Tomcat Clustering and JavaGroups

1
Tomcat Clustering and JavaGroups

• Tomcat Java web container for building java
  servlet applications.
• Session Replication is the main clustering issue.
• JavaGroups provides an out of the box messaging
  framework for synchronizing server session
  information.

2
Channel

• Channel abstraction creates boundry between
  application development and protocol
  implementation.

3
Channels

• Address is opaque, hidden from developer.
• Communication is handled like messages, either
  unicast or multicast.
• Channel Group my a common String name.
• Channel Instance identified by name and address
  (IP port).
• Must connect and disconnect one at a time.

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Micro Protocols

• TCP
• TCPPING
• TCPGOSSIP
• TUNNEL
• VIEW_ENFORCER
• STABLE
• VERIFY_SUSPECT
• UDP
• PING
• pbcast.GMS
• pbcast.FD
• pbcast.PBCAST
• pbcast.STABLE
• pbcast.NAKACK
• pbcast.STATE_TRANSFER

• CAUSAL
• FD_SOCK
• FD_PID
• FD_PROB
• FLOW_CONTROL
• FLUSH
• FRAG
• GMS
• MERGE
• MERGE2
• NACKACK
• JMS
• STATE_TRANSFER
• UNICAST

6
Tomcat Environment

• Servlet Session object for persistence.

7
Tomcat Cluster Issue

• Session not consistent across instances.

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JavaGroups Solution replicates Session object
across VMs.
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• Tomcat Session replication demo using JavaGroups.

10
References

• High-impact Web tier clustering, Part 1 Scaling
  Web services and applications with JavaGroups
  -Sing Li (westmakaha_at_yahoo.com) Author, Wrox
  Press 1 July 2003 http//www-106.ibm.com/developer
  works/java/library/j-cluster1/
• In Memory Session Replication In Tomcat 4 -Filip
  Hanik(mail_at_filip.net) http//www.theserverside.com
  /articles/article.tss?lTomcat
• The JavaGroups Project http//www.jgroups.org/java
  groupsnew/docs/index.html