how do I log requests and responses for debugging in servicestack

This RequestFilter allows you to print raw request content. You could modify it to get more information like headers and cookies if desired. As @mythz notes in a comment, this is less detailed than the Request Logger plugin. But if you only want to add logging for a single request, it could be preferable. Disclaimer: this code is probably not production-ready and I'm not using it for production.

public class RequestDataSpyAttribute : RequestFilterAttribute
{
    // gets injected by ServiceStack
    public ILog Log { get; set; }

    private readonly string _logMessage;

    public RequestDataSpyAttribute(string logMessage)
    {
        _logMessage = logMessage;
    }

    public override void Execute(IRequest req, IResponse res, object requestDto)
    {
        System.Web.HttpRequestWrapper original = req.OriginalRequest as System.Web.HttpRequestWrapper;
        if (original == null)
            return;

        Log.Debug($"{_logMessage} Request: {original.InputStream.ReadToEnd()}");
    }
}