1.5 KiB
InvalidOperationException in ASP.Net-RecycleLimitMonitor-AlertProxyMonitors
Symptoms
ASP.Net applications may crash intermittently due to an InvalidOperationException in
System_Web_ni!System.Web.Hosting.RecycleLimitMonitor+RecycleLimitMonitorSingleton.AlertProxyMonitors.
Cause
This issue was introduced when ASP.Net 4.7 separated cache management and memory monitoring. This new RecycleLimitMonitorSingleton monitors worker process private bytes usage against the recycling limit for the process, and when
the limit is near, it alerts a set of "proxy monitors" in each registered AppDomain so they can take action to avoid a process
recycle. The collection of "proxy monitors" being enumerated was not thread-safe, though, so new AppDomains spinning up or old
AppDomains shutting down while this monitor enumerated the collection could result in this unhandled InvalidOperationException
in the default AppDomain, causing a crash.
Workaround
There is no reliable workaround. If the environment does not tend to consume private bytes near the recycling limit, or if web app domain lifetimes tend to last the entire length of the process lifetime, then chances of hitting this issue are extremely minimal. More private bytes consumption and/or more AppDomain recycling increases the odds of hitting this exception condition.
Resolution
A hotfix for this issue is planned for .Net 4.8. This page will be updated with a link to the hotfix when it becomes available.