Remove cache concurrency level settings that no longer apply

core/src/main/java/org/elasticsearch/indices/cache/request/IndicesRequestCache.java

@@ -79,7 +79,6 @@ public class IndicesRequestCache extends AbstractComponent implements RemovalLis
     @Deprecated
     public static final String DEPRECATED_INDICES_CACHE_QUERY_SIZE = "indices.cache.query.size";
     public static final String INDICES_CACHE_QUERY_EXPIRE = "indices.requests.cache.expire";
-    public static final String INDICES_CACHE_QUERY_CONCURRENCY_LEVEL = "indices.requests.cache.concurrency_level";
 
     private static final Set<SearchType> CACHEABLE_SEARCH_TYPES = EnumSet.of(SearchType.QUERY_THEN_FETCH, SearchType.QUERY_AND_FETCH);
 
@@ -96,7 +95,6 @@ public class IndicesRequestCache extends AbstractComponent implements RemovalLis
     //TODO make these changes configurable on the cluster level
     private final String size;
     private final TimeValue expire;
-    private final int concurrencyLevel;
 
     private volatile Cache<Key, Value> cache;
 
@@ -122,11 +120,6 @@ public IndicesRequestCache(Settings settings, ClusterService clusterService, Thr
         this.size = size;
 
         this.expire = settings.getAsTime(INDICES_CACHE_QUERY_EXPIRE, null);
-        // defaults to 4, but this is a busy map for all indices, increase it a bit by default
-        this.concurrencyLevel =  settings.getAsInt(INDICES_CACHE_QUERY_CONCURRENCY_LEVEL, 16);
-        if (concurrencyLevel <= 0) {
-            throw new IllegalArgumentException("concurrency_level must be > 0 but was: " + concurrencyLevel);
-        }
         buildCache();
 
         this.reaper = new Reaper();

core/src/main/java/org/elasticsearch/indices/fielddata/cache/IndicesFieldDataCache.java

@@ -55,7 +55,6 @@
 public class IndicesFieldDataCache extends AbstractComponent implements RemovalListener<IndicesFieldDataCache.Key, Accountable> {
 
     public static final String FIELDDATA_CLEAN_INTERVAL_SETTING = "indices.fielddata.cache.cleanup_interval";
-    public static final String FIELDDATA_CACHE_CONCURRENCY_LEVEL = "indices.fielddata.cache.concurrency_level";
     public static final String INDICES_FIELDDATA_CACHE_SIZE_KEY = "indices.fielddata.cache.size";
 
 

core/src/test/java/org/elasticsearch/test/InternalTestCluster.java

@@ -478,10 +478,6 @@ private Settings getRandomNodeSettings(long seed) {
             builder.put(RecoverySettings.INDICES_RECOVERY_COMPRESS, random.nextBoolean());
         }
 
-        if (random.nextBoolean()) {
-            builder.put(IndicesRequestCache.INDICES_CACHE_QUERY_CONCURRENCY_LEVEL, RandomInts.randomIntBetween(random, 1, 32));
-            builder.put(IndicesFieldDataCache.FIELDDATA_CACHE_CONCURRENCY_LEVEL, RandomInts.randomIntBetween(random, 1, 32));
-        }
         if (random.nextBoolean()) {
             builder.put(NettyTransport.PING_SCHEDULE, RandomInts.randomIntBetween(random, 100, 2000) + "ms");
         }

docs/reference/migration/migrate_3_0.asciidoc

@@ -312,3 +312,9 @@ For simplicity, only one way of adding the ids to the existing list (empty by de
 `DocumentAlreadyExistsException` is removed and a `VersionConflictException` is thrown instead (with a better
 error description). This will influence code that use the `IndexRequest.opType()` or `IndexRequest.create()`
 to index a document only if it doesn't already exist.
+
+=== Cache concurrency level settings removed
+
+Two cache concurrency level settings `indices.requests.cache.concurrency_level` and
+`indices.fielddata.cache.concurrency_level` because they no longer apply to the cache implementation used for the
+request cache and the field data cache.