executor: detect containers killed by OOMKiller

If container exits with error and has invoked OOMKiller
mark the origin error as ENOMEM so that it can be detected
on the client side.

gRPC will set ENOMEM as codes.ResouceExhausted based on #5182

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

executor/runcexecutor/executor.go

@@ -335,7 +335,7 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 	}
 	doReleaseNetwork = false
 
-	err = exitError(ctx, err)
+	err = exitError(ctx, cgroupPath, err)
 	if err != nil {
 		if rec != nil {
 			rec.Close()
@@ -351,7 +351,7 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 	return rec, rec.CloseAsync(releaseContainer)
 }
 
-func exitError(ctx context.Context, err error) error {
+func exitError(ctx context.Context, cgroupPath string, err error) error {
 	if err != nil {
 		exitErr := &gatewayapi.ExitError{
 			ExitCode: gatewayapi.UnknownExitStatus,
@@ -363,6 +363,9 @@ func exitError(ctx context.Context, err error) error {
 				ExitCode: uint32(runcExitError.Status),
 			}
 		}
+
+		detectOOM(ctx, cgroupPath, exitErr)
+
 		trace.SpanFromContext(ctx).AddEvent(
 			"Container exited",
 			trace.WithAttributes(
@@ -453,7 +456,7 @@ func (w *runcExecutor) Exec(ctx context.Context, id string, process executor.Pro
 	}
 
 	err = w.exec(ctx, id, spec.Process, process, nil)
-	return exitError(ctx, err)
+	return exitError(ctx, "", err)
 }
 
 type forwardIO struct {

executor/runcexecutor/executor_linux.go

@@ -1,14 +1,19 @@
 package runcexecutor
 
 import (
+	"bufio"
 	"context"
 	"io"
 	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
 	"syscall"
 
 	"github.com/containerd/console"
 	runc "github.com/containerd/go-runc"
 	"github.com/moby/buildkit/executor"
+	gatewayapi "github.com/moby/buildkit/frontend/gateway/pb"
 	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/sys/signal"
 	"github.com/opencontainers/runtime-spec/specs-go"
@@ -172,3 +177,44 @@ func (w *runcExecutor) callWithIO(ctx context.Context, process executor.ProcessI
 
 	return call(ctx, startedCh, runcIO, killer.pidfile)
 }
+
+func detectOOM(ctx context.Context, ns string, gwErr *gatewayapi.ExitError) {
+	const defaultCgroupMountpoint = "/sys/fs/cgroup"
+
+	if ns == "" {
+		return
+	}
+
+	count, err := readMemoryEvent(filepath.Join(defaultCgroupMountpoint, ns), "oom_kill")
+	if err != nil {
+		bklog.G(ctx).WithError(err).Warn("failed to read oom_kill event")
+		return
+	}
+	if count > 0 {
+		gwErr.Err = syscall.ENOMEM
+	}
+}
+
+func readMemoryEvent(fp string, event string) (uint64, error) {
+	f, err := os.Open(filepath.Join(fp, "memory.events"))
+	if err != nil {
+		return 0, err
+	}
+	defer f.Close()
+
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		parts := strings.Fields(s.Text())
+		if len(parts) != 2 {
+			continue
+		}
+		if parts[0] != event {
+			continue
+		}
+		v, err := strconv.ParseUint(parts[1], 10, 64)
+		if err == nil {
+			return v, nil
+		}
+	}
+	return 0, s.Err()
+}