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Last pushed: 10 months ago
Short Description
JGroups demo
Full Description


Dockerfile for a container containing JGroups and a couple of demos.

To run the image directly, execute

  docker run -p 7800:7800 -p 9000:9000 -it --rm --network=host belaban/jgroups


  docker run -p 7800:7800 -p 9000:9000 -it --rm --network=bridge belaban/jgroups

To build the image, run

  docker build .

The demos are described below. The idea is to run the demo apps in a
container each on the same host and they will form a cluster.


To run it:

  chat [-props config] [-name name], e.g. chat -props ./udp.xml -name A

Run the Chat application in multiple containers on the same host and
they will form a cluster. Typing a message into one Chat will send it
to all other chats

Distributed locks

Distributed locks are implementations of
java.util.concurrent.locks.Lock and provide locks that can be
accessed from all nodes in a cluster.

A typical use case is to lock a resource so that only 1 thread in a
given node in the cluster can access it. Should a node crash while
holding a lock, the lock is released immediately.

For more details, see the section on distributed locks at

To run the lock demo, type:

   lock [-name  name]

Typing help into the shell shows a few commands:

[jgroups@b21d0fa6c79d ~]$ lock -name A

GMS: address=A, cluster=lock-cluster, physical address=
: help

LockServiceDemo [-props properties] [-name name]
Valid commands:
    lock (<lock name>)+
    unlock (<lock name> | "ALL")+
    trylock (<lock name>)+ [<timeout>]

    lock lock lock2 lock3
    unlock all
    trylock bela michelle 300

If you start instances A and B, you can try out the following:

  1. A: lock printer
  2. B: lock printer // will block
  3. A: unlock printer // now B will get the lock

Or a lock holder can be killed:

  1. A: lock printer
  2. B: lock printer
  3. Kill A. B will now get the lock on "printer"

Distributed counters

Distributed counters are counters will can be atomically incremented,
decremented, compare-and-set etc across a cluster.

To run the demo:

count [-name name]

Run multiple instances in different containers. The demo uses a
counter named "mycounter" and there's a command prompt which shows the
commands to be executed.

Questions can be asked on the users or dev mailing lists:

Enjoy !

Bela Ban

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