/**
    * 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.client;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.net.UnknownHostException;
  import java.util.Map;
  import java.util.Map.Entry;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellScanner;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.DoNotRetryIOException;
  import org.apache.hadoop.hbase.HBaseIOException;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HRegionLocation;
  import org.apache.hadoop.hbase.NotServingRegionException;
  import org.apache.hadoop.hbase.RegionLocations;
  import org.apache.hadoop.hbase.RemoteExceptionHandler;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.UnknownScannerException;
  import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
  import org.apache.hadoop.hbase.exceptions.ScannerResetException;
  import org.apache.hadoop.hbase.ipc.PayloadCarryingRpcController;
  import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.RequestConverter;
  import org.apache.hadoop.hbase.protobuf.ResponseConverter;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.ScanRequest;
  import org.apache.hadoop.hbase.protobuf.generated.ClientProtos.ScanResponse;
  import org.apache.hadoop.hbase.regionserver.RegionServerStoppedException;
  import org.apache.hadoop.ipc.RemoteException;
  import org.apache.hadoop.net.DNS;
  
  import com.google.protobuf.ServiceException;
  import com.google.protobuf.TextFormat;
  
  /**
   * Scanner operations such as create, next, etc.
   * Used by {@link ResultScanner}s made by {@link HTable}. Passed to a retrying caller such as
   * {@link RpcRetryingCaller} so fails are retried.
   */
  @InterfaceAudience.Private
  public class ScannerCallable extends RegionServerCallable<Result[]> {
    public static final String LOG_SCANNER_LATENCY_CUTOFF
      = "hbase.client.log.scanner.latency.cutoff";
    public static final String LOG_SCANNER_ACTIVITY = "hbase.client.log.scanner.activity";
  
    // Keeping LOG public as it is being used in TestScannerHeartbeatMessages
    public static final Log LOG = LogFactory.getLog(ScannerCallable.class);
    protected long scannerId = -1L;
    protected boolean instantiated = false;
    protected boolean closed = false;
    protected boolean renew = false;
    private Scan scan;
    private int caching = 1;
    protected final ClusterConnection cConnection;
    protected ScanMetrics scanMetrics;
    private boolean logScannerActivity = false;
    private int logCutOffLatency = 1000;
    private static String myAddress;
    protected final int id;
    protected boolean serverHasMoreResultsContext;
    protected boolean serverHasMoreResults;
  
    /**
     * Saves whether or not the most recent response from the server was a heartbeat message.
     * Heartbeat messages are identified by the flag {@link ScanResponse#getHeartbeatMessage()}
     */
    protected boolean heartbeatMessage = false;
    static {
      try {
        myAddress = DNS.getDefaultHost("default", "default");
      } catch (UnknownHostException uhe) {
        LOG.error("cannot determine my address", uhe);
      }
    }
 
   // indicate if it is a remote server call
   protected boolean isRegionServerRemote = true;
   private long nextCallSeq = 0;
   protected RpcControllerFactory controllerFactory;
   protected PayloadCarryingRpcController controller;
 
   /**
    * @param connection which connection
    * @param tableName table callable is on
    * @param scan the scan to execute
    * @param scanMetrics the ScanMetrics to used, if it is null,
    *        ScannerCallable won't collect metrics
    * @param rpcControllerFactory factory to use when creating
    *        {@link com.google.protobuf.RpcController}
    */
   public ScannerCallable (ClusterConnection connection, TableName tableName, Scan scan,
       ScanMetrics scanMetrics, RpcControllerFactory rpcControllerFactory) {
     this(connection, tableName, scan, scanMetrics, rpcControllerFactory, 0);
   }
   /**
    *
    * @param connection
    * @param tableName
    * @param scan
    * @param scanMetrics
    * @param id the replicaId
    */
   public ScannerCallable (ClusterConnection connection, TableName tableName, Scan scan,
       ScanMetrics scanMetrics, RpcControllerFactory rpcControllerFactory, int id) {
     super(connection, tableName, scan.getStartRow());
     this.id = id;
     this.cConnection = connection;
     this.scan = scan;
     this.scanMetrics = scanMetrics;
     Configuration conf = connection.getConfiguration();
     logScannerActivity = conf.getBoolean(LOG_SCANNER_ACTIVITY, false);
     logCutOffLatency = conf.getInt(LOG_SCANNER_LATENCY_CUTOFF, 1000);
     this.controllerFactory = rpcControllerFactory;
   }
 
