daemon: Remove daemon datastructure dump functionality

When sending SIGUSR1 to the daemon, it can crash because of a concurrent
map access panic, showing a stack trace involving dumpDaemon. It appears
it's not possible to recover from a concurrent map access panic. Since
it's important that SIGUSR1 not be a destructive operation, sadly the
best course of action I can think of is to remove this functionality.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

daemon/debugtrap.go

@@ -1,62 +0,0 @@
-package daemon
-
-import (
-	"fmt"
-	"os"
-	"path/filepath"
-	"strings"
-	"time"
-
-	"github.com/davecgh/go-spew/spew"
-	"github.com/pkg/errors"
-)
-
-const dataStructuresLogNameTemplate = "daemon-data-%s.log"
-
-// dumpDaemon appends the daemon datastructures into file in dir and returns full path
-// to that file.
-func (d *Daemon) dumpDaemon(dir string) (string, error) {
-	// Ensure we recover from a panic as we are doing this without any locking
-	defer func() {
-		recover()
-	}()
-
-	path := filepath.Join(dir, fmt.Sprintf(dataStructuresLogNameTemplate, strings.Replace(time.Now().Format(time.RFC3339), ":", "", -1)))
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, 0666)
-	if err != nil {
-		return "", errors.Wrap(err, "failed to open file to write the daemon datastructure dump")
-	}
-	defer f.Close()
-
-	dump := struct {
-		containers      interface{}
-		names           interface{}
-		links           interface{}
-		execs           interface{}
-		volumes         interface{}
-		images          interface{}
-		layers          interface{}
-		imageReferences interface{}
-		downloads       interface{}
-		uploads         interface{}
-		registry        interface{}
-		plugins         interface{}
-	}{
-		containers:      d.containers,
-		execs:           d.execCommands,
-		volumes:         d.volumes,
-		images:          d.imageStore,
-		layers:          d.layerStore,
-		imageReferences: d.referenceStore,
-		downloads:       d.downloadManager,
-		uploads:         d.uploadManager,
-		registry:        d.RegistryService,
-		plugins:         d.PluginStore,
-		names:           d.nameIndex,
-		links:           d.linkIndex,
-	}
-
-	spew.Fdump(f, dump) // Does not return an error
-	f.Sync()
-	return path, nil
-}

daemon/debugtrap_unix.go

@@ -22,12 +22,6 @@ func (d *Daemon) setupDumpStackTrap(root string) {
 			} else {
 				logrus.Infof("goroutine stacks written to %s", path)
 			}
-			path, err = d.dumpDaemon(root)
-			if err != nil {
-				logrus.WithError(err).Error("failed to write daemon datastructure dump")
-			} else {
-				logrus.Infof("daemon datastructure dump written to %s", path)
-			}
 		}
 	}()
 }

daemon/debugtrap_windows.go

@@ -41,12 +41,6 @@ func (d *Daemon) setupDumpStackTrap(root string) {
 			} else {
 				logrus.Infof("goroutine stacks written to %s", path)
 			}
-			path, err = d.dumpDaemon(root)
-			if err != nil {
-				logrus.WithError(err).Error("failed to write daemon datastructure dump")
-			} else {
-				logrus.Infof("daemon datastructure dump written to %s", path)
-			}
 		}
 	}()
 }