perf(hooks): replace net/http with minimal HTTP/1.0 client to shrink hook binaries

experiments.md

@@ -0,0 +1,12 @@
+# Experiment journal
+
+## Campaign B: binary size
+
+Metric: sum of bytes of worker, mcp and 6 hook binaries (release flags, `-s -w -trimpath`, `-tags fts5`). Lower is better.
+Threshold: at least 3% drop, tests green. Stop: 5 consecutive no-improve trials or 15 trials.
+Mutate: Go code and build flags. Frozen: public API, DB schema, plugin manifest.
+
+| id | mutation | total bytes | delta vs base | kept? |
+|----|----------|-------------|---------------|-------|
+| 01 | baseline | 102698416 | - | base |
+| 02 | pkg/hooks: raw HTTP/1.0 client replaces net/http | 87603952 | -14.7% | KEEP |

pkg/hooks/httpclient.go

@@ -0,0 +1,81 @@
+package hooks
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// maxResponseBytes caps a worker response so a misbehaving peer cannot exhaust memory.
+const maxResponseBytes = 32 << 20
+
+// Minimal HTTP/1.0 client over a raw TCP socket. Linking net/http adds ~3 MB to
+// every hook binary; hooks only speak plain JSON to the local worker. HTTP/1.0
+// makes the server skip chunked encoding and close the connection, so the body
+// is simply everything after the header block.
+type httpResponse struct {
+	Status     int
+	StatusText string
+	Body       []byte
+}
+
+func httpDo(ctx context.Context, timeout time.Duration, method string, port int, path string, body []byte) (*httpResponse, error) {
+	ctx, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+
+	addr := net.JoinHostPort("127.0.0.1", strconv.Itoa(port))
+	var d net.Dialer
+	conn, err := d.DialContext(ctx, "tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = conn.Close() }()
+
+	if dl, ok := ctx.Deadline(); ok {
+		_ = conn.SetDeadline(dl)
+	}
+	stop := context.AfterFunc(ctx, func() { _ = conn.Close() })
+	defer stop()
+
+	var req bytes.Buffer
+	fmt.Fprintf(&req, "%s %s HTTP/1.0\r\nHost: %s\r\n", method, path, addr)
+	if body != nil {
+		fmt.Fprintf(&req, "Content-Type: application/json\r\nContent-Length: %d\r\n", len(body))
+	}
+	req.WriteString("\r\n")
+	req.Write(body)
+	if _, err := conn.Write(req.Bytes()); err != nil {
+		return nil, err
+	}
+
+	raw, err := io.ReadAll(io.LimitReader(bufio.NewReader(conn), maxResponseBytes))
+	if err != nil {
+		return nil, err
+	}
+	return parseHTTPResponse(raw)
+}
+
+func parseHTTPResponse(raw []byte) (*httpResponse, error) {
+	head, body, found := bytes.Cut(raw, []byte("\r\n\r\n"))
+	if !found {
+		return nil, errors.New("malformed http response")
+	}
+	statusLine, _, _ := strings.Cut(string(head), "\r\n")
+	_, rest, ok := strings.Cut(statusLine, " ")
+	if !ok {
+		return nil, fmt.Errorf("malformed status line %q", statusLine)
+	}
+	codeStr, _, _ := strings.Cut(rest, " ")
+	code, err := strconv.Atoi(codeStr)
+	if err != nil {
+		return nil, fmt.Errorf("malformed status line %q", statusLine)
+	}
+	return &httpResponse{Status: code, StatusText: rest, Body: body}, nil
+}

pkg/hooks/worker.go

@@ -2,12 +2,10 @@
 package hooks
 
 import (
-	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
 	"net"
-	"net/http"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -28,6 +26,9 @@ const (
 	// HealthCheckTimeout is the timeout for health checks.
 	HealthCheckTimeout = 2 * time.Second
 
+	// hookTimeout bounds a single hook->worker request.
+	hookTimeout = 10 * time.Second
+
 	// StartupTimeout is the timeout for worker startup.
 	StartupTimeout = 10 * time.Second
 
