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[SDTEST-2703] Set default parallelism to number of available CPUs #30

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Merged
anmarchenko merged 2 commits into from
Jan 30, 2026
Merged

[SDTEST-2703] Set default parallelism to number of available CPUs #30

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e01ce68
set min-parallelism and max-parallelism to the numer of logical CPUs …
anmarchenko Jan 30, 2026
4487190
fix: clamp min_parallelism to max when max < min
anmarchenko Jan 30, 2026
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7 changes: 5 additions & 2 deletions internal/cmd/cmd.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,9 @@ import (
"github.com/spf13/viper"
)

// defaultParallelism stores the computed default at init time for CLI flags
var defaultParallelism = settings.DefaultParallelism()

var rootCmd = &cobra.Command{
Use: "ddtest",
Short: "A test runner from Datadog",
Expand Down Expand Up @@ -54,8 +57,8 @@ var runCmd = &cobra.Command{
func init() {
rootCmd.PersistentFlags().String("platform", "ruby", "Platform that runs tests")
rootCmd.PersistentFlags().String("framework", "rspec", "Test framework to use")
rootCmd.PersistentFlags().Int("min-parallelism", 1, "Minimum number of parallel test processes")
rootCmd.PersistentFlags().Int("max-parallelism", 1, "Maximum number of parallel test processes")
rootCmd.PersistentFlags().Int("min-parallelism", defaultParallelism, "Minimum number of parallel test processes (default: number of CPUs)")
rootCmd.PersistentFlags().Int("max-parallelism", defaultParallelism, "Maximum number of parallel test processes (default: number of CPUs)")
rootCmd.PersistentFlags().String("worker-env", "", "Worker environment configuration")
rootCmd.PersistentFlags().String("command", "", "Test command that ddtest should wrap")
rootCmd.PersistentFlags().String("tests-location", "", "Glob pattern used to discover test files")
Expand Down
4 changes: 2 additions & 2 deletions internal/runner/parallelism.go
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Expand Up @@ -24,9 +24,9 @@ func calculateParallelRunnersWithParams(skippablePercentage float64, minParallel
}

if maxParallelism < minParallelism {
slog.Warn("max_parallelism is less than min_parallelism, using min_parallelism",
slog.Warn("max_parallelism is less than min_parallelism, clamping min to max",
"max_parallelism", maxParallelism, "min_parallelism", minParallelism)
return minParallelism
minParallelism = maxParallelism
}

percentage := math.Max(0.0, math.Min(100.0, skippablePercentage)) // Clamp to [0, 100]
Expand Down
4 changes: 3 additions & 1 deletion internal/runner/parallelism_test.go
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Expand Up @@ -50,8 +50,10 @@ func TestCalculateParallelRunners_MinParallelismLessThanOne(t *testing.T) {
}

func TestCalculateParallelRunners_MaxLessThanMin(t *testing.T) {
// When max < min, min is clamped to max. This ensures that a user who only
// sets --max-parallelism to a lower value gets the expected behavior.
result := testCalculateParallelRunners(50.0, 5, 3) // max < min
expected := 5 // Should return min_parallelism
expected := 3 // Should clamp min to max and return max
if result != expected {
t.Errorf("calculateParallelRunners(50.0) = %d, expected %d when max < min", result, expected)
}
Expand Down
27 changes: 27 additions & 0 deletions internal/runner/runner_test.go
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Expand Up @@ -242,6 +242,15 @@ func TestTestRunner_Setup_WithParallelRunners(t *testing.T) {
// Create .testoptimization directory
_ = os.MkdirAll(constants.PlanDirectory, 0755)

// Set parallelism to 1 to test single runner behavior
_ = os.Setenv("DD_TEST_OPTIMIZATION_RUNNER_MIN_PARALLELISM", "1")
_ = os.Setenv("DD_TEST_OPTIMIZATION_RUNNER_MAX_PARALLELISM", "1")
defer func() {
_ = os.Unsetenv("DD_TEST_OPTIMIZATION_RUNNER_MIN_PARALLELISM")
_ = os.Unsetenv("DD_TEST_OPTIMIZATION_RUNNER_MAX_PARALLELISM")
}()
settings.Init()

// Setup mocks for a test with 40% skippable percentage
mockFramework := &MockFramework{
FrameworkName: "rspec",
Expand Down Expand Up @@ -299,6 +308,15 @@ func TestTestRunner_Setup_WithCIProvider(t *testing.T) {
// Create .testoptimization directory
_ = os.MkdirAll(constants.PlanDirectory, 0755)

// Set parallelism to 1 to test single runner behavior
_ = os.Setenv("DD_TEST_OPTIMIZATION_RUNNER_MIN_PARALLELISM", "1")
_ = os.Setenv("DD_TEST_OPTIMIZATION_RUNNER_MAX_PARALLELISM", "1")
defer func() {
_ = os.Unsetenv("DD_TEST_OPTIMIZATION_RUNNER_MIN_PARALLELISM")
_ = os.Unsetenv("DD_TEST_OPTIMIZATION_RUNNER_MAX_PARALLELISM")
}()
settings.Init()

// Setup mocks for test with CI provider
mockFramework := &MockFramework{
FrameworkName: "rspec",
Expand Down Expand Up @@ -455,6 +473,15 @@ func TestTestRunner_Setup_WithTestSplit(t *testing.T) {
// Create .testoptimization directory
_ = os.MkdirAll(constants.PlanDirectory, 0755)

