From 754f00fad76781e1fa289d6ae7baa4aa7261392e Mon Sep 17 00:00:00 2001
From: chrislu <chris.lu@gmail.com>
Date: Thu, 30 Oct 2025 16:37:14 -0700
Subject: [PATCH] more doc

---
 weed/util/net_timeout.go | 51 +++++++++++++++++++++++++++++++++-------
 1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/weed/util/net_timeout.go b/weed/util/net_timeout.go
index c0bba1bef..7d4749dfc 100644
--- a/weed/util/net_timeout.go
+++ b/weed/util/net_timeout.go
@@ -9,6 +9,16 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/stats"
 )
 
+const (
+	// minThroughputBytesPerSecond defines the minimum expected throughput (4KB/s)
+	// Used to calculate timeout scaling based on data transferred
+	minThroughputBytesPerSecond = 4000
+	
+	// graceTimeCapMultiplier caps the grace period for slow clients at 3x base timeout
+	// This prevents indefinite connections while allowing time for server-side chunk fetches
+	graceTimeCapMultiplier = 3
+)
+
 // Listener wraps a net.Listener, and gives a place to store the timeout
 // parameters. On Accept, it will wrap the net.Conn with our own Conn for us.
 type Listener struct {
@@ -45,7 +55,15 @@ type Conn struct {
 
 func (c *Conn) Read(b []byte) (count int, e error) {
 	if c.ReadTimeout != 0 {
-		err := c.Conn.SetReadDeadline(time.Now().Add(c.ReadTimeout * time.Duration(c.bytesRead/40000+1)))
+		// Calculate expected bytes per timeout period based on minimum throughput (4KB/s)
+		// Example: with ReadTimeout=30s, bytesPerTimeout = 4000 * 30 = 120KB
+		// After reading 1MB: multiplier = 1,000,000/120,000 + 1 ≈ 9, deadline = 30s * 9 = 270s
+		bytesPerTimeout := int64(float64(minThroughputBytesPerSecond) * c.ReadTimeout.Seconds())
+		if bytesPerTimeout <= 0 {
+			bytesPerTimeout = 1 // Prevent division by zero
+		}
+		timeoutMultiplier := time.Duration(c.bytesRead/bytesPerTimeout + 1)
+		err := c.Conn.SetReadDeadline(time.Now().Add(c.ReadTimeout * timeoutMultiplier))
 		if err != nil {
 			return 0, err
 		}
@@ -62,25 +80,42 @@ func (c *Conn) Write(b []byte) (count int, e error) {
 	if c.WriteTimeout != 0 {
 		now := time.Now()
 		// Calculate timeout with two components:
-		// 1. Base timeout scaled by cumulative data (minimum 4KB/s throughput)
+		// 1. Base timeout scaled by cumulative data (minimum throughput of 4KB/s)
 		// 2. Additional grace period if there was a gap since last write (for chunk fetch delays)
-		timeoutMultiplier := time.Duration(c.bytesWritten/40000 + 1)
+		
+		// Calculate expected bytes per timeout period based on minimum throughput (4KB/s)
+		// Example: with WriteTimeout=30s, bytesPerTimeout = 4000 * 30 = 120KB
+		// After writing 1MB: multiplier = 1,000,000/120,000 + 1 ≈ 9, baseTimeout = 30s * 9 = 270s
+		bytesPerTimeout := int64(float64(minThroughputBytesPerSecond) * c.WriteTimeout.Seconds())
+		if bytesPerTimeout <= 0 {
+			bytesPerTimeout = 1 // Prevent division by zero
+		}
+		timeoutMultiplier := time.Duration(c.bytesWritten/bytesPerTimeout + 1)
 		baseTimeout := c.WriteTimeout * timeoutMultiplier
-
+		
 		// If it's been a while since last write, add grace time for server-side chunk fetches
 		// But cap it to avoid keeping slow clients connected indefinitely
+		// 
+		// The comparison uses unscaled WriteTimeout intentionally: triggers grace when idle time
+		// exceeds base timeout, independent of throughput scaling.
 		if !c.lastWrite.IsZero() {
 			timeSinceLastWrite := now.Sub(c.lastWrite)
 			if timeSinceLastWrite > c.WriteTimeout {
-				// Add grace time, but cap at 3x base timeout to handle slow clients
+				// Add grace time capped at graceTimeCapMultiplier * scaled timeout.
+				// This allows total deadline up to 4x scaled timeout for server-side delays.
+				//
+				// Example: WriteTimeout=30s, 1MB written (multiplier≈9), baseTimeout=270s
+				// If 400s gap occurs fetching chunks: graceTime capped at 270s*3=810s
+				// Final deadline: 270s + 810s = 1080s (~18min) to accommodate slow storage
+				// But if only 50s gap: graceTime = 50s, final deadline = 270s + 50s = 320s
 				graceTime := timeSinceLastWrite
-				if graceTime > baseTimeout*3 {
-					graceTime = baseTimeout * 3
+				if graceTime > baseTimeout*graceTimeCapMultiplier {
+					graceTime = baseTimeout * graceTimeCapMultiplier
 				}
 				baseTimeout += graceTime
 			}
 		}
-
+		
 		err := c.Conn.SetWriteDeadline(now.Add(baseTimeout))
 		if err != nil {
 			return 0, err