   PayloadCarryingRpcController getController() {
     return controller;
   }
 
   /**
    * @param reload force reload of server location
    * @throws IOException
    */
   @Override
   public void prepare(boolean reload) throws IOException {
     if (Thread.interrupted()) {
       throw new InterruptedIOException();
     }
     RegionLocations rl = RpcRetryingCallerWithReadReplicas.getRegionLocations(!reload,
         id, getConnection(), getTableName(), getRow());
     location = id < rl.size() ? rl.getRegionLocation(id) : null;
     if (location == null || location.getServerName() == null) {
       // With this exception, there will be a retry. The location can be null for a replica
       //  when the table is created or after a split.
       throw new HBaseIOException("There is no location for replica id #" + id);
     }
     ServerName dest = location.getServerName();
     setStub(super.getConnection().getClient(dest));
     if (!instantiated || reload) {
       checkIfRegionServerIsRemote();
       instantiated = true;
     }
 
     // check how often we retry.
     // HConnectionManager will call instantiateServer with reload==true
     // if and only if for retries.
     if (reload && this.scanMetrics != null) {
       this.scanMetrics.countOfRPCRetries.incrementAndGet();
       if (isRegionServerRemote) {
         this.scanMetrics.countOfRemoteRPCRetries.incrementAndGet();
       }
     }
   }
 
   /**
    * compare the local machine hostname with region server's hostname
    * to decide if hbase client connects to a remote region server
    */
   protected void checkIfRegionServerIsRemote() {
     if (getLocation().getHostname().equalsIgnoreCase(myAddress)) {
       isRegionServerRemote = false;
     } else {
       isRegionServerRemote = true;
     }
   }
 
 
   @Override
   public Result [] call(int callTimeout) throws IOException {
     if (Thread.interrupted()) {
       throw new InterruptedIOException();
     }
 
     if (controller == null) {
       controller = controllerFactory.newController();
       controller.setPriority(getTableName());
       controller.setCallTimeout(callTimeout);
     }
 
