/*
    * 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.coprocessor;
  
  import com.google.common.collect.ImmutableMap;
  import java.io.IOException;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CoprocessorEnvironment;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.client.Delete;
  import org.apache.hadoop.hbase.client.Durability;
  import org.apache.hadoop.hbase.client.Get;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Row;
  import org.apache.hadoop.hbase.ipc.RpcServer;
  import org.apache.hadoop.hbase.metrics.MetricRegistry;
  import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.LossyCounting;
  
  /**
   * A coprocessor that collects metrics from meta table.
   * <p>
   * These metrics will be available through the regular Hadoop metrics2 sinks (ganglia, opentsdb,
   * etc) as well as JMX output.
   * </p>
   *
   * @see MetaTableMetrics
   */
  @InterfaceAudience.Private
  public class MetaTableMetrics extends BaseRegionObserver {
  
    private MetricRegistry registry;
    private LossyCounting<String> clientMetricsLossyCounting, regionMetricsLossyCounting;
    private boolean active = false;
    private Set<String> metrics = new HashSet<>();
  
    enum MetaTableOps {
      GET, PUT, DELETE,
    }
  
    private ImmutableMap<Class<? extends Row>, MetaTableOps> opsNameMap =
        ImmutableMap.<Class<? extends Row>, MetaTableOps>builder()
                .put(Put.class, MetaTableOps.PUT)
                .put(Get.class, MetaTableOps.GET)
                .put(Delete.class, MetaTableOps.DELETE)
                .build();
  
    @Override
    public void preGetOp(ObserverContext<RegionCoprocessorEnvironment> e, Get get, List<Cell> results)
        throws IOException {
      registerAndMarkMetrics(e, get);
    }
  
    @Override
    public void prePut(ObserverContext<RegionCoprocessorEnvironment> e, Put put, WALEdit edit,
        Durability durability) throws IOException {
      registerAndMarkMetrics(e, put);
    }
  
    @Override
    public void preDelete(ObserverContext<RegionCoprocessorEnvironment> e, Delete delete,
        WALEdit edit, Durability durability) throws IOException {
      registerAndMarkMetrics(e, delete);
    }
  
    private void registerAndMarkMetrics(ObserverContext<RegionCoprocessorEnvironment> e, Row row) {
      if (!active || !isMetaTableOp(e)) {
        return;
      }
      tableMetricRegisterAndMark(row);
      clientMetricRegisterAndMark();
      regionMetricRegisterAndMark(row);
      opMetricRegisterAndMark(row);
      opWithClientMetricRegisterAndMark(row);
    }
  
    /**
    * Get table name from Ops such as: get, put, delete.
    *
    * @param op such as get, put or delete.
    */
   private String getTableNameFromOp(Row op) {
     final String tableRowKey = Bytes.toString(op.getRow());
     if (tableRowKey.isEmpty()) {
       return null;
     }
     final String[] splits = tableRowKey.split(",");
     return splits.length > 0 ? splits[0] : null;
   }
 
   /**
    * Get regionId from Ops such as: get, put, delete.
    *
    * @param op such as get, put or delete.
    */
   private String getRegionIdFromOp(Row op) {
     final String tableRowKey = Bytes.toString(op.getRow());
     if (tableRowKey.isEmpty()) {
       return null;
     }
     final String[] splits = tableRowKey.split(",");
     return splits.length > 2 ? splits[2] : null;
   }
 
   private boolean isMetaTableOp(ObserverContext<RegionCoprocessorEnvironment> e) {
     return TableName.META_TABLE_NAME.equals(e.getEnvironment().getRegionInfo().getTable());
   }
 
   private void clientMetricRegisterAndMark() {
     // Mark client metric
     String clientIP = RpcServer.getRemoteIp() != null ? RpcServer.getRemoteIp().toString() : null;
     if (clientIP == null || clientIP.isEmpty()) {
       return;
     }
 
