com.hazelcast.spi.discovery

Interface DiscoveryStrategy

All Known Implementing Classes:

AbstractDiscoveryStrategy, MulticastDiscoveryStrategy

public interface DiscoveryStrategy

The DiscoveryStrategy itself is the actual implementation to discover nodes based on whatever environment is used to run the Hazelcast cloud. The internal implementation is completely vendor specific and might use external Java libraries to query APIs or send requests to a external REST service.

DiscoveryStrategies are also free to define any kind of properties that might be necessary to discover eligible nodes based on configured attributes, tags or any other kind of metadata.

Using the simple lifecycle management strategies like multicast discovery is able to register and destroy sockets based on Hazelcast’s lifecycle. Deactivated services will also never be started.

Attention: Instead of implementing this interface directly, implementors should consider using the abstract class AbstractDiscoveryStrategy instead for easier upgradeability while this interface evolves.

Since:

3.6

Method Summary

Modifier and Type	Method and Description
void	destroy() The stop method is used to stop internal services, sockets or to destroy any kind of internal state.
Map<String,String>	discoverLocalMetadata() Returns a map with discovered metadata provided by the runtime environment.
Iterable<DiscoveryNode>	discoverNodes() Returns a set of all discovered nodes based on the defined properties that were used to create the DiscoveryStrategy instance.
PartitionGroupStrategy	getPartitionGroupStrategy() Returns a custom implementation of a PartitionGroupStrategy to override default behavior of zone aware backup strategies PartitionGroupMetaData or to provide a specific behavior in case the discovery environment does not provide information about the infrastructure to be used for automatic configuration.
void	start() The start method is used to initialize internal state and perform any kind of startup procedure like multicast socket creation.

Method Detail

start

void start()

The start method is used to initialize internal state and perform any kind of startup procedure like multicast socket creation. The behavior of this method might change based on the DiscoveryNode instance passed to the DiscoveryStrategyFactory.

discoverNodes

Iterable<DiscoveryNode> discoverNodes()

Returns a set of all discovered nodes based on the defined properties that were used to create the DiscoveryStrategy instance.

Returns:

a set of all discovered nodes

destroy

void destroy()

The stop method is used to stop internal services, sockets or to destroy any kind of internal state.

getPartitionGroupStrategy

PartitionGroupStrategy getPartitionGroupStrategy()

Returns a custom implementation of a PartitionGroupStrategy to override default behavior of zone aware backup strategies PartitionGroupMetaData or to provide a specific behavior in case the discovery environment does not provide information about the infrastructure to be used for automatic configuration.

Returns:

a custom implementation of a PartitionGroupStrategy otherwise null in case of the default implementation is to be used

Since:

3.7

discoverLocalMetadata

Map<String,String> discoverLocalMetadata()

Returns a map with discovered metadata provided by the runtime environment. Those information may include, but are not limited, to location information like datacenter, rack, host, node name or additional tags to be used for custom purpose.

Information discovered from this method are shaded into the Members attributes. Existing attributes will not be overridden, that way local attribute configuration overrides provided metadata.

The default implementation provides an empty map with no further metadata configured. Returning null is not permitted and will most probably result in an NullPointerException inside the cluster system.

Returns:

a map of discovered metadata as provided by the runtime environment

Since:

3.7