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POMySql *completely random* Unable to connect to any of the specified MySQL hosts
 

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  1. POMySql *completely random* Unable to connect to any of the specified MySQL hosts
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    <p>This one is killing me. We have an ASP.NET/Mono application on a MySQL database. For months we've been plagued by a completely random but consistent occurrence of "Unable to connect to any of the specified MySQL hosts". I'm by no means a MySQL pro, and I hope this is something silly.</p> <p>Specifics:<br /> MySQL 5.5.17<br /> MySQL Connector/Net 6.4.4<br /> Mono 2.10.8<br /> MonoDevelop 2.8.6.5<br /></p> <p>Connection string: SERVER=localhost,3306;DATABASE=xxx;UID=xxx;PWD=xxx;CONNECTION TIMEOUT=90;Encrypt=false;</p> <p>Max_connections is set to 150. There are never more than 5 connections, and they are all active (probably due to the pooling).</p> <ul> <li><p>The application is C# ASP.NET 3.5. Runs solid as a rock for years on Windows/IIS. Nine months ago our market led us to get off Windows, so we (easily I might add) moved the whole thing to Mono/Apache.</p></li> <li><p>The issue only occurs on the Mono side, but that's critical since we've retired our Windows support.</p></li> <li><p>Happens on average about 10 times an hour, but spacing varies wildly.</p></li> <li><p>The issue has been witnessed in the following configurations:</p></li> </ul> <p>Ubuntu 11/Apache2/mod_mono<br /> OSX Lion/Apacke2/mod_mono<br /> Ubuntu 11/xsp2/MonoDevelop debug server<br /> OSX Lion/xsp2/MonoDevelop debug server<br /></p> <ul> <li><p>Have messed with keepalive, wait_timeout, connectionreset, etc to no avail. Timings seem to have no effect. The error is instantaneous on conn.open - not after any connection timeout.</p></li> <li><p>Here's a clue - the app absolutely will not run with Pooling=false. Nearly every connection attempt fails. Of course I want pooling on, but I'm not sure why it wouldn't work without.</p></li> <li><p>The application has a built in "heartbeat" (user's session in the database) - every 2 minutes.</p></li> <li><p>The most maddening of all? It absolutely cannot be reproduced on demand in a running environment - it's random. I've examined query sizes, execution times, etc.</p></li> <li><p>In exactly one scenario can I make it happen: On initial startup of an Ubuntu server or OSX, the very first time Mono makes it's first connection to MySQL - it will happen then. After that, it's anybody's guess.</p></li> </ul>
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    1. UShikaru
    1. UShikaru
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      1. VTUpMod
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      1. VTUpMod
    1. COHow about max_connections limits? You could be hitting the max allowed at various times.
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      1. POMySql *completely random* Unable to connect to any of the specified MySQL hosts
      1. USMarc B
    2. COSeems unlikely given that it happens on first connection
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      1. USDNA
    3. CO+1 for a well asked question, but I think it would fare better on serverfault.com
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      1. POMySql *completely random* Unable to connect to any of the specified MySQL hosts
      1. USMike Purcell
 

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