     String clientRequestMeter = clientRequestMeterName(clientIP);
     clientMetricsLossyCounting.add(clientRequestMeter);
     registerAndMarkMeter(clientRequestMeter);
   }
 
   private void tableMetricRegisterAndMark(Row op) {
     // Mark table metric
     String tableName = getTableNameFromOp(op);
     if (tableName == null || tableName.isEmpty()) {
       return;
     }
     String tableRequestMeter = tableMeterName(tableName);
     registerAndMarkMeter(tableRequestMeter);
   }
 
   private void regionMetricRegisterAndMark(Row op) {
     // Mark region metric
     String regionId = getRegionIdFromOp(op);
     if (regionId == null || regionId.isEmpty()) {
       return;
     }
     String regionRequestMeter = regionMeterName(regionId);
     regionMetricsLossyCounting.add(regionRequestMeter);
     registerAndMarkMeter(regionRequestMeter);
   }
 
   private void opMetricRegisterAndMark(Row op) {
     // Mark access type ["get", "put", "delete"] metric
     String opMeterName = opMeterName(op);
     if (opMeterName == null || opMeterName.isEmpty()) {
       return;
     }
     registerAndMarkMeter(opMeterName);
   }
 
   private void opWithClientMetricRegisterAndMark(Object op) {
     // Mark client + access type metric
     String opWithClientMeterName = opWithClientMeterName(op);
     if (opWithClientMeterName == null || opWithClientMeterName.isEmpty()) {
       return;
     }
     registerAndMarkMeter(opWithClientMeterName);
   }
 
   private void registerAndMarkMeter(String requestMeter) {
     if (requestMeter.isEmpty()) {
       return;
     }
     if (!registry.get(requestMeter).isPresent()){
       metrics.add(requestMeter);
     }
     registry.meter(requestMeter).mark();
   }
 
   private String opWithClientMeterName(Object op) {
     // Extract meter name containing the client IP
     String clientIP = RpcServer.getRemoteIp() != null ? RpcServer.getRemoteIp().toString() : "";
     if (clientIP.isEmpty()) {
       return "";
     }
     MetaTableOps ops = opsNameMap.get(op.getClass());
     String opWithClientMeterName = "";
     switch (ops) {
       case GET:
         opWithClientMeterName = String.format("MetaTable_client_%s_get_request", clientIP);
         break;
       case PUT:
         opWithClientMeterName = String.format("MetaTable_client_%s_put_request", clientIP);
         break;
       case DELETE:
         opWithClientMeterName = String.format("MetaTable_client_%s_delete_request", clientIP);
         break;
       default:
         break;
     }
     return opWithClientMeterName;
   }
 
   private String opMeterName(Object op) {
     MetaTableOps ops = opsNameMap.get(op.getClass());
     String opMeterName = "";
     switch (ops) {
       case GET:
         opMeterName = "MetaTable_get_request";
         break;
       case PUT:
         opMeterName = "MetaTable_put_request";
         break;
       case DELETE:
         opMeterName = "MetaTable_delete_request";
         break;
       default:
         break;
     }
     return opMeterName;
   }
 
   private String tableMeterName(String tableName) {
     // Extract meter name containing the table name
     return String.format("MetaTable_table_%s_request", tableName);
   }
 
   private String clientRequestMeterName(String clientIP) {
     // Extract meter name containing the client IP
     if (clientIP.isEmpty()) {
       return "";
     }
     return String.format("MetaTable_client_%s_lossy_request", clientIP);
   }
 
   private String regionMeterName(String regionId) {
     // Extract meter name containing the region ID
     return String.format("MetaTable_region_%s_lossy_request", regionId);
   }
 
   @Override
   public void start(CoprocessorEnvironment env) throws IOException {
     if (env instanceof RegionCoprocessorEnvironment
         && ((RegionCoprocessorEnvironment) env).getRegionInfo().getTable() != null
         && ((RegionCoprocessorEnvironment) env).getRegionInfo().getTable()
         .equals(TableName.META_TABLE_NAME)) {
       RegionCoprocessorEnvironment regionCoprocessorEnv = (RegionCoprocessorEnvironment) env;
       registry = regionCoprocessorEnv.getMetricRegistryForRegionServer();
       LossyCounting.LossyCountingListener<String> listener =
         new LossyCounting.LossyCountingListener<String>() {
           @Override public void sweep(String key) {
             registry.remove(key);
             metrics.remove(key);
           }
       };
       final Configuration conf = regionCoprocessorEnv.getConfiguration();
       clientMetricsLossyCounting = new LossyCounting<>("clientMetaMetrics", conf, listener);
       regionMetricsLossyCounting = new LossyCounting<>("regionMetaMetrics", conf, listener);
       // only be active mode when this region holds meta table.
       active = true;
     }
   }
 
   @Override
   public void stop(CoprocessorEnvironment env) throws IOException {
     // since meta region can move around, clear stale metrics when stop.
     for (String metric:metrics){
       registry.remove(metric);
     }
   }
 }