apache / apache/beam

Merge, Split, Delay, and Reorder bundles in the DirectRunner

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direct improvement P3 runners
Dominant language
Java
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Description

PCollections have no guarantees about the ordering of elements between steps

Randomly reordering, splitting and merging bundles will break user pipelines which assume some order will be maintained between steps and within a bundle. This assumption is not correct, so should break in the Direct Runner.

Imported from Jira [BEAM-344](https://issues.apache.org/jira/browse/BEAM-344). Original Jira may contain additional context.
Reported by: tgroh.

Contributor guide

Open the contributing guide

Research direction

Start by reading the DirectRunner's bundle-processing paths and the linked BEAM-344 context; the issue does not name specific files or tests. Determine where bundles are merged, split, delayed, and ordered, then verify that pipelines relying on accidental ordering no longer pass under the DirectRunner.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
distributed-systems
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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