bin/*.dll locked when deploying website after app_offline.htm copied and active (shadow copy off)

Question

I am running into an issue deploying a website. Shadow copy is turned off after previous deployment issues with it and deploying the site.

Specifically at deploy time I find that even after copying app_offline.htm and verifying that the site/application is offline, the files in bin/*.dll are often locked.

With shadow copy off I would still expect the locks on the dll's to be free'd when the appdomain is unloaded on app_offline.htm appearance.

I have tried deploying a temporary web.config found on Stack Overflow which aims to prevent changes (to bin/) being picked up immediately just before I try to delete the contents of bin/ I even pause for 10s after copying the new web.config.

?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.web>
    <httpRuntime waitChangeNotification="300"
       maxWaitChangeNotification="300"/>
  </system.web>
  <system.webServer>
    <modules runAllManagedModulesForAllRequests="true"  />
  </system.webServer>
</configuration>

I have confirmed with the handles util that my application pool (w3wp.exe process) is the holder of a lock on the dlls so am assuming this is the reason why I cannot delete/overwrite the files. If i manually recycle the app pool it frees it up and I am able to deploy just fine. Unfortunately as part of the deploy process copying the app_offline and changing the web.config are possible but performing IIS appcmd recycles are not (for permissions/group policy reasons) so I really need to be able to free up this lock with just app_offline.htm and the web.config.

Turning shadow copy back on does 'solve' this particular issue but if a lock is still held on the dll. However I wonder / and concerned if I am just postponing the problem. Unless the lock on the old dll is free'd when the appdomain is loaded again?

When copying the app_offline.htm the w3wp process id doesn't change like it does with a hard recycle but I assume it is unloading the appdomain which should free the bin/ files it has locked.

Another interesting point is that this only appears to happen on our production servers, I cannot recreate it locally or on our dev/staging sites. I don't believe there is any config difference with the app_pools or IIS config but could this possible cause this behavior.

Also to clarify shadowCopyBinAssemblies has been set to false for over 3 years without this problem happening (same deploy process) so I really feel like something that happened recently caused this, but I have no idea what.

Thanks for any ideas on how to solve this or even what might be causing it.

(I believe the server is IIS7 or 7.5)

This is an old question, but were you able to resolve this? We are having a very similar issue. If so, you should post the solution as an answer here. Thanks! — Marcus Swope
Any ideas, we have same problem, can you share solution? Thanks. — Irakli Gabisonia

Gaurav Gaurav · Accepted Answer · 2018-11-21T16:37:08

I am running into a similar issue where a DLL is locked by IIS even with the presence of app_offline.htm.
Restarting the pool solves the issue but it is manual. Looking for an automated way. In my case the DLL is PDFium.dll it is likely an unmanaged dll

bin/*.dll locked when deploying website after app_offline.htm copied and active (shadow copy off)

1 Answers