@@ -52,26 +53,6 @@ var (
 	// circuitBreakerMu protects lastStartupFailure.
 	circuitBreakerMu   sync.Mutex
 	lastStartupFailure time.Time
-
-	// hookClient is a shared HTTP client for hook->worker requests.
-	// DisableKeepAlives prevents TIME_WAIT connection leaks since each hook
-	// is a separate OS process that exits quickly.
-	hookClient = &http.Client{
-		Timeout: 10 * time.Second,
-		Transport: &http.Transport{
-			DisableKeepAlives: true,
-			MaxIdleConns:      1,
-		},
-	}
-
-	// healthClient is a shared HTTP client for health/version checks.
-	healthClient = &http.Client{
-		Timeout: HealthCheckTimeout,
-		Transport: &http.Transport{
-			DisableKeepAlives: true,
-			MaxIdleConns:      1,
-		},
-	}
 )
 
 // IsWorkerAvailable performs a fast check without network calls.
@@ -110,22 +91,21 @@ func GetWorkerPort() int {
 // Parses the JSON health response to check the "ready" field when available.
 // Falls back to HTTP status code check for backwards compatibility.
 func IsWorkerRunning(port int) bool {
-	resp, err := healthClient.Get(fmt.Sprintf("http://127.0.0.1:%d/api/health", port))
+	resp, err := httpDo(context.Background(), HealthCheckTimeout, "GET", port, "/api/health", nil)
 	if err != nil {
 		return false
 	}
-	defer func() { _ = resp.Body.Close() }()
 
 	// Try to parse JSON response for structured health check
 	var health struct {
 		Ready bool `json:"ready"`
 	}
-	if err := json.NewDecoder(resp.Body).Decode(&health); err == nil {
+	if err := json.Unmarshal(resp.Body, &health); err == nil {
 		return health.Ready
 	}
 
 	// Fallback: treat HTTP 200 as healthy (backwards compatibility)
-	return resp.StatusCode == http.StatusOK
+	return resp.Status == 200
 }
 
 // workerCachePath returns the path to the worker cache file.
@@ -396,18 +376,17 @@ func updateCacheFromPort(port int) {
 
 // GetWorkerVersion gets the version of the running worker.
 func GetWorkerVersion(port int) string {
-	resp, err := healthClient.Get(fmt.Sprintf("http://127.0.0.1:%d/api/version", port))
+	resp, err := httpDo(context.Background(), HealthCheckTimeout, "GET", port, "/api/version", nil)
 	if err != nil {
 		return ""
 	}
-	defer func() { _ = resp.Body.Close() }()
 
-	if resp.StatusCode != http.StatusOK {
+	if resp.Status != 200 {
 		return ""
 	}
 
 	var result map[string]string
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+	if err := json.Unmarshal(resp.Body, &result); err != nil {
 		return ""
 	}
 
@@ -510,58 +489,46 @@ func findWorkerBinary() string {
 	return ""
 }
 
-// POST sends a POST request to the worker.
-func POST(port int, path string, body interface{}) (map[string]interface{}, error) {
-	jsonBody, err := json.Marshal(body)
+// request performs one worker call and returns the decoded JSON object.
+// A non-JSON body yields (nil, nil) when lenient, else the decode error.
+func request(ctx context.Context, method string, port int, path string, body interface{}, lenient bool) (map[string]interface{}, error) {
+	var payload []byte
+	if body != nil {
+		var err error
+		if payload, err = json.Marshal(body); err != nil {
+			return nil, err
+		}
+	}
+
+	resp, err := httpDo(ctx, hookTimeout, method, port, path, payload)
 	if err != nil {
 		return nil, err
 	}
-
-	resp, err := hookClient.Post(
-		fmt.Sprintf("http://127.0.0.1:%d%s", port, path),
-		"application/json",
-		bytes.NewReader(jsonBody),
-	)
-	if err != nil {
-		return nil, err
-	}
-	defer func() { _ = resp.Body.Close() }()
-
-	if resp.StatusCode >= 400 {
-		return nil, fmt.Errorf("request failed: %s", resp.Status)
+	if resp.Status >= 400 {
+		return nil, fmt.Errorf("request failed: %s", resp.StatusText)
 	}
 
 	var result map[string]interface{}
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+	if err := json.Unmarshal(resp.Body, &result); err != nil {
+		if lenient {
 			// Not all endpoints return JSON
 			return nil, nil
 		}
-
+		return nil, err
+	}
 	return result, nil
 }
 
