to-do.txt

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Next actions
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- Membership coordinator logic and membership view Id.
 
- Implement primary/secondary replication logic (fhanik)
  Idea for implementation: Cookie stores info primary/backup node and hit counter.
  Steps to implement: (coming soon)
  Scenarios: 
  1. Request in: new session dest: any
  2. Request in: existing session dest: primary server
  3. Request in: existing session dest: non-primary server (fail over)
  4. Request in: existing session dest: backup server 
  5. Backup node crash
  6. Primary node crash (step 3)
  7. Sequence 6. then 2. (hit counter)
  8. Sequence 5. then 4. (swap)
  9. New member joins 
  10. Backup and primary crash -> death!
  11. Sequence 2. in: invalid hit counter 
  12. Sequence 4. in: invalid hit counter
  13. Session expires
  14. Sequence 3. then 13. on the old primary
  
  Notes:
  Ability to add a custom "Session expired" redirect for global 
  redirects to never forward an invalid session into the server
  when the session data has gone lost.
  Ie, in a normal scenario, the session is viewed as "new"
  but they may wanna display a session expired redirect.
  Security:
  Dont store any sensitive info in the new cookie.
  only pointers to members.

  
- break out membership/messaging module and improve JMX
  The clustering code has become very cluttered.
  We need to break out the membership and the messaging 
  away from the logic of session handling and JMX.
  The latter should be built on top of the clustering module, and not baked into it.
  (maybe complete refactor for Tomcat 6)
  Steps:
  1. Build a group object, to allow sending of messages
     The group object will handle encompass membership and 
     messaging under one umbrella.
  2. Enable group RPC
     Through the group object, enable RPC style messaging
     This should be used for message like state transfers, instead of waiting for a timeout.
     RCP strategies - first response, majority response, all response
  3. Group/Message interceptors - to perform logic such as fragmentation, ordering etc.
  4. JMX  
     JMX should be added on top of the core code, not inside the core code.
     The idea of JMX as management should be added outside to the core components.
     For example, SimpleTCPCluster should not contain JMX code, if I want to create
     a different cluster class, I have to rewrite all the JMX code again.
     Instead, create JMX beans that reference core components through interfaces.

- Create stats object
   Instead of keeping stats embedded in the code, make it reusable in
   a shared component.

- support CrossContext session replication
    Idea: use endAccess to signal replicationValve that session from other app has changed.
    refactor ReplicationValve 
    When session is serialzed from other app, set right app classloader
    endaccess is also send at CoyoteAdpater for context session as recycle the request
- Add MbeanFactory to generate dynamic cluster at runtime.
    Problem: How we can start those central services?
    - StandardEngine support load Mbean from external file.     
- when a lot of messages expire it comes to burst of messages 
     - all 60 Sec when ManagerBase#processExpires is called a lot of messages are send!
     - Better is to transfer a spezial epxire message with an array of expired session messages.
     - This reduce message transfer and reduce waits for acks.
     - complicated implementation thing , sessions expires when call isValid :-(     
- build a tool that receive the stage and present it as simple web app.
    	detect some problems
    	different active sessions
    	long queues
    	detect long wait acks
        Idea: Wrote a ant script with the new jmx tasks!
        Optimzied information access:
        	Create a MBean.attribute that store the complete cluster state 
        	information inside one attribute from type TabularData and CompositeData!
        	Implement as SimpleTcpCluster operation
        	Cluster <CompositeData>
        	  -- Attributes <SimpleType>
        	  -- ClusterMembership
        	      -- Attributes <SimpleType>
        	      -- Members <CompositeType>
        	         -- Attributes <SimpeType>
        	  -- ClusterReceiver
        	      -- Attributes <SimpleType>
        	  -- ClusterSender
        	      -- Attributes <SimpleType>
        	      -- DataSenders <TabularData>
        	         -- Sender <CompositeType>
        	         	-- Attributes <SimpeType>
        	         	-- (optional)Queue Stats <CompositeData>
 	       	         		-- Attributes <SimpeType>      	    
- add cluster setup template (src)	
- documentation
	wrote a complete new how-to
	add example configurations
	add complete attribute descriptions
	add JMX information
	add deployment help
	Need help (pero)
- implement fragmentation of large replication objects
  (note this will be done in the Group object, see top.)
	Compress at message level - this will go away! instead there will be a GZip interceptor
	Splitting Messages ala FarmDeployer war handling
- add a message type to the message header.
    - filtering at receiver that drop message before build Object
    - define short type definition.
       - Every Session message with differenz type
       - type with String
- add test cluster project
	functional testing a lot of szenarios
		differen replication mode
		restart after failure
		crash under load
		compress and uncompressed
    Junit test ( started)
    automated regression testing with some standard configs
    wrote a test client that can get a JMX State to verify the different cluster testszenarios
	 - direct JSR 160 client - preferred option
	 - via mx4j http adaptor ( xml protocol)
	 - setup different szenarios
	use new remote jmx ant tasks to grab information from mbeans 
- filter all cluster messages 
     - Filtering that no all message send to all member.
     - Now with domain mode registeration session message only send to
       members from same domain.
- setup a Cluster LifecycleListener to send the cluster status! (monitoring)
     - Make the compact state via JMX API avialable first.
     - setup cluster Listener that send own state to spezial member (sender from a message like GET_ALL_SESSIONS)
     - create a cluster status app (html/xml)
         - attributes
            - send message
            - current members
            - receive message
            - active session at different clustered manager
            - which app are clusters (registered managers)
            - avg processing times
         
         - operations
            - resetStats
            - send a message (String)
            - getDisplay state from other members??
            - stop queue to send
            - queue receiver message from some members ( later send after redeploying)
            - configure some send parameters
                 - keepalive
                 - compress
                 - wait for ack
         - other things
            - based on Cluster JMX API                     
            - watch some values from complete cluster and display some graphs
            - display the informations from all nodes
            - display informations from other cluster domains
            	via XML documents and http
            - display stats as xml
            - operation via JMX (MX4J adaptor)	    

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problems
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- How we can stop the request traffic when restart an application?
    currently the jk 1.2.10 can only disable the complete loadbalancer,
    but this detect only the new session request desicion.
    Request with sessions marks send to tomcat. 
    Fix: jk > 1.2.11 has a stopped flag, but then all application stop traffic
    and session transfer from other nodes not stopped!!
    	Stop MembershipService via JMX and after redeploying application,
    	start MembershipService and restart the application Session Manager or send GETALL Session from backup?
    	then enable apache worker again !! :-(
    	easier stop tomcats, deploy new app and start again... 
- Can't stop message replication for a spezial member and application
   - this need a spezial cluster message and send filter at SimpleTcpCluster 
- Don't generate cluster message when no member is at cluster!
   - Register DeltaManager as Cluster LifecycleListener and stop cresting and sending
   - Reduce memory consume when only local node is active
   - Important feature when nodes crashed, and only one server exists under load...
   
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Nice to have:
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- Replication ContextAttributes	
- Configure the McastService no accept every member.
	- receive a secret key
	- have a allow or deny list like RequestFilterValve
	- Also receiver don't accept request from not allowed members
- ReplicationListener and SocketReplicationListener only accept data from cluster member (low level ip restriction)
- PooledSocketSender
	Add more stats
	check all Pooled sender checkKeepAlive
- Implement a NonSerializable interface for session attributes that do not
wish to be replicated
        Then we must have ClusterNonSerializable at common classloader