Implementation:Ray project Ray Serve DAGNode

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

Overview

DAGNode is the abstract base class for all nodes in a Ray Serve deployment graph, providing bound arguments, options, a stable UUID, and recursive tree traversal logic.

Description

DAGNode implements the DAGNodeBase interface and provides the core infrastructure for building directed acyclic graphs of deployments. It stores bound arguments, bound options, and additional arguments to resolve, each assigned at construction time. The class implements recursive traversal via applyRecursive(), which uses an internal CachingFn to avoid duplicate processing of shared nodes in the graph. The copy() method preserves the stable UUID across node copies to maintain identity consistency.

Usage

Use DAGNode as the base class when implementing custom node types in the deployment graph composition system. Concrete subclasses (such as ClassNode or InputNode) extend this class to represent specific computation units in multi-deployment pipelines.

Code Reference

Source Location

• Repository: Ray
• File: java/serve/src/main/java/io/ray/serve/dag/DAGNode.java

Signature

public abstract class DAGNode implements DAGNodeBase {

    public DAGNode(
        Object[] args,
        Map<String, Object> options,
        Map<String, Object> otherArgsToResolve)

    public <T> T applyRecursive(Function<DAGNodeBase, T> fn)

    public <T> DAGNodeBase applyAndReplaceAllChildNodes(Function<DAGNodeBase, T> fn)

    public DAGNodeBase copy(
        Object[] newArgs,
        Map<String, Object> newOptions,
        Map<String, Object> newOtherArgsToResolve)
}

Import

import io.ray.serve.dag.DAGNode;

I/O Contract

Constructor Parameters

Parameter	Type	Description
args	Object[]	Bound arguments for the node (defaults to empty array if null)
options	Map<String, Object>	Bound options for the node (defaults to empty map if null)
otherArgsToResolve	Map<String, Object>	Additional arguments resolved at graph build time (defaults to empty map if null)

Key Methods

Method	Return Type	Description
applyRecursive(fn)	T	Recursively applies a function to the entire DAG, using caching to avoid reprocessing shared nodes
applyAndReplaceAllChildNodes(fn)	DAGNodeBase	Applies a function to all child DAGNodeBase arguments and returns a copy with replaced children
copy(newArgs, newOptions, newOtherArgsToResolve)	DAGNodeBase	Creates a copy of the node with new arguments while preserving the stable UUID
getBoundArgs()	Object[]	Returns the bound arguments
getBoundOptions()	Map<String, Object>	Returns the bound options
getBoundOtherArgsToResolve()	Map<String, Object>	Returns additional arguments to resolve
getStableUuid()	String	Returns the stable UUID identifying this node across copies

Abstract Methods (to implement in subclasses)

Method	Return Type	Description
copyImpl(newArgs, newOptions, newOtherArgsToResolve)	DAGNodeBase	Subclass-specific copy logic that creates a new instance with the given parameters

Usage Examples

// DAGNode is abstract; usage is via concrete subclasses.
// Example of recursive traversal over a deployment graph:
DAGNode rootNode = buildDeploymentGraph();

// Apply a transformation to every node in the graph
Object result = rootNode.applyRecursive(node -> {
    // Process each node (shared nodes are visited only once due to caching)
    System.out.println("Visiting node: " + node.getStableUuid());
    return processNode(node);
});

Related Pages

• Environment:Ray_project_Ray_Java_Build_Environment