Add HTTP(S) Proxy support

2 files changed, 123 insertions, 0 deletions

diff --git a/modules/proxy/proxy.go b/modules/proxy/proxy.go
new file mode 100644
index 0000000..120a856
--- /dev/null
+++ b/modules/proxy/proxy.go
@@ -0,0 +1,61 @@
+// 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 proxy
+
+import (
+	"crypto/tls"
+	"math/rand"
+	"net/http"
+	"net/url"
+
+	"github.com/philippta/flyscrape"
+)
+
+func init() {
+	flyscrape.RegisterModule(Module{})
+}
+
+type Module struct {
+	Proxies []string `json:"proxies"`
+
+	transports []*http.Transport
+}
+
+func (Module) ModuleInfo() flyscrape.ModuleInfo {
+	return flyscrape.ModuleInfo{
+		ID:  "proxy",
+		New: func() flyscrape.Module { return new(Module) },
+	}
+}
+
+func (m *Module) Provision(ctx flyscrape.Context) {
+	if m.disabled() {
+		return
+	}
+
+	for _, purl := range m.Proxies {
+		if parsed, err := url.Parse(purl); err == nil {
+			m.transports = append(m.transports, &http.Transport{
+				Proxy:           http.ProxyURL(parsed),
+				TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+			})
+		}
+	}
+}
+
+func (m *Module) AdaptTransport(t http.RoundTripper) http.RoundTripper {
+	if m.disabled() {
+		return t
+	}
+
+	return flyscrape.RoundTripFunc(func(r *http.Request) (*http.Response, error) {
+		transport := m.transports[rand.Intn(len(m.transports))]
+		return transport.RoundTrip(r)
+	})
+}
+
+func (m *Module) disabled() bool {
+	return len(m.Proxies) == 0
+}
diff --git a/modules/proxy/proxy_test.go b/modules/proxy/proxy_test.go
new file mode 100644
index 0000000..e6058b8
--- /dev/null
+++ b/modules/proxy/proxy_test.go
@@ -0,0 +1,62 @@
+// 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 proxy_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/philippta/flyscrape"
+	"github.com/philippta/flyscrape/modules/proxy"
+	"github.com/philippta/flyscrape/modules/starturl"
+	"github.com/stretchr/testify/require"
+)
+
+func TestProxy(t *testing.T) {
+	var called bool
+	p := newProxy(func() { called = true })
+	defer p.Close()
+
+	scraper := flyscrape.NewScraper()
+	scraper.LoadModule(&starturl.Module{URL: "http://www.example.com"})
+	scraper.LoadModule(&proxy.Module{
+		Proxies: []string{p.URL},
+	})
+
+	scraper.Run()
+	require.True(t, called)
+}
+
+func TestProxyMultiple(t *testing.T) {
+	calls := []int{0, 0}
+	p0 := newProxy(func() { calls[0]++ })
+	p1 := newProxy(func() { calls[1]++ })
+	defer p0.Close()
+	defer p1.Close()
+
+	mod := &proxy.Module{Proxies: []string{p0.URL, p1.URL}}
+	mod.Provision(nil)
+	trans := mod.AdaptTransport(nil)
+
+	req := httptest.NewRequest("GET", "http://www.example.com/", nil)
+
+	for i := 0; i < 10; i++ {
+		resp, err := trans.RoundTrip(req)
+		require.NoError(t, err)
+		require.Equal(t, http.StatusOK, resp.StatusCode)
+	}
+
+	require.Greater(t, calls[0], 1)
+	require.Greater(t, calls[1], 1)
+	require.Equal(t, 10, calls[0]+calls[1])
+}
+
+func newProxy(f func()) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		f()
+		w.Write([]byte("response from proxy"))
+	}))
+}