Files
http-latency-prober/go/main.go
Jan Novak 8ec926bbcd feat(go): step 3 — multiple URLs and -n sampling with min/avg/max
Add probe.Summarize to aggregate N Results into per-phase min/avg/max
stats. Wire up -n/--count flag in main to repeat each URL N times and
display an aligned three-column table. Single-sample output (n=1) is
unchanged. URLs are grouped with a blank line between them.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-07-01 00:29:36 +02:00

132 lines
3.2 KiB
Go

package main
import (
"flag"
"fmt"
"os"
"strings"
"time"
"latprobe/internal/probe"
)
const usageText = `latprobe — measure per-phase HTTP request latency
Usage:
latprobe [flags] <url> [url ...]
Flags:
-n, --count int Number of requests per URL (default 1)
--json Output results as JSON instead of text
-h, --help Show this help
Examples:
latprobe https://example.com
latprobe -n 5 https://example.com https://www.google.com
latprobe --json https://example.com | jq .
`
func main() {
count := flag.Int("count", 1, "number of requests per URL")
flag.IntVar(count, "n", 1, "number of requests per URL (shorthand)")
jsonOut := flag.Bool("json", false, "output results as JSON")
flag.Usage = func() { fmt.Fprint(os.Stderr, usageText) }
flag.Parse()
urls := flag.Args()
if len(urls) == 0 {
fmt.Fprint(os.Stderr, usageText)
os.Exit(1)
}
// --json parsed but not yet functional (wired in Step 4).
_ = jsonOut
failed := false
for i, url := range urls {
if i > 0 {
fmt.Println()
}
results := make([]probe.Result, 0, *count)
for j := 0; j < *count; j++ {
r := probe.Measure(url)
if r.Err != nil {
fmt.Fprintf(os.Stderr, "error %s (sample %d/%d): %v\n", url, j+1, *count, r.Err)
failed = true
break
}
results = append(results, r)
}
if len(results) == 0 {
continue
}
if *count == 1 {
printResult(results[0])
} else {
printAggregate(probe.Summarize(results))
}
}
if failed {
os.Exit(1)
}
}
// ── single-sample output ──────────────────────────────────────────────────────
func printResult(r probe.Result) {
fmt.Printf("%s (%d)\n", r.URL, r.StatusCode)
phases := []struct {
label string
p probe.Phase
}{
{"DNS lookup ", r.DNS},
{"TCP connect ", r.Connect},
{"TLS handshake ", r.TLS},
{"Server (TTFB) ", r.TTFB},
{"Transfer ", r.Transfer},
}
for _, ph := range phases {
if ph.p.Present {
fmt.Printf(" %s : %8.2f ms\n", ph.label, ms(ph.p.Duration))
}
}
fmt.Println(" " + strings.Repeat("─", 29))
fmt.Printf(" %s : %8.2f ms\n", "Total ", ms(r.Total.Duration))
}
// ── multi-sample output ───────────────────────────────────────────────────────
func printAggregate(a probe.Aggregate) {
fmt.Printf("%s (%d, %d samples)\n", a.URL, a.StatusCode, a.Count)
fmt.Printf(" %-14s %9s %9s %9s\n", "", "min", "avg", "max")
phases := []struct {
label string
p probe.PhaseStats
}{
{"DNS lookup ", a.DNS},
{"TCP connect ", a.Connect},
{"TLS handshake ", a.TLS},
{"Server (TTFB) ", a.TTFB},
{"Transfer ", a.Transfer},
}
for _, ph := range phases {
if ph.p.Present {
fmt.Printf(" %s : %6.2f ms %6.2f ms %6.2f ms\n",
ph.label, ms(ph.p.Min), ms(ph.p.Avg), ms(ph.p.Max))
}
}
fmt.Println(" " + strings.Repeat("─", 49))
fmt.Printf(" %s : %6.2f ms %6.2f ms %6.2f ms\n",
"Total ", ms(a.Total.Min), ms(a.Total.Avg), ms(a.Total.Max))
}
func ms(d time.Duration) float64 {
return float64(d.Microseconds()) / 1000
}