use duration for offset

fortio_main.go

@@ -104,7 +104,7 @@ var (
 	durationFlag    = flag.Duration("t", defaults.Duration, "How long to run the test or 0 to run until ^C")
 	percentilesFlag = flag.String("p", "50,75,90,99,99.9", "List of pXX to calculate")
 	resolutionFlag  = flag.Float64("r", defaults.Resolution, "Resolution of the histogram lowest buckets in seconds")
-	offsetFlag      = flag.Float64("o", defaults.Offset, "Offset of the histogram data in seconds")
+	offsetFlag      = flag.Duration("o", defaults.Offset, "Offset duration of the histogram data")
 	goMaxProcsFlag  = flag.Int("gomaxprocs", 0, "Setting for runtime.GOMAXPROCS, <1 doesn't change the default")
 	profileFlag     = flag.String("profile", "", "write .cpu and .mem profiles to `file`")
 	grpcFlag        = flag.Bool("grpc", false, "Use GRPC (health check by default, add -ping for ping) for load testing")

periodic/periodic.go

@@ -134,8 +134,8 @@ type RunnerOptions struct {
 	Jitter bool
 	// Optional run id; used by the server to identify runs.
 	RunID int64
-	// Optional Offect; to offset the histogram function duration
-	Offset float64
+	// Optional Offect Duration; to offset the histogram function duration
+	Offset time.Duration
 }
 
 // RunnerResults encapsulates the actual QPS observed and duration histogram.
@@ -408,7 +408,8 @@ func (r *periodicRunner) Run() RunnerResults {
 	}
 	start := time.Now()
 	// Histogram  and stats for Function duration - millisecond precision
-	functionDuration := stats.NewHistogram(r.Offset, r.Resolution)
+	offsetSec := float64(r.Offset) / float64(time.Second)
+	functionDuration := stats.NewHistogram(offsetSec, r.Resolution)
 	// Histogram and stats for Sleep time (negative offset to capture <0 sleep in their own bucket):
 	sleepTime := stats.NewHistogram(-0.001, 0.001)
 	if r.NumThreads <= 1 {