Package org.opensearch.index

Class ShardIndexingPressureTracker

java.lang.Object
org.opensearch.index.ShardIndexingPressureTracker
public class ShardIndexingPressureTracker
extends java.lang.Object
This class is responsible for all the tracking that needs to be performed at every Shard Level for Indexing Operations on the node. Info is maintained at the granularity of three kinds of write operation (tasks) on the node i.e. coordinating, primary and replica. This is useful in evaluating the shard indexing back-pressure on the node, to throttle requests and also to publish runtime stats. There can be four kinds of operation tracking on a node which needs to performed for a shard: 1. Coordinating Operation : To track all the individual shard bulk request on the coordinator node. 2. Primary Operation : To track all the individual shard bulk request on the primary node. 3. Replica Operation : To track all the individual shard bulk request on the replica node. 4. Common Operation : To track values applicable across the specific shard role. ShardIndexingPressureTracker therefore provides the construct to track all the write requests targeted for a ShardId on the node, across all possible transport-write-actions i.e. Coordinator, Primary and Replica. Tracker is uniquely identified against a Shard-Id on the node. Currently the knowledge of shard roles (such as primary vs replica) is not explicit to the tracker, and it is able to track different values simultaneously based on the interaction hooks of the operation type i.e. write-action layers. There is room for introducing more unique identity to the trackers based on Shard-Role or Shard-Allocation-Id, but that will also increase the complexity of handling shard-lister events and handling other race scenarios such as request-draining etc. To prefer simplicity we have modelled by keeping explicit fields for different operation tracking, while tracker by itself is agnostic of the actual shard role.