// Set parallelism to 1 to test single runner behavior
_ = os.Setenv("DD_TEST_OPTIMIZATION_RUNNER_MIN_PARALLELISM", "1")
_ = os.Setenv("DD_TEST_OPTIMIZATION_RUNNER_MAX_PARALLELISM", "1")
defer func() {
_ = os.Unsetenv("DD_TEST_OPTIMIZATION_RUNNER_MIN_PARALLELISM")
_ = os.Unsetenv("DD_TEST_OPTIMIZATION_RUNNER_MAX_PARALLELISM")
}()
settings.Init()

// Setup mocks for single runner scenario
mockFramework := &MockFramework{
FrameworkName: "rspec",
Expand Down
11 changes: 9 additions & 2 deletions internal/settings/settings.go
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Expand Up @@ -4,11 +4,18 @@ import (
"encoding/json"
"fmt"
"os"
"runtime"
"strings"

"github.com/spf13/viper"
)

// DefaultParallelism returns the default parallelism value, which is the number
// of available CPUs. This respects container CPU limits in cloud CI environments.
func DefaultParallelism() int {
return runtime.NumCPU()
}

type Config struct {
Platform string `mapstructure:"platform"`
Framework string `mapstructure:"framework"`
Expand Down Expand Up @@ -42,8 +49,8 @@ func Init() {
func setDefaults() {
viper.SetDefault("platform", "ruby")
viper.SetDefault("framework", "rspec")
viper.SetDefault("min_parallelism", 1)
viper.SetDefault("max_parallelism", 1)
viper.SetDefault("min_parallelism", DefaultParallelism())
viper.SetDefault("max_parallelism", DefaultParallelism())
viper.SetDefault("worker_env", "")
viper.SetDefault("ci_node", -1)
viper.SetDefault("command", "")
Expand Down
41 changes: 29 additions & 12 deletions internal/settings/settings_test.go
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Expand Up @@ -2,11 +2,24 @@ package settings

import (
"os"
"runtime"
"testing"

"github.com/spf13/viper"
)

func TestDefaultParallelism(t *testing.T) {
result := DefaultParallelism()
expected := runtime.NumCPU()

if result != expected {
t.Errorf("expected DefaultParallelism() to return %d (runtime.NumCPU()), got %d", expected, result)
}
if result < 1 {
t.Errorf("expected DefaultParallelism() to be at least 1, got %d", result)
}
}

func TestInit(t *testing.T) {
// Clear any existing config
config = nil
Expand All @@ -25,11 +38,12 @@ func TestInit(t *testing.T) {
if config.Framework != "rspec" {
t.Errorf("expected default framework to be 'rspec', got %q", config.Framework)
}
if config.MinParallelism != 1 {
t.Errorf("expected default min_parallelism to be 1, got %d", config.MinParallelism)
expectedParallelism := runtime.NumCPU()
if config.MinParallelism != expectedParallelism {
t.Errorf("expected default min_parallelism to be %d (CPU count), got %d", expectedParallelism, config.MinParallelism)
}
if config.MaxParallelism != 1 {
t.Errorf("expected default max_parallelism to be 1, got %d", config.MaxParallelism)
if config.MaxParallelism != expectedParallelism {
t.Errorf("expected default max_parallelism to be %d (CPU count), got %d", expectedParallelism, config.MaxParallelism)
}
if config.WorkerEnv != "" {
t.Errorf("expected default worker_env to be empty, got %q", config.WorkerEnv)
Expand Down Expand Up @@ -59,11 +73,12 @@ func TestSetDefaults(t *testing.T) {
if viper.GetString("framework") != "rspec" {
t.Errorf("expected default framework to be 'rspec', got %q", viper.GetString("framework"))
}
if viper.GetInt("min_parallelism") != 1 {
t.Errorf("expected default min_parallelism to be 1, got %d", viper.GetInt("min_parallelism"))
expectedParallelism := runtime.NumCPU()
if viper.GetInt("min_parallelism") != expectedParallelism {
t.Errorf("expected default min_parallelism to be %d (CPU count), got %d", expectedParallelism, viper.GetInt("min_parallelism"))
}
if viper.GetInt("max_parallelism") != 1 {
t.Errorf("expected default max_parallelism to be 1, got %d", viper.GetInt("max_parallelism"))
if viper.GetInt("max_parallelism") != expectedParallelism {
t.Errorf("expected default max_parallelism to be %d (CPU count), got %d", expectedParallelism, viper.GetInt("max_parallelism"))
}
if viper.GetString("worker_env") != "" {
t.Errorf("expected default worker_env to be empty, got %q", viper.GetString("worker_env"))
Expand Down Expand Up @@ -199,9 +214,10 @@ func TestGetMinParallelism(t *testing.T) {
config = nil
viper.Reset()

expectedParallelism := runtime.NumCPU()
minParallelism := GetMinParallelism()
if minParallelism != 1 {
t.Errorf("expected min_parallelism to be 1, got %d", minParallelism)
if minParallelism != expectedParallelism {
t.Errorf("expected min_parallelism to be %d (CPU count), got %d", expectedParallelism, minParallelism)
}

// Test with custom value
Expand All @@ -217,9 +233,10 @@ func TestGetMaxParallelism(t *testing.T) {
config = nil
viper.Reset()

expectedParallelism := runtime.NumCPU()
maxParallelism := GetMaxParallelism()
if maxParallelism != 1 {
t.Errorf("expected max_parallelism to be 1, got %d", maxParallelism)
if maxParallelism != expectedParallelism {
t.Errorf("expected max_parallelism to be %d (CPU count), got %d", expectedParallelism, maxParallelism)
}

// Test with custom value
Expand Down
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