[Refactor] Recyclers to Common Library (#9028) (#9064)

This commit refactors the common recylers logic from the server module
to the core library to make the base functionality available to concrete
implementations across the codebase. This is done to support cloud
native or serverless implementations. Until JPM is enabled, the classes
remain marked for internal use only. Determining which classes will be
exported will dictate if/when these doc labels are switched to API.


(cherry picked from commit 22893b1)

Signed-off-by: Nicholas Walter Knize <[email protected]>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

server/src/main/java/org/opensearch/common/recycler/Recyclers.java → libs/common/src/main/java/org/opensearch/common/recycler/Recyclers.java

@@ -75,6 +75,8 @@ public static <T> Recycler.Factory<T> dequeFactory(final Recycler.C<T> c, final
     /**
      * Wrap the provided recycler so that calls to {@link Recycler#obtain()} and {@link Recycler.V#close()} are protected by
      * a lock.
+     *
+     * @opensearch.internal
      */
     public static <T> Recycler<T> locked(final Recycler<T> recycler) {
         return new FilterRecycler<T>() {
@@ -140,7 +142,7 @@ public static <T> Recycler<T> concurrent(final Recycler.Factory<T> factory, fina
             private final Recycler<T>[] recyclers;
 
             {
-                @SuppressWarnings("unchecked")
+                @SuppressWarnings({ "rawtypes", "unchecked" })
                 final Recycler<T>[] recyclers = new Recycler[concurrencyLevel];
                 this.recyclers = recyclers;
                 for (int i = 0; i < concurrencyLevel; ++i) {

libs/common/src/main/java/org/opensearch/common/recycler/package-info.java

@@ -0,0 +1,10 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+/** Common Recycler functionality for recycling objects */
+package org.opensearch.common.recycler;