace("Invoking method {} on target {} with arguments {}",
        method, localHandler, args);
    return method.invoke(localHandler, args);
  }

  /**
   * TODO.
   */
  private Object invokeRatis(Method method, Object[] args)
      throws Exception {
    long startTime = Time.monotonicNowNanos();
    Preconditions.checkNotNull(ratisHandler);
    final SCMRatisResponse response =  ratisHandler.submitRequest(
        SCMRatisRequest.of(requestType, method.getName(), args));
    LOG.info("Invoking method {} on target {}, cost {}us",
        method, ratisHandler, (Time.monotonicNowNanos() - startTime) / 1000.0);
    if (response.isSuccess()) {
      return response.getResult();
    }
    // Should we unwrap and throw proper exception from here?
    throw response.getException();
  }

}