Sometimes node.js application users encounter the error message "iisnode encountered an error when processing the request" while accessing Node.js sites.
Generally, this error happens when the application does not have the necessary permissions.
The IIS node error generally triggers while accessing a Node.js site. This error message includes an internal server error.
Basically, this error happens when the application pool doesn't have enough permissions to write to the current folder.
In order to fix this error, you need to give the IIS_IUSRS full permission.
This can be performed with the series of steps below:
1. Go to your windows folder application ad right click on properties.
2. From the Security section, click on Edit and then click on Add.
3. Now, from the Advanced, use the Find Now and then select the IIS_IUSRS option.
4. Then, Allow the following option: Full control.
5. Finally, Restart the application on IIS.
Sometimes, users don't prefer to give the entire IIS_IUSRS group full control. A possible solution in such cases is to get into the advanced settings menu and under Process Model. Then, from identity change the user account to a user that already has write permissions.
Another possible reason for this error could be the use of an older version of windows.
We have noticed a similar error on a system with windows server 2008 R2.
An upgrade to a recent windows version fixed the issue here.