Replace timer with ticker in download progress reporter (#3548) (#3579)

* Replace timer with ticker in download progress reporter

* Adding CHANGELOG entry

* Refactoring: extracting common code into helper function

(cherry picked from commit 1c5010f)

Co-authored-by: Shaunak Kashyap <[email protected]>

changelog/fragments/1696530758-bugfix-upgrade-progress-reporter.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: bug-fix
+
+# Change summary; a 80ish characters long description of the change.
+summary: Periodically report progress of Elastic Agent artifact download during upgrade
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+#description:
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: elastic-agent
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+pr: https://github.com/elastic/elastic-agent/pull/3548
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+#issue: https://github.com/owner/repo/1234

internal/pkg/agent/application/upgrade/artifact/download/http/downloader.go

@@ -35,6 +35,10 @@ const (
 	// the default timeout is 10 minutes and this will have it log every 30 seconds.
 	downloadProgressIntervalPercentage = 0.05
 
+	// downloadProgressDefaultInterval defines the default interval at which the current download progress will be reported.
+	// This value is used if the timeout is not specified (and therefore equal to 0).
+	downloadProgressMinInterval = 10 * time.Second
+
 	// warningProgressIntervalPercentage defines how often to log messages as a warning once the amount of time
 	// passed is this percentage or more of the total allotted time to download.
 	warningProgressIntervalPercentage = 0.75
@@ -223,7 +227,6 @@ func (e *Downloader) downloadFile(ctx context.Context, artifactName, filename, f
 type downloadProgressReporter struct {
 	log         progressLogger
 	sourceURI   string
-	timeout     time.Duration
 	interval    time.Duration
 	warnTimeout time.Duration
 	length      float64
@@ -233,11 +236,15 @@ type downloadProgressReporter struct {
 }
 
 func newDownloadProgressReporter(log progressLogger, sourceURI string, timeout time.Duration, length int) *downloadProgressReporter {
+	interval := time.Duration(float64(timeout) * downloadProgressIntervalPercentage)
+	if interval == 0 {
+		interval = downloadProgressMinInterval
+	}
+
 	return &downloadProgressReporter{
 		log:         log,
 		sourceURI:   sourceURI,
-		timeout:     timeout,
-		interval:    time.Duration(float64(timeout) * downloadProgressIntervalPercentage),
+		interval:    interval,
 		warnTimeout: time.Duration(float64(timeout) * warningProgressIntervalPercentage),
 		length:      float64(length),
 	}
@@ -259,7 +266,7 @@ func (dp *downloadProgressReporter) Report(ctx context.Context) {
 	interval := dp.interval
 
 	go func() {
-		t := time.NewTimer(interval)
+		t := time.NewTicker(interval)
 		defer t.Stop()
 		for {
 			select {

internal/pkg/agent/application/upgrade/artifact/download/http/downloader_test.go

@@ -75,11 +75,11 @@ func TestDownloadBodyError(t *testing.T) {
 }
 
 func TestDownloadLogProgressWithLength(t *testing.T) {
-	fileSize := 100 * units.MiB
+	fileSize := 100 * units.MB
 	chunks := 100
 	chunk := make([]byte, fileSize/chunks)
 	delayBetweenChunks := 10 * time.Millisecond
-	totalTime := time.Duration(chunks) * (delayBetweenChunks + 1*time.Millisecond)
+	totalTime := time.Duration(chunks) * delayBetweenChunks
 
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Length", strconv.Itoa(fileSize))
@@ -120,24 +120,32 @@ func TestDownloadLogProgressWithLength(t *testing.T) {
 	log.lock.RLock()
 	defer log.lock.RUnlock()
 
-	// 2 files are downloaded so 4 log messages are expected in the info level and only the complete is over the warn
-	// window as 2 log messages for warn.
-	require.Len(t, log.info, 4)
-	assert.Equal(t, log.info[0].record, "download progress from %s is %s/%s (%.2f%% complete) @ %sps")
-	assert.Equal(t, log.info[1].record, "download from %s completed in %s @ %sps")
-	assert.Equal(t, log.info[2].record, "download progress from %s is %s/%s (%.2f%% complete) @ %sps")
-	assert.Equal(t, log.info[3].record, "download from %s completed in %s @ %sps")
-	require.Len(t, log.warn, 2)
-	assert.Equal(t, log.warn[0].record, "download from %s completed in %s @ %sps")
-	assert.Equal(t, log.warn[1].record, "download from %s completed in %s @ %sps")
+	expectedProgressMsg := "download progress from %s is %s/%s (%.2f%% complete) @ %sps"
+
+	// Two files are downloaded. Each file is being downloaded in 100 chunks with a delay of 10ms between chunks. The
+	// expected time to download is, therefore, 100 * 10ms = 1000ms. In reality, the actual download time will be a bit
+	// more than 1000ms because some time is spent downloading the chunk, in between inter-chunk delays.
+	// Reporting happens every 0.05 * 1000ms = 50ms. We expect there to be as many log messages at that INFO level as
+	// the actual total download time / 50ms, for each file. That works out to at least 1000ms / 50ms = 20 INFO log
+	// messages, for each file, about its download progress. Additionally, we should expect 1 INFO log message, for
+	// each file, about the download completing.
+	assertLogs(t, log.info, 20, expectedProgressMsg)
+
+	// By similar math as above, since the download of each file is expected to take 1000ms, and the progress logger
+	// starts issuing WARN messages once the download has taken more than 75% of the expected time,
+	// we should see warning messages for at least the last 250 seconds of the download. Given that
+	// reporting happens every 50 seconds, we should see at least 250s / 50s = 5 WARN log messages, for each file,
+	// about its download progress. Additionally, we should expect 1 WARN message, for each file, about the download
+	// completing.
+	assertLogs(t, log.warn, 5, expectedProgressMsg)
 }
 
