Comments on: 10+ Ways to Crash or Overload MySQL http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/ Everything about MySQL Performance Tue, 02 Dec 2008 18:33:56 +0000 http://wordpress.org/?v=2.5.1 By: MySQL for Hosting Providers - how do they manage ? | MySQL Performance Blog http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-395135 MySQL for Hosting Providers - how do they manage ? | MySQL Performance Blog Fri, 28 Nov 2008 22:24:32 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-395135 [...] to really restrict how much resources single user can consume. I have written over a year ago about 10+ ways to crash or overload MySQL and since that people have come to me and suggested more ways to do the [...] [...] to really restrict how much resources single user can consume. I have written over a year ago about 10+ ways to crash or overload MySQL and since that people have come to me and suggested more ways to do the [...]

]]> By: 5 kedvenc oldalam, amin hasznos volt kockulni | http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-364231 5 kedvenc oldalam, amin hasznos volt kockulni | Thu, 23 Oct 2008 09:45:42 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-364231 [...] - http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/ [...] [...] - http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/ [...]

]]> By: gigiduru http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-198728 gigiduru Tue, 20 Nov 2007 00:43:02 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-198728 Given this statement: "Really - there are many ways to crash or otherwise made unavailable server with any MySQL version if you have access to it with normal privileges", shouldn't the title be something like "10+ Ways to keep alive MySQL"? Not to mention, this blog entry would be even shorter than it actually is right now. Given this statement: “Really - there are many ways to crash or otherwise made unavailable server with any MySQL version if you have access to it with normal privileges”, shouldn’t the title be something like “10+ Ways to keep alive MySQL”?

Not to mention, this blog entry would be even shorter than it actually is right now.

]]> By: 10 moyens de crasher MySQL http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-196993 10 moyens de crasher MySQL Sun, 18 Nov 2007 16:18:18 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-196993 [...]  10+ Ways to Crash or Overload MySQL (0 visite) [...] [...]  10+ Ways to Crash or Overload MySQL (0 visite) [...]

]]> By: Pythian Group Blog » Blog Archive » Log Buffer #71: a Carnival of the Vanities for DBAs http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-195202 Pythian Group Blog » Blog Archive » Log Buffer #71: a Carnival of the Vanities for DBAs Fri, 16 Nov 2007 17:53:16 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-195202 [...] the MySQL Performance Blog, Peter Zaitsev has another list: 10+ Ways to Crash or Overload MySQL. Writes Peter, “[There] are many ways to crash or otherwise made unavailable server with any [...] [...] the MySQL Performance Blog, Peter Zaitsev has another list: 10+ Ways to Crash or Overload MySQL. Writes Peter, “[There] are many ways to crash or otherwise made unavailable server with any [...]

]]> By: peter http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-195176 peter Fri, 16 Nov 2007 17:07:48 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-195176 Gleb, What does BENCHMARK give you comparing (for example) to self join of same table without indexes few times or other cpu hog query ? Gleb,

What does BENCHMARK give you comparing (for example) to self join of same table without indexes few times or other cpu hog query ?

]]> By: Gleb Pakharenko http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-195001 Gleb Pakharenko Fri, 16 Nov 2007 12:57:37 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-195001 There is a famous BENCHMARK() to DOS web-sites :) There is a famous BENCHMARK() to DOS web-sites :)

]]> By: peter http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-193109 peter Wed, 14 Nov 2007 18:45:17 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-193109 OK Jeremy, I agree with you - whatever way you look at it it is either bug or nonsense :) OK Jeremy, I agree with you - whatever way you look at it it is either bug or nonsense :)

]]> By: Jeremy Cole http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-193108 Jeremy Cole Wed, 14 Nov 2007 18:38:58 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-193108 Actually, to add one further bullet point: * localhost doesn't count either, as it's not really looked up and thus doesn't have an entry to hostname_cache in order to keep count of errors. Actually, to add one further bullet point:

* localhost doesn’t count either, as it’s not really looked up and thus doesn’t have an entry to hostname_cache in order to keep count of errors.

]]> By: Jeremy Cole http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-193096 Jeremy Cole Wed, 14 Nov 2007 18:15:54 +0000 http://www.mysqlperformanceblog.com/2007/11/13/10-ways-to-crash-or-overload-mysql/#comment-193096 Hi Peter, Yes, it's strange. Aborted_connects has no relation to max_connect_errors. The only place it's ever checked is in sql/sql_parse.cc: 848 if (!(specialflag & SPECIAL_NO_RESOLVE)) 849 { ... 861 if (connect_errors > max_connect_errors) 862 return(ER_HOST_IS_BLOCKED); 863 } Where connect_errors comes from: 851 thd->main_security_ctx.host= 852 ip_to_hostname(&thd->remote.sin_addr, &connect_errors); There are a couple of things to consider with this: * Since inc_host_errors is never called on password failure, bad password attempts don't count. * If you use skip_name_resolve, none of that code is called at all. * If a host doesn't have a valid PTR (ip to host mapping), nothing is ever counted. As you probably know, I've been trying to get MySQL to overhaul how it handles hosts for a long time now. My host cache patches are a good start to this: http://jcole.us/patches/mysql/5.0/host_cache/ Regards, Jeremy Hi Peter,

Yes, it’s strange. Aborted_connects has no relation to max_connect_errors. The only place it’s ever checked is in sql/sql_parse.cc:

848 if (!(specialflag & SPECIAL_NO_RESOLVE))
849 {
…
861 if (connect_errors > max_connect_errors)
862 return(ER_HOST_IS_BLOCKED);
863 }

Where connect_errors comes from:

851 thd->main_security_ctx.host=
852 ip_to_hostname(&thd->remote.sin_addr, &connect_errors);

There are a couple of things to consider with this:
* Since inc_host_errors is never called on password failure, bad password attempts don’t count.
* If you use skip_name_resolve, none of that code is called at all.
* If a host doesn’t have a valid PTR (ip to host mapping), nothing is ever counted.

As you probably know, I’ve been trying to get MySQL to overhaul how it handles hosts for a long time now. My host cache patches are a good start to this:

http://jcole.us/patches/mysql/5.0/host_cache/

Regards,

Jeremy

]]>