pulumi/pulumi · error

could not start CPU profile: %w

Error message

could not start CPU profile: %w

What it means

InitProfiling wraps failures from either creating the CPU profile output file or starting pprof.StartCPUProfile. Both the file-create error and the pprof start error share this message, prefixed with the given prefix and PID.

Source

Thrown at sdk/go/common/util/cmdutil/profile.go:31

// limitations under the License.

package cmdutil

import (
	"fmt"
	"os"
	"runtime"
	"runtime/pprof"
	"runtime/trace"
	"time"

	"github.com/pulumi/pulumi/sdk/v3/go/common/util/contract"
)

func InitProfiling(prefix string, memProfileRate int) error {
	cpu, err := os.Create(fmt.Sprintf("%s.%v.cpu", prefix, os.Getpid()))
	if err != nil {
		return fmt.Errorf("could not start CPU profile: %w", err)
	}
	if err = pprof.StartCPUProfile(cpu); err != nil {
		return fmt.Errorf("could not start CPU profile: %w", err)
	}

	exec, err := os.Create(fmt.Sprintf("%s.%v.trace", prefix, os.Getpid()))
	if err != nil {
		return fmt.Errorf("could not start execution trace: %w", err)
	}
	if err = trace.Start(exec); err != nil {
		return fmt.Errorf("could not start execution trace: %w", err)
	}

	if memProfileRate > 0 {
		runtime.MemProfileRate = memProfileRate
		go memoryProfileWriteLoop(prefix)
	}

View on GitHub (pinned to 793f7b2e16)

Solutions

1. Ensure the profiling output prefix points to an existing writable directory (e.g. /tmp)
2. Check disk space and file permissions for the profile file location
3. Disable profiling (unset the profiling env/flag) if you don't need it
4. Verify only one InitProfiling call per process lifetime

Example fix

// before
PULUMI_PROFILE_PREFIX=/nonexistent/dir/pulumi
// after
PULUMI_PROFILE_PREFIX=/tmp/pulumi

// ensure profile output location is writable before enabling profiling
if err := os.MkdirAll(profDir, 0o755); err != nil { return err }
if f, err := os.CreateTemp(profDir, "prof-check"); err != nil { return err } else { f.Close(); os.Remove(f.Name()) }

if err := cmdutil.InitProfiling(prefix, memProfileRate); err != nil {
    // profiling is best-effort: log and continue without profiling
    log.Printf("profiling disabled: %v", err)
}

When it happens

Trigger: Running the CLI with profiling enabled (e.g. PULUMI_SKIP_AUTOMATION... / profiling flags or env enabling InitProfiling) where the <prefix>.<pid>.cpu file cannot be created (bad path, read-only dir, permissions) or a CPU profile is already running in-process.

Common situations: Profiling output directory doesn't exist or is not writable; running as a user without write permission to prefix location; nested/second call to StartCPUProfile within the same process; disk full.

Related errors

• parse input file: %w
• resolve pulumi home: %w
• invalid --approval-mode %q: expected one of manual, balanced
• invalid --permission-mode %q: expected one of default, read-
• parsing CLI version %q: %w

AI-assisted analysis of pulumi/pulumi@793f7b2e16 (2026-08-31). Data as JSON: /api/errors/64edc9ef6e035c3c. Report an issue: GitHub.