Core group communications using the core group bridge service

The core group bridge service can be configured to share availability information about internal WAS components between core groups. For example, by configuring the core group bridge service, each core group can be aware of the status of all of the application servers that are configured in all of the core groups. Use access point groups to define the core groups that communicate. Do not use the core group bridge service to share application information among core groups.

A core group is a statically defined component of the high availability manager. Each cell must have at least one core group. WebSphere Application Server creates a default core group called DefaultCoreGroup for each cell. For more information about core groups, see Core groups. Two or more core groups can be set up to communicate with each other and share workload management information by defining access point groups. The core groups that communicate can be in the same cell or in different cells.

Core group bridge overview

To configure communication between core groups, configure an access point group. An access point group is a collection of the core groups that communicate with each other. Add a core group access point to the access point group for each core group that needs to communicate.

A core group access point is a collection of server, node, and transport channel chain combinations that communicate for the core group. Each core group has one or more defined core group access points. The DefaultCoreGroup has one default core group access point. However, you might consider configuring more than one core group access point for a core group if that particular core group needs to be connected to other core groups that are on different networks.

The node, server, and transport channel chain combinations that are in a core group access point are called bridge interfaces. A server that hosts the bridge interfaces is a core group bridge server. The transport channel chain defines the set of channels that are used to communicate with other core group bridge servers. Each transport channel chain has a configured port that the core group bridge uses to listen for messages from other core group bridge servers.

Each core group bridge server must have at least one bridge interface for each core group access point. However, to prevent failure of your configuration, configure multiple bridge interfaces for each core group access point. Then, if one server in one of the bridge interfaces fails, the other bridge interface can still receive information and the core group access point remains functional.

If you are configuring communication between core groups that are in the same cell, create one access point group and add a core group access point for each core group that needs to communicate. The following diagram shows an example configuration in a single cell: Figure 1. Core group bridge configuration in a single cell

If you are configuring the core group bridge between core groups that are in different cells, you still use an access point group. However, create and configure the access point group for each cell. Each cell has an access point group that contains a core group access point for the core group that is in the cell, and a peer access point for each peer cell.

A peer access point references a core group access point that is configured in a different cell. Each access point group must have one peer access point for each different cell. Do not configure multiple peer access points that reference the same cell.

Each peer access point has one or more peer ports or one proxy peer access point.

A peer port corresponds to a bridge interface that is defined in the peer cell. We can define several peer ports for each peer access point.

Define a proxy peer access point if the peer access point cannot be reached directly by using a peer port, but can be reached by using another peer access point. The proxy peer access point specifies a peer access point that can communicate with the peer core group that cannot be reached directly. The proxy peer must have defined peer ports. Specify one proxy peer or one or more peer ports, but not both.

The following diagram shows a core group bridge configuration between two different cells that is using peer access points with peer ports. Figure 1. Core group bridge configuration in two different cells

Configuration scenarios

One can configure core groups

Communication between core groups that are in

the same cell

All core groups that are in the same cell must be configured to communicate with each other. To configure core group communication within a cell, create one access point group with one core group access point for each core group. Select one or more servers to be core group bridge servers, and define a bridge interface for each server. The following image shows an example of three core groups that are in the same cell and are connected by one access point group. The sample configuration shows how communication between core groups in the same cell is configured in the administrative console.Figure 1. Communication between core groups that are in the same cell See Configuring communication between core groups that are in the same cell for more information.

Communication between core groups that

are in different cells

When two core groups in different cells need to communicate, add peer access points to the access point groups. To configure the core group in cell_x to communicate with the core group in cell_y, add a peer access point to the access point group in cell_x. The peer access point is equal to the core group access point for cell_y. Configure an access point group that has the same name for cell_y that contains the core group access point for the core group in cell_y and a peer access point that corresponds to the core group access point for the core group in cell_x. Each peer access point also contains peer ports that identify bridge interfaces in the opposite cells. See Configuring communication between core groups that are in different cells for more information.

Communication between core groups across

different networks

In this scenario, one core group is configured to communicate with two or more core groups in different cells across two or more networks. For example, a core group in cell_x needs to communicate with core groups in cell_y and cell_z. Create two access point groups in cell_x. The first access point group, access_point_group_xy, in cell_x contains a core group access point and a peer access point for the core group in cell_y. The second access point group in cell_x, access_point_group_xz, contains a core group access point and a peer access point for the core group in cell_z. Cell_y has an access point group named access_point_group_xy, which has a core group access point and a peer access point for cell_x. Cell_z has an access point group named access_point_group_xz which has a core group access point and a peer access point for cell_x. See Configuring communication between core groups that are in different cells for more information.

Communication between core groups using a proxy

peer access point

Use a proxy peer when the core groups cannot directly communicate. The two core groups must have access to a single core group that can pass information between the two core groups. To understand what a proxy peer access point does, consider a connecting flight when flying on an airplane. To fly from Pittsburgh to London you first have to fly to New York City, where you change planes and then fly to London. New York City is the proxy peer access point for London.

When defining a proxy peer, x_core_group_2 in cell_x cannot communicate directly with the core group in cell_z. However, both core groups can communicate with the core group in cell_y. To configure communication between cell_x and cell_z, configure two access point groups. The core group access point in cell_y is in both of these access point groups, named access_point_group_xy and access_point_group_yz. The following image shows an overview of a proxy peer configuration.Figure 1. Core group communication using a proxy peer access point See Configuring core group communication using a proxy peer access point for more information.