Source:
<code>public void init() throws DBException { if ("true" .equals(getProperties().getProperty("clientbuffering", "false"))) { this.clientSideBuffering = true; } if (getProperties().containsKey("writebuffersize")) { writeBufferSize = Long.parseLong(getProperties().getProperty("writebuffersize")); } if (getProperties().getProperty("durability") != null) { this.durability = Durability.valueOf(getProperties().getProperty("durability")); } if ("kerberos".equalsIgnoreCase(config.get("hbase.security.authentication"))) { config.set("hadoop.security.authentication", "Kerberos"); UserGroupInformation.setConfiguration(config); } if ((getProperties().getProperty("principal")!=null) && (getProperties().getProperty("keytab")!=null)) { try { UserGroupInformation.loginUserFromKeytab(getProperties().getProperty("principal"), getProperties().getProperty("keytab")); } catch (IOException e) { System.err.println("Keytab file is not readable or not found"); throw new DBException(e); } } try { synchronized(THREAD_COUNT) { <START> THREAD_COUNT.getAndIncrement(); <END> if (connection == null) { connection = ConnectionFactory.createConnection(config); } } } catch (java.io.IOException e) { throw new DBException(e); } if ((getProperties().getProperty("debug") != null) && (getProperties().getProperty("debug").compareTo("true") == 0)) { debug = true; } if ("false" .equals(getProperties().getProperty("hbase.usepagefilter", "true"))) { usePageFilter = false; } columnFamily = getProperties().getProperty("columnfamily"); if (columnFamily == null) { System.err.println("Error, must specify a columnfamily for HBase table"); throw new DBException("No columnfamily specified"); } columnFamilyBytes = Bytes.toBytes(columnFamily); String table = com.yahoo.ycsb.workloads.CoreWorkload.table; try { final TableName tName = TableName.valueOf(table); connection.getTable(tName).getTableDescriptor(); } catch (IOException e) { throw new DBException(e); } }</code><technical_language>I guess synchronize Connection object, a proper Object shared THREAD_COUNT is</technical_language>

Target:
public void init() throws DBException { if ("true" .equals(getProperties().getProperty("clientbuffering", "false"))) { this.clientSideBuffering = true; } if (getProperties().containsKey("writebuffersize")) { writeBufferSize = Long.parseLong(getProperties().getProperty("writebuffersize")); } if (getProperties().getProperty("durability") != null) { this.durability = Durability.valueOf(getProperties().getProperty("durability")); } if ("kerberos".equalsIgnoreCase(config.get("hbase.security.authentication"))) { config.set("hadoop.security.authentication", "Kerberos"); UserGroupInformation.setConfiguration(config); } if ((getProperties().getProperty("principal")!=null) && (getProperties().getProperty("keytab")!=null)) { try { UserGroupInformation.loginUserFromKeytab(getProperties().getProperty("principal"), getProperties().getProperty("keytab")); } catch (IOException e) { System.err.println("Keytab file is not readable or not found"); throw new DBException(e); } } try { synchronized(threadCount) { ++threadCount; if (connection == null) { connection = ConnectionFactory.createConnection(config); } } } catch (java.io.IOException e) { throw new DBException(e); } if ((getProperties().getProperty("debug") != null) && (getProperties().getProperty("debug").compareTo("true") == 0)) { debug = true; } if ("false" .equals(getProperties().getProperty("hbase.usepagefilter", "true"))) { usePageFilter = false; } columnFamily = getProperties().getProperty("columnfamily"); if (columnFamily == null) { System.err.println("Error, must specify a columnfamily for HBase table"); throw new DBException("No columnfamily specified"); } columnFamilyBytes = Bytes.toBytes(columnFamily); String table = com.yahoo.ycsb.workloads.CoreWorkload.table; try { final TableName tName = TableName.valueOf(table); connection.getTable(tName).getTableDescriptor(); } catch (IOException e) { throw new DBException(e); } }