Programming Model

About 308 wordsAbout 1 min

A RayOrch workload has two user-owned pieces:

batched Python UDFs + one declarative Pipeline

UDFs are ordinary batch functions

A UDF is a class with run() or any callable. Each argument is a column containing one value per scheduled Grain. Every output column must have the same row count.

class Normalize:
    def __init__(self, prefix=""):
        self.prefix = prefix

    def run(self, texts):
        return [self.prefix + text.strip().lower() for text in texts]

Keep heavyweight imports and model construction inside the UDF module or class. RayOrch constructs one UDF instance per persistent actor.

`RayModule` describes a stage

self.normalize = (
    ro.RayModule(Normalize)
    .pre_init(prefix="normalized: ")
    .ray_options(replicas=4, batch_size=32, num_cpus=1)
)

pre_init() records constructor arguments.
ray_options() records replicas, RayOrch batch_size, recovery, and normal Ray actor options.
.returns(n) or num_outputs=n declares multiple output columns.

Each use of a RayModule inside forward() becomes a distinct logical Call with its own actor pool.

`Pipeline.forward()` declares, rather than executes

During compilation, forward() receives symbolic Port objects. It may compose Calls and structural operations, but it cannot branch on runtime data. Use F.filter() for item-level filtering, or put an item-level condition inside a UDF. Normal configuration booleans may still choose a static graph branch in forward().

Recommended workload layout

A private experiment does not need the Benchmark framework:

my_workload/
  udfs.py       # business/model code
  pipeline.py   # graph and resources
  run.py        # load inputs and call rayorch.run/Executor

Start with these three files. Add configuration machinery only when the experiment becomes reusable.

Continue from here

Need a variable number of children? Read Cardinality and Lineage.
Need to understand dropped, failed, and suppressed outputs? Read Results, Failures, and Recovery.
Need to tune actors and batches? Read Resources and Batching.
Need to run across machines or environments? Read Distributed Execution and Cross-environment Stages.