From 1a5378b64b9b5574f8eb7a9996ced9ac932f6b52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=2E=20Mert=20Y=C4=B1ld=C4=B1ran?= <mehmet@up9.com>
Date: Wed, 13 Apr 2022 23:58:05 -0700
Subject: [PATCH] Increase the OOM risk in exchange of less idle CPU usage
 (#979)

* Increase the OOM risk in exchange of less idle CPU usage

* Read the interval from an environment variable named `CLOSE_TIMEDOUT_TCP_STREAM_CHANNELS_INTERVAL_MS`

* Log the `getCloseTimedoutTcpChannelsInterval` return value
---
 tap/settings.go        |  1 +
 tap/tcp_streams_map.go | 31 +++++++++++++++++++++++++++++--
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/tap/settings.go b/tap/settings.go
index b9e25da6d..0a8c573f1 100644
--- a/tap/settings.go
+++ b/tap/settings.go
@@ -13,6 +13,7 @@ const (
 	MaxBufferedPagesTotalEnvVarName           = "MAX_BUFFERED_PAGES_TOTAL"
 	MaxBufferedPagesPerConnectionEnvVarName   = "MAX_BUFFERED_PAGES_PER_CONNECTION"
 	TcpStreamChannelTimeoutMsEnvVarName       = "TCP_STREAM_CHANNEL_TIMEOUT_MS"
+	CloseTimedoutTcpChannelsIntervalMsEnvVar  = "CLOSE_TIMEDOUT_TCP_STREAM_CHANNELS_INTERVAL_MS"
 	MaxBufferedPagesTotalDefaultValue         = 5000
 	MaxBufferedPagesPerConnectionDefaultValue = 5000
 	TcpStreamChannelTimeoutMsDefaultValue     = 10000
diff --git a/tap/tcp_streams_map.go b/tap/tcp_streams_map.go
index 7e4489dd7..9a94f41ce 100644
--- a/tap/tcp_streams_map.go
+++ b/tap/tcp_streams_map.go
@@ -1,8 +1,10 @@
 package tap
 
 import (
+	"os"
 	"runtime"
 	_debug "runtime/debug"
+	"strconv"
 	"sync"
 	"time"
 
@@ -34,10 +36,35 @@ func (streamMap *tcpStreamMap) nextId() int64 {
 	return streamMap.streamId
 }
 
+func (streamMap *tcpStreamMap) getCloseTimedoutTcpChannelsInterval() time.Duration {
+	defaultDuration := 1000 * time.Millisecond
+	rangeMin := 10
+	rangeMax := 10000
+	closeTimedoutTcpChannelsIntervalMsStr := os.Getenv(CloseTimedoutTcpChannelsIntervalMsEnvVar)
+	if closeTimedoutTcpChannelsIntervalMsStr == "" {
+		return defaultDuration
+	} else {
+		closeTimedoutTcpChannelsIntervalMs, err := strconv.Atoi(closeTimedoutTcpChannelsIntervalMsStr)
+		if err != nil {
+			logger.Log.Warningf("Error parsing environment variable %s: %v\n", CloseTimedoutTcpChannelsIntervalMsEnvVar, err)
+			return defaultDuration
+		} else {
+			if closeTimedoutTcpChannelsIntervalMs < rangeMin || closeTimedoutTcpChannelsIntervalMs > rangeMax {
+				logger.Log.Warningf("The value of environment variable %s is not in acceptable range: %d - %d\n", CloseTimedoutTcpChannelsIntervalMsEnvVar, rangeMin, rangeMax)
+				return defaultDuration
+			} else {
+				return time.Duration(closeTimedoutTcpChannelsIntervalMs) * time.Millisecond
+			}
+		}
+	}
+}
+
 func (streamMap *tcpStreamMap) closeTimedoutTcpStreamChannels() {
 	tcpStreamChannelTimeout := GetTcpChannelTimeoutMs()
+	closeTimedoutTcpChannelsIntervalMs := streamMap.getCloseTimedoutTcpChannelsInterval()
+	logger.Log.Infof("Using %d ms as the close timedout TCP stream channels interval", closeTimedoutTcpChannelsIntervalMs/time.Millisecond)
 	for {
-		time.Sleep(10 * time.Millisecond)
+		time.Sleep(closeTimedoutTcpChannelsIntervalMs)
 		_debug.FreeOSMemory()
 		streamMap.streams.Range(func(key interface{}, value interface{}) bool {
 			streamWrapper := value.(*tcpStreamWrapper)
@@ -47,7 +74,7 @@ func (streamMap *tcpStreamMap) closeTimedoutTcpStreamChannels() {
 					stream.Close()
 					diagnose.AppStats.IncDroppedTcpStreams()
 					logger.Log.Debugf("Dropped an unidentified TCP stream because of timeout. Total dropped: %d Total Goroutines: %d Timeout (ms): %d",
-						diagnose.AppStats.DroppedTcpStreams, runtime.NumGoroutine(), tcpStreamChannelTimeout/1000000)
+						diagnose.AppStats.DroppedTcpStreams, runtime.NumGoroutine(), tcpStreamChannelTimeout/time.Millisecond)
 				}
 			} else {
 				if !stream.superIdentifier.IsClosedOthers {