draft (#32598)

aspnetcore/release-notes/aspnetcore-9.0.md

@@ -49,3 +49,5 @@ The following sections describe miscellaneous new features.
 [!INCLUDE[](~/release-notes/aspnetcore-9/includes/endpoint-metadata.md)]
 
 [!INCLUDE[](~/release-notes/aspnetcore-9/includes/debugger.md)]
+
+[!INCLUDE[](~/release-notes/aspnetcore-9/includes/fix-for-503s.md)]

aspnetcore/release-notes/aspnetcore-9/includes/fix-for-503s.md

@@ -0,0 +1,23 @@
+### Fix for 503's during app recycle in IIS
+
+By default there is now a 1 second delay between when IIS is notified of a recycle or shutdown and when ANCM tells the managed server to start shutting down. The delay is configurable via the `ANCM_shutdownDelay` environment variable or by setting the `shutdownDelay` handler setting. Both values are in milliseconds. The delay is mainly to reduce the likelihood of a race where:
+
+* IIS hasn't started queuing requests to go to the new app.
+* ANCM starts rejecting new requests that come into the old app.
+
+Slower machines or machines with heavier CPU usage may want to adjust this value to reduce 503 likelihood.
+
+Example of setting `shutdownDelay`:
+
+```xml
+<aspNetCore processPath="dotnet" arguments="myapp.dll" stdoutLogEnabled="false" stdoutLogFile=".logsstdout">
+  <handlerSettings>
+    <!-- Milliseconds to delay shutdown by.
+    this doesn't mean incoming requests will be delayed by this amount,
+    but the old app instance will start shutting down after this timeout occurs -->
+    <handlerSetting name="shutdownDelay" value="5000" />
+  </handlerSettings>
+</aspNetCore>
+```
+
+The fix is in the globally installed ANCM module that comes from the hosting bundle.