refactor: remove standalone Solr support, require SolrCloud (#71)

---------

Signed-off-by: adityamparikh <aditya.m.parikh@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: adityamparikh

src/main/java/org/apache/solr/mcp/server/collection/CollectionService.java

@@ -31,17 +31,13 @@
 import org.apache.solr.client.solrj.SolrQuery;
 import org.apache.solr.client.solrj.SolrRequest;
 import org.apache.solr.client.solrj.SolrServerException;
-import org.apache.solr.client.solrj.impl.CloudSolrClient;
 import org.apache.solr.client.solrj.request.CollectionAdminRequest;
-import org.apache.solr.client.solrj.request.CoreAdminRequest;
 import org.apache.solr.client.solrj.request.GenericSolrRequest;
 import org.apache.solr.client.solrj.request.LukeRequest;
 import org.apache.solr.client.solrj.response.CollectionAdminResponse;
-import org.apache.solr.client.solrj.response.CoreAdminResponse;
 import org.apache.solr.client.solrj.response.LukeResponse;
 import org.apache.solr.client.solrj.response.QueryResponse;
 import org.apache.solr.client.solrj.response.SolrPingResponse;
-import org.apache.solr.common.params.CoreAdminParams;
 import org.apache.solr.common.params.ModifiableSolrParams;
 import org.apache.solr.common.util.NamedList;
 import org.apache.solr.mcp.server.config.SolrConfigurationProperties;
@@ -67,8 +63,8 @@
  * <strong>Core Capabilities:</strong>
  *
  * <ul>
- * <li><strong>Collection Discovery</strong>: Lists available collections with
- * automatic SolrCloud vs standalone detection
+ * <li><strong>Collection Discovery</strong>: Lists available collections using
+ * the SolrCloud Collections API
  * <li><strong>Performance Monitoring</strong>: Comprehensive metrics collection
  * including index, query, cache, and handler statistics
  * <li><strong>Health Monitoring</strong>: Real-time health checks with
@@ -100,7 +96,6 @@
  *
  * <ul>
  * <li><strong>SolrCloud</strong>: Distributed mode using Collections API
- * <li><strong>Standalone</strong>: Single-node mode using Core Admin API
  * </ul>
  *
  * <p>
@@ -319,23 +314,16 @@ public List<String> completeCollectionForSchema() {
 	}
 
 	/**
-	 * Lists all available Solr collections in the cluster.
+	 * Lists all available Solr collections in the SolrCloud cluster.
 	 *
 	 * <p>
-	 * This method automatically detects the Solr deployment type and uses the
-	 * appropriate API:
-	 *
-	 * <ul>
-	 * <li><strong>SolrCloud</strong>: Uses Collections API to list distributed
-	 * collections
-	 * <li><strong>Standalone</strong>: Uses Core Admin API to list individual
-	 * collections
-	 * </ul>
+	 * This method uses the SolrCloud Collections API to retrieve the list of
+	 * available collections. Standalone Solr instances are not supported.
 	 *
 	 * <p>
-	 * In SolrCloud environments, the returned names may include shard identifiers
-	 * (e.g., "films_shard1_replica_n1"). Use {@link #extractCollectionName(String)}
-	 * to get the base collection name if needed.
+	 * The returned names may include shard identifiers (e.g.,
+	 * "films_shard1_replica_n1"). Use {@link #extractCollectionName(String)} to get
+	 * the base collection name if needed.
 	 *
 	 * <p>
 	 * <strong>Error Handling:</strong>
@@ -356,33 +344,17 @@ public List<String> completeCollectionForSchema() {
 	 * @return a list of collection names, or an empty list if unable to retrieve
 	 *         them
 	 * @see CollectionAdminRequest.List
-	 * @see CoreAdminRequest
 	 */
 	@McpTool(name = "list-collections", description = "List solr collections")
 	public List<String> listCollections() {
 		try {
-			if (solrClient instanceof CloudSolrClient) {
-				// For SolrCloud - use Collections API
-				CollectionAdminRequest.List request = new CollectionAdminRequest.List();
-				CollectionAdminResponse response = request.process(solrClient);
+			CollectionAdminRequest.List request = new CollectionAdminRequest.List();
+			CollectionAdminResponse response = request.process(solrClient);
 
