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  1. MariaDB Server
  2. MDEV-14608

mysqlbinlog lastest backupfile size is 0

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    Description

      In centos7.3,7.4 , mariadb (10.1.28,10.1.29,10.2.11，)has the following problem:

      comand like this:
      /usr/bin/mysqlbinlog --raw --read-from-remote-server --stop-never --host=localhost --port=3306 --user=root --password=root --result-file=/backup/binlog/ mysql-bin.000001

      lastest backupfile size is 0:

      1. ll

      rw-rw-r- 1 mysql mysql 441 Dec 7 09:22 mysql-bin.000076
      rw-rw-r- 1 mysql mysql 3230 Dec 8 03:20 mysql-bin.000077
      rw-rw-r- 1 mysql mysql 0 Dec 8 03:20 mysql-bin.000078

      OTHER:
      mariadb10.1.29 In Cent6.8, percona5.7,mysql5.7 in centos7.3,cent7.4 , There is no such problem

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          elenst Elena Stepanova added a comment -

          Thanks for the report.

          I'm not sure about the difference on different versions of CentOS, but the problem is reproducible on my machine (Debian Jessie) with 10.1 and 10.2, and not reproducible on the same machine with MySQL 5.7.

          elenst Elena Stepanova added a comment - Thanks for the report. I'm not sure about the difference on different versions of CentOS, but the problem is reproducible on my machine (Debian Jessie) with 10.1 and 10.2, and not reproducible on the same machine with MySQL 5.7.
          sachin.setiya.007 Sachin Setiya (Inactive) added a comment -

          I think this is is not a bug , Actually culprit is fwrite , which buffers the data
          So cli_safe_read(mysqlbinlog) reads the actual data from server binlog file
          And handle_event_raw_mode calls the fwrite which should have written data but it writes into its buffer
          (for proof ) I have changed the my_fwrite function to add fflush in end , with this modification tha latest binlog file(created by myysqlbinlog) was no longer of zero size (edited)
          drwxr-xr-x 2 sachin users 4.0K Oct 21 21:10 .
          drwxr-xr-x 28 sachin users 4.0K Oct 21 21:05 ..
          rw-rr- 1 sachin users 314 Oct 21 21:10 master-bin.000001

          sachin.setiya.007 Sachin Setiya (Inactive) added a comment - I think this is is not a bug , Actually culprit is fwrite , which buffers the data So cli_safe_read(mysqlbinlog) reads the actual data from server binlog file And handle_event_raw_mode calls the fwrite which should have written data but it writes into its buffer (for proof ) I have changed the my_fwrite function to add fflush in end , with this modification tha latest binlog file(created by myysqlbinlog) was no longer of zero size (edited) drwxr-xr-x 2 sachin users 4.0K Oct 21 21:10 . drwxr-xr-x 28 sachin users 4.0K Oct 21 21:05 .. rw-rr- 1 sachin users 314 Oct 21 21:10 master-bin.000001
          Elkin Andrei Elkin added a comment -

          sachin.setiya.007 You mention fflush is not done. Probably it's not done too when there's nothing to retrieve from
          the server in which case I believe we should take care of doing that.

          Elkin Andrei Elkin added a comment - sachin.setiya.007 You mention fflush is not done. Probably it's not done too when there's nothing to retrieve from the server in which case I believe we should take care of doing that.
          bnestere Brandon Nesterenko added a comment -

          Hi Andrei,

          This is ready for review.

          Commit: ff5a568
          Buildbot: bb-10.2-MDEV-14608

          bnestere Brandon Nesterenko added a comment - Hi Andrei, This is ready for review. Commit: ff5a568 Buildbot: bb-10.2-MDEV-14608
          Elkin Andrei Elkin added a comment -

          Analyzed, reviewed.

          Elkin Andrei Elkin added a comment - Analyzed, reviewed.
          Elkin Andrei Elkin added a comment -

          bnestere, the patch looks good. Thanks for taking the time on it. I also spent a little time figuring out if fflush could be executed
          not per event but rather when the source file is found empty (that is before sink to waiting).
          However there seems to be no straightforward way and a non-blocking attempt read would be required
          inside a low-level ma_net_safe_read.

          Elkin Andrei Elkin added a comment - bnestere , the patch looks good. Thanks for taking the time on it. I also spent a little time figuring out if fflush could be executed not per event but rather when the source file is found empty (that is before sink to waiting). However there seems to be no straightforward way and a non-blocking attempt read would be required inside a low-level ma_net_safe_read .
          bnestere Brandon Nesterenko added a comment -

          Manual cherry picking resulted in no merge conflicts in later versions.

          bnestere Brandon Nesterenko added a comment - Manual cherry picking resulted in no merge conflicts in later versions.

          People

            bnestere Brandon Nesterenko
            tanqingru tanqingru
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              Resolved:

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