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10 Newer Entries Showing entries 31 to 40 of 83 10 Older Entries

Displaying posts with tag: performance_schema (reset)

MySQL 5.6 users – prevent host blocked errors
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The much-improved PERFORMANCE_SCHEMA in MySQL 5.6 provides visibility into MySQL’s host cache, including the ability to monitor for impending blocked hosts.  You can do this with the following query:

mysql> SELECT
    ->  ip,
    ->  host,
    ->  host_validated,
    ->  sum_connect_errors
    -> FROM performance_schema.host_cache\G
*************************** 1. row ***************************
                ip: 192.168.2.4
              host: TFARMER-MYSQL.wh.oracle.com
    host_validated: YES
sum_connect_errors: 3
1 row in set …
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Spring Cleaning: Useless protocol commands
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In an earlier post, I commented on clients and utility programs which seem to no longer be useful, and opened (or referenced existing) public bug reports to deprecate and remove, where appropriate.  That effort came actually was the product of a different initiative:  I was looking for clients which might leverage the full spectrum of MySQL protocol commands in an effort to understand whether certain protocol commands are in use.  …

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Practical P_S: Fixing gaps in GLOBAL STATUS
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Over three years ago, I noticed that there was no STATUS counter for COM_PING commands – something that is useful for ensuring proper configuration of JDBC connection pools.  Mark Leith even provided a patch, but it’s never been incorporated.  With the advances PERFORMANCE_SCHEMA makes in MySQL 5.6, that’s OK – a STATUS counter becomes somewhat redundant:

mysql> SELECT SUM(count_star) as pings
    -> FROM events_statements_summary_global_by_event_name …
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Fun with Bugs #21 - recently verified bugs in MySQL 5.6.13
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Notable contribution of MySQL Community to MySQL 5.6.13 was explicitly recognized recently. But users and contributors still continue their efforts, as well as Oracle engineers. Even though MySQL 5.6.13 has been generally available just for few days, we already have several new bug reports and updates to known bugs at http://bugs.mysql.com. Let me present a short list with some comments.



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Practical P_S: How idle are your connections?
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Idle connections can cause problems both at the application side, increasing the risk of connection timeouts for applications where persistent connections are used, and the server side, where resources remain allocated to idle connections.  Any application with persistent connections, such as a JDBC application using a connection pool, will have periods where connections are idle – but it’s good to know how much time is spent idle.  Too much idle time might mean connections pools configured to …

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Practical P_S: How old are your connections?
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I’ve often wished that PROCESSLIST exposed when a connection was first established, and I find myself wishing for this information more now with MySQL 5.6.  Improvements to PERFORMANCE_SCHEMA make it trivial to see how much time is being spent in various operations for a given connection – but it would make some analysis (“what percentage of connection time is spent doing X?”) easier.

That said, it is possible to approximate connection age with PERFORMANCE_SCHEMA in MySQL 5.6.  I say “approximate” because results will vary based on what instrumentation …

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Practical P_S: Finding the KILLer
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In a previous post, I described how to leverage PERFORMANCE_SCHEMA in MySQL 5.6 to identify connections which had not been properly closed by the client.  One possible cause of connections being closed without explicit request from the client is when another process issues a KILL CONNECTION command:

mysql> SHOW GLOBAL STATUS LIKE 'aborted_clients';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| Aborted_clients | 0     |
+-----------------+-------+
1 row in set …
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Practical P_S: From which hosts are connections being attempted?
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MySQL Server has an aborted_connect status counter which will show you the number of failed attempts to establish a new connection.  The manual describes potential causes as follows:

  • A client does not have privileges to connect to a database.
  • A client uses an incorrect password.
  • A connection packet does not contain the right information.
  • It takes more than …
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Practical P_S: Extending PROCESSLIST
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MySQL 5.6 introduced major advances to monitoring made via PERFORMANCE_SCHEMA, but also made a change in how it binds to the network by default.  In MySQL 5.5, the –bind-address configuration option defaulted to “0.0.0.0″, meaning only IPv4.  This …

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Practical P_S: Finding which accounts fail to properly close connections
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I’ve previously written about several problems which can benefit from additional visibility provided by PERFORMANCE_SCHEMA in MySQL 5.6, and it’s time to add to that list.  A very common problem involves connections which are not properly closed – they simply idle until they reach wait_timeout (or interactive_timeout, depending on the client flags set), and the server …

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10 Newer Entries Showing entries 31 to 40 of 83 10 Older Entries

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