ActiveSpaces Host-Aware Replication

Overview

Host-aware replication is used to group seeders of a space together so that the data being stored by the seeders in one group is replicated on seeders in a different group. This helps to prevent data loss when a group of seeders goes down, because their data has been replicated elsewhere.

By default, data is not replicated when it is put into a space and host-aware replication does not occur. A space must be defined with a replication count greater than 0 for replication to occur.

You must run an ActiveSpaces application to define and put data into the spaces of a metaspace. However, you cannot use ActiveSpaces Enabler to do this. Using ActiveSpaces Enabler you can configure and start as-agents. An as-agent does not define any spaces. The role of an as-agent is to automatically join any space created in a metaspace and act as a seeder for that space.

For information on replicating data in spaces, see TIBCO ActiveSpaces Developer's Guide. For more information about as-agents, see TIBCO ActiveSpaces Administration.

Specifying Member Name Prefixes for Host-Aware Replication

With host-aware replication, seeders of a space are grouped based on their member names. To organize seeders into groups, the following member naming convention is used:

<group_name>.<member_name>

 

AS_MEMBER_NAME_PREFIX must be unique for each component that you configure.

ActiveSpaces groups all seeders with the same group_name together and their data is replicated on seeders outside of that group.

To use host-aware replication with a component configured using the ActiveSpaces Enabler, prepend a <group_name> and '.' (dot) to the AS_MEMBER_NAME_PREFIX.

If you configured a component but did not previously specify an AS_MEMBER_NAME_PREFIX setting, the component name was used as the AS_MEMBER_NAME_PREFIX. In this case, add the AS_MEMBER_NAME_PREFIX Runtime Context Variable to your configuration and specify the following as your member name prefix:

<group_name>.<component_name>

For example, suppose you have components that are named as follows:

•

NotreDame

•

Purdue

•	UniversityOfMichigan

•	MichiganState

You have configured NotreDame and Purdue to both run-on machines physically located in Indiana, and you want to make sure that if a tornado hits Indiana and those machines go down, you do not lose any data. So you want to replicate your data on the machines in Michigan that run the components UniversityOfMichigan and MichiganState.

By adding and modifying the AS_MEMBER_NAME_PREFIX values of the components as follows, you ensure that any data seeded by NotreDame or Purdue component instances is replicated on component instances of UniversityOfMichigan or MichiganState:

•	Indiana.NotreDame

•	Indiana.Purdue

•	Michigan.UniversityOfMichigan

•	Michigan.MichiganState

See Controlling Where Components Run to learn how to create stack configurations that control which machines the components are run on.

 

When using host-aware replication with shared-nothing persistence, the shared-nothing persistence data store still uses the same directory and file naming format for storing data: <root_directory>/<metaspace_name>/<space_name>/<member_name>/<member_name>_store_<timestamp> The <member_name> portion will include the <group_name> and dot (.) that are part of the member name when host-aware replication is used.