MySQL Bugs: #45817: Please add SHOW command for inc_host_errors(max_connect

Bug #45817	Please add SHOW command for inc_host_errors(max_connect_errors)
Submitted:	29 Jun 2009 7:17	Modified:	20 Mar 2012 16:35
Reporter:	Meiji KIMURA	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Performance Schema	Severity:	S4 (Feature request)
Version:		OS:	Any
Assigned to:	Marc ALFF	CPU Architecture:	Any

Description:
Now inc_host_errors() increase error count for max_connect_errors.
But there is no methond to check current count.

Please add feature for checking current error count for max_connect_errors.
I supposed that it should be implemented as 'SHOW GLOBAL VARIABLES;'.

How to repeat:
N/A.

Suggested fix:
N/A.

Do you want current number of errors to be reported for each host? Then it is NOT for SHOW GLOBAL STATUS, IMHO, as there can be hundred(s) of individual hosts...

You are right.

It is impossible to show all cached host via 'SHOW GLOBAL VARIABLES;'.

So we have to make new 'SHOW' option like 'SHOW HOSTCACHELIST;'.

Thank you for clarification. I had changed Synopsis a bit to reflect the real feature that would be nice to have some day.

I made a patch which displays host information from I_S like below:

mysql> select * from information_schema.known_hosts;
+--------------+----------+--------+
| IP_ADDRESS   | HOSTNAME | ERRORS |
+--------------+----------+--------+
| 192.168.1.8  | xel-naga |      0 | 
| 192.168.1.33 | sol-hfx  |      0 | 
+--------------+----------+--------+
2 rows in set (0.00 sec)

Looks good?

patch for mysql 5.1.35

Attachment: known_hosts.patch (application/octet-stream, text), 3.99 KiB.

another patch

Attachment: show-hosts.patch (application/octet-stream, text), 5.84 KiB.

i modified something in show-hosts.patch as follows:

o made INFORMATION_SCHEMA.KNOWN_TABLES hidden
o added SHOW HOSTS command
o ensure SHOW HOSTS command needs SUPER priv

This must be secure enough.

Kind regards ;)

See bug 24906

This is related to this feature request:
http://bugs.mysql.com/bug.php?id=50963

Noted in 5.6.5 changelog.

MySQL now provides improved access to the host cache, which contains
client host name and IP address information and is used to avoid DNS
lookups. These improvements have been implemented:

* A host_cache Performance Schema table exposes the contents of the
  host cache so that it can be examined using SELECT statements. The
  Performance Schema must be enabled or this table is empty.

  If you upgrade to this release of MySQL from an earlier version, you
  must run mysql_upgrade (and restart the server) to incorporate this
  change into the performance_schema database.

* The cache size is configurable using the host_cache_size system
  variable. Setting the size to 0 disables the host cache.This is
  similar to starting the server with --skip-host-cache, but
  host_cache_size is more flexible because it can also be used to
  resize, enable, or disable the host cache at runtime, not just at
  server startup. If you start the server with --skip-host-cache to
  disable the host cache, it cannot be re-enabled at runtime.

* There are Connection_errors_xxx status variables that provide
  information about the nature of connection errors and that can help
  diagnose connection problems.

Improved access to host cache contents makes it possible to answer
questions such as how many hosts are cached, or how close hosts are
to being blocked (by checking whether the
host_cache.SUM_CONNECT_ERRORS column is approaching the value of the
max_connect_errors system variable).