From ff507aa8c3d0587bd5beac1d1c04edb9337cbd91 Mon Sep 17 00:00:00 2001
From: Denis Machard <5562930+dmachard@users.noreply.github.com>
Date: Wed, 9 Oct 2024 22:08:31 +0200
Subject: [PATCH] file logger: reducing the frequency of disk writes (#841)

* reducing the frequency of disk writes
* default config
---
 config.yml                  |  2 +-
 docs/loggers/logger_file.md |  6 ++++-
 pkgconfig/loggers.go        |  3 ++-
 workers/logfile.go          | 47 +++++++++++++++++++++++++++----------
 4 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/config.yml b/config.yml
index 3cc25714..29eeb190 100644
--- a/config.yml
+++ b/config.yml
@@ -17,7 +17,7 @@ global:
   text-jinja: ""
   worker:
     interval-monitor: 10
-    buffer-size: 4096
+    buffer-size: 8192
   telemetry:
     enabled: false
     web-path: "/metrics"
diff --git a/docs/loggers/logger_file.md b/docs/loggers/logger_file.md
index 28a49119..e45e8955 100644
--- a/docs/loggers/logger_file.md
+++ b/docs/loggers/logger_file.md
@@ -26,6 +26,9 @@ Options:
 * `max-files` (integer)
   > maximum number of files to retain. Set to zero if you want to disable this feature
 
+* `max-batch-size` (integer)
+  > accumulate data before writing it to the file
+
 * `flush-interval` (integer)
   > flush buffer to log file every X seconds
 
@@ -62,7 +65,8 @@ logfile:
   file-path: null
   max-size: 100
   max-files: 10
-  flush-interval: 10
+  max-batch-size: 65536
+  flush-interval: 1
   compress: false
   compress-interval: 5
   compress-postcommand: null
diff --git a/pkgconfig/loggers.go b/pkgconfig/loggers.go
index 55adc6a6..a664b56b 100644
--- a/pkgconfig/loggers.go
+++ b/pkgconfig/loggers.go
@@ -72,7 +72,8 @@ type ConfigLoggers struct {
 		FilePath            string `yaml:"file-path" default:""`
 		MaxSize             int    `yaml:"max-size" default:"100"`
 		MaxFiles            int    `yaml:"max-files" default:"10"`
-		FlushInterval       int    `yaml:"flush-interval" default:"10"`
+		MaxBatchSize        int    `yaml:"max-batch-size" default:"65536"`
+		FlushInterval       int    `yaml:"flush-interval" default:"1"`
 		Compress            bool   `yaml:"compress" default:"false"`
 		CompressInterval    int    `yaml:"compress-interval" default:"60"`
 		CompressPostCommand string `yaml:"compress-postcommand" default:""`
diff --git a/workers/logfile.go b/workers/logfile.go
index d9bd1477..f7e4bdb7 100644
--- a/workers/logfile.go
+++ b/workers/logfile.go
@@ -158,8 +158,7 @@ func (w *LogFile) OpenFile() error {
 
 	switch w.GetConfig().Loggers.LogFile.Mode {
 	case pkgconfig.ModeText, pkgconfig.ModeJSON, pkgconfig.ModeFlatJSON:
-		bufferSize := 4096
-		w.writerPlain = bufio.NewWriterSize(fd, bufferSize)
+		w.writerPlain = bufio.NewWriterSize(fd, w.config.Loggers.LogFile.MaxBatchSize)
 
 	case pkgconfig.ModePCAP:
 		w.writerPcap = pcapgo.NewWriter(fd)
@@ -469,6 +468,11 @@ func (w *LogFile) StartLogging() {
 	var data []byte
 	var err error
 
+	// Max size of a batch before forcing a write
+	batch := new(bytes.Buffer)
+	maxBatchSize := w.config.Loggers.LogFile.MaxBatchSize
+	batchSize := 0 // Current batch size
+
 	for {
 		select {
 		case <-w.OnLoggerStopped():
@@ -476,6 +480,11 @@ func (w *LogFile) StartLogging() {
 			flushTimer.Stop()
 			w.commpressTimer.Stop()
 
+			// Force write remaining batch data
+			if batchSize > 0 {
+				w.WriteToPlain(batch.Bytes())
+			}
+
 			// flush writer
 			w.FlushWriters()
 
@@ -494,18 +503,15 @@ func (w *LogFile) StartLogging() {
 				return
 			}
 
-			// write to file
+			// Process the message based on the configured mode
+			var message []byte
 			switch w.GetConfig().Loggers.LogFile.Mode {
 
 			// with basic text mode
 			case pkgconfig.ModeText:
-				w.WriteToPlain(dm.Bytes(w.textFormat,
-					w.GetConfig().Global.TextFormatDelimiter,
-					w.GetConfig().Global.TextFormatBoundary))
-
-				var delimiter bytes.Buffer
-				delimiter.WriteString("\n")
-				w.WriteToPlain(delimiter.Bytes())
+				message = dm.Bytes(w.textFormat, w.GetConfig().Global.TextFormatDelimiter, w.GetConfig().Global.TextFormatBoundary)
+				batch.Write(message)
+				batch.WriteString("\n")
 
 			// with custom text mode
 			case pkgconfig.ModeJinja:
@@ -514,7 +520,7 @@ func (w *LogFile) StartLogging() {
 					w.LogError("jinja template: %s", err)
 					continue
 				}
-				w.WriteToPlain([]byte(textLine))
+				batch.Write([]byte(textLine))
 
 			// with json mode
 			case pkgconfig.ModeFlatJSON:
@@ -530,7 +536,7 @@ func (w *LogFile) StartLogging() {
 			// with json mode
 			case pkgconfig.ModeJSON:
 				json.NewEncoder(buffer).Encode(dm)
-				w.WriteToPlain(buffer.Bytes())
+				batch.Write(buffer.Bytes())
 				buffer.Reset()
 
 			// with dnstap mode
@@ -554,7 +560,24 @@ func (w *LogFile) StartLogging() {
 				w.WriteToPcap(dm, pkt)
 			}
 
+			// Update the batch size
+			batchSize += batch.Len()
+
+			// If the batch exceeds the max size, force a write
+			if batchSize >= maxBatchSize {
+				w.WriteToPlain(batch.Bytes())
+				batch.Reset() // Reset batch after write
+				batchSize = 0
+			}
+
 		case <-flushTimer.C:
+			// Flush the current batch, then flush the writers
+			if batchSize > 0 {
+				w.WriteToPlain(batch.Bytes())
+				batch.Reset()
+				batchSize = 0
+			}
+
 			// flush writer
 			w.FlushWriters()