/**
    * 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.hadoop.hbase.regionserver;
  
  import java.lang.reflect.Method;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.ipc.PriorityFunction;
  import org.apache.hadoop.hbase.ipc.QosPriority;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.CloseRegionRequest;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.CompactRegionRequest;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.FlushRegionRequest;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.GetRegionInfoRequest;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.GetStoreFileRequest;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.SplitRegionRequest;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.GetRequest;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.MutateRequest;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.ScanRequest;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.RegionSpecifier;
  import org.apache.hadoop.hbase.protobuf.generated.RPCProtos.RequestHeader;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.protobuf.Message;
  import com.google.protobuf.TextFormat;
  import org.apache.hadoop.hbase.security.User;
  
  /**
   * Reads special method annotations and table names to figure a priority for use by QoS facility in
   * ipc; e.g: rpcs to hbase:meta get priority.
   */
  // TODO: Remove.  This is doing way too much work just to figure a priority.  Do as Elliott
  // suggests and just have the client specify a priority.
  
  //The logic for figuring out high priority RPCs is as follows:
  //1. if the method is annotated with a QosPriority of QOS_HIGH,
  //   that is honored
  //2. parse out the protobuf message and see if the request is for meta
  //   region, and if so, treat it as a high priority RPC
  //Some optimizations for (2) are done here -
  //Clients send the argument classname as part of making the RPC. The server
  //decides whether to deserialize the proto argument message based on the
  //pre-established set of argument classes (knownArgumentClasses below).
  //This prevents the server from having to deserialize all proto argument
  //messages prematurely.
  //All the argument classes declare a 'getRegion' method that returns a
  //RegionSpecifier object. Methods can be invoked on the returned object
  //to figure out whether it is a meta region or not.
  @InterfaceAudience.Private
  public class AnnotationReadingPriorityFunction implements PriorityFunction {
    private static final Log LOG =
      LogFactory.getLog(AnnotationReadingPriorityFunction.class.getName());
  
    /** Used to control the scan delay, currently sqrt(numNextCall * weight) */
    public static final String SCAN_VTIME_WEIGHT_CONF_KEY = "hbase.ipc.server.scan.vtime.weight";
  
    protected final Map<String, Integer> annotatedQos;
    //We need to mock the regionserver instance for some unit tests (set via
    //setRegionServer method.
    private RSRpcServices rpcServices;
    @SuppressWarnings("unchecked")
    private final Class<? extends Message>[] knownArgumentClasses = new Class[]{
        GetRegionInfoRequest.class,
        GetStoreFileRequest.class,
        CloseRegionRequest.class,
        FlushRegionRequest.class,
        SplitRegionRequest.class,
        CompactRegionRequest.class,
        GetRequest.class,
        MutateRequest.class,
        ScanRequest.class
    };
  
    // Some caches for helping performance
    private final Map<String, Class<? extends Message>> argumentToClassMap =
      new HashMap<String, Class<? extends Message>>();
    private final Map<String, Map<Class<? extends Message>, Method>> methodMap =
      new HashMap<String, Map<Class<? extends Message>, Method>>();
  
   private final float scanVirtualTimeWeight;
 
   /**
    * Calls {@link #AnnotationReadingPriorityFunction(RSRpcServices, Class)} using the result of
    * {@code rpcServices#getClass()}
    *
    * @param rpcServices
    *          The RPC server implementation
    */
   public AnnotationReadingPriorityFunction(final RSRpcServices rpcServices) {
     this(rpcServices, rpcServices.getClass());
   }
 
   /**
    * Constructs the priority function given the RPC server implementation and the annotations on the
    * methods in the provided {@code clz}.
    *
    * @param rpcServices
    *          The RPC server implementation
    * @param clz
    *          The concrete RPC server implementation's class
    */
   public AnnotationReadingPriorityFunction(final RSRpcServices rpcServices,
       Class<? extends RSRpcServices> clz) {
     Map<String,Integer> qosMap = new HashMap<String,Integer>();
     for (Method m : clz.getMethods()) {
       QosPriority p = m.getAnnotation(QosPriority.class);
       if (p != null) {
         // Since we protobuf'd, and then subsequently, when we went with pb style, method names
         // are capitalized.  This meant that this brittle compare of method names gotten by
         // reflection no longer matched the method names coming in over pb.  TODO: Get rid of this
         // check.  For now, workaround is to capitalize the names we got from reflection so they
         // have chance of matching the pb ones.
         String capitalizedMethodName = capitalize(m.getName());
         qosMap.put(capitalizedMethodName, p.priority());
       }
     }
     this.rpcServices = rpcServices;
     this.annotatedQos = qosMap;
     if (methodMap.get("getRegion") == null) {
       methodMap.put("hasRegion", new HashMap<Class<? extends Message>, Method>());
       methodMap.put("getRegion", new HashMap<Class<? extends Message>, Method>());
     }
     for (Class<? extends Message> cls : knownArgumentClasses) {
       argumentToClassMap.put(cls.getName(), cls);
       try {
         methodMap.get("hasRegion").put(cls, cls.getDeclaredMethod("hasRegion"));
         methodMap.get("getRegion").put(cls, cls.getDeclaredMethod("getRegion"));
       } catch (Exception e) {
         throw new RuntimeException(e);
       }
     }
 
