Retry web service call if authentication failure requires re-login

Question

I'm consuming a web service from C#, and the web service requires a login call and then uses cookie sessions. The web service will time out sessions after a certain timeframe, after which the client will have to re-login. I'd like to find a way to automatically catch the soap fault the service sends back in this scenario, and handle it by re-logging in and then retrying the previously attempted call.

I would prefer to do this somehow automatically for all the web service methods in question, rather than having to manually wrap the calls with the retry logic.

Suggestions?

Answer 1

To avoid a similar issue in the past I actually "pinged" the service occasionally (I had control over the service at other end and created a very light-wight "ping" method but even if there is something simple you can use that would not contitute a denial of service!)

I think I pinged every 2 to 5 minutes or so, it would depend on the web service config etc... That way the authentication issue never really happened and I did not need to do the funky auto re-login thing :-)

-- otherwise... --

If you do need to do the re-login I would be wrapping the whole thing in an interface, this is good practice anyway with web-services, can stub them out etc. Design a class with utility methods to handle the logging in, you will find it hard to get around not re-typing alot of calls but thats just the way it is!

Example....

public interface ISomeService
{
    string Method1();
    string Method2();
}

public class ReLoginWebService : ISomeService
{
    readonly WebServiceProxy _proxy;
    string _username;
    string _password;

    public ReLoginWebService(string username, string password)
    {
        _username = username;
        _password = password;
        _proxy = new WebServiceProxy();
        Login();
    }

    public string Method1()
    {
        try
        {
            _proxy.Method1();
        }
        catch (Exception exp) // filter appropriatly...
        {
            // if its a login error...
            if (Login())
                _proxy.Method1();
            else
                throw;
        }
        return "";
    }


    public string Method2()
    {
        try
        {
            _proxy.Method2();
        }
        catch (Exception exp) // filter appropriatly...
        {
            // if its a login error...
            if (Login())
                _proxy.Method2();
            else
                throw;
        }
        return "";
    }

    protected bool Login()
    {
        return true; // i.e. success
    }
}