Optimizing Solr Client Usage by Caching for Each Collection

Introduction

When working with Apache Solr, especially in applications with multiple collections, it’s common to create a new Solr client instance for each connection. While this may seem straightforward, it can lead to performance issues due to the overhead of repeatedly initializing clients. Instead, a more efficient approach is to cache the Solr client for each collection, reducing resource usage and improving performance.

Implementation: Caching Solr Clients

Here’s a step-by-step guide on how to implement a caching mechanism for Solr clients based on collections.

1. Define a Cache for Solr Clients

First, you’ll need a data structure to store the cached clients. A Map or Dictionary works well for this purpose.

import org.apache.solr.client.solrj.SolrClient;
import org.apache.solr.client.solrj.impl.HttpSolrClient;

import java.util.HashMap;
import java.util.Map;

public class SolrClientCache {
    private static final Map<String, SolrClient> clientCache = new HashMap<>();

    public static SolrClient getClientForCollection(String collectionName) {
        return clientCache.computeIfAbsent(collectionName, SolrClientCache::createClient);
    }

    private static SolrClient createClient(String collectionName) {
        String solrUrl = "http://localhost:8983/solr/" + collectionName;
        return new HttpSolrClient.Builder(solrUrl).build();
    }
}

2. Accessing the Cached Client

Whenever you need to perform operations on a specific Solr collection, retrieve the client from the cache:

public class SolrService {
    public void querySolr(String collectionName, String query) {
        SolrClient client = SolrClientCache.getClientForCollection(collectionName);
        // Perform your query using the client
    }
}

3. Cleaning Up Clients

It's important to ensure that clients are properly closed when no longer needed, particularly when your application shuts down:

public class SolrClientCache {
    // Existing code...

    public static void closeAllClients() {
        for (SolrClient client : clientCache.values()) {
            try {
                client.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}