-				@SuppressWarnings("unchecked")
-				List<String> collections = (List<String>) response.getResponse().get(COLLECTIONS_KEY);
-				return collections != null ? collections : new ArrayList<>();
-			} else {
-				// For standalone Solr - use Core Admin API
-				CoreAdminRequest coreAdminRequest = new CoreAdminRequest();
-				coreAdminRequest.setAction(CoreAdminParams.CoreAdminAction.STATUS);
-				CoreAdminResponse coreResponse = coreAdminRequest.process(solrClient);
-
-				List<String> cores = new ArrayList<>();
-				NamedList<NamedList<Object>> coreStatus = coreResponse.getCoreStatus();
-				for (int i = 0; i < coreStatus.size(); i++) {
-					cores.add(coreStatus.getName(i));
-				}
-				return cores;
-			}
-		} catch (SolrServerException | IOException _) {
+			@SuppressWarnings("unchecked")
+			List<String> collections = (List<String>) response.getResponse().get(COLLECTIONS_KEY);
+			return collections != null ? collections : new ArrayList<>();
+		} catch (SolrServerException | IOException e) {
 			return new ArrayList<>();
 		}
 	}
@@ -952,9 +924,8 @@ String extractCollectionName(String collectionOrShard) {
 	 * </ol>
 	 *
 	 * <p>
-	 * This dual approach ensures compatibility with both standalone Solr (which
-	 * returns collection names directly) and SolrCloud (which may return shard
-	 * names).
+	 * This dual approach ensures compatibility with SolrCloud environments where
+	 * shard names may be returned alongside collection names.
 	 *
 	 * <p>
 	 * <strong>Error Handling:</strong>

src/main/java/org/apache/solr/mcp/server/config/SolrConfig.java

@@ -139,9 +139,8 @@ public class SolrConfig {
 	 *
 	 * <p>
 	 * Creates an {@code HttpSolrClient} configured for standard HTTP-based
-	 * communication with Solr servers. This client type is suitable for both
-	 * standalone Solr instances and SolrCloud deployments when used with load
-	 * balancers.
+	 * communication with SolrCloud servers. This client type is suitable for
+	 * SolrCloud deployments when used with load balancers.
 	 *
 	 * <p>
 	 * <strong>Error Handling:</strong>

src/test/java/org/apache/solr/mcp/server/collection/CollectionServiceTest.java

@@ -30,7 +30,6 @@
 import org.apache.solr.client.solrj.SolrClient;
 import org.apache.solr.client.solrj.SolrRequest;
 import org.apache.solr.client.solrj.SolrServerException;
-import org.apache.solr.client.solrj.impl.CloudSolrClient;
 import org.apache.solr.client.solrj.response.LukeResponse;
 import org.apache.solr.client.solrj.response.QueryResponse;
 import org.apache.solr.client.solrj.response.SolrPingResponse;
@@ -48,9 +47,6 @@ class CollectionServiceTest {
 	@Mock
 	private SolrClient solrClient;
 
-	@Mock
-	private CloudSolrClient cloudSolrClient;
-
 	@Mock
 	private QueryResponse queryResponse;
 
@@ -75,32 +71,17 @@ void constructor_ShouldInitializeWithSolrClient() {
 		assertNotNull(collectionService);
 	}
 
-	@Test
-	void listCollections_WithCloudSolrClient_ShouldReturnCollections() throws Exception {
-		// Given - This test verifies the service can be constructed with
-		// CloudSolrClient
-		CollectionService cloudService = new CollectionService(cloudSolrClient, objectMapper);
-
-		// Note: This test cannot fully exercise listCollections() because it requires
-		// mocking static methods in CollectionAdminRequest which requires PowerMock or
-		// Mockito inline. The actual behavior is tested in integration tests.
-
-		// When/Then - Verify service construction
-		assertNotNull(cloudService, "Should be able to construct service with CloudSolrClient");
-	}
-
 	@Test
 	void listCollections_WhenExceptionOccurs_ShouldReturnEmptyList() throws Exception {
-		// Note: This test cannot fully exercise listCollections() with mock SolrClient
-		// because it requires mocking CoreAdminRequest processing. The actual error
-		// handling behavior is tested in integration tests.
+		// Given - mock throws exception
+		when(solrClient.request(any(), any())).thenThrow(new SolrServerException("Connection error"));
 
-		// Given/When - Using regular SolrClient (non-cloud) which will attempt
-		// CoreAdmin
-		// The mock doesn't have a real CoreAdmin implementation
+		// When
+		List<String> result = collectionService.listCollections();
 
-		// Then - Verify service is constructed
-		assertNotNull(collectionService, "Service should be constructed successfully");
+		// Then
+		assertNotNull(result);
+		assertTrue(result.isEmpty());
 	}
 
 	// Collection name extraction tests
@@ -697,16 +678,13 @@ void isHandlerStatsEmpty() throws Exception {
 
 	// List collections tests
 	@Test
-	void listCollections_CloudClient_Success() throws Exception {
-		CloudSolrClient cloudClient = mock(CloudSolrClient.class);
-
+	void listCollections_Success() throws Exception {
 		NamedList<Object> response = new NamedList<>();
 		response.add("collections", Arrays.asList("collection1", "collection2"));
 
-		when(cloudClient.request(any(), any())).thenReturn(response);
+		when(solrClient.request(any(), any())).thenReturn(response);
 
