Merge pull request #2631 from masters-of-cats/shim-io-redirect

Use named pipes for shim logs

cmd/containerd-shim/main_unix.go

@@ -23,6 +23,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io"
 	"net"
 	"os"
 	"os/exec"
@@ -36,6 +37,7 @@ import (
 
 	"github.com/containerd/containerd/events"
 	"github.com/containerd/containerd/namespaces"
+	shimlog "github.com/containerd/containerd/runtime/v1"
 	"github.com/containerd/containerd/runtime/v1/linux/proc"
 	"github.com/containerd/containerd/runtime/v1/shim"
 	shimapi "github.com/containerd/containerd/runtime/v1/shim/v1"
@@ -92,12 +94,38 @@ func main() {
 		runtime.GOMAXPROCS(2)
 	}
 
+	stdout, stderr, err := openStdioKeepAlivePipes(workdirFlag)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "containerd-shim: %s\n", err)
+		os.Exit(1)
+	}
+	defer func() {
+		stdout.Close()
+		stderr.Close()
+	}()
+
 	if err := executeShim(); err != nil {
 		fmt.Fprintf(os.Stderr, "containerd-shim: %s\n", err)
 		os.Exit(1)
 	}
 }
 
+// If containerd server process dies, we need the shim to keep stdout/err reader
+// FDs so that Linux does not SIGPIPE the shim process if it tries to use its end of
+// these pipes.
+func openStdioKeepAlivePipes(dir string) (io.ReadCloser, io.ReadCloser, error) {
+	background := context.Background()
+	keepStdoutAlive, err := shimlog.OpenShimStdoutLog(background, dir)
+	if err != nil {
+		return nil, nil, err
+	}
+	keepStderrAlive, err := shimlog.OpenShimStderrLog(background, dir)
+	if err != nil {
+		return nil, nil, err
+	}
+	return keepStdoutAlive, keepStderrAlive, nil
+}
+
 func executeShim() error {
 	// start handling signals as soon as possible so that things are properly reaped
 	// or if runtime exits before we hit the handler