Deprecation check renamed bulk threadpool settings (#36662)

Adds a deprecation check for renamed settings related to bulk threadpool
which has been renamed to write threadpool.

Author: gwbrown

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationChecks.java

@@ -41,6 +41,7 @@ private DeprecationChecks() {
             NodeDeprecationChecks::httpEnabledSettingRemoved,
             NodeDeprecationChecks::auditLogPrefixSettingsCheck,
             NodeDeprecationChecks::indexThreadPoolCheck,
+            NodeDeprecationChecks::bulkThreadPoolCheck,
             NodeDeprecationChecks::tribeNodeCheck,
             NodeDeprecationChecks::httpPipeliningCheck,
             NodeDeprecationChecks::discoveryConfigurationCheck,

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecks.java

@@ -68,6 +68,20 @@ static DeprecationIssue indexThreadPoolCheck(List<NodeInfo> nodeInfos, List<Node
         }
         return null;
     }
+    static DeprecationIssue bulkThreadPoolCheck(List<NodeInfo> nodeInfos, List<NodeStats> nodeStats) {
+        List<String> nodesFound = nodeInfos.stream()
+            .filter(nodeInfo -> nodeInfo.getSettings().getByPrefix("thread_pool.bulk.").isEmpty() == false)
+            .map(nodeInfo -> nodeInfo.getNode().getName())
+            .collect(Collectors.toList());
+        if (nodesFound.size() > 0) {
+            return new DeprecationIssue(DeprecationIssue.Level.CRITICAL,
+                "Bulk thread pool renamed to write thread pool",
+                "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_70_cluster_changes.html" +
+                    "#write-thread-pool-fallback",
+                "nodes with bulk thread pool settings: " + nodesFound);
+        }
+        return null;
+    }
 
     static DeprecationIssue tribeNodeCheck(List<NodeInfo> nodeInfos, List<NodeStats> nodeStats) {
         List<String> nodesFound = nodeInfos.stream()

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/NodeDeprecationChecksTests.java

@@ -94,6 +94,16 @@ public void testIndexThreadPoolCheck() {
         assertSettingsAndIssue("thread_pool.index.queue_size", Integer.toString(randomIntBetween(1, 20000)), expected);
     }
 
+    public void testBulkThreadPoolCheck() {
+        DeprecationIssue expected = new DeprecationIssue(DeprecationIssue.Level.CRITICAL,
+            "Bulk thread pool renamed to write thread pool",
+            "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_70_cluster_changes.html" +
+                "#write-thread-pool-fallback",
+            "nodes with bulk thread pool settings: [node_check]");
+        assertSettingsAndIssue("thread_pool.bulk.size", Integer.toString(randomIntBetween(1, 20000)), expected);
+        assertSettingsAndIssue("thread_pool.bulk.queue_size", Integer.toString(randomIntBetween(1, 20000)), expected);
+    }
+
     public void testTribeNodeCheck() {
         String tribeSetting = "tribe." + randomAlphaOfLengthBetween(1, 20) + ".cluster.name";
         DeprecationIssue expected = new DeprecationIssue(DeprecationIssue.Level.CRITICAL,