49 messages in com.mysql.lists.win32Re: Connections from localhost fast. ...
FromSent OnAttachments
James Frankman03 Jun 2005 13:17 
SGr...@unimin.com03 Jun 2005 13:20 
Daniel da Veiga03 Jun 2005 13:32 
James Frankman03 Jun 2005 13:52 
Greg Quinn03 Jun 2005 14:25 
Daniel da Veiga03 Jun 2005 14:27 
James Frankman03 Jun 2005 15:17 
James Frankman03 Jun 2005 15:23 
warren03 Jun 2005 15:29 
cor...@bbqguys.com03 Jun 2005 18:58 
Wade Smart03 Jun 2005 19:07 
Ryan Paulson04 Jun 2005 06:18 
Greg Quinn04 Jun 2005 06:52 
Ryan Paulson04 Jun 2005 07:01 
Daniel da Veiga04 Jun 2005 13:42 
Leigh Sharpe05 Jun 2005 16:51 
James Frankman06 Jun 2005 08:31 
Daniel da Veiga06 Jun 2005 09:18 
James Frankman06 Jun 2005 09:35 
Ryan Paulson06 Jun 2005 09:46 
SGr...@unimin.com06 Jun 2005 09:52 
Brandon Schenz06 Jun 2005 09:56 
Daniel da Veiga06 Jun 2005 09:56 
James Frankman06 Jun 2005 09:59 
James Frankman06 Jun 2005 10:05 
Brandon Schenz06 Jun 2005 10:08 
Daniel da Veiga06 Jun 2005 10:08 
James Frankman06 Jun 2005 10:11 
Brandon Schenz06 Jun 2005 10:34 
Ryan Paulson06 Jun 2005 11:46 
James Frankman06 Jun 2005 12:00 
Ryan Paulson06 Jun 2005 12:03 
Brandon Schenz06 Jun 2005 12:08 
Daniel da Veiga06 Jun 2005 12:08 
James Frankman06 Jun 2005 12:13 
James Frankman06 Jun 2005 12:14 
Daniel da Veiga06 Jun 2005 12:20 
James Frankman06 Jun 2005 12:25 
Ryan Paulson06 Jun 2005 12:36 
James Frankman06 Jun 2005 13:26 
Leigh Sharpe06 Jun 2005 17:59 
Erich Dollansky06 Jun 2005 18:25 
Armando06 Jun 2005 22:33 
James Frankman07 Jun 2005 07:18 
Leigh Sharpe07 Jun 2005 16:55 
James Frankman08 Jun 2005 07:02 
Ryan Paulson08 Jun 2005 07:07 
Leigh Sharpe08 Jun 2005 16:47 
Nabble-Member119 Dec 2007 11:52 
Subject:Re: Connections from localhost fast. Connections anywhere else slow.
From:Leigh Sharpe (lsha@pacificwireless.com.au)
Date:06/07/2005 04:55:54 PM
List:com.mysql.lists.win32

If this is the case at my company, would this imply that MySQL was

invoking reverse DNS lookups with an external DNS server?

As I understand it, MySQL does a reverse lookup on all incoming connections unless specifically told not to (by using skip-name-resolve). As with all DNS lookups, if the answer is not known by your local nameserver, it goes further upstream for the answer.

With that being said, how can we explain MySQL working for the past three

years now and then have our reverse DNS lookup disappear. You >mention that most network admins do not enable reverse DNS lookup internally. I have a couple questions:

Perhaps I wasn't as clear as I wanted to be. I was referring to reverse DNS lookups on private IP addresses. There is no authoritative domain for 192.168.x.x , 172.16.x.x or 10.x.x.x addresses, but local admins are free to add their own entries for these zones. Very few actually bother, as it is generally more hassle than it is worth. Some people, however, find it useful.

I am at a loss to explain why lookups would stop suddenly. All I can suggest is head over to www.dnsstuff.com and have a look. There are some really good tools there for DNS diagnostics, and some fairly comprehensive explanations. Who knows, the answer may be in there somewhere.

