Migrate NodeHealthAPI to JAX-RS, flip delegation so V2 owns logic, add replication lag monitoring docs

changelog/unreleased/SOLR-16458-migrate-node-health-api.yml

@@ -0,0 +1,8 @@
+title: "SolrJ now offers a SolrRequest class allowing users to perform v2 single-node healthchecks: NodeApi.Healthcheck"
+type: added
+authors:
+  - name: Eric Pugh
+  - name: Jason Gerlowski
+links:
+  - name: SOLR-16458
+    url: https://issues.apache.org/jira/browse/SOLR-16458

changelog/unreleased/SOLR-17973-fix-shards-preference-cross-collection-join.yml

@@ -0,0 +1,7 @@
+title: "SOLR-17973: Fix `shards.preference` not respected for cross-collection join queries"
+type: fixed
+authors:
+  - name: khushjain
+links:
+  - name: SOLR-17973
+    url: https://issues.apache.org/jira/browse/SOLR-17973

changelog/unreleased/SOLR-18155-election-leak.yml

@@ -0,0 +1,7 @@
+title: Abort shard leader election if container shutdown sequence has started, so we don't have leaders elected very late and not properly closed.
+type: fixed
+authors:
+  - name: Pierre Salagnac
+links:
+  - name: SOLR-18155
+    url: https://issues.apache.org/jira/browse/SOLR-18155

changelog/unreleased/SOLR-18159-physical-memory-metrics.yml

@@ -0,0 +1,9 @@
+title: Add new metric jvm_system_memory_bytes
+type: added
+authors:
+  - name: Jan Høydahl
+    url: https://home.apache.org/phonebook.html?uid=janhoy
+  - name: Matthew Biscocho
+links:
+  - name: SOLR-18159
+    url: https://issues.apache.org/jira/browse/SOLR-18159

solr/api/src/java/org/apache/solr/client/api/endpoint/NodeHealthApi.java

@@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.solr.client.api.endpoint;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.Parameter;
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.QueryParam;
+import org.apache.solr.client.api.model.NodeHealthResponse;
+
+/** V2 API definition for checking the health of a Solr node. */
+@Path("/node/health")
+public interface NodeHealthApi {
+
+  @GET
+  @Operation(
+      summary = "Determine the health of a Solr node.",
+      tags = {"node"})
+  NodeHealthResponse healthcheck(
+      @QueryParam("requireHealthyCores") Boolean requireHealthyCores,
+      @Parameter(
+              description =
+                  "Maximum number of index generations a follower replica may lag behind its"
+                      + " leader before the health check reports FAILURE. Only relevant when"
+                      + " running in Standalone mode with leader/follower replication.")
+          @QueryParam("maxGenerationLag")
+          Integer maxGenerationLag);
+}

solr/api/src/java/org/apache/solr/client/api/model/NodeHealthResponse.java

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.solr.client.api.model;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+/** Response body for the '/api/node/health' endpoint. */
+public class NodeHealthResponse extends SolrJerseyResponse {
+
+  /** The possible health statuses for a Solr node. */
+  public enum NodeStatus {
+    OK,
+    FAILURE
+  }
+
+  @JsonProperty public NodeStatus status;
+
+  @JsonProperty public String message;
+
+  @JsonProperty("num_cores_unhealthy")
+  public Integer numCoresUnhealthy;
+}