Custom maintenance mode module does not work on Azure Web Role

Question

I've created and registered custom http module to show maintenance message to user after administrator turns on maintenance mode via configuration change.

When I pass request for html it should return custom html loaded from file, but it returns message: "The service is unavailable." I can't find that string in my entire solution. Custom log message from custom maintenance module is written to log4net logs.

... INFO DdiPlusWeb.Common.MaintenanceResponder - Maintenance mode is on. Request rejected. RequestUrl=...

Seems something is miss configured in IIS on Azure. Something intercepts my 503 response. How to fix it?

Module code

    void context_BeginRequest(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        HttpContext context = application.Context;
        if (AppConfig.Azure.IsMaintenance)
        {
            MaintenanceResponder responder = new MaintenanceResponder(context, MaintenaceHtmlFileName);
            responder.Respond();
        }
    }

Interesting part of responder code.

    private void SetMaintenanceResponse(string message = null)
    {
        _context.Response.Clear();
        _context.Response.StatusCode = 503;
        _context.Response.StatusDescription = "Maintenance";
        if (string.IsNullOrEmpty(message))
        {
            _context.Response.Write("503, Site is under maintenance. Please try again a bit later.");
        }
        else
        {
            _context.Response.Write(message);
        }
        _context.Response.Flush();
        _context.Response.End();
    }

EDIT: I lied. Sorry. Maintenance module returns the same message for requests that expect json or html.

Fosna Fosna · Accepted Answer · 2014-10-07T11:09:19

This answer led me to the solution.

I've added another line to SetMaintenanceResponse method.

_context.Response.TrySkipIisCustomErrors = true;

It works now. Here is more about what it exactly means.

Custom maintenance mode module does not work on Azure Web Role

1 Answers