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  1. MariaDB Server
  2. MDEV-10286

Adjustment of table_open_cache according to system limits does not work when open-files-limit option is provided

Details

    • Bug
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Fixed
    • 10.1(EOL)
    • 10.1.32
    • Server
    • None
    • 10.1.17-1, 10.1.18, 10.1.30

    Description

      table_open_cache is supposed to be adjusted (decreased) automatically if system limit on open files does not allow the desired value. It works all right until we also provide open-files-limit option. The option itself does not really do much (as explained here, for example: https://bugs.mysql.com/bug.php?id=34870), but it somehow affects the adjustment; so, table_open_cache can end up with a higher value than the system allows, which leads to obvious problems.

      MySQL 5.6 and 5.7 are not affected.
      10.1 and 10.2 are affected the most, because default value for table_open_cache there is 2000, and it remains such in the described scenario.
      10.0 is also affected, but since the default value there is 400, it is less of a problem.

      Example:

      $ ulimit -n
      		 
      1024

      Server started with all defaults, no extra options - OK

      		 
      +-----------------------+-------------------+--------------------+
      		 
      | @@version             | @@max_connections | @@table_open_cache |
      		 
      +-----------------------+-------------------+--------------------+
      		 
      | 10.1.15-MariaDB-debug |               151 |                431 |
      		 
      +-----------------------+-------------------+--------------------+

      Server started with all defaults and --open-files-limit=1024 - Problem

      		 
      +-----------------------+-------------------+--------------------+
      		 
      | @@version             | @@max_connections | @@table_open_cache |
      		 
      +-----------------------+-------------------+--------------------+
      		 
      | 10.1.15-MariaDB-debug |               151 |               2000 |
      		 
      +-----------------------+-------------------+--------------------+

      MySQL servers started with all defaults and --open-files-limit=1024 - OK

      		 
      +--------------+-------------------+--------------------+
      		 
      | @@version    | @@max_connections | @@table_open_cache |
      		 
      +--------------+-------------------+--------------------+
      		 
      | 5.6.31-debug |               151 |                431 |
      		 
      +--------------+-------------------+--------------------+
      		 
      +--------------+-------------------+--------------------+
      		 
      | @@version    | @@max_connections | @@table_open_cache |
      		 
      +--------------+-------------------+--------------------+
      		 
      | 5.7.13-debug |               151 |                431 |
      		 
      +--------------+-------------------+--------------------+

      Consequences of the problem are very easily reproducible on 10.1 with MTR, because MTR quite conveniently a) sets system limit to 1024 for any platform, and b) has open-files-limit=1024 in the default config template.

      MTR test case

      		 
      --let $cnt= 2000
      		 
       
      		 
      while ($cnt)
      		 
      {
      		 
          eval CREATE TABLE t_$cnt (i INT) ENGINE=MyISAM;
      		 
          eval INSERT INTO t_$cnt VALUES (1);
      		 
          --dec $cnt
      		 
      }


      ....
      		 
      INSERT INTO t_1518 VALUES (1);
      		 
      CREATE TABLE t_1517 (i INT) ENGINE=MyISAM;
      		 
      INSERT INTO t_1517 VALUES (1);
      		 
      CREATE TABLE t_1516 (i INT) ENGINE=MyISAM;
      		 
      bug.t1                                   [ fail ]
      		 
              Test ended at 2016-06-25 21:15:21
      		 
       
      		 
      CURRENT_TEST: bug.t1
      		 
      mysqltest: At line 8: query 'CREATE TABLE t_$cnt (i INT) ENGINE=MyISAM' failed: 1005: Can't create table `test`.`t_1516` (errno: 24 "Too many open files")

      Attachments

        Issue Links

          duplicates

          Bug - A problem which impairs or prevents the functions of the product. MDEV-15609 engines/funcs.crash_manytables_number crashes with error 24 (too many open files)

          • Major - Major loss of function.
          • Closed

          Activity

            People

              monty Michael Widenius
              elenst Elena Stepanova
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              Dates

                Created:
                Updated:
                Resolved:

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