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From:claudio.nanni Date:February 26 2010 7:23am
Subject:Re: Re: What is "unusually high" for the # of connections to MySQL?
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Hi Jesse,

as you can see the most relevant is connection timed out, you could focus  
on this, this problem is typical of ODBC.
this can happen because you use the persistent connection pool in your DSN  
So I would start focusing on the connection time out.
I could say raise the timeout time but you could always meet the problem  
you have to see if you can set the driver (odbc) to refresh the connection  
automatically when it expires.
Also in the code if you trap the error you can refresh the connection from  
the code.

This is just where I would start.

let me know


Il giorno 26/feb/2010 00.38, Jesse <jc@stripped> ha scritto:

> Thank you so much for the reply. I think we
> may have stepped outside of the MySQL realm now, but here is what I
> know:

> * At least a couple times, recycling the
> application pool started things right up, but that did not always
> work.

> * When this is going on, I cannot even get to a
> page itself, let alone execute a function that runs a query.

> * One time when this happened, we moved the entire
> app to an OLD WS03 server. It had only 2 GB, I believe, and it ran like
> champ after that. Due to "circumstances beyond our control", we had to  
> move it
> back to the WS08 server, and here we are again with the same
> problem.

> * I can log on to the server, no problem. I
> can also log on to MySQL and run queries. I would think that if the
> database server were the problem, I would not be able to do that.

> * Do do frequently get errors when this is
> occurring. These are errors. here are a few of those:

> MySql.Data.MySqlClient.MySqlException:
> error connecting: Timeout expired

> System.IndexOutOfRangeException: Could not find specified column in
> results

> Object
> reference not set to an instance of an object

> System.IO.IOException:
> Unable to write data to the transport connection: An existing connection  
> was
> forcibly closed by the remote host

> 42000You
> have an error in your SQL syntax; check the manual that corresponds to  
> your
> MySQL server version for the right syntax to use near ''SHOW VARIABLE''

> Key
> cannot be null

> The
> list goes on. As you can see, the errors are all over the board. Some make
> sense, some do not. For instance, the "you have an error in your sql"  
> does not,
> because this same area of code works perfectly Many times throughout the
> day, and I or no one else has changed it. Plus, the one stating ''SHOW
> VARIABLE'' makes no sense at all. I have not executed such a
> function in my code.

> Thanks,

> Jesse

> ----- Original Message -----

> From:
> Claudio
> Nanni

> To: Jesse

> Cc: mysql@stripped

> Sent: Thursday, February 25, 2010 6:28
> PM

> Subject: Re: What is "unusually high" for
> the # of connections to MySQL?

> It depends, but 100 is not strange at all, particularly if
> you have sleeping connections
> (usually due to slow page loading (ajax?) and/or persistent connections
> from the app)

> and any number of connections cannot crash a server, can make it slow or
> unusable, but not crash it.

> Watch the app, you could have for loops banging the database, a not
> optimized app can kill cause a DOS(=bad) of MySQL.

> Anyway the point is another.

> I think you cant afford guessing, it will take a huge amount of effort to
> try to guess why it crashes.

> Find the more information you can enabling all the logging
> possible, put server parameters under graphing,

> the more information you have on the crash, the less you will need to
> guess.

> Watch, cpu(load, context switches), ram(usage,swapping), IO.

> Guess less, know more.

> Claudio

> 2010/2/26 Jesse jc@stripped>

> I was wondering what would be considered "unusually high"
> for the # of connections to a MySQL Server? Also, if a high number of
> these are in "sleep" mode,does it make a difference?

> We have a web
> site (a few, actually) and MySQL (Version 5.0.67-community-nt-log)
> running on a WS08 server, and several times now, we have basically had
> the web site "crash" on us. One tech thought that it may be the # of
> connections. I have seen between 100 to 125 connections or so at one
> time 98% of them all from the same user. This is from our web  
> application that we're
> using for testing. The app basically becomes unresponsive, but I'm not  
> 100%
> convinced that this is a MySQL problem. The site does not even seem to
> be serving up pages when it gets into this "mode".

> Also, there are
> other web sites on this same server (not being used a lot at all), and  
> these
> sites all seem to come up just fine. There are no connection issues with  
> the
> pages or with the data in those applications.

> My main questio is
> this. Is 100 to 125 unusually high? I have implemented a
> connection pool into my connection string in hopes that this will resolve
> the problem. Here is that
> string:

> uid=usernamer;password=password;Server=;port=3306;Database=mydatabase;Allow
> Zero Datetime=true;pooling=true; max pool size=10; min pool
> size=3

> Someone else suggested this string, but after implementing it
> and re-starting the server, we still had the same problem. My plan is
> to move the app to a WS03 server tonight in hopes that the issue is the
> O/S.

> Can anyone fill me in?

> Thanks,
> Jesse

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> Claudio

What is "unusually high" for the # of connections to MySQL?Jesse26 Feb
  • Re: What is "unusually high" for the # of connections to MySQL?Claudio Nanni26 Feb
  • Re: What is "unusually high" for the # of connections to MySQL?Jesse26 Feb
    • Re: Re: What is "unusually high" for the # of connections to MySQL?claudio.nanni26 Feb
      • Re: Re: What is "unusually high" for the # of connections to MySQL?Ananda Kumar26 Feb