The Cluster Membership object

Table of Contents

Introduction

The membership component in the Apache Tribes Channel is responsible for dynamic discovery of other members(nodes) in the cluster.

Default Implementation

The default implementation of the cluster group notification is built on top of multicast heartbeats sent using UDP packets to a multicast IP address. Cluster members are grouped together by using the same multicast address/port combination. Each member sends out a heartbeat with a given interval (frequency), and this heartbeat is used for dynamic discovery. In a similar fashion, if a heartbeat has not been received in a timeframe specified by dropTime ms. a member is considered suspect and the channel and any membership listener will be notified.

Attributes

Multicast Attributes

Attribute Description
className

The default value is org.apache.catalina.tribes.membership.McastService and is currently the only implementation. This implementation uses multicast heartbeats for member discovery.

address

The multicast address that the membership will broadcast its presence and listen for other heartbeats on. The default value is 228.0.0.4 Make sure your network is enabled for multicast traffic.
The multicast address, in conjunction with the port is what creates a cluster group. To divide up your farm into several different group, or to split up QA from production, change the port or the address
Previously known as mcastAddr.

port

The multicast port, the default value is 45564
The multicast port, in conjunction with the address is what creates a cluster group. To divide up your farm into several different group, or to split up QA from production, change the port or the address

frequency

The frequency in milliseconds in which heartbeats are sent out. The default value is 500 ms.
In most cases the default value is sufficient. Changing this value, simply changes the interval in between heartbeats.

dropTime

The membership component will time out members and notify the Channel if a member fails to send a heartbeat within a give time. The default value is 3000 ms. This means, that if a heartbeat is not received from a member in that timeframe, the membership component will notify the cluster of this.
On a high latency network you may wish to increase this value, to protect against false positives.
Apache Tribes also provides a