profiler: add CPUProfileRate option

profiler/options.go

@@ -98,6 +98,7 @@ type config struct {
 	types             map[ProfileType]struct{}
 	period            time.Duration
 	cpuDuration       time.Duration
+	cpuProfileRate    int
 	uploadTimeout     time.Duration
 	maxGoroutinesWait int
 	mutexFraction     int
@@ -126,6 +127,7 @@ func logStartup(c *config) {
 		ProfilePeriod        string   `json:"profile_period"`
 		EnabledProfiles      []string `json:"enabled_profiles"`
 		CPUDuration          string   `json:"cpu_duration"`
+		CPUProfileRate       int      `json:"cpu_profile_rate"`
 		BlockProfileRate     int      `json:"block_profile_rate"`
 		MutexProfileFraction int      `json:"mutex_profile_fraction"`
 		MaxGoroutinesWait    int      `json:"max_goroutines_wait"`
@@ -146,6 +148,7 @@ func logStartup(c *config) {
 		Tags:                 c.tags,
 		ProfilePeriod:        c.period.String(),
 		CPUDuration:          c.cpuDuration.String(),
+		CPUProfileRate:       c.cpuProfileRate,
 		BlockProfileRate:     c.blockRate,
 		MutexProfileFraction: c.mutexFraction,
 		MaxGoroutinesWait:    c.maxGoroutinesWait,
@@ -346,6 +349,21 @@ func CPUDuration(d time.Duration) Option {
 	}
 }
 
+// CPUProfileRate sets the sampling frequency for CPU profiling. A sample will
+// be taken once for every (1 / hz) seconds of on-CPU time. If not given,
+// profiling will use the default rate from the runtime/pprof.StartCPUProfile
+// function, which is 100 as of Go 1.0.
+//
+// Setting a different profile rate will result in a spurious warning every time
+// CPU profling is started, like "cannot set cpu profile rate until previous
+// profile has finished". This is a known issue, but the rate will still be set
+// correctly and CPU profiling will work.
+func CPUProfileRate(hz int) Option {
+	return func(cfg *config) {
+		cfg.cpuProfileRate = hz
+	}
+}
+
 // MutexProfileFraction turns on mutex profiles with rate indicating the fraction
 // of mutex contention events reported in the mutex profile.
 // On average, 1/rate events are reported.

profiler/options_test.go

@@ -105,6 +105,12 @@ func TestOptions(t *testing.T) {
 		assert.Equal(t, 3*time.Second, cfg.cpuDuration)
 	})
 
+	t.Run("CPUProfileRate", func(t *testing.T) {
+		var cfg config
+		CPUProfileRate(1000)(&cfg)
+		assert.Equal(t, 1000, cfg.cpuProfileRate)
+	})
+
 	t.Run("MutexProfileFraction", func(t *testing.T) {
 		var cfg config
 		MutexProfileFraction(1)(&cfg)
@@ -330,6 +336,7 @@ func TestDefaultConfig(t *testing.T) {
 		assert.True(ok)
 		assert.Equal(DefaultPeriod, cfg.period)
 		assert.Equal(DefaultDuration, cfg.cpuDuration)
+		assert.Equal(0, cfg.cpuProfileRate)
 		assert.Equal(DefaultMutexFraction, cfg.mutexFraction)
 		assert.Equal(DefaultBlockRate, cfg.blockRate)
 		assert.Contains(cfg.tags, "runtime-id:"+globalconfig.RuntimeID())

profiler/profile.go

@@ -81,6 +81,13 @@ var profileTypes = map[ProfileType]profileType{
 		Filename: "cpu.pprof",
 		Collect: func(_ profileType, p *profiler) ([]byte, error) {
 			var buf bytes.Buffer
+			if p.cfg.cpuProfileRate != 0 {
+				// The profile has to be set each time before
+				// profiling is started. Otherwise,
+				// runtime/pprof.StartCPUProfile will set the
+				// rate itself.
+				runtime.SetCPUProfileRate(p.cfg.cpuProfileRate)
+			}
 			if err := startCPUProfile(&buf); err != nil {
 				return nil, err
 			}