Proxy, Serverlet and Cluster

Question

1. We plan to use ISS as proxy and route jsp request to a cluster of
          Serverlet/EJB. We will track session data in each server.
          Question : How do the ISS proxy know to route browser request to the server
          in cluster ?
          2. If we use Weblogic server without ISS to server static/dynamic pages. We
          have load balance router in front of Weblogic cluster.
          Question : How did load balance router know to route the request from
          browser to the server which track session data in the cluster ?
          Thanks in advance.
          Mickey Hsieh
          

Answer 1

          Comments inline.
          Jim Zhou
          "Mickey Hsieh" <[email protected]> wrote:
          >Thanks Jim
          >I had two follow up questions.
          >
          >Q: Can I put many IIS to server static page and Proxy ? then I put one
          >hardware LB in front of IIS Web farm ?
          Definitly. Ultimately you have 3 level of LB. First level is LB hardware (CISCO Load Director, for example) will route
          the traffic to a farm of IIS/Proxies, which serves only static contents (HTML, image). Second level is proxy will LB the servlet requests to WLS clustered
          servers. The third level is when servlet is calling EJB, it get load balanced if your EJBs are deployed in a
          different cluster than your presentation (servlet/JSP).
          >
          >
          >> For WLS 4.51 and 5.1, you load balance router can only be used to load
          >balanced HTTP reuqests to a
          >> farm of IIS servers. You can't have the router to load balance directly to
          >WLS cluster, because your load
          >> balance router will not read the cookie embeded in every HTTP request. But
          >that will be changed in WLS 6.0
          >Q: Is there any hardware LB can perform routing as well ?
          > If not, How WLS 6.0 take care routing without Proxy ?
          I don't think any hardware LB is designed to read BEA's propritory cookie to find out the primary server
          for it to route to. My understanding in WLS 6.0, BEA is promoting people to use WLS to serve both static
          and dynamic content. So IIS/Proxy is not needed any more. I am not an expert on LB hardware, I am also
          puzzled by how does hardware LB route all the HTTP request that belong to same session to one
          particular primary server, but I know how the failover situation get handled in WLS 6.0, LB hardware just
          choose another primary server based on its LB algorithm when the previous primary server goes down.
          The new primary server will recover the session data from secondary server ( it finds out the secondary by
          reading the cookie).
          >
          >
          >
          >
          >
          >"Jim Zhou" <[email protected]> wrote in message
          >news:[email protected]...
          >>
          >> Comments inline.
          >>
          >> Jim Zhou.
          >>
          >> "Mickey Hsieh" <[email protected]> wrote:
          >> >1. We plan to use ISS as proxy and route jsp request to a cluster of
          >> >Serverlet/EJB. We will track session data in each server.
          >> >Question : How do the ISS proxy know to route browser request to the
          >server
          >> >in cluster ?
          >> >
          >> When first HTTP request comes to IIS proxy, proxy will pick one server
          >in the cluster to serve the
          >> servlet reuqest. WebLogic servlet engine will put a cookie in the servlet
          >response. So next click from the
          >> browser client, proxy will examine the cookie, inside the cookie, BEA
          >embeded the primary server and
          >> secondary server that holds the HTTP session. So proxy will get the
          >primary server name from cookie,
          >> and relay the request to that WLS server in the cluster which holds the
          >session data. In case the primary
          >> server is down, proxy is smart enough to route the request to secondary
          >server, for that particular session,
          >> secondary server will change itself to primary server, and find another
          >live WLS instance in the cluster to be
          >> the secondary server for that session.
          >> Be aware that in WLS 6.0, servlet load balancing does not require
          >proxy to examine the cookie anymore.
          >> You can use hardware load balancing in front of WLS cluster. In the case
          >of failure, hardware LB will pick
          >> another primary server, the new primary server will examine the cookie,
          >find the secondary server, and
          >> replicate the session data from the secondary server. So in WLS 6.0, once
          >you are secondary server, you
          >> are always secondary server. Quite different than 4.51 and 5.1.
          >> In case browser does not support cookie, URL rewriting is used.
          >>
          >> >2. If we use Weblogic server without ISS to server static/dynamic pages.
          >We
          >> >have load balance router in front of Weblogic cluster.
          >> >Question : How did load balance router know to route the request from
          >> >browser to the server which track session data in the cluster ?
          >>
          >> For WLS 4.51 and 5.1, you load balance router can only be used to
          >load balanced HTTP reuqests to a
          >> farm of IIS servers. You can't have the router to load balance directly to
          >WLS cluster, because your load
          >> balance router will not read the cookie embeded in every HTTP request. But
          >that will be changed in WLS 6.0
          >>
          >> >
          >> >Thanks in advance.
          >> >
          >> >Mickey Hsieh
          >> >
          >> >
          >> >
          >>
          >
          >