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jakarta-eeglassfishterminology
George
George

Reputation: 255

Application Server clustering

What does clustering means in terms of application server, especially GlassFish? does it mean that we can connect difference app servers and make them as a single unit.

Thanks.

Upvotes: 2

Views: 155

Answers (1)

John Clingan
John Clingan

Reputation: 3334

I'd split clustering into two aspects:

  1. Manageability. Cluster more than one instance together to manage those instances as one. Make a change to one instance and your really making changes to all instances in a cluster. Different application servers implement this differently. With GlassFish Server, instances in a cluster share a "configuration". If you make a change to that configuration, then all instances inherit those changes. Also, deploy an an application to a cluster, it is deployed to all instances in a cluster. Disable that application on a cluster, and it is disabled on all instances.

  2. Availability. There are basically two levels of availability. This first is service availability, where if one instance fails, other instances can pick up the load. However, any active user sessions are lost (the lose the contents of a hypothetical "shopping cart"). With "high availability" clustering, if one instance fails, one or more additional instances will pick up the load, including an user session data. In this case, the hypothetical "shopping cart" contents are not lost.

Check out the GlassFish Server High Availability Guide, which goes into clustering in more detail.

Hope this helps.

Upvotes: 1

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