Add retry module and change rate to requests per minute (#37)v0.7.0

2 files changed, 286 insertions, 0 deletions

diff --git a/modules/retry/retry.go b/modules/retry/retry.go
new file mode 100644
index 0000000..9c00275
--- /dev/null
+++ b/modules/retry/retry.go
@@ -0,0 +1,145 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package retry
+
+import (
+	"errors"
+	"io"
+	"net"
+	"net/http"
+	"slices"
+	"strconv"
+	"time"
+
+	"github.com/philippta/flyscrape"
+)
+
+func init() {
+	flyscrape.RegisterModule(Module{})
+}
+
+type Module struct {
+	ticker    *time.Ticker
+	semaphore chan struct{}
+
+	RetryDelays []time.Duration
+}
+
+func (Module) ModuleInfo() flyscrape.ModuleInfo {
+	return flyscrape.ModuleInfo{
+		ID:  "retry",
+		New: func() flyscrape.Module { return new(Module) },
+	}
+}
+
+func (m *Module) Provision(flyscrape.Context) {
+	if m.RetryDelays == nil {
+		m.RetryDelays = defaultRetryDelays
+	}
+}
+
+func (m *Module) AdaptTransport(t http.RoundTripper) http.RoundTripper {
+	return flyscrape.RoundTripFunc(func(r *http.Request) (*http.Response, error) {
+		resp, err := t.RoundTrip(r)
+		if !shouldRetry(resp, err) {
+			return resp, err
+		}
+
+		for _, delay := range m.RetryDelays {
+			drainBody(resp, err)
+
+			time.Sleep(retryAfter(resp, delay))
+
+			resp, err = t.RoundTrip(r)
+			if !shouldRetry(resp, err) {
+				break
+			}
+		}
+
+		return resp, err
+	})
+}
+
+func shouldRetry(resp *http.Response, err error) bool {
+	statusCodes := []int{
+		http.StatusRequestTimeout,
+		http.StatusTooEarly,
+		http.StatusTooManyRequests,
+		http.StatusInternalServerError,
+		http.StatusBadGateway,
+		http.StatusServiceUnavailable,
+		http.StatusGatewayTimeout,
+	}
+
+	if resp != nil {
+		if slices.Contains(statusCodes, resp.StatusCode) {
+			return true
+		}
+	}
+	if err == nil {
+		return false
+	}
+	if _, ok := err.(net.Error); ok {
+		return true
+	}
+	if errors.Is(err, io.ErrUnexpectedEOF) {
+		return true
+	}
+
+	return false
+}
+
+func drainBody(resp *http.Response, err error) {
+	if err == nil && resp != nil && resp.Body != nil {
+		io.Copy(io.Discard, resp.Body)
+		resp.Body.Close()
+	}
+}
+
+func retryAfter(resp *http.Response, fallback time.Duration) time.Duration {
+	if resp == nil {
+		return fallback
+	}
+
+	timeexp := resp.Header.Get("Retry-After")
+	if timeexp == "" {
+		return fallback
+	}
+
+	if seconds, err := strconv.Atoi(timeexp); err == nil {
+		return time.Duration(seconds) * time.Second
+	}
+
+	formats := []string{
+		time.RFC1123, // HTTP Spec
+		time.RFC1123Z,
+		time.ANSIC,
+		time.UnixDate,
+		time.RubyDate,
+		time.RFC822,
+		time.RFC822Z,
+		time.RFC850,
+		time.RFC3339,
+	}
+	for _, format := range formats {
+		if t, err := time.Parse(format, timeexp); err == nil {
+			return t.Sub(time.Now())
+		}
+	}
+
+	return fallback
+}
+
+var defaultRetryDelays = []time.Duration{
+	1 * time.Second,
+	2 * time.Second,
+	5 * time.Second,
+	10 * time.Second,
+}
+
+var (
+	_ flyscrape.TransportAdapter = (*Module)(nil)
+	_ flyscrape.Provisioner      = (*Module)(nil)
+)
diff --git a/modules/retry/retry_test.go b/modules/retry/retry_test.go
new file mode 100644
index 0000000..b979320
--- /dev/null
+++ b/modules/retry/retry_test.go
