use innobackupex to backup a specific database

I want to create a slave to sync a specific database which is used to read. So i use innobackupex to backup the database and use it to init my slave.
i use the command

innobackupex --user=xxx --password=xxx --databases=rpt_version /mnt/bak

and completed ok. However when i in apply-log stage,it come to some error but it also print completed ok at the last.
The apply command is

innobackupex --user=xxx --password=xxx --databases=rpt_version --apply-log /mnt/bak

.
The output of

xtrabackup --print-defatlts

is
[HTML] --log-error=/var/log/mysql/error.log --log-output=FILE --general_log=0 --general_log_file=/infobright_datadir/datadir_new/general_query.log --slow_query_log=1 --long_query_time=5 --slow_query_log_file=/infobright_datadir/datadir_new/slow_query.log --log_error_verbosity=2 --server-id=1 --binlog_format=ROW --log-bin=/infobright_datadir/datadir_new/mysql-bin.log --binlog_do_db=dj_version --binlog_do_db=out_version --binlog_do_db=rpt_version --expire_logs_days=7 --collation-server=utf8_unicode_ci --init-connect=SET NAMES utf8 --character-set-server=utf8 --secure-file-priv= --sql_mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION --symbolic-links=0 --innodb_buffer_pool_size=2048M --innodb_read_io_threads=20 --query_cache_size=128M --tmp_table_size=128M --key_buffer_size=128M --max_allowed_packet=256M --innodb_file_per_table=1 --innodb_data_home_dir=/infobright_datadir/datadir_new --innodb_log_group_home_dir=/infobright_datadir/datadir_new [/HTML]
and the output of apply-log stage :
[HTML] 160505 14:34:04 innobackupex: Starting the apply-log operation IMPORTANT: Please check that the apply-log run completes successfully. At the end of a successful apply-log run innobackupex prints “completed OK!”. innobackupex version 2.4.2 based on MySQL server 5.7.11 Linux (x86_64) (revision id: 8e86a84) xtrabackup: cd to /infobright_datadir/bak/2016-05-05_12-26-48 xtrabackup: This target seems to be already prepared. InnoDB: Number of pools: 1 xtrabackup: notice: xtrabackup_logfile was already used to ‘–prepare’. xtrabackup: using the following InnoDB configuration for recovery: xtrabackup: innodb_data_home_dir = . xtrabackup: innodb_data_file_path = ibdata1:12M:autoextend xtrabackup: innodb_log_group_home_dir = . xtrabackup: innodb_log_files_in_group = 2 xtrabackup: innodb_log_file_size = 50331648 xtrabackup: using the following InnoDB configuration for recovery: xtrabackup: innodb_data_home_dir = . xtrabackup: innodb_data_file_path = ibdata1:12M:autoextend xtrabackup: innodb_log_group_home_dir = . xtrabackup: innodb_log_files_in_group = 2 xtrabackup: innodb_log_file_size = 50331648 xtrabackup: Starting InnoDB instance for recovery. xtrabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter) InnoDB: PUNCH HOLE support available InnoDB: Mutexes and rw_locks use GCC atomic builtins InnoDB: Uses event mutexes InnoDB: GCC builtin __sync_synchronize() is used for memory barrier InnoDB: Compressed tables use zlib 1.2.3.4 InnoDB: Number of pools: 1 InnoDB: Using CPU crc32 instructions InnoDB: Initializing buffer pool, total size = 100M, instances = 1, chunk size = 100M InnoDB: Completed initialization of buffer pool InnoDB: page_cleaner coordinator priority: -20 InnoDB: Highest supported file format is Barracuda. InnoDB: Removed temporary tablespace data file: “ibtmp1” InnoDB: Creating shared tablespace for temporary tables InnoDB: Setting file ‘./ibtmp1’ size to 12 MB. Physically writing the file full; Please wait … InnoDB: File ‘./ibtmp1’ size is now 12 MB. InnoDB: 96 redo rollback segment(s) found. 