[bugfix] add Promtail cloudflare close (grafana#7394)

**What this PR does / why we need it**:
If the http server closes the connection, the client may also return a
non-empty reader io.ReadCloser.

**Which issue(s) this PR fixes**:
Fixes grafana#6150

Co-authored-by: Christian Haudum <christian.haudum@gmail.com>

CHANGELOG.md

@@ -98,6 +98,7 @@ Check the history of the branch FIXME.
 * [7414](https://github.com/grafana/loki/pull/7414) **thepalbi**: Add basic tracing support
 
 ##### Fixes
+* [7394](https://github.com/grafana/loki/pull/7394) **liguozhong**: Fix issue with the Cloudflare target that caused it to stop working after it received an error in the logpull request as explained in issue https://github.com/grafana/loki/issues/6150
 * [6766](https://github.com/grafana/loki/pull/6766) **kavirajk**: fix(logql): Make `LabelSampleExtractor` ignore processing the line if it doesn't contain that specific label. Fixes unwrap behavior explained in the issue https://github.com/grafana/loki/issues/6713
 * [7016](https://github.com/grafana/loki/pull/7016) **chodges15**: Fix issue with dropping logs when a file based SD target's labels are updated
 * [7461](https://github.com/grafana/loki/pull/7461) **MarNicGit**: Promtail: Fix collecting userdata field from Windows Event Log

clients/pkg/promtail/targets/cloudflare/target.go

@@ -158,6 +158,9 @@ func (t *Target) pull(ctx context.Context, start, end time.Time) error {
 			level.Warn(t.logger).Log("msg", "failed iterating over logs, out of cloudflare range, not retrying", "err", err, "start", start, "end", end, "retries", backoff.NumRetries())
 			return nil
 		} else if err != nil {
+			if it != nil {
+				it.Close()
+			}
 			errs.Add(err)
 			backoff.Wait()
 			continue

clients/pkg/promtail/targets/cloudflare/target_test.go

@@ -101,6 +101,37 @@ func Test_CloudflareTarget(t *testing.T) {
 	require.Greater(t, newPos, end.UnixNano())
 }
 
+func Test_RetryErrorLogpullReceived(t *testing.T) {
+	var (
+		w        = log.NewSyncWriter(os.Stderr)
+		logger   = log.NewLogfmtLogger(w)
+		end      = time.Unix(0, time.Hour.Nanoseconds())
+		start    = time.Unix(0, end.Add(-30*time.Minute).UnixNano())
+		client   = fake.New(func() {})
+		cfClient = newFakeCloudflareClient()
+	)
+	cfClient.On("LogpullReceived", mock.Anything, start, end).Return(&fakeLogIterator{
+		err: ErrorLogpullReceived,
+	}, nil).Times(2) // just retry once
+	// replace the client
+	getClient = func(apiKey, zoneID string, fields []string) (Client, error) {
+		return cfClient, nil
+	}
+	defaultBackoff.MinBackoff = 0
+	defaultBackoff.MaxBackoff = 5
+	ta := &Target{
+		logger:  logger,
+		handler: client,
+		client:  cfClient,
+		config: &scrapeconfig.CloudflareConfig{
+			Labels: make(model.LabelSet),
+		},
+		metrics: NewMetrics(nil),
+	}
+
+	require.NoError(t, ta.pull(context.Background(), start, end))
+}
+
 func Test_RetryErrorIterating(t *testing.T) {
 	var (
 		w        = log.NewSyncWriter(os.Stderr)
@@ -124,6 +155,9 @@ func Test_RetryErrorIterating(t *testing.T) {
 			`{"EdgeStartTimestamp":3, "EdgeRequestHost":"foo.com"}`,
 		},
 	}, nil).Once()
+	cfClient.On("LogpullReceived", mock.Anything, start, end).Return(&fakeLogIterator{
+		err: ErrorLogpullReceived,
+	}, nil).Once()
 	// replace the client.
 	getClient = func(apiKey, zoneID string, fields []string) (Client, error) {
 		return cfClient, nil

clients/pkg/promtail/targets/cloudflare/util_test.go

@@ -9,6 +9,8 @@ import (
 	"github.com/stretchr/testify/mock"
 )
 
+var ErrorLogpullReceived = errors.New("error logpull received")
+
 type fakeCloudflareClient struct {
 	mock.Mock
 }
@@ -45,7 +47,12 @@ func (f *fakeLogIterator) Next() bool {
 func (f *fakeLogIterator) Err() error                         { return f.err }
 func (f *fakeLogIterator) Line() []byte                       { return []byte(f.current) }
 func (f *fakeLogIterator) Fields() (map[string]string, error) { return nil, nil }
-func (f *fakeLogIterator) Close() error                       { return nil }
+func (f *fakeLogIterator) Close() error {
+	if f.err == ErrorLogpullReceived {
+		f.err = nil
+	}
+	return nil
+}
 
 func newFakeCloudflareClient() *fakeCloudflareClient {
 	return &fakeCloudflareClient{}
@@ -54,7 +61,11 @@ func newFakeCloudflareClient() *fakeCloudflareClient {
 func (f *fakeCloudflareClient) LogpullReceived(ctx context.Context, start, end time.Time) (cloudflare.LogpullReceivedIterator, error) {
 	r := f.Called(ctx, start, end)
 	if r.Get(0) != nil {
-		return r.Get(0).(cloudflare.LogpullReceivedIterator), nil
+		it := r.Get(0).(cloudflare.LogpullReceivedIterator)
+		if it.Err() == ErrorLogpullReceived {
+			return it, it.Err()
+		}
+		return it, nil
 	}
 	return nil, r.Error(1)
 }