-		CollectionService service = new CollectionService(cloudClient, objectMapper);
-		List<String> result = service.listCollections();
+		List<String> result = collectionService.listCollections();
 
 		assertNotNull(result);
 		assertEquals(2, result.size());
@@ -715,64 +693,33 @@ void listCollections_CloudClient_Success() throws Exception {
 	}
 
 	@Test
-	void listCollections_CloudClient_NullCollections() throws Exception {
-		CloudSolrClient cloudClient = mock(CloudSolrClient.class);
-
+	void listCollections_NullCollections() throws Exception {
 		NamedList<Object> response = new NamedList<>();
 		response.add("collections", null);
 
-		when(cloudClient.request(any(), any())).thenReturn(response);
+		when(solrClient.request(any(), any())).thenReturn(response);
 
-		CollectionService service = new CollectionService(cloudClient, objectMapper);
-		List<String> result = service.listCollections();
+		List<String> result = collectionService.listCollections();
 
 		assertNotNull(result);
 		assertTrue(result.isEmpty());
 	}
 
 	@Test
-	void listCollections_CloudClient_Error() throws Exception {
-		CloudSolrClient cloudClient = mock(CloudSolrClient.class);
-		when(cloudClient.request(any(), any())).thenThrow(new SolrServerException("Connection error"));
+	void listCollections_Error() throws Exception {
+		when(solrClient.request(any(), any())).thenThrow(new SolrServerException("Connection error"));
 
-		CollectionService service = new CollectionService(cloudClient, objectMapper);
-		List<String> result = service.listCollections();
+		List<String> result = collectionService.listCollections();
 
 		assertNotNull(result);
 		assertTrue(result.isEmpty());
 	}
 
 	@Test
-	void listCollections_NonCloudClient_Success() throws Exception {
-		// Create a NamedList to represent the core status response
-		NamedList<Object> response = new NamedList<>();
-		NamedList<Object> status = new NamedList<>();
-
-		NamedList<Object> core1Status = new NamedList<>();
-		NamedList<Object> core2Status = new NamedList<>();
-
-		status.add("core1", core1Status);
-		status.add("core2", core2Status);
-		response.add("status", status);
-
-		// Mock the solrClient request to return the response
-		when(solrClient.request(any(), any())).thenReturn(response);
-
-		CollectionService service = new CollectionService(solrClient, objectMapper);
-		List<String> result = service.listCollections();
-
-		assertNotNull(result);
-		assertEquals(2, result.size());
-		assertTrue(result.contains("core1"));
-		assertTrue(result.contains("core2"));
-	}
-
-	@Test
-	void listCollections_NonCloudClient_Error() throws Exception {
+	void listCollections_IOError() throws Exception {
 		when(solrClient.request(any(), any())).thenThrow(new IOException("IO error"));
 
-		CollectionService service = new CollectionService(solrClient, objectMapper);
-		List<String> result = service.listCollections();
+		List<String> result = collectionService.listCollections();
 
 		assertNotNull(result);
 		assertTrue(result.isEmpty());
@@ -897,38 +844,22 @@ private NamedList<Object> createCompleteHandlerData() {
 
 	// createCollection tests
 	@Test
-	void createCollection_success_cloudClient() throws Exception {
-		CloudSolrClient cloudClient = mock(CloudSolrClient.class);
-		when(cloudClient.request(any(), any())).thenReturn(new NamedList<>());
-
-		CollectionService service = new CollectionService(cloudClient, objectMapper);
-		CollectionCreationResult result = service.createCollection("new_collection", "_default", 1, 1);
-
-		assertNotNull(result);
-		assertTrue(result.success());
-		assertEquals("new_collection", result.name());
-		assertNotNull(result.createdAt());
-	}
-
-	@Test
-	void createCollection_success_standaloneClient() throws Exception {
+	void createCollection_success() throws Exception {
 		when(solrClient.request(any(), isNull())).thenReturn(new NamedList<>());
 
-		CollectionCreationResult result = collectionService.createCollection("new_core", null, null, null);
+		CollectionCreationResult result = collectionService.createCollection("new_collection", "_default", 1, 1);
 
 		assertNotNull(result);
 		assertTrue(result.success());
-		assertEquals("new_core", result.name());
+		assertEquals("new_collection", result.name());
 		assertNotNull(result.createdAt());
 	}
 
 	@Test
 	void createCollection_defaultsApplied() throws Exception {
-		CloudSolrClient cloudClient = mock(CloudSolrClient.class);
-		when(cloudClient.request(any(), any())).thenReturn(new NamedList<>());
+		when(solrClient.request(any(), isNull())).thenReturn(new NamedList<>());
 
-		CollectionService service = new CollectionService(cloudClient, objectMapper);
-		CollectionCreationResult result = service.createCollection("defaults_collection", null, null, null);
+		CollectionCreationResult result = collectionService.createCollection("defaults_collection", null, null, null);
 
 		assertTrue(result.success());
 		assertEquals("defaults_collection", result.name());