Why its mysqld error occurs during Mariabackup

The error message is shown below.

[00] 2020-01-14 16:06:37 Using server version 10.4.8-MariaDB-log
mariabackup based on MariaDB server 10.4.11-MariaDB Linux (x86_64)
[00] 2020-01-14 16:06:37 uses posix_fadvise().
[00] 2020-01-14 16:06:37 cd to /home/data/mysql/
[00] 2020-01-14 16:06:37 open files limit requested 0, set to 1024
[00] 2020-01-14 16:06:37 mariabackup: using the following InnoDB configuration:
[00] 2020-01-14 16:06:37 innodb_data_home_dir =
[00] 2020-01-14 16:06:37 innodb_data_file_path = ibdata1:12M:autoextend
[00] 2020-01-14 16:06:37 innodb_log_group_home_dir = ./
[00] 2020-01-14 16:06:37 InnoDB: Using Linux native AIO
2020-01-14 16:06:37 0 [Note] InnoDB: Number of pools: 1
[00] 2020-01-14 16:06:37 mariabackup: Generating a list of tablespaces
2020-01-14 16:06:37 0 [Warning] InnoDB: Allocated tablespace ID 28 for UYeG_Cloud/HisItemCurrRMinute, old maximum was 0
2020-01-14 16:06:39 0 [ERROR] InnoDB: Operating system error number 24 in a file operation.
2020-01-14 16:06:39 0 [ERROR] InnoDB: Error number 24 means 'Too many open files'
2020-01-14 16:06:39 0 [Note] InnoDB: Some operating system error numbers are described at https://mariadb.com/kb/en/library/operating-system-error-codes/
2020-01-14 16:06:39 0 [ERROR] InnoDB: File ./UYeG_Cloud/HisAvg#P#p730.ibd: 'open' returned OS error 224.
2020-01-14 16:06:39 0x7f5f7a95d8c0  InnoDB: Assertion failure in file /home/buildbot/buildbot/padding_for_CPACK_RPM_BUILD_SOURCE_DIRS_PREFIX/mariadb-10.4.11/storage/innobase/fil/fil0fil.cc line 576
InnoDB: Failing assertion: success
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to https://jira.mariadb.org/
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: https://mariadb.com/kb/en/library/innodb-recovery-modes/
InnoDB: about forcing recovery.
200114 16:06:39 [ERROR] mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.

To report this bug, see https://mariadb.com/kb/en/reporting-bugs

We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.

Server version: 10.4.11-MariaDB
key_buffer_size=0
read_buffer_size=131072
max_used_connections=0
max_threads=1
thread_count=0
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 5919 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0x0 thread_stack 0x49000
mariabackup(my_print_stacktrace+0x2e)[0x55c824a9937e]
mariabackup(handle_fatal_signal+0x30f)[0x55c824595b5f]
/lib64/libpthread.so.0(+0xf5f0)[0x7f5f7a5495f0]
/lib64/libc.so.6(gsignal+0x37)[0x7f5f7881a337]
/lib64/libc.so.6(abort+0x148)[0x7f5f7881ba28]
mariabackup(+0x5b0574)[0x55c824201574]
mariabackup(+0xad4c41)[0x55c824725c41]
mariabackup(+0xad9eb7)[0x55c82472aeb7]
mariabackup(+0x5e40c5)[0x55c8242350c5]
mariabackup(+0x5e33ad)[0x55c8242343ad]
mariabackup(+0x5e3849)[0x55c824234849]
mariabackup(+0x5e63ec)[0x55c8242373ec]
mariabackup(main+0x185)[0x55c8242047d5]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7f5f78806505]
mariabackup(+0x5dc554)[0x55c82422d554]
The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.
Writing a core file...
Working directory at /home/data/mysql

stopped.

What are the causes and measures?