@@ -0,0 +1,141 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package retry_test
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/philippta/flyscrape"
+	"github.com/philippta/flyscrape/modules/followlinks"
+	"github.com/philippta/flyscrape/modules/hook"
+	"github.com/philippta/flyscrape/modules/retry"
+	"github.com/philippta/flyscrape/modules/starturl"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRetry(t *testing.T) {
+	t.Parallel()
+	var count int
+
+	mods := []flyscrape.Module{
+		&starturl.Module{URL: "http://www.example.com"},
+		&followlinks.Module{},
+		hook.Module{
+			AdaptTransportFn: func(rt http.RoundTripper) http.RoundTripper {
+				return flyscrape.RoundTripFunc(func(r *http.Request) (*http.Response, error) {
+					count++
+					return flyscrape.MockResponse(http.StatusServiceUnavailable, "service unavailable")
+				})
+			},
+		},
+		&retry.Module{
+			RetryDelays: []time.Duration{
+				100 * time.Millisecond,
+				200 * time.Millisecond,
+			},
+		},
+	}
+
+	scraper := flyscrape.NewScraper()
+	scraper.Modules = mods
+	scraper.Run()
+
+	require.Equal(t, 3, count)
+}
+
+func TestRetryStatusCodes(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		statusCode int
+		retry      bool
+	}{
+		{statusCode: http.StatusBadGateway, retry: true},
+		{statusCode: http.StatusTooManyRequests, retry: true},
+		{statusCode: http.StatusBadRequest, retry: false},
+		{statusCode: http.StatusOK, retry: false},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("%s_%t", http.StatusText(test.statusCode), test.retry), func(t *testing.T) {
+			t.Parallel()
+			var count int
+			mods := []flyscrape.Module{
+				&starturl.Module{URL: "http://www.example.com"},
+				&followlinks.Module{},
+				hook.Module{
+					AdaptTransportFn: func(rt http.RoundTripper) http.RoundTripper {
+						return flyscrape.RoundTripFunc(func(r *http.Request) (*http.Response, error) {
+							count++
+							return flyscrape.MockResponse(test.statusCode, http.StatusText(test.statusCode))
+						})
+					},
+				},
+				&retry.Module{
+					RetryDelays: []time.Duration{
+						100 * time.Millisecond,
+						200 * time.Millisecond,
+					},
+				},
+			}
+
+			scraper := flyscrape.NewScraper()
+			scraper.Modules = mods
+			scraper.Run()
+
+			if test.retry {
+				require.NotEqual(t, 1, count)
+			} else {
+				require.Equal(t, 1, count)
+			}
+		})
+	}
+}
+
+func TestRetryErrors(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		error error
+	}{
+		{error: &net.OpError{}},
+		{error: io.ErrUnexpectedEOF},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("%T", test.error), func(t *testing.T) {
+			t.Parallel()
+			var count int
+			mods := []flyscrape.Module{
+				&starturl.Module{URL: "http://www.example.com"},
+				&followlinks.Module{},
+				hook.Module{
+					AdaptTransportFn: func(rt http.RoundTripper) http.RoundTripper {
+						return flyscrape.RoundTripFunc(func(r *http.Request) (*http.Response, error) {
+							return nil, test.error
+						})
+					},
+				},
+				&retry.Module{
+					RetryDelays: []time.Duration{
+						100 * time.Millisecond,
+						200 * time.Millisecond,
+					},
+				},
+			}
+
+			scraper := flyscrape.NewScraper()
+			scraper.Modules = mods
+			scraper.Run()
+
+			require.NotEqual(t, 1, count)
+		})
+	}
+}