SolrCoreReloader.java

import java.io.IOException;
import java.lang.invoke.MethodHandles;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CompletableFuture;

import org.apache.solr.client.solrj.request.CollectionAdminRequest;
import org.apache.solr.client.solrj.response.CollectionAdminResponse;
import org.apache.solr.common.cloud.*;
import org.apache.solr.common.util.NamedList;
import org.apache.zookeeper.KeeperException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class SolrCoreReloader {

    public static void main(String[] args) {
        try (SolrZkClient zkClient = new SolrZkClient.Builder().withUrl(args[0]).build()) {
            ZkStateReader zkStateReader = new ZkStateReader(zkClient);
            List<String> solrCoreUrls = fetchSolrCoreUrls(zkStateReader, args[1]);
            reloadSolrCores(solrCoreUrls).join();
            System.out.println("All cores reloaded.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static List<String> fetchSolrCoreUrls(ZkStateReader zkStateReader, String collectionName) throws KeeperException, InterruptedException, IOException {
        List<String> solrCoreUrls = new ArrayList<>();
        zkStateReader.createClusterStateWatchersAndUpdate();
        Map<String, ClusterState.CollectionRef> collectionStates = zkStateReader.getClusterState().getCollectionStates();

        if (collectionStates.containsKey(collectionName)) {
            ClusterState.CollectionRef collectionState = collectionStates.get(collectionName);
            Collection<Slice> slices = collectionState.get().getSlices();
            for (Slice slice : slices) {
                Collection<Replica> replicas = slice.getReplicas();
                for (Replica replica : replicas) {
                    String coreUrl = replica.getBaseUrl() + "/admin/cores?action=RELOAD&core=" + replica.get("core");
                    System.out.println("Core URL: " + coreUrl);
                    solrCoreUrls.add(coreUrl);
                }
            }
        }

        return solrCoreUrls;
    }

    private static CompletableFuture<Void> reloadSolrCores(List<String> solrCoreUrls) {
        HttpClient client = HttpClient.newHttpClient();
        List<CompletableFuture<Void>> futures = new ArrayList<>();

        for (String url : solrCoreUrls) {
            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create(url))
                    .header("Content-Type", "application/json")
                    .GET()
                    .build();

            CompletableFuture<Void> future = client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
                    .thenApply(HttpResponse::body)
                    .thenAccept(body -> System.out.println("Reloaded core: " + url + " Response: " + body))
                    .exceptionally(e -> {
                        System.err.println("Failed to reload core: " + url + " Error: " + e.getMessage());
                        return null;
                    });
            futures.add(future);
        }

        return CompletableFuture.allOf(futures.toArray(new CompletableFuture[0]));
    }
}