logtail: remove LowMemory mode

LowMemory shrank the pending ring buffer, upload batch size, and text
truncation limit for iOS, back when network extensions were limited to
15 MB. All supported iOS versions now allow 50 MB, so the savings are
negligible and the extra code paths are not worth maintaining.

Fixes #13685

Change-Id: Ic0c26f899ce00f105399c7b1e687e2b92194687e
Co-authored-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Signed-off-by: Andrea Gottardo <andrea@gottardo.me>

logtail/config.go

@@ -32,7 +32,6 @@ type Config struct {
 	BaseURL        string          // if empty defaults to "https://log.tailscale.com"
 	HTTPC          *http.Client    // if empty defaults to http.DefaultClient
 	SkipClientTime bool            // if true, client_time is not written to logs
-	LowMemory      bool            // if true, logtail minimizes memory use
 	Clock          tstime.Clock    // if set, Clock.Now substitutes uses of time.Now
 	Stderr         io.Writer       // if set, logs are sent here instead of os.Stderr
 	Bus            *eventbus.Bus   // if set, uses the eventbus for awaitInternetUp instead of callback

logtail/logtail.go

@@ -51,9 +51,6 @@ const maxSize = 256 << 10
 // Note that JSON log messages can be as large as maxSize.
 const maxTextSize = 16 << 10
 
-// lowMemRatio reduces maxSize and maxTextSize by this ratio in lowMem mode.
-const lowMemRatio = 4
-
 // bufferSize is the typical buffer size to retain.
 // It is large enough to handle most log messages,
 // but not too large to be a notable waste of memory if retained forever.
@@ -76,11 +73,7 @@ func newLogger(cfg Config) *Logger {
 		cfg.Stderr = os.Stderr
 	}
 	if cfg.Buffer == nil {
-		pendingSize := 256
-		if cfg.LowMemory {
-			pendingSize = 64
-		}
-		cfg.Buffer = NewMemoryBuffer(pendingSize)
+		cfg.Buffer = NewMemoryBuffer(256)
 	}
 	var procID uint32
 	if cfg.IncludeProcID {
@@ -113,7 +106,6 @@ func newLogger(cfg Config) *Logger {
 		stderrLevel:    int64(cfg.StderrLevel),
 		httpc:          cfg.HTTPC,
 		url:            cfg.BaseURL + "/c/" + cfg.Collection + "/" + cfg.PrivateID.String() + urlSuffix,
-		lowMem:         cfg.LowMemory,
 		buffer:         cfg.Buffer,
 		maxUploadSize:  cfg.MaxUploadSize,
 		skipClientTime: cfg.SkipClientTime,
@@ -217,9 +209,6 @@ func UploadLogs[T any](ctx context.Context, conf Config, entries iter.Seq[LogEnt
 	lg := newLogger(conf)
 
 	maxLen := cmp.Or(lg.maxUploadSize, maxSize)
-	if lg.lowMem {
-		maxLen /= lowMemRatio
-	}
 
 	// body accumulates a JSON array of encoded entries: "[e1,e2,...]".
 	// The framing mirrors Logger.drainPending.
@@ -302,7 +291,6 @@ type Logger struct {
 	stderrLevel    int64 // accessed atomically
 	httpc          *http.Client
 	url            string
-	lowMem         bool
 	skipClientTime bool
 	netMonitor     *netmon.Monitor
 	buffer         Buffer
@@ -457,13 +445,6 @@ func (lg *Logger) drainPending() (b []byte) {
 	}()
 
 	maxLen := cmp.Or(lg.maxUploadSize, maxSize)
-	if lg.lowMem {
-		// When operating in a low memory environment, it is better to upload
-		// in multiple operations than it is to allocate a large body and OOM.
-		// Even if maxLen is less than maxSize, we can still upload an entry
-		// that is up to maxSize if we happen to encounter one.
-		maxLen /= lowMemRatio
-	}
 	for len(b) < maxLen {
 		line, err := lg.buffer.TryReadLine()
 		switch {
@@ -882,12 +863,8 @@ func (lg *Logger) appendText(dst, src []byte, skipClientTime bool, procID uint32
 
 	// Append the text string, which may be truncated.
 	// Invalid UTF-8 will be mangled with the Unicode replacement character.
-	max := maxTextSize
-	if lg.lowMem {
-		max /= lowMemRatio
-	}
 	dst = append(dst, `"text":`...)
-	dst = appendTruncatedString(dst, src, max)
+	dst = appendTruncatedString(dst, src, maxTextSize)
 	return append(dst, "}\n"...)
 }
 

logtail/logtail_test.go

@@ -759,7 +759,6 @@ func TestAppendText(t *testing.T) {
 	var lg Logger
 	lg.clock = tstest.NewClock(tstest.ClockOpts{Start: time.Date(2000, 01, 01, 0, 0, 0, 0, time.UTC)})
 	lg.metricsDelta = func() string { return "metrics" }
-	lg.lowMem = true
 
 	for _, tt := range []struct {
 		text           string
@@ -774,7 +773,7 @@ func TestAppendText(t *testing.T) {
 		{skipClientTime: true, procID: 1, procSeq: 2, want: `{"logtail":{"proc_id":1,"proc_seq":2},"metrics":"metrics"}`},
 		{text: "fizz buzz", want: `{"logtail":{"client_time":"2000-01-01T00:00:00Z"},"metrics":"metrics","text":"fizz buzz"}`},
 		{text: "\b\f\n\r\t\"\\", want: `{"logtail":{"client_time":"2000-01-01T00:00:00Z"},"metrics":"metrics","text":"\b\f\n\r\t\"\\"}`},
-		{text: "x" + strings.Repeat("😐", maxSize), want: `{"logtail":{"client_time":"2000-01-01T00:00:00Z"},"metrics":"metrics","text":"x` + strings.Repeat("😐", 1023) + `…+1044484"}`},
+		{text: "x" + strings.Repeat("😐", maxSize), want: `{"logtail":{"client_time":"2000-01-01T00:00:00Z"},"metrics":"metrics","text":"x` + strings.Repeat("😐", 4095) + `…+1032196"}`},
 	} {
 		got := string(lg.appendText(nil, []byte(tt.text), tt.skipClientTime, tt.procID, tt.procSeq, tt.level))
 		if !strings.HasSuffix(got, "\n") {
@@ -794,7 +793,6 @@ func TestAppendTextOrJSON(t *testing.T) {
 	var lg Logger
 	lg.clock = tstest.NewClock(tstest.ClockOpts{Start: time.Date(2000, 01, 01, 0, 0, 0, 0, time.UTC)})
 	lg.metricsDelta = func() string { return "metrics" }
-	lg.lowMem = true
 
 	for _, tt := range []struct {
 		in    string