[BUG] do not output error message for connections closed due to timeo…

…ut (#241)

* do not output error log for connection closed

transport/logging.go

@@ -47,7 +47,7 @@ func LoggingDialer(d Dialer, logger *logp.Logger) Dialer {
 
 func (l *loggingConn) Read(b []byte) (int, error) {
 	n, err := l.Conn.Read(b)
-	if err != nil && !errors.Is(err, io.EOF) {
+	if err != nil && !errors.Is(err, io.EOF) && !errors.Is(err, net.ErrClosed) {
 		l.logger.Debugf("Error reading from connection: %v", err)
 	}
 	return n, err

transport/logging_test.go

@@ -0,0 +1,76 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package transport
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/elastic/elastic-agent-libs/logp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCloseConnectionError(t *testing.T) {
+	// observe all logs
+	if err := logp.DevelopmentSetup(logp.ToObserverOutput()); err != nil {
+		t.Fatalf("cannot initialise logger on development mode: %+v", err)
+	}
+
+	// Set up a test HTTP server
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, `{"status": "ok"}`)
+	}))
+	defer server.Close()
+
+	logger := logp.NewLogger("test")
+	// Set IdleConnTimeout to 2 seconds and a custom dialer
+	transport := &http.Transport{
+		IdleConnTimeout: 2 * time.Second,
+		// uses our implementation of custom dialer
+		DialContext: LoggingDialer(NetDialer(10*time.Second), logger).DialContext,
+	}
+
+	client := &http.Client{
+		Transport: transport,
+	}
+
+	// First request to the test server
+	resp, err := client.Get(server.URL) //nolint:noctx // It is a test
+	require.NoError(t, err, "first request failed")
+	_, _ = io.ReadAll(resp.Body)
+	resp.Body.Close()
+
+	// Wait for a duration longer than IdleConnTimeout
+	waitTime := 6 * time.Second
+	time.Sleep(waitTime)
+
+	// Second request to the test server after idle timeout
+	resp, err = client.Get(server.URL) //nolint:noctx // It is a test
+	require.NoError(t, err, "second request failed")
+	_, _ = io.ReadAll(resp.Body)
+	resp.Body.Close()
+
+	logs := logp.ObserverLogs().FilterMessageSnippet("Error reading from connection:").TakeAll()
+	assert.Equal(t, 0, len(logs), "did not ignore use of closed connection error")
+
+}