 func TestDownloadLogProgressWithoutLength(t *testing.T) {
 	fileSize := 100 * units.MiB
 	chunks := 100
 	chunk := make([]byte, fileSize/chunks)
 	delayBetweenChunks := 10 * time.Millisecond
-	totalTime := time.Duration(chunks) * (delayBetweenChunks + 1*time.Millisecond)
+	totalTime := time.Duration(chunks) * delayBetweenChunks
 
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
@@ -177,16 +185,24 @@ func TestDownloadLogProgressWithoutLength(t *testing.T) {
 	log.lock.RLock()
 	defer log.lock.RUnlock()
 
-	// 2 files are downloaded so 4 log messages are expected in the info level and only the complete is over the warn
-	// window as 2 log messages for warn.
-	require.Len(t, log.info, 4)
-	assert.Equal(t, log.info[0].record, "download progress from %s has fetched %s @ %sps")
-	assert.Equal(t, log.info[1].record, "download from %s completed in %s @ %sps")
-	assert.Equal(t, log.info[2].record, "download progress from %s has fetched %s @ %sps")
-	assert.Equal(t, log.info[3].record, "download from %s completed in %s @ %sps")
-	require.Len(t, log.warn, 2)
-	assert.Equal(t, log.warn[0].record, "download from %s completed in %s @ %sps")
-	assert.Equal(t, log.warn[1].record, "download from %s completed in %s @ %sps")
+	expectedProgressMsg := "download progress from %s has fetched %s @ %sps"
+
+	// Two files are downloaded. Each file is being downloaded in 100 chunks with a delay of 10ms between chunks. The
+	// expected time to download is, therefore, 100 * 10ms = 1000ms. In reality, the actual download time will be a bit
+	// more than 1000ms because some time is spent downloading the chunk, in between inter-chunk delays.
+	// Reporting happens every 0.05 * 1000ms = 50ms. We expect there to be as many log messages at that INFO level as
+	// the actual total download time / 50ms, for each file. That works out to at least 1000ms / 50ms = 20 INFO log
+	// messages, for each file, about its download progress. Additionally, we should expect 1 INFO log message, for
+	// each file, about the download completing.
+	assertLogs(t, log.info, 20, expectedProgressMsg)
+
+	// By similar math as above, since the download of each file is expected to take 1000ms, and the progress logger
+	// starts issuing WARN messages once the download has taken more than 75% of the expected time,
+	// we should see warning messages for at least the last 250 seconds of the download. Given that
+	// reporting happens every 50 seconds, we should see at least 250s / 50s = 5 WARN log messages, for each file,
+	// about its download progress. Additionally, we should expect 1 WARN message, for each file, about the download
+	// completing.
+	assertLogs(t, log.warn, 5, expectedProgressMsg)
 }
 
 type logMessage struct {
@@ -227,3 +243,31 @@ func containsMessage(logs []logMessage, msg string) bool {
 	}
 	return false
 }
+func assertLogs(t *testing.T, logs []logMessage, minExpectedProgressLogs int, expectedProgressMsg string) {
+	t.Helper()
+
+	// Verify that we've logged at least minExpectedProgressLogs (about download progress) + 1 log
+	// message (about download completion), for each of the two files being downloaded.
+	require.GreaterOrEqual(t, len(logs), (minExpectedProgressLogs+1)*2)
+
+	// Verify that the first minExpectedProgressLogs messages are about the download progress (for the first file).
+	i := 0
+	for ; i < minExpectedProgressLogs; i++ {
+		assert.Equal(t, logs[i].record, expectedProgressMsg)
+	}
+
+	// Find the next message that's about the download being completed (for the first file).
+	found := false
+	for ; i < len(logs) && !found; i++ {
+		found = logs[i].record == "download from %s completed in %s @ %sps"
+	}
+	assert.True(t, found)
+
+	// Verify that the next minExpectedProgressLogs messages are about the download progress (for the second file).
+	for j := 0; j < minExpectedProgressLogs; j++ {
+		assert.Equal(t, logs[i+j].record, expectedProgressMsg)
+	}
+
+	// Verify that the last message is about the download being completed (for the second file).
+	assert.Equal(t, logs[len(logs)-1].record, "download from %s completed in %s @ %sps")
+}