Add shim for collecting logs

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

cmd/collect.go

@@ -0,0 +1,56 @@
+package cmd
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/containerd/containerd/runtime/v2/logging"
+	"github.com/coreos/go-systemd/journal"
+	"github.com/spf13/cobra"
+)
+
+var collectCmd = &cobra.Command{
+	Use:   "collect",
+	Short: "Collect logs to the journal",
+	RunE:  runCollect,
+}
+
+func runCollect(_ *cobra.Command, _ []string) error {
+	logging.Run(logStdio)
+	return nil
+}
+
+// logStdio copied from
+// https://github.com/containerd/containerd/pull/3085
+// https://github.com/stellarproject/orbit
+func logStdio(ctx context.Context, config *logging.Config, ready func() error) error {
+	// construct any log metadata for the container
+	vars := map[string]string{
+		"SYSLOG_IDENTIFIER": fmt.Sprintf("%s:%s", config.Namespace, config.ID),
+	}
+	var wg sync.WaitGroup
+	wg.Add(2)
+	// forward both stdout and stderr to the journal
+	go copy(&wg, config.Stdout, journal.PriInfo, vars)
+	go copy(&wg, config.Stderr, journal.PriErr, vars)
+	// signal that we are ready and setup for the container to be started
+	if err := ready(); err != nil {
+		return err
+	}
+	wg.Wait()
+	return nil
+}
+
+func copy(wg *sync.WaitGroup, r io.Reader, pri journal.Priority, vars map[string]string) {
+	defer wg.Done()
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		if s.Err() != nil {
+			return
+		}
+		journal.Send(s.Text(), pri, vars)
+	}
+}