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Learning MCollective by Jo Rhett

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Chapter 10. Creating Collectives

A Collective is a set of ActiveMQ topics and queues used to group request traffic. In small installations you should use a single Collective. The installation we have done in this book uses the default collective name mcollective for all configurations.

You may want to create multiple collectives for the following reasons:

  1. Collectives can be used to limit traffic in large clusters or between sites.
  2. Collectives can be used to group nodes together for restricting client access.

Deciding When to Create More

There are a few reasons why you may want to implement multiple collectives in your network:

  1. You have more than a thousand servers.
  2. You have multiple locations with high latency between them.
  3. You have multiple locations and you’d like to reduce the network traffic between them.
  4. You want to allow local admins control of their own hosts, while allowing a global team to administer all hosts.

Following are a few reasons you don’t want to implement multiple collectives:

  1. You want fault tolerance in your middleware setup.

    Sub-Collectives do not intrinsically provide fault tolerance. That can be created by using a Network of Brokers or Master/Slave setup, as documented in ActiveMQ Clusters. Collectives are most effective at limiting traffic when placed on brokers localized to each site.

  2. You want to implement barriers for authorization control.

    While you can restrict clients to specific collectives to limit server access, this isn’t a granular authorization ...

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