1 redo rollback segment(s) are active. InnoDB: 32 non-redo rollback segment(s) are active. InnoDB: 5.7.11 started; log sequence number 1301619091050 InnoDB: Failed to find tablespace for table mysql.innodb_table_stats in the cache. Attempting to load the tablespace with space id 321 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Cannot open datafile for read-only: ‘./mysql/innodb_table_stats.ibd’ OS error: 71 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Could not find a valid tablespace file for mysql/innodb_table_stats. Please refer to MySQL :: MySQL 5.7 Reference Manual :: 14.22.3 Troubleshooting InnoDB Data Dictionary Operations for how to resolve the issue. InnoDB: Failed to find tablespace for table mysql.innodb_index_stats in the cache. Attempting to load the tablespace with space id 320 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Cannot open datafile for read-only: ‘./mysql/innodb_index_stats.ibd’ OS error: 71 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Could not find a valid tablespace file for mysql/innodb_index_stats. Please refer to MySQL :: MySQL 5.7 Reference Manual :: 14.22.3 Troubleshooting InnoDB Data Dictionary Operations for how to resolve the issue. InnoDB: xtrabackup: Last MySQL binlog file position 8202245, file name mysql-bin.000122 xtrabackup: starting shutdown with innodb_fast_shutdown = 1 InnoDB: FTS optimize thread exiting. InnoDB: Starting shutdown… InnoDB: Shutdown completed; log sequence number 1301619092641 InnoDB: Number of pools: 1 xtrabackup: using the following InnoDB configuration for recovery: xtrabackup: innodb_data_home_dir = . xtrabackup: innodb_data_file_path = ibdata1:12M:autoextend xtrabackup: innodb_log_group_home_dir = . xtrabackup: innodb_log_files_in_group = 2 xtrabackup: innodb_log_file_size = 50331648 InnoDB: PUNCH HOLE support available InnoDB: Mutexes and rw_locks use GCC atomic builtins InnoDB: Uses event mutexes InnoDB: GCC builtin __sync_synchronize() is used for memory barrier InnoDB: Compressed tables use zlib 1.2.3.4 InnoDB: Number of pools: 1 InnoDB: Using CPU crc32 instructions InnoDB: Initializing buffer pool, total size = 100M, instances = 1, chunk size = 100M InnoDB: Completed initialization of buffer pool InnoDB: page_cleaner coordinator priority: -20 InnoDB: Highest supported file format is Barracuda. InnoDB: Removed temporary tablespace data file: “ibtmp1” InnoDB: Creating shared tablespace for temporary tables InnoDB: Setting file ‘./ibtmp1’ size to 12 MB. Physically writing the file full; Please wait … InnoDB: File ‘./ibtmp1’ size is now 12 MB. InnoDB: 96 redo rollback segment(s) found. 1 redo rollback segment(s) are active. InnoDB: 32 non-redo rollback segment(s) are active. InnoDB: 5.7.11 started; log sequence number 1301619092641 xtrabackup: starting shutdown with innodb_fast_shutdown = 1 InnoDB: FTS optimize thread exiting. InnoDB: Starting shutdown… InnoDB: Failed to find tablespace for table mysql.innodb_index_stats in the cache. Attempting to load the tablespace with space id 320 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Cannot open datafile for read-only: ‘./mysql/innodb_index_stats.ibd’ OS error: 71 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Could not find a valid tablespace file for mysql/innodb_index_stats. Please refer to MySQL :: MySQL 5.7 Reference Manual :: 14.22.3 Troubleshooting InnoDB Data Dictionary Operations for how to resolve the issue. InnoDB: Failed to find tablespace for table mysql.innodb_table_stats in the cache. Attempting to load the tablespace with space id 321 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Cannot open datafile for read-only: ‘./mysql/innodb_table_stats.ibd’ OS error: 71 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: Could not find a valid tablespace file for mysql/innodb_table_stats. Please refer to MySQL :: MySQL 5.7 Reference Manual :: 14.22.3 Troubleshooting InnoDB Data Dictionary Operations for how to resolve the issue. InnoDB: Shutdown completed; log sequence number 1301619094187 160505 14:34:08 completed OK!
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the Mysql server is 5.7.10.