+// POST sends a POST request to the worker.
+func POST(port int, path string, body interface{}) (map[string]interface{}, error) {
+	return request(context.Background(), "POST", port, path, body, true)
+}
+
 // POSTWithContext sends a POST request using the provided context.
 // Used for fire-and-forget calls where we want to control the timeout externally.
 func POSTWithContext(ctx context.Context, port int, path string, body interface{}) error {
-	jsonBody, err := json.Marshal(body)
-	if err != nil {
+	_, err := request(ctx, "POST", port, path, body, true)
 	return err
-	}
-
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
-		fmt.Sprintf("http://127.0.0.1:%d%s", port, path),
-		bytes.NewReader(jsonBody))
-	if err != nil {
-		return err
-	}
-	req.Header.Set("Content-Type", "application/json")
-
-	resp, err := hookClient.Do(req)
-	if err != nil {
-		return err
-	}
-	defer func() { _ = resp.Body.Close() }()
-	return nil
 }
 
 // POSTWithContextResult sends a POST request using the provided context and
@@ -570,56 +537,12 @@ func POSTWithContext(ctx context.Context, port int, path string, body interface{
 // aborts at the hook deadline instead of blocking for the full client timeout.
 // A non-JSON body is returned as (nil, nil), matching POST's behavior.
 func POSTWithContextResult(ctx context.Context, port int, path string, body interface{}) (map[string]interface{}, error) {
-	jsonBody, err := json.Marshal(body)
-	if err != nil {
-		return nil, err
-	}
-
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
-		fmt.Sprintf("http://127.0.0.1:%d%s", port, path),
-		bytes.NewReader(jsonBody))
-	if err != nil {
-		return nil, err
-	}
-	req.Header.Set("Content-Type", "application/json")
-
-	resp, err := hookClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer func() { _ = resp.Body.Close() }()
-
-	if resp.StatusCode >= 400 {
-		return nil, fmt.Errorf("request failed: %s", resp.Status)
-	}
-
-	var result map[string]interface{}
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-		// Not all endpoints return JSON
-		return nil, nil
-	}
-
-	return result, nil
+	return request(ctx, "POST", port, path, body, true)
 }
 
 // GET sends a GET request to the worker.
 func GET(port int, path string) (map[string]interface{}, error) {
-	resp, err := hookClient.Get(fmt.Sprintf("http://127.0.0.1:%d%s", port, path))
-	if err != nil {
-		return nil, err
-	}
-	defer func() { _ = resp.Body.Close() }()
-
-	if resp.StatusCode >= 400 {
-		return nil, fmt.Errorf("request failed: %s", resp.Status)
-	}
-
-	var result map[string]interface{}
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-		return nil, err
-	}
-
-	return result, nil
+	return request(context.Background(), "GET", port, path, nil, false)
 }
 
 // GETWithContext sends a GET request using the provided context and decodes the
@@ -627,28 +550,7 @@ func GET(port int, path string) (map[string]interface{}, error) {
 // Used on the prompt critical path so a wedged worker aborts at the hook
 // deadline instead of blocking for the full client timeout.
 func GETWithContext(ctx context.Context, port int, path string) (map[string]interface{}, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet,
-		fmt.Sprintf("http://127.0.0.1:%d%s", port, path), nil)
-	if err != nil {
-		return nil, err
-	}
-
-	resp, err := hookClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer func() { _ = resp.Body.Close() }()
-
-	if resp.StatusCode >= 400 {
-		return nil, fmt.Errorf("request failed: %s", resp.Status)
-	}
-
-	var result map[string]interface{}
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-		return nil, err
-	}
-
-	return result, nil
+	return request(ctx, "GET", port, path, nil, false)
 }
 
 // versionsCompatible checks if two versions are compatible for dev builds.

pkg/hooks/worker_test.go

@@ -5,8 +5,12 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
+	"net"
 	"net/http"
 	"net/http/httptest"
+	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -1481,22 +1485,101 @@ func TestSleepCtx_Cancelled(t *testing.T) {
 	assert.Less(t, elapsed, 500*time.Millisecond)
 }
 