     Configuration conf = rpcServices.getConfiguration();
     scanVirtualTimeWeight = conf.getFloat(SCAN_VTIME_WEIGHT_CONF_KEY, 1.0f);
   }
 
   private String capitalize(final String s) {
     StringBuilder strBuilder = new StringBuilder(s);
     strBuilder.setCharAt(0, Character.toUpperCase(strBuilder.charAt(0)));
     return strBuilder.toString();
   }
 
   /**
    * Returns a 'priority' based on the request type.
    *
    * Currently the returned priority is used for queue selection.
    * See the SimpleRpcScheduler as example. It maintains a queue per 'priory type'
    * HIGH_QOS (meta requests), REPLICATION_QOS (replication requests),
    * NORMAL_QOS (user requests).
    */
   @Override
   public int getPriority(RequestHeader header, Message param, User user) {
     int priorityByAnnotation = getAnnotatedPriority(header);
 
     if (priorityByAnnotation >= 0) {
       return priorityByAnnotation;
     }
     return getBasePriority(header, param);
   }
 
   /**
    * See if the method has an annotation.
    * @param header
    * @return Return the priority from the annotation. If there isn't
    * an annotation, this returns something below zero.
    */
   protected int getAnnotatedPriority(RequestHeader header) {
     String methodName = header.getMethodName();
     Integer priorityByAnnotation = annotatedQos.get(methodName);
     if (priorityByAnnotation != null) {
       return priorityByAnnotation;
     }
     return -1;
   }
 
   /**
    * Get the priority for a given request from the header and the param
    * This doesn't consider which user is sending the request at all.
    * This doesn't consider annotations
    */
   protected int getBasePriority(RequestHeader header, Message param) {
     if (param == null) {
       return HConstants.NORMAL_QOS;
     }
 
     // Trust the client-set priorities if set
     if (header.hasPriority()) {
       return header.getPriority();
     }
 
     String cls = param.getClass().getName();
     Class<? extends Message> rpcArgClass = argumentToClassMap.get(cls);
     RegionSpecifier regionSpecifier = null;
     //check whether the request has reference to meta region or now.
     try {
       // Check if the param has a region specifier; the pb methods are hasRegion and getRegion if
       // hasRegion returns true.  Not all listed methods have region specifier each time.  For
       // example, the ScanRequest has it on setup but thereafter relies on the scannerid rather than
       // send the region over every time.
       Method hasRegion = methodMap.get("hasRegion").get(rpcArgClass);
       if (hasRegion != null && (Boolean)hasRegion.invoke(param, (Object[])null)) {
         Method getRegion = methodMap.get("getRegion").get(rpcArgClass);
         regionSpecifier = (RegionSpecifier)getRegion.invoke(param, (Object[])null);
         Region region = rpcServices.getRegion(regionSpecifier);
         if (region.getRegionInfo().isSystemTable()) {
           if (LOG.isTraceEnabled()) {
             LOG.trace("High priority because region=" +
               region.getRegionInfo().getRegionNameAsString());
           }
           return HConstants.SYSTEMTABLE_QOS;
         }
       }
     } catch (Exception ex) {
       // Not good throwing an exception out of here, a runtime anyways.  Let the query go into the
       // server and have it throw the exception if still an issue.  Just mark it normal priority.
       if (LOG.isTraceEnabled()) LOG.trace("Marking normal priority after getting exception=" + ex);
       return HConstants.NORMAL_QOS;
     }
 
     if (param instanceof ScanRequest) { // scanner methods...
       ScanRequest request = (ScanRequest)param;
       if (!request.hasScannerId()) {
         return HConstants.NORMAL_QOS;
       }
       RegionScanner scanner = rpcServices.getScanner(request.getScannerId());
       if (scanner != null && scanner.getRegionInfo().isSystemTable()) {
         if (LOG.isTraceEnabled()) {
           // Scanner requests are small in size so TextFormat version should not overwhelm log.
           LOG.trace("High priority scanner request " + TextFormat.shortDebugString(request));
         }
         return HConstants.SYSTEMTABLE_QOS;
       }
     }
 
     return HConstants.NORMAL_QOS;
   }
 
   /**
    * Based on the request content, returns the deadline of the request.
    *
    * @param header
    * @param param
    * @return Deadline of this request. 0 now, otherwise msec of 'delay'
    */
   @Override
   public long getDeadline(RequestHeader header, Message param) {
     if (param instanceof ScanRequest) {
       ScanRequest request = (ScanRequest)param;
       if (!request.hasScannerId()) {
         return 0;
       }
 
       // get the 'virtual time' of the scanner, and applies sqrt() to get a
       // nice curve for the delay. More a scanner is used the less priority it gets.
       // The weight is used to have more control on the delay.
       long vtime = rpcServices.getScannerVirtualTime(request.getScannerId());
       return Math.round(Math.sqrt(vtime * scanVirtualTimeWeight));
     }
     return 0;
   }
 
   @VisibleForTesting
   void setRegionServer(final HRegionServer hrs) {
     this.rpcServices = hrs.getRSRpcServices();
   }
 }