Deprecate fixed_auto_queue_size thread pool type (#52399)

Relates #52280

Author: ywelsch

docs/reference/modules/threadpool.asciidoc

@@ -20,8 +20,8 @@ There are several thread pools, but the important ones include:
     `1000`.
 
 [[search-throttled]]`search_throttled`::
-    For count/search/suggest/get operations on `search_throttled indices`. 
-    Thread pool type is `fixed_auto_queue_size` with a size of `1`, and initial 
+    For count/search/suggest/get operations on `search_throttled indices`.
+    Thread pool type is `fixed_auto_queue_size` with a size of `1`, and initial
     queue_size of `100`.
 
 `get`::
@@ -30,7 +30,7 @@ There are several thread pools, but the important ones include:
     queue_size of `1000`.
 
 `analyze`::
-    For analyze requests. Thread pool type is `fixed` with a size of `1`, queue 
+    For analyze requests. Thread pool type is `fixed` with a size of `1`, queue
     size of `16`.
 
 `write`::
@@ -51,8 +51,8 @@ There are several thread pools, but the important ones include:
     keep-alive of `5m` and a max of `min(10, (# of available processors)/2)`.
 
 `listener`::
-    Mainly for java client executing of action when listener threaded is set to 
-    `true`. Thread pool type is `scaling` with a default max of 
+    Mainly for java client executing of action when listener threaded is set to
+    `true`. Thread pool type is `scaling` with a default max of
     `min(10, (# of available processors)/2)`.
 
 `fetch_shard_started`::
@@ -125,6 +125,9 @@ thread_pool:
 
 experimental[]
 
+deprecated[7.7.0,The experimental `fixed_auto_queue_size` thread pool type is
+deprecated and will be removed in 8.0.]
+
 The `fixed_auto_queue_size` thread pool holds a fixed size of threads to handle
 the requests with a bounded queue for pending requests that have no threads to
 service them. It's similar to the `fixed` threadpool, however, the `queue_size`
@@ -202,13 +205,13 @@ processors: 2
 There are a few use-cases for explicitly overriding the `processors`
 setting:
 
-. If you are running multiple instances of {es} on the same host but want {es} 
-to size its thread pools as if it only has a fraction of the CPU, you should 
-override the `processors` setting to the desired fraction, for example, if 
+. If you are running multiple instances of {es} on the same host but want {es}
+to size its thread pools as if it only has a fraction of the CPU, you should
+override the `processors` setting to the desired fraction, for example, if
 you're running two instances of {es} on a 16-core machine, set `processors` to 8.
-Note that this is an expert-level use case and there's a lot more involved 
-than just setting the `processors` setting as there are other considerations 
-like changing the number of garbage collector threads, pinning processes to 
+Note that this is an expert-level use case and there's a lot more involved
+than just setting the `processors` setting as there are other considerations
+like changing the number of garbage collector threads, pinning processes to
 cores, and so on.
 . Sometimes the number of processors is wrongly detected and in such
 cases explicitly setting the `processors` setting will workaround such

server/src/main/java/org/elasticsearch/threadpool/AutoQueueAdjustingExecutorBuilder.java

@@ -67,11 +67,13 @@ public final class AutoQueueAdjustingExecutorBuilder extends ExecutorBuilder<Aut
         final String frameSizeKey = settingsKey(prefix, "auto_queue_frame_size");
         final String targetedResponseTimeKey = settingsKey(prefix, "target_response_time");
         this.targetedResponseTimeSetting = Setting.timeSetting(targetedResponseTimeKey, TimeValue.timeValueSeconds(1),
-                TimeValue.timeValueMillis(10), Setting.Property.NodeScope);
+                TimeValue.timeValueMillis(10), Setting.Property.NodeScope, Setting.Property.Deprecated);
         this.queueSizeSetting = Setting.intSetting(queueSizeKey, initialQueueSize, Setting.Property.NodeScope);
         // These temp settings are used to validate the min and max settings below
-        Setting<Integer> tempMaxQueueSizeSetting = Setting.intSetting(maxSizeKey, maxQueueSize, Setting.Property.NodeScope);
-        Setting<Integer> tempMinQueueSizeSetting = Setting.intSetting(minSizeKey, minQueueSize, Setting.Property.NodeScope);
+        Setting<Integer> tempMaxQueueSizeSetting = Setting.intSetting(maxSizeKey, maxQueueSize, Setting.Property.NodeScope,
+            Setting.Property.Deprecated);
+        Setting<Integer> tempMinQueueSizeSetting = Setting.intSetting(minSizeKey, minQueueSize, Setting.Property.NodeScope,
+            Setting.Property.Deprecated);
 
         this.minQueueSizeSetting = new Setting<>(
             minSizeKey,
@@ -126,8 +128,9 @@ public Iterator<Setting<?>> settings() {
                     }
 
                 },
-                Setting.Property.NodeScope);
-        this.frameSizeSetting = Setting.intSetting(frameSizeKey, frameSize, 100, Setting.Property.NodeScope);
+                Setting.Property.NodeScope, Setting.Property.Deprecated);
+        this.frameSizeSetting = Setting.intSetting(frameSizeKey, frameSize, 100, Setting.Property.NodeScope, Setting.Property.Deprecated,
+            Setting.Property.Deprecated);
     }
 
     @Override

server/src/test/java/org/elasticsearch/threadpool/AutoQueueAdjustingExecutorBuilderTests.java

@@ -78,6 +78,8 @@ public void testValidatingMinMaxSettings() {
         } catch (IllegalArgumentException e) {
             assertEquals(e.getMessage(), "Failed to parse value [100] for setting [thread_pool.test.min_queue_size] must be <= 99");
         }
+
+        assertSettingDeprecationsAndWarnings(new String[]{"thread_pool.test.max_queue_size"});
     }
 
     public void testSetLowerSettings() {
@@ -89,6 +91,8 @@ public void testSetLowerSettings() {
         AutoQueueAdjustingExecutorBuilder.AutoExecutorSettings s = test.getSettings(settings);
         assertEquals(10, s.maxQueueSize);
         assertEquals(10, s.minQueueSize);
+
+        assertSettingDeprecationsAndWarnings(new String[]{"thread_pool.test.min_queue_size", "thread_pool.test.max_queue_size"});
     }
 
     public void testSetHigherSettings() {
@@ -100,6 +104,8 @@ public void testSetHigherSettings() {
         AutoQueueAdjustingExecutorBuilder.AutoExecutorSettings s = test.getSettings(settings);
         assertEquals(3000, s.maxQueueSize);
         assertEquals(2000, s.minQueueSize);
+
+        assertSettingDeprecationsAndWarnings(new String[]{"thread_pool.test.min_queue_size", "thread_pool.test.max_queue_size"});
     }
 
 }