[rush] Support percentage-based weights for operationSettings in rush-project.json by LPegasus · Pull Request #5679 · microsoft/rushstack

LPegasus · 2026-03-03T12:28:17Z

Summary

Add issue #5607 proposal 1 feature.

Details

WeightedOperationPlugin: Added a function to convert weight settings in RushProjectConfiguration.operationSettings percentage string to integer based on os.availableParallelism().
WeightedOperationPlugin.test.ts: Added some tests.
RushProjectConfiguration.ts: Updated IOperationSettings.weight type definition.
rush-project.schema.json: Updated weight field json schema.
If the calculated result of the specified percentage has decimals, use Math.floor to round down to an integer. Maximize CPU utilization as much as possible.

How it was tested

Add unit test cases.
Tested in my test rush repo.

Impacted documentation

None

…sh-project.json

octogonz · 2026-03-10T02:54:28Z

+    const percentValue: number = parseFloat(weight.slice(0, -1));
+
+    // Use as much CPU as possible, so we round down the weight here
+    return Math.floor((percentValue / 100) * availableParallelism);


@dmichon-msft Is it okay if this rounds down to 0?

I'd be tempted to suggest that if it rounds down to 0, you use the raw value just so it doesn't produce infinite parallelism, but passing floats to the concurrency engine isn't terribly advisable (you can accumulate error from adding and subtracting them). Probably restrict values to [1,Infinity) from percentage weights.

If we want to support fractional units we should redefine 1 concurrency unit as some power-of-two fraction of a CPU core (maybe 1/4?) and then propagate that all the way through the system.

I changed it to:

return Math.max(1, Math.floor((percentValue / 100) * availableParallelism));

1. libraries/rush-lib/src/logic/operations/WeightedOperationPlugin.ts - Added more comments to explain the percentage weight convert function. - Use `as` syntax to cast error to Error type for better readability. 2. libraries/rush-lib/src/schemas/rush-project.schema.json - Updated the description of the weight property to reflect that the maximum concurrency units is determined by `os.availableParallelism()`. 3. libraries/rush-lib/src/logic/operations/test/WeightedOperationPlugin.test.ts - Fix a test name.

dmichon-msft · 2026-03-10T17:45:20Z

  context: ICreateOperationsContext
 ): Map<Operation, IOperationExecutionResult> {
  const { projectConfigurations } = context;
+  const availableParallelism: number = os.availableParallelism();


I'd consider it cleaner, especially for mocking, to pass this value to the plugin constructor.

dmichon-msft · 2026-03-10T17:47:21Z

+      throw new Error(`Expected a percentage string like "100%".`);
+    }
+
+    const percentValue: number = parseFloat(weight.slice(0, -1));


parseFloat doesn't mind the trailing %. Parsing stops as soon as it hits a character that isn't part of the float.

I think the current code might be better; it is still correct and doesn't require the reader to have intimate knowledge of quirky API designs that were acceptable when JavaScript was first invented. :)

dmichon-msft · 2026-03-10T17:50:02Z

+    const percentValue: number = parseFloat(weight.slice(0, -1));
+
+    // Use as much CPU as possible, so we round down the weight here
+    return Math.floor((percentValue / 100) * availableParallelism);


I'd be tempted to suggest that if it rounds down to 0, you use the raw value just so it doesn't produce infinite parallelism, but passing floats to the concurrency engine isn't terribly advisable (you can accumulate error from adding and subtracting them). Probably restrict values to [1,Infinity) from percentage weights.

If we want to support fractional units we should redefine 1 concurrency unit as some power-of-two fraction of a CPU core (maybe 1/4?) and then propagate that all the way through the system.

dmichon-msft · 2026-03-10T17:52:04Z

      const projectConfiguration: RushProjectConfiguration | undefined = projectConfigurations.get(project);
      const operationSettings: IOperationSettings | undefined =
        operation.settings ?? projectConfiguration?.operationSettingsByOperationName.get(phase.name);


I find myself wondering why this layer is here; operation.settings should always already be defined if projectConfigurations.get(project)?.operationSettingsByOperationName.get(phase.name) returns a truthy value.

Seems out of scope

Co-authored-by: David Michon <dmichon@microsoft.com>

…-project.json (microsoft#5679) * feature: Support percentage-based weights for operationSettings in rush-project.json * Resolve CodeReview comments for: 1. libraries/rush-lib/src/logic/operations/WeightedOperationPlugin.ts - Added more comments to explain the percentage weight convert function. - Use `as` syntax to cast error to Error type for better readability. 2. libraries/rush-lib/src/schemas/rush-project.schema.json - Updated the description of the weight property to reflect that the maximum concurrency units is determined by `os.availableParallelism()`. 3. libraries/rush-lib/src/logic/operations/test/WeightedOperationPlugin.test.ts - Fix a test name. * Update libraries/rush-lib/src/schemas/rush-project.schema.json Co-authored-by: David Michon <dmichon@microsoft.com> * Update libraries/rush-lib/src/schemas/rush-project.schema.json Co-authored-by: David Michon <dmichon@microsoft.com> * PR feedback * PR feedback * Prepare to publish a MINOR release of Rush --------- Co-authored-by: LPegasus <lpegasus@users.noreply.github.com> Co-authored-by: David Michon <dmichon@microsoft.com> Co-authored-by: Pete Gonzalez <4673363+octogonz@users.noreply.github.com>

feature: Support percentage-based weights for operationSettings in ru…

02dea2d

…sh-project.json

LPegasus requested review from apostolisms, bmiddha, dmichon-msft, iclanton, jxanthony and octogonz as code owners March 3, 2026 12:28

github-project-automation Bot added this to Bug Triage Mar 3, 2026

github-project-automation Bot moved this to Needs triage in Bug Triage Mar 3, 2026

octogonz reviewed Mar 10, 2026

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Comment thread libraries/rush-lib/src/logic/operations/test/WeightedOperationPlugin.test.ts Outdated

octogonz reviewed Mar 10, 2026

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Comment thread libraries/rush-lib/src/schemas/rush-project.schema.json Outdated

octogonz reviewed Mar 10, 2026

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Comment thread libraries/rush-lib/src/logic/operations/WeightedOperationPlugin.ts Outdated

octogonz reviewed Mar 10, 2026

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Comment thread libraries/rush-lib/src/logic/operations/WeightedOperationPlugin.ts Outdated

LPegasus force-pushed the rush-pr-issue-5607 branch from dd7ca9a to 53b44c6 Compare March 10, 2026 09:33

LPegasus force-pushed the rush-pr-issue-5607 branch from 53b44c6 to 50b9ee3 Compare March 10, 2026 09:58

dmichon-msft reviewed Mar 10, 2026

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LPegasus and others added 4 commits March 12, 2026 10:35

Update libraries/rush-lib/src/schemas/rush-project.schema.json

2fdb23d

Co-authored-by: David Michon <dmichon@microsoft.com>

Update libraries/rush-lib/src/schemas/rush-project.schema.json

ab905d9

Co-authored-by: David Michon <dmichon@microsoft.com>

PR feedback

afb6812

PR feedback

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octogonz approved these changes Mar 12, 2026

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Prepare to publish a MINOR release of Rush

d05a579

octogonz merged commit fb0341f into microsoft:main Mar 12, 2026
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github-project-automation Bot moved this from Needs triage to Closed in Bug Triage Mar 12, 2026

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LPegasus commented Mar 3, 2026

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