/*
 * Copyright 2017-2020 original authors
 *
 * 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
 *
 * https://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 io.micronaut.http.client.loadbalance;

import io.micronaut.core.async.publisher.Publishers;
import io.micronaut.discovery.DiscoveryClient;
import io.micronaut.discovery.ServiceInstance;
import org.reactivestreams.Publisher;

A LoadBalancer that uses the DiscoveryClient and a ServiceInstance ID to automatically load balance between discovered clients in a non-blocking manner.

Note that the when DiscoveryClient caching is enabled then this load balancer may not always have the latest server list from the DiscoveryClient (the default TTL is 30 seconds)
Author:
Graeme Rocher
Since:
1.0/**
 * <p>A {@link io.micronaut.http.client.LoadBalancer} that uses the {@link DiscoveryClient} and a
 * {@link ServiceInstance} ID to automatically load balance between discovered clients in a non-blocking manner.</p>
 * <p>
 * <p>Note that the when {@link DiscoveryClient} caching is enabled then this load balancer may not always have the
 * latest server list from the {@link DiscoveryClient} (the default TTL is 30 seconds)</p>
 *
 * @author Graeme Rocher
 * @since 1.0
 */
public class DiscoveryClientRoundRobinLoadBalancer extends AbstractRoundRobinLoadBalancer {

    private final String serviceID;
    private final DiscoveryClient discoveryClient;

    
Params:
serviceID –       The service ID
discoveryClient – The discovery client/**
     * @param serviceID       The service ID
     * @param discoveryClient The discovery client
     */
    public DiscoveryClientRoundRobinLoadBalancer(String serviceID, DiscoveryClient discoveryClient) {
        this.serviceID = serviceID;
        this.discoveryClient = discoveryClient;
    }

    
Returns:
The service ID/**
     * @return The service ID
     */
    @Override
    public String getServiceID() {
        return serviceID;
    }

    @Override
    public Publisher<ServiceInstance> select(Object discriminator) {
        return Publishers.map(discoveryClient.getInstances(serviceID), this::getNextAvailable);
    }
}