http-latency-prober/CHANGELOG.md

Changelog

All completed features are logged here in reverse-chronological order.

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2026-07-01 01:23 — Concurrency (Go, Step 7)

• Added -c/--concurrency flag: max URLs probed in parallel (0 = auto)
• Default auto-concurrency: min(numURLs, 8) — scales with workload, caps at 8
• Parallelism is across URLs only; the N samples of each URL stay sequential to preserve the accuracy of per-URL min/avg/max statistics
• Output buffered and printed in original input order (deterministic for both text and JSON), exit-code accumulation unchanged
• Implementation: semaphore channel + sync.WaitGroup, each goroutine writes only its own indexed result slot — verified clean with go test -race
• Added make go-test-race target to the Makefile
• 3 new tests: TestRunConcurrentOrder, TestConcurrentWorstCode, TestConcurrentJSONOrder
• Updated runtime estimates in docs/custom-usage-examples.md
• User doc: docs/usage/step-7-concurrency.md

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2026-07-01 01:05 — Root Makefile

• Namespaced targets: go-build, go-run, go-test, go-test-verbose, go-check, go-cover, go-fmt, go-vet, go-tidy, go-install, go-lint, go-clean
• Umbrella targets (build, test, check, fmt, vet, clean, all) delegate to Go now; py-* will slot in during the Python port
• help is the default target; auto-generated from ## comments
• go-run accepts ARGS= for passing flags, go-lint guards for golangci-lint
• .gitignore updated with coverage artifacts

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2026-07-01 00:49 — Integration tests (Go, Step 6)

• Extracted run(args, stdout, stderr) int from main() to make the CLI testable in-process
• Fixed TLS classification bug: TLSHandshakeDone fires with the error on cert rejection, so tlsErr is now captured and checked before the stale tlsStart.IsZero() guard
• run_test.go: 14 in-process tests covering exit codes 0–6, multi-URL, sampling, and JSON structure assertions
• cli_test.go: TestMain builds the real binary; 3 subprocess smoke tests exercise the actual os.Exit path
• All test servers use httptest + stdlib; .invalid TLD for deterministic DNS failures; no external network dependency

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2026-07-01 00:38 — Failure handling (Go, Step 5)

• Classified network failures into dns / connect / timeout / tls with distinct exit codes (2–5)
• Partial timing preserved up to the failure point (e.g. DNS phase shown on NXDOMAIN)
• --timeout flag (default 10s) applied via context.WithTimeout
• --fail flag: HTTP status ≥ 400 → exit code 6 (curl-style)
• -n sampling continues on network failure; aggregates successes, reports fail count + cause
• JSON output extended with succeeded, failed, errors[] fields
• Highest exit code across all URLs/failure types is used as the process exit

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2026-07-01 00:08 — JSON output flag (Go, Step 4)

• --json flag emits a JSON array with one entry per URL
• Schema always uses min/avg/max shape (consistent regardless of -n)
• Phases absent from the request (e.g. TLS on HTTP) are omitted from the JSON object
• Failed URLs are excluded from JSON output and reported to stderr
• Text output unchanged and remains the default

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2026-07-01 00:08 — Multiple URLs + sampling (Go, Step 3)

• -n/--count flag repeats each URL N times and reports min/avg/max per phase
• probe.Summarize aggregates a slice of Results into per-phase PhaseStats
• Multi-sample output shows an aligned min/avg/max table with a header row
• Single-sample output (n=1) is unchanged from Step 2

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2026-07-01 00:08 — Per-phase breakdown (Go, Step 2)

• Instrumented requests with net/http/httptrace.ClientTrace
• DNS lookup, TCP connect, TLS handshake, Server/TTFB, Transfer, Total phases
• TLS row omitted automatically for plain http:// URLs
• Aligned text output with separator before Total

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2026-07-01 00:08 — Simple total latency (Go, Step 1)

• probe.Measure performs an HTTP GET and records wall-clock total time
• main.go prints URL, HTTP status code, and total duration for each URL
• Exits with code 1 if any URL fails
• Multiple URLs accepted as positional arguments

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2026-07-01 00:08 — Project scaffold (Go, Step 0)

• Created project structure: go/, python/, docs/plans/, docs/usage/
• Initialised Go module latprobe (go/go.mod)
• Minimal go/main.go that prints usage and exits cleanly when no URL is given
• Stub go/internal/probe/probe.go defining the Result type and Measure signature
• Foundation files: README.md, CLAUDE.md, CHANGELOG.md
• Saved initial plan to docs/plans/2026-07-01-00-08-go-latency-tool.md