.

go/neo/server/storage.go

@@ -29,6 +29,7 @@ import (
 	"lab.nexedi.com/kirr/neo/go/neo"
 	"lab.nexedi.com/kirr/neo/go/zodb"
 	"lab.nexedi.com/kirr/neo/go/xcommon/xnet"
+	"lab.nexedi.com/kirr/neo/go/xcommon/xcontext"
 
 	"lab.nexedi.com/kirr/go123/xerr"
 )
@@ -48,7 +49,7 @@ type Storage struct {
 
 	// context for providing operational service
 	// it is renewed every time master tells us StartOpertion, so users
-	// must read it initially only once under opMu
+	// must read it initially only once under opMu via opCtxRead
 	opMu  sync.Mutex
 	opCtx context.Context
 
@@ -160,7 +161,11 @@ func (stor *Storage) talkMaster1(ctx context.Context) error {
 		return err
 	}
 
-	// TODO Mlink.Close() on return / cancel
+	defer func() {
+		errClose := Mlink.Close()
+		err = xerr.First(err, errClose)
+		// TODO Mlink.Close() on return / cancel
+	}()
 
 	// request identification this way registering our node to master
 	accept, err := neo.IdentifyWith(neo.MASTER, Mlink, stor.myInfo, stor.clusterName)
@@ -180,13 +185,20 @@ func (stor *Storage) talkMaster1(ctx context.Context) error {
 	}
 
 	// now handle notifications and commands from master
+	var Mconn *neo.Conn
 	for {
+		// accept next connection from master. only 1 connection is served at any given time
 		// XXX every new connection from master means previous connection was closed
 		// XXX how to do so and stay compatible to py?
 		//
 		// XXX or simply use only the first connection and if M decides
 		// to cancel - close whole nodelink and S reconnects?
-		Mconn, err := Mlink.Accept()
+		if Mconn != nil {
+			Mconn.Close()	// XXX err
+			Mconn = nil
+		}
+
+		Mconn, err = Mlink.Accept()
 		if err != nil {
 			return err // XXX ?
 		}
@@ -200,7 +212,7 @@ func (stor *Storage) talkMaster1(ctx context.Context) error {
 
 		err = stor.m1serve(ctx, Mconn)
 		fmt.Println("stor: %v: master: %v", err)
-		// XXX check if it was command to shotdown and if so break
+		// XXX check if it was command to shutdown and if so break
 		continue // retry from initializing
 	}
 
@@ -320,6 +332,13 @@ func (stor *Storage) m1serve(ctx context.Context, Mconn *neo.Conn) (err error) {
 	}
 }
 
+// XXX naming -> withOpCtx? withUntilOperational?
+func (stor *Storage) opCtxRead() context.Context {
+	stor.opMu.Lock()
+	defer stor.opMu.Unlock()
+	return stor.opCtx
+}
+
 // ServeLink serves incoming node-node link connection
 // XXX +error return?
 func (stor *Storage) ServeLink(ctx context.Context, link *neo.NodeLink) {
@@ -382,36 +401,18 @@ func (stor *Storage) ServeLink(ctx context.Context, link *neo.NodeLink) {
 func (stor *Storage) ServeClient(ctx context.Context, conn *neo.Conn) {
 	fmt.Printf("stor: %s: serving new client conn\n", conn)
 
-	// rederive ctx from ctx and .operationCtx (which is cancelled when M tells us StopOperation)
-	// XXX -> xcontext ?
-	ctx, opCancel := context.WithCancel(ctx)
-	go func() {
-		// cancel ctx when global operation context is cancelled
-		stor.opMu.Lock()
-		opCtx := stor.opCtx
-		stor.opMu.Unlock()
-		select {
-		case <-opCtx.Done():
-			opCancel()
-
-		case <-ctx.Done():
-			// noop - to avoid goroutine leak
-		}
-	}()
+	// rederive ctx to be also cancelled if M tells us StopOperation
+	ctx, cancel := xcontext.Merge(ctx, stor.opCtxRead())
+	//ctx, cancel := stor.withWhileOperational(ctx)
+	defer cancel()
 
 	// close connection when either cancelling or returning (e.g. due to an error)
 	// ( when cancelling - conn.Close will signal to current IO to
 	//   terminate with an error )
-	// XXX dup -> utility
-	retch := make(chan struct{})
-	defer func() { close(retch) }()
 	go func() {
-		select {
-		case <-ctx.Done():
-			// XXX tell client we are shutting down?
-			// XXX ret err = cancelled ?
-		case <-retch:
-		}
+		<-ctx.Done()
+		// XXX tell client if we are shutting down?
+		// XXX ret err = cancelled ?
 		fmt.Printf("stor: %v: closing client conn\n", conn)
 		conn.Close()	// XXX err
 	}()