Having said that, there is one more possibility to consider. Are you connecting from a public IP or a private one? If you are using a public IP, you are probably not even aware of any reverse entries for it. They are usually handled by your ISP. They may have changed without your knowledge. Worth asking, in my opinion. I'm lucky enough that I am in control of my own reverse entries, so I managed to fix this problem fairly quickly when it occured. Others may not be.

----- Original Message ----- From: "James Frankman" <jfra@idfbins.com> To: "MySQL Win32 List" <win@lists.mysql.com> Sent: Wednesday, June 08, 2005 12:19 AM Subject: RE: Connections from localhost fast. Connections anywhere else slow.

Thanks Leigh for the input. I agree with your appraisal of the situation.

The reverse DNS lookup seems to be the problem here. While I don't think we can dismiss it entirely, I think we should shelve the patch/virus/worm theory and focus on more likely scenarios.

With that being said, how can we explain MySQL working for the past three

years now and then have our reverse DNS lookup disappear. You mention that most network admins do not enable reverse DNS lookup internally. I have a couple questions:

If this is the case at my company, would this imply that MySQL was invoking reverse DNS lookups with an external DNS server?

What would have caused the reverse DNS lookup to fail so suddenly on

external DNS servers? One minute MySQL is humming along just as it has the past three years, the next minute it takes several seconds to connect to it due to the reverse DNS lookup issue.

-----Original Message----- From: Leigh Sharpe [mailto:lsha@pacificwireless.com.au] Sent: Monday, June 06, 2005 7:00 PM To: Daniel da Veiga; MySQL Win32 List Subject: Re: Connections from localhost fast. Connections anywhere else slow.

Guys, (Being in the wrong timezone really hurts here.)

I think you might be looking in the wrong places. Let's gather a few thoughts here:

When it happened to me, all apps, including my web server, even acessing using IP at the machine running the server was laggy, that's why I think its a network issue, because as James said, not only MySQL is affected...

No. It's a reverse DNS issue. Lots of apps look up the reverse DNS entry for connecting clients. Linux aps such as SSH also do it. How they handle the missing record varies.

But we never had reverse DNS, it all happens when our primary gateway goes down or when our DNS server crashes...

Reverse DNS does not necessarily have to be on your own DNS. If your MySQL server can't get an answer locally, it goes out to the internet looking for the PTR record. If your gateway is down, it will wait until it times out before granting the connection. Hence a slow connection.

I think we can discount updates/patches/worms. I have a hard time beleiving any of those could affect DNS. The only thing which could cause a problem to occur on everybody's system at the same time would be a global DNS issue. If that had happened, I think someone here (or some other list) would know by now. Anybody heard anything?

I am running Windows 2003 Standard Server. We have no domain or internal DNS server and our "network" is running as a workgroup. All my servers run MySQL 4.1.11a and when this problem started, it started across all my DB servers. That is why I don't think it is limited to MySQL, but why all of a sudden did it quite.

They're all looking up on the same DNS? They will all be affected.

Another thing to consider is that if you are using private IP space rather than public IPs, you will have a problem with reverse DNS unless your local DNS admin has set it up locally, which very few ever do.

As a workaround, if you know all of the clients who will be connecting, use a host file entry. It should speed thing up a lot.

I must admit though I don't see the point if you supply an IP Address in the connection string why dns's and name resolutions should ever play a factor??? Maybe this can be fixed in an updated version

It's a reverse lookup. The server looks up the client's IP address to find out what it's name is. This is used for a) making the 'show processlist' command look prettier/more readable and b) authentication in some cases. eg: Permissions are granted to user fr@foo.com. When a connection conmes in from fred on IP address 1.2.3.4, the server looks up 1.2.3.4 to find out if it is foo.com.

Hope some of this can clear the air a bit.

Regards, Leigh.

-- MySQL Windows Mailing List For list archives: http://lists.mysql.com/win32 To unsubscribe: http://lists.mysql.com/win32?unsub=jfra@idfbins.com

-- MySQL Windows Mailing List For list archives: http://lists.mysql.com/win32 To unsubscribe: http://lists.mysql.com/win32?unsub=lsha@pacificwireless.com.au