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Testing: Run all test SPM executable actions in a operation queue #9243

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5da76a3
[WIP] Experiment with adding a operation queue
kcieplak Oct 10, 2025
e99a75c
Updates based on PR review
kcieplak Oct 14, 2025
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51 changes: 31 additions & 20 deletions Sources/_InternalTestSupport/SwiftPMProduct.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,9 @@ import struct Basics.AsyncProcessResult

import enum TSCBasic.ProcessEnv

// Fan out from invocation of SPM 'swift-*' commands can be quite large. Limit the number of concurrent tasks to a fraction of total CPUs.
private let swiftPMExecutionQueue = AsyncOperationQueue(concurrentTasks: Int(Double(ProcessInfo.processInfo.activeProcessorCount) * 0.5))

/// Defines the executables used by SwiftPM.
/// Contains path to the currently built executable and
/// helper method to execute them.
Expand Down Expand Up @@ -82,28 +85,36 @@ extension SwiftPM {
env: Environment? = nil,
throwIfCommandFails: Bool = true
) async throws -> (stdout: String, stderr: String) {
let result = try await executeProcess(
args,
packagePath: packagePath,
env: env
)
//Remove /r from stdout/stderr so that tests do not have to deal with them
let stdout = try String(decoding: result.output.get().filter( { $0 != 13 }), as: Unicode.UTF8.self)
let stderr = try String(decoding: result.stderrOutput.get().filter( { $0 != 13 }), as: Unicode.UTF8.self)

let returnValue = (stdout: stdout, stderr: stderr)
if (!throwIfCommandFails) { return returnValue }

if result.exitStatus == .terminated(code: 0) {
return returnValue
// Swift Testing uses Swift concurrency for test execution and creates a task for each test to run in parallel.
// A single invocation of "swift build" can spawn a large number of subprocesses.
// When this pattern is repeated across many tests, thousands of processes compete for
// CPU/disk/network resources. Tests can take thousands of seconds to complete, with periods
// of no stdout/stderr output that can cause activity timeouts in CI pipelines.
// Run all SPM executions under a queue to limit the maximum number of concurrent SPM processes.
try await swiftPMExecutionQueue.withOperation {
let result = try await executeProcess(
args,
packagePath: packagePath,
env: env
)
// Remove /r from stdout/stderr so that tests do not have to deal with them
let stdout = try String(decoding: result.output.get().filter { $0 != 13 }, as: Unicode.UTF8.self)
let stderr = try String(decoding: result.stderrOutput.get().filter { $0 != 13 }, as: Unicode.UTF8.self)

let returnValue = (stdout: stdout, stderr: stderr)
if !throwIfCommandFails { return returnValue }

if result.exitStatus == .terminated(code: 0) {
return returnValue
}
throw SwiftPMError.executionFailure(
underlying: AsyncProcessResult.Error.nonZeroExit(result),
stdout: stdout,
stderr: stderr
)
}
throw SwiftPMError.executionFailure(
underlying: AsyncProcessResult.Error.nonZeroExit(result),
stdout: stdout,
stderr: stderr
)
}

private func executeProcess(
_ args: [String],
packagePath: AbsolutePath? = nil,
Expand Down