     if (closed) {
       if (scannerId != -1) {
         close();
       }
     } else {
       if (scannerId == -1L) {
         this.scannerId = openScanner();
       } else {
         Result [] rrs = null;
         ScanRequest request = null;
         // Reset the heartbeat flag prior to each RPC in case an exception is thrown by the server
         setHeartbeatMessage(false);
         try {
           incRPCcallsMetrics();
           request =
               RequestConverter.buildScanRequest(scannerId, caching, false, nextCallSeq,
                 this.scanMetrics != null, renew);
           ScanResponse response = null;
           try {
             response = getStub().scan(controller, request);
             // Client and RS maintain a nextCallSeq number during the scan. Every next() call
             // from client to server will increment this number in both sides. Client passes this
             // number along with the request and at RS side both the incoming nextCallSeq and its
             // nextCallSeq will be matched. In case of a timeout this increment at the client side
             // should not happen. If at the server side fetching of next batch of data was over,
             // there will be mismatch in the nextCallSeq number. Server will throw
             // OutOfOrderScannerNextException and then client will reopen the scanner with startrow
             // as the last successfully retrieved row.
             // See HBASE-5974
             nextCallSeq++;
             long timestamp = System.currentTimeMillis();
             setHeartbeatMessage(response.hasHeartbeatMessage() && response.getHeartbeatMessage());
             // Results are returned via controller
             CellScanner cellScanner = controller.cellScanner();
             rrs = ResponseConverter.getResults(cellScanner, response);
             if (logScannerActivity) {
               long now = System.currentTimeMillis();
               if (now - timestamp > logCutOffLatency) {
                 int rows = rrs == null ? 0 : rrs.length;
                 LOG.info("Took " + (now-timestamp) + "ms to fetch "
                   + rows + " rows from scanner=" + scannerId);
               }
             }
             updateServerSideMetrics(response);
             // moreResults is only used for the case where a filter exhausts all elements
             if (response.hasMoreResults() && !response.getMoreResults()) {
               scannerId = -1L;
               closed = true;
               // Implied that no results were returned back, either.
               return null;
             }
             // moreResultsInRegion explicitly defines when a RS may choose to terminate a batch due
             // to size or quantity of results in the response.
             if (response.hasMoreResultsInRegion()) {
               // Set what the RS said
               setHasMoreResultsContext(true);
               setServerHasMoreResults(response.getMoreResultsInRegion());
             } else {
               // Server didn't respond whether it has more results or not.
               setHasMoreResultsContext(false);
             }
           } catch (ServiceException se) {
             throw ProtobufUtil.getRemoteException(se);
           }
           updateResultsMetrics(rrs);
         } catch (IOException e) {
           if (logScannerActivity) {
             LOG.info("Got exception making request " + TextFormat.shortDebugString(request)
               + " to " + getLocation(), e);
           }
           IOException ioe = e;
           if (e instanceof RemoteException) {
             ioe = RemoteExceptionHandler.decodeRemoteException((RemoteException)e);
           }
           if (logScannerActivity) {
             if (ioe instanceof UnknownScannerException) {
               try {
                 HRegionLocation location =
                     getConnection().relocateRegion(getTableName(), scan.getStartRow());
                 LOG.info("Scanner=" + scannerId
                   + " expired, current region location is " + location.toString());
               } catch (Throwable t) {
                 LOG.info("Failed to relocate region", t);
               }
             } else if (ioe instanceof ScannerResetException) {
               LOG.info("Scanner=" + scannerId + " has received an exception, and the server "
                   + "asked us to reset the scanner state.", ioe);
             }
           }
           // The below convertion of exceptions into DoNotRetryExceptions is a little strange.
           // Why not just have these exceptions implment DNRIOE you ask?  Well, usually we want
           // ServerCallable#withRetries to just retry when it gets these exceptions.  In here in
           // a scan when doing a next in particular, we want to break out and get the scanner to
           // reset itself up again.  Throwing a DNRIOE is how we signal this to happen (its ugly,
           // yeah and hard to follow and in need of a refactor).
           if (ioe instanceof NotServingRegionException) {
             // Throw a DNRE so that we break out of cycle of calling NSRE
             // when what we need is to open scanner against new location.
             // Attach NSRE to signal client that it needs to re-setup scanner.
             if (this.scanMetrics != null) {
               this.scanMetrics.countOfNSRE.incrementAndGet();
             }
             throw new DoNotRetryIOException("Resetting the scanner -- see exception cause", ioe);
           } else if (ioe instanceof RegionServerStoppedException) {
             // Throw a DNRE so that we break out of cycle of the retries and instead go and
             // open scanner against new location.
             throw new DoNotRetryIOException("Resetting the scanner -- see exception cause", ioe);
           } else {
             // The outer layers will retry
             throw ioe;
           }
         }
         return rrs;
       }
     }
     return null;
   }
 
   /**
    * @return true when the most recent RPC response indicated that the response was a heartbeat
    *         message. Heartbeat messages are sent back from the server when the processing of the
    *         scan request exceeds a certain time threshold. Heartbeats allow the server to avoid
    *         timeouts during long running scan operations.
    */
   protected boolean isHeartbeatMessage() {
     return heartbeatMessage;
   }
 
   protected void setHeartbeatMessage(boolean heartbeatMessage) {
     this.heartbeatMessage = heartbeatMessage;
   }
 
   private void incRPCcallsMetrics() {
     if (this.scanMetrics == null) {
       return;
     }
     this.scanMetrics.countOfRPCcalls.incrementAndGet();
     if (isRegionServerRemote) {
       this.scanMetrics.countOfRemoteRPCcalls.incrementAndGet();
     }
   }
 
   protected void updateResultsMetrics(Result[] rrs) {
     if (this.scanMetrics == null || rrs == null || rrs.length == 0) {
       return;
     }
     long resultSize = 0;
     for (Result rr : rrs) {
       for (Cell cell : rr.rawCells()) {
         resultSize += CellUtil.estimatedSerializedSizeOf(cell);
       }
     }
     this.scanMetrics.countOfBytesInResults.addAndGet(resultSize);
     if (isRegionServerRemote) {
       this.scanMetrics.countOfBytesInRemoteResults.addAndGet(resultSize);
     }
   }
 
