Refactoring Targets

Prioritize improvements to these files since they have the highest technical debt interest rate.


elasticsearch/server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
elasticsearch/server/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
elasticsearch/test/framework/src/main/java/org/elasticsearch/test/ESIntegTestCase.java
elasticsearch/server/src/test/java/org/elasticsearch/index/engine/InternalEngineTests.java
elasticsearch/server/src/main/java/org/elasticsearch/search/SearchService.java
elasticsearch/test/framework/src/main/java/org/elasticsearch/test/InternalTestCluster.java
elasticsearch/server/src/main/java/org/elasticsearch/index/mapper/MapperService.java
elasticsearch/server/src/main/java/org/elasticsearch/node/Node.java
elasticsearch/server/src/main/java/org/elasticsearch/index/engine/Engine.java
elasticsearch/server/src/main/java/org/elasticsearch/action/support/replication/TransportReplicationAction.java
elasticsearch/server/src/main/java/org/elasticsearch/index/IndexService.java
elasticsearch/test/framework/src/main/java/org/elasticsearch/test/AbstractQueryTestCase.java
elasticsearch/server/src/main/java/org/elasticsearch/indices/cluster/IndicesClusterStateService.java
elasticsearch/test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java
elasticsearch/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/Security.java
elasticsearch/server/src/main/java/org/elasticsearch/search/builder/SearchSourceBuilder.java
elasticsearch/server/src/main/java/org/elasticsearch/cluster/metadata/MetaDataCreateIndexService.java