Factored throttling client out of aggregator.

util/client.go

@@ -0,0 +1,63 @@
+// This file is Free Software under the MIT License
+// without warranty, see README.md and LICENSES/MIT.txt for details.
+//
+// SPDX-License-Identifier: MIT
+//
+// SPDX-FileCopyrightText: 2022 German Federal Office for Information Security (BSI) <https://www.bsi.bund.de>
+// Software-Engineering: 2022 Intevation GmbH <https://intevation.de>
+
+package util
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/url"
+
+	"golang.org/x/time/rate"
+)
+
+// Client is an interface to abstract http.Client.
+type Client interface {
+	Do(req *http.Request) (*http.Response, error)
+	Get(url string) (*http.Response, error)
+	Head(url string) (*http.Response, error)
+	Post(url, contentType string, body io.Reader) (*http.Response, error)
+	PostForm(url string, data url.Values) (*http.Response, error)
+}
+
+// LimitingClient is a Client implementing rate throttling.
+type LimitingClient struct {
+	Client
+	Limiter *rate.Limiter
+}
+
+// Do implements the respective method of the Client interface.
+func (lc *LimitingClient) Do(req *http.Request) (*http.Response, error) {
+	lc.Limiter.Wait(context.Background())
+	return lc.Client.Do(req)
+}
+
+// Get implements the respective method of the Client interface.
+func (lc *LimitingClient) Get(url string) (*http.Response, error) {
+	lc.Limiter.Wait(context.Background())
+	return lc.Client.Get(url)
+}
+
+// Head implements the respective method of the Client interface.
+func (lc *LimitingClient) Head(url string) (*http.Response, error) {
+	lc.Limiter.Wait(context.Background())
+	return lc.Client.Head(url)
+}
+
+// Post implements the respective method of the Client interface.
+func (lc *LimitingClient) Post(url, contentType string, body io.Reader) (*http.Response, error) {
+	lc.Limiter.Wait(context.Background())
+	return lc.Client.Post(url, contentType, body)
+}
+
+// PostForm implements the respective method of the Client interface.
+func (lc *LimitingClient) PostForm(url string, data url.Values) (*http.Response, error) {
+	lc.Limiter.Wait(context.Background())
+	return lc.Client.PostForm(url, data)
+}