feat: simplify HTTP client proxy pools and authenticated JSON calls

httpc/client.go

@@ -3,9 +3,7 @@
 package httpc
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -22,18 +20,6 @@ import (
 var ErrClosed = errors.New("httpc: closed")
 var ErrResponseTooLarge = errors.New("httpc: response exceeds limit")
 
-type Config struct {
-	Timeout          time.Duration     `json:"timeout"`
-	MaxRetries       int               `json:"maxRetries"`
-	Backoff          time.Duration     `json:"backoff"`
-	MaxBackoff       time.Duration     `json:"maxBackoff"`
-	MaxConnsPerHost  int               `json:"maxConnsPerHost"`
-	MaxResponseBytes int64             `json:"maxResponseBytes"`
-	DisableRequestID bool              `json:"disableRequestId"`
-	DisableLogging   bool              `json:"disableLogging"`
-	Transport        http.RoundTripper `json:"-"` // Borrowed. The caller owns its lifecycle.
-}
-
 type Client struct {
 	config Config
 	client *http.Client
@@ -41,43 +27,19 @@ type Client struct {
 	closed atomic.Bool
 }
 
+// New creates a reusable client. Close it after callers and response streams drain.
 func New(cfg Config) (*Client, error) {
-	if cfg.Timeout < 0 || cfg.Backoff < 0 || cfg.MaxBackoff < 0 || cfg.MaxRetries < 0 || cfg.MaxRetries > 5 || cfg.MaxConnsPerHost < 0 || cfg.MaxResponseBytes < 0 {
-		return nil, errors.New("httpc: invalid configuration")
+	normalized, err := normalizeConfig(cfg)
+	if err != nil {
+		return nil, err
 	}
-	if cfg.Timeout == 0 {
-		cfg.Timeout = 10 * time.Second
-	}
-	if cfg.Backoff == 0 {
-		cfg.Backoff = 100 * time.Millisecond
-	}
-	if cfg.MaxBackoff == 0 {
-		cfg.MaxBackoff = 2 * time.Second
-	}
-	if cfg.Backoff > cfg.MaxBackoff {
-		return nil, errors.New("httpc: backoff exceeds maxBackoff")
-	}
-	if cfg.MaxConnsPerHost == 0 {
-		cfg.MaxConnsPerHost = 64
-	}
-	if cfg.MaxResponseBytes == 0 {
-		cfg.MaxResponseBytes = 1 << 20
-	}
-	if cfg.MaxResponseBytes > 1<<30 || cfg.MaxConnsPerHost > 65536 {
-		return nil, errors.New("httpc: response or connection limit exceeds supported capacity")
-	}
-	c := &Client{config: cfg}
+	c := &Client{config: normalized}
 	transport := cfg.Transport
 	if transport == nil {
-		// Own a private pool; never mutate the process-wide DefaultTransport.
-		base, ok := http.DefaultTransport.(*http.Transport)
-		if !ok {
-			return nil, errors.New("httpc: provide Transport when DefaultTransport is replaced")
+		c.owned, err = ownedTransport(normalized)
+		if err != nil {
+			return nil, err
 		}
-		c.owned = base.Clone()
-		c.owned.MaxConnsPerHost = cfg.MaxConnsPerHost
-		c.owned.MaxIdleConnsPerHost = cfg.MaxConnsPerHost
-		c.owned.MaxIdleConns = cfg.MaxConnsPerHost * 2
 		transport = c.owned
 	}
 	c.client = &http.Client{Transport: transport, CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
@@ -114,7 +76,10 @@ func (c *Client) Do(request *http.Request) (*http.Response, error) {
 	}
 	replayable := (base.Method == "" || base.Method == "GET" || base.Method == "HEAD" || base.Method == "OPTIONS") && (base.Body == nil || base.Body == http.NoBody || base.GetBody != nil)
 	for attempt := 0; ; attempt++ {
-		req := base.Clone(ctx)
+		req := base
+		if attempt > 0 {
+			req = base.Clone(ctx)
+		}
 		if attempt > 0 && base.Body != nil && base.Body != http.NoBody {
 			body, err := base.GetBody()
 			if err != nil {
@@ -133,23 +98,9 @@ func (c *Client) Do(request *http.Request) (*http.Response, error) {
 			logx.InfoContext(ctx, "http.client", "method", req.Method, "host", req.URL.Hostname(), "status", status, "attempt", attempt+1, "durationMs", time.Since(started).Seconds()*1000, "failed", err != nil)
 		}
 		retry := replayable && attempt < c.config.MaxRetries && ctx.Err() == nil && (err != nil || status == 429 || status == 502 || status == 503 || status == 504)
-		delay := c.config.Backoff
-		for i := 0; i < attempt && delay < c.config.MaxBackoff; i++ {
-			if delay > c.config.MaxBackoff/2 {
-				delay = c.config.MaxBackoff
-			} else {
-				delay *= 2
-			}
-		}
-		if response != nil && response.Header.Get("Retry-After") != "" {
-			if value, ok := retryAfter(response.Header.Get("Retry-After")); ok {
-				delay = value
-			}
-		} else if delay > 1 {
-			delay = delay/2 + time.Duration(rand.Int63n(int64(delay/2)+1))
-		}
-		if delay > c.config.MaxBackoff {
-			retry = false
+		var delay time.Duration
+		if retry {
+			delay, retry = c.retryDelay(attempt, response)
 		}
 		if !retry {
 			if err != nil {
@@ -160,9 +111,7 @@ func (c *Client) Do(request *http.Request) (*http.Response, error) {
 			return response, nil
 		}
 		if response != nil {
-			if response.ContentLength >= 0 && response.ContentLength <= 32<<10 {
-				_, _ = io.Copy(io.Discard, response.Body)
-			}
+			drainSmallBody(response, 32<<10)
 			_ = response.Body.Close()
 		}
 		timer := time.NewTimer(delay)
@@ -204,48 +153,6 @@ type StatusError struct{ StatusCode int }
 
