well-known-addresses

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well-known-addresses

Used in: unicast-listener.

Use of the Well Known Addresses (WKA) feature is not supported by Standard Edition. If you are having difficulties in establishing a cluster via multicast, see the Performing a Multicast Connectivity Test.

Description

By default Coherence uses a multicast protocol to discover other nodes when forming a cluster. If multicast networking is undesirable, or unavailable in your environment, the Well Known Addresses feature may be used to eliminate the need for multicast traffic. When in use the cluster is configured with a relatively small list of nodes which are allowed to start the cluster, and which are likely to remain available over the cluster lifetime. There is no requirement for all WKA nodes to be simultaneously active at any point in time. This list is used by all other nodes to find their way into the cluster without the use of multicast, thus at least one well known node must be running for other nodes to be able to join.

This is not a security-related feature, and does not limit the addresses which are allowed to join the cluster. See the authorized-hosts element for details on limiting cluster membership.

Example

The following configuration specifies two well-known-addresses, with the default port.

Elements

The following table describes the elements you can define within the well-known-addresses element.

Element Required/Optional Description
<socket-address> Optional Specifies a list of "well known" addresses (WKA) that are used by the cluster discovery protocol in place of multicast broadcast. If one or more WKA is specified, for a member to join the cluster it will either have to be a WKA or there will have to be at least one WKA member running. Additionally, all cluster communication will be performed using unicast. If empty or unspecified multicast communications will be used.

Preconfigured overrides are tangosol.coherence.wka and tangosol.coherence.wka.port.
<address-provider> Optional Specifies the configuration for the com.tangosol.util.AddressProvider address factory that will supply the WKA addresses.

The calling component will attempt to obtain the full list upon node startup, the provider must return a terminating null address to indicate that all available addresses have been returned.

The content override attribute xml-override can be optionally used to fully or partially override the contents of this element with XML document that is external to the base document.

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