This article will introduce the basic concepts of JGroups and then implement a task java,spring boot,errror response,http,tutorial,customize. JGroups is a library for reliable one-to-one or one-to-many communication written in the Java language. It can be used to create groups of processes whose. JGroup is the corner stone for clustering. It is a reliable multicast system. As we know, using IP multicasting we can set a group of computers to.

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JGroup is the corner stone for clustering. It is a reliable multicast system. As we know, using IP multicasting we can set a group of computers to use tutoriwl multicast IP address, and all the messages sent to this multicast IP address will be received by all the computers in the group.

JGroups Cluster in the Cloud

IP multicasting is usually used together with UDP protocol. Meanwhile, the sender of this UDP datagram don’t care whether destination computers received this datagram or not. Here is the diagram that shows a IP multicasting group that contains three members:.

UDP is suitable for this scenario. Because if we use TCP, then the sender must establish connections with all the members in a multicasting group, and check the messages are received successfully by all the members.


However, UDP is not a reliable protocol, the datagram maybe lost during transmission and it won’t be checked:. Besides, UDP datagrams may also arrived in random sequence and not sorted by timeline: If the sender sends packet 1 firstly, and then packet 2, the receiver may receive packet 2 firstly and then One example is like numbering all the datagrams we’ve sent in application layer.

And the receiver will need to check the data is not lost and then sort the packets into correct order. JGroup is certainly much more complex than above example but the design concept is basically the same.

In JGroup, the minimal group unit is called ‘Channel’. Members in a channel can talk with each other. Here is the use case:. Generally speaking, JGroup is designed as a ‘layered protocol stack’. In the bottom of the stack it’s the ‘UDP’ protocol. Other protocols are built on top of it to meet different requirements of a cluster. For example, some protocol ensures the packet reliability like the example shown above: You can even guess some protocol’s purpose by its name.

The complete description of each protocol could be found here:. JGroup – List of Protocols. I wish you have caught the general design concepts of JGroup with above description.


Now let’s get into the code:.

In JGroup a cluster is called tutorlal channel. The members in the channel can send messages to or receive messages from this channel. We will develop an example that creates a channel and have two members in it: A sender that sends messages to the channel and a receiver that receive messages from the channel.

Please note a member in a channel can be both a sender a receiver. We just simplify the scenario in the example for the code to be better explained.

JGroups Cluster with Jelastic Cloud | Jelastic Dev Docs

From the above diagram we can see the first step to setup a cluster is to ask members to join to a same channel, then they can communicate with other members in this group. In below are the real codes:.

Each protocol is focusing on its own task, for a complete definition of each stack, please check JGroup Protocol Link. A ProtocolStack instance is created with the current Channel config, and two xml files are loaded into ClassConfigurator:.

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