integrate github.com/moby/buildkit/util/appcontext

Makefile

@@ -1,4 +1,4 @@
-PACKAGES ?= mountinfo mount sequential signal symlink
+PACKAGES ?= appcontext mountinfo mount sequential signal symlink
 BINDIR ?= _build/bin
 CROSS ?= linux/arm linux/arm64 linux/ppc64le linux/s390x \
 	freebsd/amd64 openbsd/amd64 darwin/amd64 darwin/arm64 windows/amd64

appcontext/appcontext.go

@@ -0,0 +1,45 @@
+package appcontext
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"sync"
+)
+
+var (
+	appContextCache context.Context
+	appContextOnce  sync.Once
+)
+
+// Context returns a static context that reacts to termination signals of the
+// running process. Useful in CLI tools.
+func Context() context.Context {
+	appContextOnce.Do(func() {
+		signals := make(chan os.Signal, 2048)
+		signal.Notify(signals, terminationSignals...)
+
+		const exitLimit = 3
+		retries := 0
+
+		ctx := context.Background()
+		for _, f := range inits {
+			ctx = f(ctx)
+		}
+
+		ctx, cancel := context.WithCancel(ctx)
+		appContextCache = ctx
+
+		go func() {
+			for {
+				<-signals
+				cancel()
+				retries++
+				if retries >= exitLimit {
+					os.Exit(1)
+				}
+			}
+		}()
+	})
+	return appContextCache
+}

appcontext/appcontext_unix.go

@@ -0,0 +1,12 @@
+//go:build !windows
+// +build !windows
+
+package appcontext
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+var terminationSignals = []os.Signal{unix.SIGTERM, unix.SIGINT}

appcontext/appcontext_windows.go

@@ -0,0 +1,7 @@
+package appcontext
+
+import (
+	"os"
+)
+
+var terminationSignals = []os.Signal{os.Interrupt}

appcontext/go.mod

@@ -0,0 +1,5 @@
+module github.com/moby/sys/appcontext
+
+go 1.17
+
+require golang.org/x/sys v0.11.0

appcontext/go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

appcontext/register.go

@@ -0,0 +1,14 @@
+package appcontext
+
+import (
+	"context"
+)
+
+type Initializer func(context.Context) context.Context
+
+var inits []Initializer
+
+// Register stores a new context initializer that runs on app context creation
+func Register(f Initializer) {
+	inits = append(inits, f)
+}