go/xcommon/xcontext/xcontext.go

+// Copyright (C) 2017  Nexedi SA and Contributors.
+//                     Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
+
+// Package xcontext provides addons to std package context.
+package xcontext
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// Merge merges 2 contexts into 1.
+//
+// The result context:
+// - is done when ctx1 or ctx2 is done, or cancel called, whichever happens first,
+// - has deadline = min(ctx1.Deadline, ctx2.Deadline),
+// - has associated values merged from ctx1 and ctx2.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func Merge(ctx1, ctx2 context.Context) (context.Context, context.CancelFunc) {
+	mc := &mergeCtx{
+		ctx1:     ctx1,
+		ctx2:     ctx2,
+		done:     make(chan struct{}),
+		cancelCh: make(chan struct{}),
+	}
+	go mc.wait()
+	return mc, mc.cancel
+}
+
+type mergeCtx struct {
+	ctx1, ctx2 context.Context
+
+	done    chan struct{}
+	doneErr error
+
+	cancelCh   chan struct{}
+	cancelOnce sync.Once
+}
+
+// wait waits when .ctx1 or .ctx2 is done and then mark mergeCtx as done
+func (mc *mergeCtx) wait() {
+	select {
+	case <-mc.ctx1.Done():
+		mc.doneErr = mc.ctx1.Err()
+
+	case <-mc.ctx2.Done():
+		mc.doneErr = mc.ctx2.Err()
+
+	case <-mc.cancelCh:
+		mc.doneErr = context.Canceled
+	}
+
+	close(mc.done)
+}
+
+// cancel sends signal to wait to shutdown
+// cancel is the context.CancelFunc returned for mergeCtx by Merge
+func (mc *mergeCtx) cancel() {
+	mc.cancelOnce.Do(func() {
+		close(mc.cancelCh)
+	})
+}
+
+func (mc *mergeCtx) Done() <-chan struct{} {
+	return mc.done
+}
+
+func (mc *mergeCtx) Err() error {
+	// synchronize on .done to avoid .doneErr read races
+	select {
+	case <-mc.done:
+
+	default:
+		// done not yet closed
+		return nil
+	}
+
+	// .done closed; .doneErr was set before - no race
+	return mc.doneErr
+}
+
+func (mc *mergeCtx) Deadline() (time.Time, bool) {
+	d1, ok1 := mc.ctx1.Deadline()
+	d2, ok2 := mc.ctx2.Deadline()
+	switch {
+	case !ok1:
+		return d2, ok2
+	case !ok2:
+		return d1, ok1
+	case d1.Before(d2):
+		return d1, true
+	default:
+		return d2, true
+	}
+}
+
+func (mc *mergeCtx) Value(key interface{}) interface{} {
+	v := mc.ctx1.Value(key)
+	if v != nil {
+		return v
+	}
+	return mc.ctx2.Value(key)
+}

go/xcommon/xcontext/xcontext_test.go

+// Copyright (C) 2017  Nexedi SA and Contributors.
+//                     Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// You can also Link and Combine this program with other software covered by
+// the terms of any of the Free Software licenses or any of the Open Source
+// Initiative approved licenses and Convey the resulting work. Corresponding
+// source of such a combination shall include the source code for all other
+// software used.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+// See https://www.nexedi.com/licensing for rationale and options.
+
+// Package xcontext provides addons to std package context.
+package xcontext
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestMerge(t *testing.T) {
+	bg := context.Background()
+	ctx1, cancel1 := context.WithCancel(bg)
+	ctx2, cancel2 := context.WithCancel(bg)
+
+	ctx1 = context.WithValue(ctx1, 1, "hello")
+	ctx2 = context.WithValue(ctx2, 2, "world")
+
+	mc, _ := Merge(ctx1, ctx2)
+
+	assertEq := func(a, b interface{}) {
+		t.Helper()
+		if a != b {
+			t.Fatalf("%v != %v", a, b)
+		}
+	}
+
+	assertEq(mc.Value(1), "hello")
+	assertEq(mc.Value(2), "world")
+	assertEq(mc.Value(3), nil)
+
+	t0 := time.Time{}
+
+	d, ok := mc.Deadline()
+	if !(d == t0 && ok == false) {
+		t.Fatal("deadline must be unset")
+	}
+
+	assertEq(mc.Err(), nil)
+
+	select {
+	case <-mc.Done():
+		t.Fatal("done before any parent done")
+	default:
+	}
+
+	cancel2()
+	<-mc.Done()
+	assertEq(mc.Err(), context.Canceled)
+
+	////////
+	mc, _ = Merge(ctx1, bg)
+	assertEq(mc.Value(1), "hello")
+	assertEq(mc.Value(2), nil)
+	assertEq(mc.Value(3), nil)
+
+	d, ok = mc.Deadline()
+	if !(d == t0 && ok == false) {
+		t.Fatal("deadline must be unset")
+	}
+
+	assertEq(mc.Err(), nil)
+
+	select {
+	case <-mc.Done():
+		t.Fatal("done before any parent done")
+	default:
+	}
+
+	cancel1()
+	<-mc.Done()
+	assertEq(mc.Err(), context.Canceled)
+
+	////////
+	t1 := t0.AddDate(7777, 1, 1)
+	t2 := t0.AddDate(9999, 1, 1)
+	ctx1, _ = context.WithDeadline(bg, t1)
+	ctx2, _ = context.WithDeadline(bg, t2)
+
+	checkDeadline := func(a, b context.Context, tt time.Time) {
+		t.Helper()
+		m, _ := Merge(a, b)
+		d, ok := m.Deadline()
+		if !ok {
+			t.Fatal("no deadline returned")
+		}
+		if d != tt {
+			t.Fatalf("incorrect deadline: %v  ; want %v", d, tt)
+		}
+	}
+
+	checkDeadline(ctx1, bg, t1)
+	checkDeadline(bg, ctx2, t2)
+	checkDeadline(ctx1, ctx2, t1)
+	checkDeadline(ctx2, ctx1, t1)
+
+	////////
+	mc, mcancel := Merge(bg, bg)
+
+	select {
+	case <-mc.Done():
+		t.Fatal("done before any parent done")
+	default:
+	}
+
+	mcancel()
+	mcancel()
+	<-mc.Done()
+	assertEq(mc.Err(), context.Canceled)
+}