Hello,
We have set up web farm with 8 web nodes (Win 2008 R2 servers). These servers are used for running a .NET application for approx 900 different customers, all running in separate app-pools. Each node serves their portion of the customer portifolio, and every node should be able to run any customer when needed. For that reason, we have set up shared configuration on IIS, and web app files reside on a UNC share.
For HA reasons, we set up the file server that holds the SharedConfig files (applicationHost.config, administration.config and encryption keys) and web app files on DFS. And ever since we did that, we've experienced weird behavior.
One or more of the webservers will occasionally stop serving web applications, as it seems it has lost connection with DFS. The event log will show an IIS-W3SVC-WP error:
The worker process for application pool 'cust1159' encountered an error 'Configuration file is not well-formed XML
' trying to read configuration data from file '\\?\C:\inetpub\temp\apppools\cust1159\cust1159.config', line number '3'. The data field contains the error code.
Interestingly, this hits all customers on that particular server at once, and the application log is filled.
Examining the temp .configfile in c:\inetpub\temp\apppools shows that it's not the cached copy of the applicationhost.config, rather than two lines of text:
<!-- ERROR: There's been an error reading or processing the applicationhost.config file. Line number: 0 Error message: Cannot read configuration file
-->
We have several other examples where the applicationHost.config seems unavailable, where we have indications that something has locked the file. (when provisioning a new customer application, and the .config needs to be opened in order to inject new strings for app-pool and application, for instance). For some time we believed it had something to do with Antivirus, but after disabling AV on the DFS members, that seems ruled out.
DFS must have something to do with this. We did not experience this kind of errors before implementing DFS.
Any advice would be appreciated.