Openshift's haproxy hits '/' every 2 seconds with a null user agent to see if your scalable app is up. If "/" does not respond with a 200 OK, haproxy marks the server as down even if it's actually up. This filter generates an empty 200 OK when it detects a haproxy ping..

OpenshiftHaproxyFilter.java

package com.gabrielbauman.gists;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter(urlPatterns = "/")
public class OpenshiftHaproxyFilter implements Filter {

    public void init(FilterConfig config) throws ServletException {
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {

        if (null == ((HttpServletRequest) request).getHeader("user-agent")) {
            ((HttpServletResponse) response).setStatus(HttpServletResponse.SC_OK);
        } else {
            chain.doFilter(request, response);
        }
    }

    public void destroy() {
    }
}