Add 'runsc debug' command

It prints sandbox stacks to the log to help debug stuckness. I expect
that many more options will be added in the future.

PiperOrigin-RevId: 201405931
Change-Id: I87e560800cd5a5a7b210dc25a5661363c8c3a16e

2 files changed, 109 insertions, 0 deletions

diff --git a/runsc/cmd/BUILD b/runsc/cmd/BUILD
index fffb6f359..747793efc 100644
--- a/runsc/cmd/BUILD
+++ b/runsc/cmd/BUILD
@@ -10,6 +10,7 @@ go_library(
         "checkpoint.go",
         "cmd.go",
         "create.go",
+        "debug.go",
         "delete.go",
         "events.go",
         "exec.go",
diff --git a/runsc/cmd/debug.go b/runsc/cmd/debug.go
new file mode 100644
index 000000000..87ad21c9a
--- /dev/null
+++ b/runsc/cmd/debug.go
@@ -0,0 +1,108 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"context"
+	"flag"
+	"github.com/google/subcommands"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/runsc/boot"
+	"gvisor.googlesource.com/gvisor/runsc/container"
+)
+
+// Debug implements subcommands.Command for the "debug" command.
+type Debug struct {
+	pid    int
+	stacks bool
+}
+
+// Name implements subcommands.Command.
+func (*Debug) Name() string {
+	return "debug"
+}
+
+// Synopsis implements subcommands.Command.
+func (*Debug) Synopsis() string {
+	return "shows a variety of debug information"
+}
+
+// Usage implements subcommands.Command.
+func (*Debug) Usage() string {
+	return `debug [flags] <container id>`
+}
+
+// SetFlags implements subcommands.Command.
+func (d *Debug) SetFlags(f *flag.FlagSet) {
+	f.IntVar(&d.pid, "pid", 0, "sandbox process ID. Container ID is not necessary if this is set")
+	f.BoolVar(&d.stacks, "stacks", false, "if true, dumps all sandbox stacks to the log")
+}
+
+// Execute implements subcommands.Command.Execute.
+func (d *Debug) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	var c *container.Container
+	conf := args[0].(*boot.Config)
+
+	if d.pid == 0 {
+		// No pid, container ID must have been provided.
+		if f.NArg() != 1 {
+			f.Usage()
+			return subcommands.ExitUsageError
+		}
+		var err error
+		c, err = container.Load(conf.RootDir, f.Arg(0))
+		if err != nil {
+			Fatalf("error loading container %q: %v", f.Arg(0), err)
+		}
+	} else {
+		if f.NArg() != 0 {
+			f.Usage()
+			return subcommands.ExitUsageError
+		}
+		// Go over all sandboxes and find the one that matches PID.
+		ids, err := container.List(conf.RootDir)
+		if err != nil {
+			Fatalf("error listing containers: %v", err)
+		}
+		for _, id := range ids {
+			candidate, err := container.Load(conf.RootDir, id)
+			if err != nil {
+				Fatalf("error loading container %q: %v", id, err)
+			}
+			if candidate.Pid() == d.pid {
+				c = candidate
+				break
+			}
+		}
+		if c == nil {
+			Fatalf("container with PID %d not found", d.pid)
+		}
+	}
+
+	log.Infof("Found sandbox %q, PID: %d", c.Sandbox.ID, c.Sandbox.Pid)
+	if !c.Sandbox.IsRunning() {
+		Fatalf("sandbox %q is not running", c.Sandbox.ID)
+	}
+
+	if d.stacks {
+		log.Infof("Retrieving sandbox stacks")
+		stacks, err := c.Sandbox.Stacks()
+		if err != nil {
+			Fatalf("error retrieving stacks: %v", err)
+		}
+		log.Infof("     *** Stack dump ***\n%s", stacks)
+	}
+	return subcommands.ExitSuccess
+}