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  1. MariaDB MaxScale
  2. MXS-38

bugzillaId-688: Incorrect backend state leads to confusing and untraced client errors

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Details

    • Bug
    • Status: Closed (View Workflow)
    • Minor
    • Resolution: Not a Bug
    • 1.0.3
    • 1.3.0
    • Core
    • None
    • All OS

    Description

      This is imported from bugzilla item:
      http://bugs.mariadb.com/show_bug.cgi?id=688

      Description Kolbe Kegel 2015-01-08 22:44:19 UTC
      I shutdown my "monitor" manually. I stopped the mysql service of one of the nodes. I left that node marked as "master". It appears that I can connect to the cluster using MaxScale, but my session is ended right away and on my first attempt to execute a query I get "MySQL server has gone away".

       
      [root@db3 ~]# mysql -h 192.168.30.38 -P 4006 -u maxuser -pmaxpwd
      Welcome to the MariaDB monitor.  Commands end with ; or \g.
      Your MariaDB connection id is 2140
      Server version: 10.0.14-MariaDB-Enterprise-Cluster
       
      Copyright (c) 2000, 2014, Oracle, SkySQL Ab and others.
       
      Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
       
      MariaDB [test]>
       
      MariaDB [test]> select @@hostname;
      ERROR 2006 (HY000): MySQL server has gone away
      No connection. Trying to reconnect...
      Connection id:    2140
      Current database: test
       
      ERROR 2013 (HY000): Lost connection to MySQL server during query
      MariaDB [test]>
       
       

      Nothing is logged in this situation in the MaxScale error log or message log and nothing relevant seems to be written to the trace log, either:

       
      2015-01-08 14:35:35   Servers and router connection counts:
      2015-01-08 14:35:35   current operations : 0 in         192.168.30.33:3306 RUNNING MASTER
      2015-01-08 14:35:35   current operations : 0 in         192.168.30.32:3306 RUNNING SLAVE
      2015-01-08 14:35:35   current operations : 0 in         192.168.30.31:3306 RUNNING JOINED
      2015-01-08 14:35:35   Selected RUNNING MASTER in        192.168.30.33:3306
      2015-01-08 14:35:35   Selected RUNNING SLAVE in         192.168.30.32:3306
      2015-01-08 14:35:35   Started RW Split Router client session [125] for 'maxuser' from 192.168.30.38
      2015-01-08 14:35:36   [125]  Stopped RW Split Router client session [125]
      2015-01-08 14:35:36   Servers and router connection counts:
      2015-01-08 14:35:36   current operations : 0 in         192.168.30.33:3306 RUNNING MASTER
      2015-01-08 14:35:36   current operations : 0 in         192.168.30.32:3306 RUNNING SLAVE
      2015-01-08 14:35:36   current operations : 0 in         192.168.30.31:3306 RUNNING JOINED
      2015-01-08 14:35:36   Selected RUNNING MASTER in        192.168.30.33:3306
      2015-01-08 14:35:36   Selected RUNNING SLAVE in         192.168.30.32:3306
      2015-01-08 14:35:36   Started RW Split Router client session [126] for 'maxuser' from 192.168.30.38
      2015-01-08 14:35:36   [126]  > Autocommit: [enabled], trx is [not open], cmd: COM_QUERY, type: QUERY_TYPE_SYSVAR_READ, stmt: select @@version_comment limit 1
      2015-01-08 14:35:36   [126]  Route query to slave       192.168.30.32:3306 <
      2015-01-08 14:35:37   [126]  Stopped RW Split Router client session [126]
       

      I think it would be good if this kind of anomaly were noted in the error log as well as the trace log. An failed attempt to connect to a server is a serious problem, since it means that the server state in MaxScale doesn't match reality.

      Ideally, a better error message could be given by MaxScale to the client, too. It appears that the connection is simply severed without giving any information at all.

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            Massimiliano Pinto Massimiliano Pinto (Inactive)
            kolbe Kolbe Kegel (Inactive)
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