-// TestHookClients_DisableKeepAlives asserts shared clients disable keep-alives
-// to prevent TIME_WAIT connection leaks in short-lived hook processes.
-func TestHookClients_DisableKeepAlives(t *testing.T) {
-	hTransport, ok := hookClient.Transport.(*http.Transport)
-	require.True(t, ok, "hookClient.Transport should be *http.Transport")
-	assert.True(t, hTransport.DisableKeepAlives, "hookClient must disable keep-alives")
-	assert.Equal(t, 1, hTransport.MaxIdleConns)
+// TestHTTPDo_Behaviour covers the raw HTTP/1.0 client against a real server.
+func TestHTTPDo_Behaviour(t *testing.T) {
+	big := strings.Repeat("x", 200_000)
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/echo":
+			b, _ := io.ReadAll(r.Body)
+			assert.Equal(t, "application/json", r.Header.Get("Content-Type"))
+			_, _ = w.Write(b)
+		case "/big":
+			_, _ = w.Write([]byte(`{"v":"` + big + `"}`))
+		case "/missing":
+			w.WriteHeader(http.StatusNotFound)
+		case "/empty":
+			w.WriteHeader(http.StatusNoContent)
+		}
+	}))
+	defer srv.Close()
+	port, err := strconv.Atoi(srv.URL[strings.LastIndex(srv.URL, ":")+1:])
+	require.NoError(t, err)
 
-	hcTransport, ok := healthClient.Transport.(*http.Transport)
-	require.True(t, ok, "healthClient.Transport should be *http.Transport")
-	assert.True(t, hcTransport.DisableKeepAlives, "healthClient must disable keep-alives")
-	assert.Equal(t, 1, hcTransport.MaxIdleConns)
+	tests := []struct {
+		name       string
+		method     string
+		path       string
+		body       []byte
+		wantStatus int
+		wantLen    int
+	}{
+		{"post echoes body", "POST", "/echo", []byte(`{"a":1}`), 200, 7},
+		{"large body over server buffer", "GET", "/big", nil, 200, len(big) + 8},
+		{"not found", "GET", "/missing", nil, 404, 0},
+		{"no content", "GET", "/empty", nil, 204, 0},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			resp, err := httpDo(context.Background(), time.Second, tt.method, port, tt.path, tt.body)
+			require.NoError(t, err)
+			assert.Equal(t, tt.wantStatus, resp.Status)
+			assert.Len(t, resp.Body, tt.wantLen)
+		})
+	}
 }
 
-// TestHookClient_Timeout verifies hookClient timeout is set.
-func TestHookClient_Timeout(t *testing.T) {
-	assert.Equal(t, 10*time.Second, hookClient.Timeout)
-	assert.Equal(t, HealthCheckTimeout, healthClient.Timeout)
+// TestHTTPDo_Failures covers connection, timeout, cancel and malformed replies.
+func TestHTTPDo_Failures(t *testing.T) {
+	t.Run("connection refused", func(t *testing.T) {
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		require.NoError(t, err)
+		port := l.Addr().(*net.TCPAddr).Port
+		require.NoError(t, l.Close())
+		_, err = httpDo(context.Background(), time.Second, "GET", port, "/", nil)
+		assert.Error(t, err)
+	})
+
+	t.Run("wedged server times out", func(t *testing.T) {
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		require.NoError(t, err)
+		defer func() { _ = l.Close() }()
+		go func() {
+			c, err := l.Accept()
+			if err == nil {
+				defer func() { _ = c.Close() }()
+				time.Sleep(2 * time.Second)
+			}
+		}()
+		start := time.Now()
+		_, err = httpDo(context.Background(), 200*time.Millisecond, "GET", l.Addr().(*net.TCPAddr).Port, "/", nil)
+		assert.Error(t, err)
+		assert.Less(t, time.Since(start), time.Second)
+	})
+
+	t.Run("cancelled context aborts", func(t *testing.T) {
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		require.NoError(t, err)
+		defer func() { _ = l.Close() }()
+		go func() {
+			c, err := l.Accept()
+			if err == nil {
+				defer func() { _ = c.Close() }()
+				time.Sleep(2 * time.Second)
+			}
+		}()
+		ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+		defer cancel()
+		start := time.Now()
+		_, err = httpDo(ctx, 5*time.Second, "GET", l.Addr().(*net.TCPAddr).Port, "/", nil)
+		assert.Error(t, err)
+		assert.Less(t, time.Since(start), time.Second)
+	})
+
+	t.Run("malformed response", func(t *testing.T) {
+		for _, raw := range []string{"", "garbage", "HTTP/1.0\r\n\r\n", "HTTP/1.0 abc OK\r\n\r\n"} {
+			_, err := parseHTTPResponse([]byte(raw))
+			assert.Error(t, err, "input %q", raw)
+		}
+	})
 }