com.hazelcast.spi.discovery.DiscoveryStrategyFactory Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2024, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.spi.discovery;
import com.hazelcast.config.properties.PropertyDefinition;
import com.hazelcast.core.HazelcastInstance;
import com.hazelcast.logging.ILogger;
import java.util.Collection;
import java.util.Map;
import static com.hazelcast.spi.discovery.DiscoveryStrategyFactory.DiscoveryStrategyLevel.UNKNOWN;
/**
* The DiscoveryStrategyFactory is the entry point for strategy vendors. Every
* {@link DiscoveryStrategy} should have its own factory building it. In rare cases (like
* multiple version support or similar) one factory might return different provider
* implementations based on certain criteria. It is also up to the DiscoveryStrategyFactory
* to cache instances and return them in some kind of a Singleton-like fashion.
*
* The defined set of configuration properties describes the existing properties inside
* of the Hazelcast configuration. It will be used for automatic conversion,
* type-checking and validation before handing them to the {@link DiscoveryStrategy}.
* This removes a lot of boilerplate from the provider vendor and provides some convenience as
* well as guarantee to execute the expected configuration checks. The later is especially
* important because there is no schema support for properties necessary or provided by the
* provider plugins. Any kind of violation while verification of any type conversion error
* as well as missing non-optional properties will throw an exception and prevent the node
* from starting up.
*
* @since 3.6
*/
public interface DiscoveryStrategyFactory {
/**
* Returns the type of the {@link DiscoveryStrategy} itself.
*
* @return the type of the discovery strategy
*/
Class getDiscoveryStrategyType();
/**
* Instantiates a new instance of the {@link DiscoveryStrategy} with the given configuration
* properties. The provided {@link HazelcastInstance} can be used to register instances in
* a service registry whenever the discovery strategy is started.
*
* @param discoveryNode the current local DiscoveryNode, representing the local
* connection information if running on a Hazelcast member, otherwise on
* Hazelcast clients always null
* @param logger the logger instance
* @param properties the properties parsed from the configuration
* @return a new instance of the discovery strategy
*/
DiscoveryStrategy newDiscoveryStrategy(DiscoveryNode discoveryNode, ILogger logger, Map properties);
/**
* Returns a set of the expected configuration properties. These properties contain
* information about the value type of the property, if it is required and a possible
* validator to automatically test and convert values from the XML configuration.
*
* @return a set of expected configuration properties
*/
Collection getConfigurationProperties();
/**
* Checks whether the given discovery strategy may be applied with no additional config to the environment in which Hazelcast
* is currently running.
*
* Used by the auto detection mechanism to decide which strategy should be used.
*/
default boolean isAutoDetectionApplicable() {
return false;
}
/**
* Level of the discovery strategy.
*/
default DiscoveryStrategyLevel discoveryStrategyLevel() {
return UNKNOWN;
}
/**
* Level of the discovery strategy.
*
* Discovery strategies can have different levels. They can be at the level of Cloud Virtual Machines, for example, AWS EC2
* Instance or GCP Virtual Machine. They can also be at the level of some specific platform or framework, like Kubernetes.
*
* It decides on the priority in the auto detection mechanism. As an example, let's take Kubernetes environment installed
* on AWS EC2 instances. In this case two plugins are auto-detected: hazelcast-aws and hazelcast-kubernetes.
* This level decides which one to pick:
*
* - hazelcast-aws implements level {@code CLOUD_VM}
* - hazelcast-kubernetes implements level {@code PLATFORM}
*
* {@code PLATFORM} has higher priority than {@code CLOUD_VM}, so hazelcast-kubernetes plugin is selected.
*/
enum DiscoveryStrategyLevel {
/**
* Level unknown, lowest priority.
*/
UNKNOWN(0),
/**
* VM Machine level, for example, hazelcast-aws or hazelcast-azure.
*/
CLOUD_VM(10),
/**
* Platform level, for example, hazelcast-kubernetes.
*/
PLATFORM(20),
/**
* Custom strategy level, highest priority.
*/
CUSTOM(50);
private int priority;
DiscoveryStrategyLevel(int priority) {
this.priority = priority;
}
public int getPriority() {
return priority;
}
}
}