 func (e *StatusError) Error() string { return fmt.Sprintf("httpc: HTTP status %d", e.StatusCode) }
 
-// JSON bounds response memory, closes the body, and decodes only 2xx responses.
-// Error bodies, URLs, credentials and query strings are not included in logs.
-func (c *Client) JSON(ctx context.Context, method, url string, input, output any) error {
-	if ctx == nil {
-		return errors.New("httpc: nil context")
-	}
-	var body io.Reader
-	if input != nil {
-		data, err := json.Marshal(input)
-		if err != nil {
-			return err
-		}
-		body = bytes.NewReader(data)
-	}
-	request, err := http.NewRequestWithContext(ctx, method, url, body)
-	if err != nil {
-		return err
-	}
-	if input != nil {
-		request.Header.Set("Content-Type", "application/json")
-	}
-	response, err := c.Do(request)
-	if err != nil {
-		return err
-	}
-	defer response.Body.Close()
-	if response.StatusCode < 200 || response.StatusCode >= 300 {
-		return &StatusError{StatusCode: response.StatusCode}
-	}
-	data, err := io.ReadAll(io.LimitReader(response.Body, c.config.MaxResponseBytes+1))
-	if err != nil {
-		return err
-	}
-	if int64(len(data)) > c.config.MaxResponseBytes {
-		return ErrResponseTooLarge
-	}
-	if output == nil || len(bytes.TrimSpace(data)) == 0 {
-		return nil
-	}
-	return json.Unmarshal(data, output)
-}
-
 func (c *Client) Close() error {
 	c.closed.Store(true)
 	if c.owned != nil {
@@ -253,3 +160,34 @@ func (c *Client) Close() error {
 	}
 	return nil
 }
+
+// retryDelay is deliberately outside the success path: no jitter/random work
+// for calls that cannot or do not need to retry.
+func (c *Client) retryDelay(attempt int, response *http.Response) (time.Duration, bool) {
+	delay := c.config.Backoff
+	for i := 0; i < attempt && delay < c.config.MaxBackoff; i++ {
+		if delay > c.config.MaxBackoff/2 {
+			delay = c.config.MaxBackoff
+		} else {
+			delay *= 2
+		}
+	}
+	if response != nil {
+		if value, ok := retryAfter(response.Header.Get("Retry-After")); ok {
+			return value, value <= c.config.MaxBackoff
+		}
+	}
+	if delay > 1 {
+		delay = delay/2 + time.Duration(rand.Int63n(int64(delay/2)+1))
+	}
+	return delay, delay <= c.config.MaxBackoff
+}
+
+// Drain only a known small error body. Unknown/large bodies are closed promptly;
+// never allocate or consume an unbounded error document just to retain a pool slot.
+func drainSmallBody(response *http.Response, limit int64) {
+	limit = min(limit, 32<<10)
+	if response.Body != nil && response.ContentLength >= 0 && response.ContentLength <= limit {
+		_, _ = io.Copy(io.Discard, io.LimitReader(response.Body, limit+1))
+	}
+}