Implementation:Ray project Ray LocalModeTaskSubmitter

Knowledge Sources	Ray
Domains	Distributed_Computing, Java_Runtime
Last Updated	2026-02-13 16:00 GMT

Overview

Full task submission implementation for local mode that simulates Ray cluster task scheduling, actor lifecycle, and concurrency groups entirely within a single JVM process.

Description

LocalModeTaskSubmitter implements the TaskSubmitter interface to provide an in-process simulation of Ray's distributed task scheduling. It builds protobuf TaskSpec messages from function descriptors and arguments, tracks dependency readiness via a waiting-tasks map, and dispatches tasks to thread pools. The class manages per-actor concurrency groups with dedicated ExecutorService instances, supports named actors via a ConcurrentHashMap, and simulates placement groups as in-memory objects.

Usage

Use LocalModeTaskSubmitter when running Ray in local mode for testing and development. It is automatically selected by the runtime when RunMode.LOCAL is configured, allowing developers to test Ray applications without a cluster by faithfully simulating task scheduling, actor concurrency, and dependency resolution in-process.

Code Reference

Source Location

• Repository: Ray
• File: java/runtime/src/main/java/io/ray/runtime/task/LocalModeTaskSubmitter.java

Signature

public class LocalModeTaskSubmitter implements TaskSubmitter {

  private final Map<ObjectId, Set<TaskSpec>> waitingTasks;
  private final Object taskAndObjectLock;
  private final AbstractRayRuntime runtime;
  private final TaskExecutor taskExecutor;
  private final LocalModeObjectStore objectStore;
  private final Map<ActorId, Integer> actorMaxConcurrency;
  private final ExecutorService normalTaskExecutorService;
  private final Map<ActorId, LocalModeActorHandle> actorHandles;
  private final Map<String, ActorHandle> namedActors;
  private final Map<ActorId, TaskExecutor.ActorContext> actorContexts;
  private final Map<PlacementGroupId, PlacementGroup> placementGroups;
  private final ActorConcurrencyGroupManager actorConcurrencyGroupManager;

  public LocalModeTaskSubmitter(
      AbstractRayRuntime runtime,
      TaskExecutor taskExecutor,
      LocalModeObjectStore objectStore) { ... }

  public void onObjectPut(ObjectId id) { ... }
}

Import

import io.ray.runtime.task.LocalModeTaskSubmitter;

I/O Contract

Input

Parameter	Type	Description
runtime	AbstractRayRuntime	The Ray runtime instance providing worker context and function management
taskExecutor	TaskExecutor	Executor responsible for running task logic (function resolution, invocation)
objectStore	LocalModeObjectStore	In-memory object store for local mode object put/get operations

Output

Method	Return Type	Description
onObjectPut	void	Triggers execution of any tasks waiting on the given object ID dependency
submitTask	List<ObjectId>	Submits a normal task and returns output object IDs
createActor	BaseActorHandle	Creates an actor and returns its handle
createPlacementGroup	PlacementGroup	Creates a simulated placement group

Usage Examples

// LocalModeTaskSubmitter is typically instantiated internally by the runtime
LocalModeTaskSubmitter submitter = new LocalModeTaskSubmitter(
    runtime, taskExecutor, objectStore);

// When an object is put into the store, notify the submitter
// so that any tasks waiting on this dependency can proceed
submitter.onObjectPut(objectId);

Related Pages

• Environment:Ray_project_Ray_Java_Build_Environment