Set self-adjusting deadline for connection writing (#16068)

* Set self-adjusting deadline for connection writing

In #16055 it appears that the simple 5s deadline doesn't work for large
file writes. Now we can't - or at least shouldn't just set no deadline
as go will happily let these connections block indefinitely. However,
what seems reasonable is to set some minimum rate we expect for writing.

This PR suggests the following algorithm:

* Every write has a minimum timeout of 5s (adjustable at compile time.)
* If there has been a previous write - then consider its previous
deadline, add half of the minimum timeout + 2s per kb about to written.
* If that new deadline is after the minimum timeout use that.

Fix #16055

* Linearly increase timeout

* Make PerWriteTimeout, PerWritePerKbTimeouts configurable

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: 6543 <6543@obermui.de>

1 files changed, 41 insertions, 23 deletions

diff --git a/modules/graceful/server.go b/modules/graceful/server.go
index 26195c6322..704aa8a2b7 100644
--- a/modules/graceful/server.go
+++ b/modules/graceful/server.go
@@ -17,6 +17,7 @@ import (
 	"time"
 
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
 )
 
 var (
@@ -26,11 +27,12 @@ var (
 	DefaultWriteTimeOut time.Duration
 	// DefaultMaxHeaderBytes default max header bytes
 	DefaultMaxHeaderBytes int
+	// PerWriteWriteTimeout timeout for writes
+	PerWriteWriteTimeout = 30 * time.Second
+	// PerWriteWriteTimeoutKbTime is a timeout taking account of how much there is to be written
+	PerWriteWriteTimeoutKbTime = 10 * time.Second
 )
 
-// PerWriteWriteTimeout timeout for writes
-const PerWriteWriteTimeout = 5 * time.Second
-
 func init() {
 	DefaultMaxHeaderBytes = 0 // use http.DefaultMaxHeaderBytes - which currently is 1 << 20 (1MB)
 }
@@ -40,14 +42,16 @@ type ServeFunction = func(net.Listener) error
 
 // Server represents our graceful server
 type Server struct {
-	network     string
-	address     string
-	listener    net.Listener
-	wg          sync.WaitGroup
-	state       state
-	lock        *sync.RWMutex
-	BeforeBegin func(network, address string)
-	OnShutdown  func()
+	network              string
+	address              string
+	listener             net.Listener
+	wg                   sync.WaitGroup
+	state                state
+	lock                 *sync.RWMutex
+	BeforeBegin          func(network, address string)
+	OnShutdown           func()
+	PerWriteTimeout      time.Duration
+	PerWritePerKbTimeout time.Duration
 }
 
 // NewServer creates a server on network at provided address
@@ -58,11 +62,13 @@ func NewServer(network, address, name string) *Server {
 		log.Info("Starting new %s server: %s:%s on PID: %d", name, network, address, os.Getpid())
 	}
 	srv := &Server{
-		wg:      sync.WaitGroup{},
-		state:   stateInit,
-		lock:    &sync.RWMutex{},
-		network: network,
-		address: address,
+		wg:                   sync.WaitGroup{},
+		state:                stateInit,
+		lock:                 &sync.RWMutex{},
+		network:              network,
+		address:              address,
+		PerWriteTimeout:      setting.PerWriteTimeout,
+		PerWritePerKbTimeout: setting.PerWritePerKbTimeout,
 	}
 
 	srv.BeforeBegin = func(network, addr string) {
@@ -224,9 +230,11 @@ func (wl *wrappedListener) Accept() (net.Conn, error) {
 	closed := int32(0)
 
 	c = wrappedConn{
-		Conn:   c,
-		server: wl.server,
-		closed: &closed,
+		Conn:                 c,
+		server:               wl.server,
+		closed:               &closed,
+		perWriteTimeout:      wl.server.PerWriteTimeout,
+		perWritePerKbTimeout: wl.server.PerWritePerKbTimeout,
 	}
 
 	wl.server.wg.Add(1)
@@ -249,13 +257,23 @@ func (wl *wrappedListener) File() (*os.File, error) {
 
 type wrappedConn struct {
 	net.Conn
-	server *Server
-	closed *int32
+	server               *Server
+	closed               *int32
+	deadline             time.Time
+	perWriteTimeout      time.Duration
+	perWritePerKbTimeout time.Duration
 }
 
 func (w wrappedConn) Write(p []byte) (n int, err error) {
-	if PerWriteWriteTimeout > 0 {
-		_ = w.Conn.SetWriteDeadline(time.Now().Add(PerWriteWriteTimeout))
+	if w.perWriteTimeout > 0 {
+		minTimeout := time.Duration(len(p)/1024) * w.perWritePerKbTimeout
+		minDeadline := time.Now().Add(minTimeout).Add(w.perWriteTimeout)
+
+		w.deadline = w.deadline.Add(minTimeout)
+		if minDeadline.After(w.deadline) {
+			w.deadline = minDeadline
+		}
+		_ = w.Conn.SetWriteDeadline(w.deadline)
 	}
 	return w.Conn.Write(p)
 }