   /**
    * Use the scan metrics returned by the server to add to the identically named counters in the
    * client side metrics. If a counter does not exist with the same name as the server side metric,
    * the attempt to increase the counter will fail.
    * @param response
    */
   private void updateServerSideMetrics(ScanResponse response) {
     if (this.scanMetrics == null || response == null || !response.hasScanMetrics()) return;
 
     Map<String, Long> serverMetrics = ResponseConverter.getScanMetrics(response);
     for (Entry<String, Long> entry : serverMetrics.entrySet()) {
       this.scanMetrics.addToCounter(entry.getKey(), entry.getValue());
     }
   }
 
   private void close() {
     if (this.scannerId == -1L) {
       return;
     }
     try {
       incRPCcallsMetrics();
       ScanRequest request =
           RequestConverter.buildScanRequest(this.scannerId, 0, true, this.scanMetrics != null);
       try {
         getStub().scan(controller, request);
       } catch (ServiceException se) {
         throw ProtobufUtil.getRemoteException(se);
       }
     } catch (IOException e) {
       LOG.warn("Ignore, probably already closed", e);
     }
     this.scannerId = -1L;
   }
 
   protected long openScanner() throws IOException {
     incRPCcallsMetrics();
     ScanRequest request =
       RequestConverter.buildScanRequest(
         getLocation().getRegionInfo().getRegionName(),
         this.scan, 0, false);
     try {
       ScanResponse response = getStub().scan(controller, request);
       long id = response.getScannerId();
       if (logScannerActivity) {
         LOG.info("Open scanner=" + id + " for scan=" + scan.toString()
           + " on region " + getLocation().toString());
       }
       return id;
     } catch (ServiceException se) {
       throw ProtobufUtil.getRemoteException(se);
     }
   }
 
   protected Scan getScan() {
     return scan;
   }
 
   /**
    * Call this when the next invocation of call should close the scanner
    */
   public void setClose() {
     this.closed = true;
   }
 
   /**
    * Indicate whether we make a call only to renew the lease, but without affected the scanner in
    * any other way.
    * @param val true if only the lease should be renewed
    */
   public void setRenew(boolean val) {
     this.renew = val;
   }
 
   /**
    * @return the HRegionInfo for the current region
    */
   @Override
   public HRegionInfo getHRegionInfo() {
     if (!instantiated) {
       return null;
     }
     return getLocation().getRegionInfo();
   }
 
   /**
    * Get the number of rows that will be fetched on next
    * @return the number of rows for caching
    */
   public int getCaching() {
     return caching;
   }
 
   @Override
   public ClusterConnection getConnection() {
     return cConnection;
   }
 
   /**
    * Set the number of rows that will be fetched on next
    * @param caching the number of rows for caching
    */
   public void setCaching(int caching) {
     this.caching = caching;
   }
 
   public ScannerCallable getScannerCallableForReplica(int id) {
     ScannerCallable s = new ScannerCallable(this.getConnection(), this.tableName,
         this.getScan(), this.scanMetrics, controllerFactory, id);
     s.setCaching(this.caching);
     return s;
   }
 
   /**
    * Should the client attempt to fetch more results from this region
    * @return True if the client should attempt to fetch more results, false otherwise.
    */
   protected boolean getServerHasMoreResults() {
     assert serverHasMoreResultsContext;
     return this.serverHasMoreResults;
   }
 
   protected void setServerHasMoreResults(boolean serverHasMoreResults) {
     this.serverHasMoreResults = serverHasMoreResults;
   }
 
   /**
    * Did the server respond with information about whether more results might exist.
    * Not guaranteed to respond with older server versions
    * @return True if the server responded with information about more results.
    */
   protected boolean hasMoreResultsContext() {
     return serverHasMoreResultsContext;
   }
 
   protected void setHasMoreResultsContext(boolean serverHasMoreResultsContext) {
     this.serverHasMoreResultsContext = serverHasMoreResultsContext;
   }
 }