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

4 files changed, 366 insertions, 30 deletions

diff --git a/modules/ratelimit/ratelimit.go b/modules/ratelimit/ratelimit.go
index b23cd7a..152c6fd 100644
--- a/modules/ratelimit/ratelimit.go
+++ b/modules/ratelimit/ratelimit.go
@@ -5,6 +5,7 @@
 package ratelimit
 
 import (
+	"math"
 	"net/http"
 	"time"
 
@@ -16,10 +17,12 @@ func init() {
 }
 
 type Module struct {
-	Rate float64 `json:"rate"`
+	Rate        int `json:"rate"`
+	Concurrency int `json:"concurrency"`
 
-	ticker    *time.Ticker
-	semaphore chan struct{}
+	ticker      *time.Ticker
+	ratelimit   chan struct{}
+	concurrency chan struct{}
 }
 
 func (Module) ModuleInfo() flyscrape.ModuleInfo {
@@ -30,41 +33,54 @@ func (Module) ModuleInfo() flyscrape.ModuleInfo {
 }
 
 func (m *Module) Provision(v flyscrape.Context) {
-	if m.disabled() {
-		return
-	}
-
-	rate := time.Duration(float64(time.Second) / m.Rate)
+	if m.rateLimitEnabled() {
+		rate := time.Duration(float64(time.Minute) / float64(m.Rate))
+		m.ticker = time.NewTicker(rate)
+		m.ratelimit = make(chan struct{}, int(math.Max(float64(m.Rate)/10, 1)))
 
-	m.ticker = time.NewTicker(rate)
-	m.semaphore = make(chan struct{}, 1)
+		go func() {
+			m.ratelimit <- struct{}{}
+			for range m.ticker.C {
+				m.ratelimit <- struct{}{}
+			}
+		}()
+	}
 
-	go func() {
-		for range m.ticker.C {
-			m.semaphore <- struct{}{}
+	if m.concurrencyEnabled() {
+		m.concurrency = make(chan struct{}, m.Concurrency)
+		for i := 0; i < m.Concurrency; i++ {
+			m.concurrency <- struct{}{}
 		}
-	}()
+	}
 }
 
 func (m *Module) AdaptTransport(t http.RoundTripper) http.RoundTripper {
-	if m.disabled() {
-		return t
-	}
 	return flyscrape.RoundTripFunc(func(r *http.Request) (*http.Response, error) {
-		<-m.semaphore
+		if m.rateLimitEnabled() {
+			<-m.ratelimit
+		}
+
+		if m.concurrencyEnabled() {
+			<-m.concurrency
+			defer func() { m.concurrency <- struct{}{} }()
+		}
+
 		return t.RoundTrip(r)
 	})
 }
 
 func (m *Module) Finalize() {
-	if m.disabled() {
-		return
+	if m.rateLimitEnabled() {
+		m.ticker.Stop()
 	}
-	m.ticker.Stop()
 }
 
-func (m *Module) disabled() bool {
-	return m.Rate == 0
+func (m *Module) rateLimitEnabled() bool {
+	return m.Rate != 0
+}
+
+func (m *Module) concurrencyEnabled() bool {
+	return m.Concurrency > 0
 }
 
 var (
diff --git a/modules/ratelimit/ratelimit_test.go b/modules/ratelimit/ratelimit_test.go
index 7be29a1..23cc8c8 100644
--- a/modules/ratelimit/ratelimit_test.go
+++ b/modules/ratelimit/ratelimit_test.go
@@ -32,7 +32,7 @@ func TestRatelimit(t *testing.T) {
 			},
 		},
 		&ratelimit.Module{
-			Rate: 100,
+			Rate: 240,
 		},
 	}
 
@@ -41,12 +41,46 @@ func TestRatelimit(t *testing.T) {
 	scraper.Modules = mods
 	scraper.Run()
 
-	first := times[0].Add(-10 * time.Millisecond)
-	second := times[1].Add(-20 * time.Millisecond)
+	first := times[0].Add(-250 * time.Millisecond)
+	second := times[1].Add(-500 * time.Millisecond)
 
-	require.Less(t, first.Sub(start), 2*time.Millisecond)
-	require.Less(t, second.Sub(start), 2*time.Millisecond)
+	require.Less(t, first.Sub(start), 250*time.Millisecond)
+	require.Less(t, second.Sub(start), 250*time.Millisecond)
 
-	require.Less(t, start.Sub(first), 2*time.Millisecond)
-	require.Less(t, start.Sub(second), 2*time.Millisecond)
+	require.Less(t, start.Sub(first), 250*time.Millisecond)
+	require.Less(t, start.Sub(second), 250*time.Millisecond)
+}
+
+func TestRatelimitConcurrency(t *testing.T) {
+	var times []time.Time
+
+	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) {
+					times = append(times, time.Now())
+					time.Sleep(10 * time.Millisecond)
+					return flyscrape.MockResponse(200, `
+						<a href="foo"></a>
+						<a href="bar"></a>
+						<a href="baz"></a>
+						<a href="qux"></a>
+					`)
+				})
+			},
+		},
+		&ratelimit.Module{
+			Concurrency: 2,
+		},
+	}
+
+	scraper := flyscrape.NewScraper()
+	scraper.Modules = mods
+	scraper.Run()
+
+	require.Len(t, times, 5)
+	require.Less(t, times[2].Sub(times[1]), time.Millisecond)
+	require.Less(t, times[4].Sub(times[3]), time.Millisecond)
 }
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)
+		})
+	}
+}