From 544557289a7536ede707bd9f8e840f17b4c5bbad Mon Sep 17 00:00:00 2001 From: Michael Crosby Date: Tue, 8 May 2018 15:27:08 -0400 Subject: [PATCH] Add oci-hook command to containerd This allows many different commands to be used as OCI hooks. It allows these commands to template out different args and env vars so that normal commands can accept the OCI spec State payload over stdin. Signed-off-by: Michael Crosby --- cmd/containerd/command/main.go | 1 + cmd/containerd/command/oci-hook.go | 131 +++++++++++++++++++++++++++++ container_test.go | 60 +++++++++++++ 3 files changed, 192 insertions(+) create mode 100644 cmd/containerd/command/oci-hook.go diff --git a/cmd/containerd/command/main.go b/cmd/containerd/command/main.go index 8fba0fa38..01364329d 100644 --- a/cmd/containerd/command/main.go +++ b/cmd/containerd/command/main.go @@ -89,6 +89,7 @@ func App() *cli.App { app.Commands = []cli.Command{ configCommand, publishCommand, + ociHook, } app.Action = func(context *cli.Context) error { var ( diff --git a/cmd/containerd/command/oci-hook.go b/cmd/containerd/command/oci-hook.go new file mode 100644 index 000000000..92f0678c7 --- /dev/null +++ b/cmd/containerd/command/oci-hook.go @@ -0,0 +1,131 @@ +/* + Copyright The containerd Authors. + + 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 command + +import ( + "bytes" + "encoding/json" + "io" + "os" + "path/filepath" + "syscall" + "text/template" + + specs "github.com/opencontainers/runtime-spec/specs-go" + "github.com/urfave/cli" +) + +var ociHook = cli.Command{ + Name: "oci-hook", + Usage: "provides a base for OCI runtime hooks that allow arguements to be templated.", + Action: func(context *cli.Context) error { + state, err := loadHookState(os.Stdin) + if err != nil { + return err + } + var ( + ctx = newTemplateContext(state) + args = []string(context.Args()) + env = os.Environ() + ) + if err := newList(&args).render(ctx); err != nil { + return err + } + if err := newList(&env).render(ctx); err != nil { + return err + } + return syscall.Exec(args[0], args, env) + }, +} + +func loadHookState(r io.Reader) (*specs.State, error) { + var s specs.State + if err := json.NewDecoder(r).Decode(&s); err != nil { + return nil, err + } + return &s, nil +} + +func newTemplateContext(state *specs.State) *templateContext { + t := &templateContext{ + state: state, + } + t.funcs = template.FuncMap{ + "id": t.id, + "bundle": t.bundle, + "rootfs": t.rootfs, + "pid": t.pid, + "annotation": t.annotation, + } + return t +} + +type templateContext struct { + state *specs.State + funcs template.FuncMap +} + +func (t *templateContext) id() string { + return t.state.ID +} + +func (t *templateContext) bundle() string { + return t.state.Bundle +} + +func (t *templateContext) rootfs() string { + return filepath.Join(t.state.Bundle, "rootfs") +} + +func (t *templateContext) pid() int { + return t.state.Pid +} + +func (t *templateContext) annotation(k string) string { + return t.state.Annotations[k] +} + +func render(ctx *templateContext, source string, out io.Writer) error { + t, err := template.New("oci-hook").Funcs(ctx.funcs).Parse(source) + if err != nil { + return err + } + return t.Execute(out, ctx) +} + +func newList(l *[]string) *templateList { + return &templateList{ + l: l, + } +} + +type templateList struct { + l *[]string +} + +func (l *templateList) render(ctx *templateContext) error { + buf := bytes.NewBuffer(nil) + for i, s := range *l.l { + buf.Reset() + if err := render(ctx, s, buf); err != nil { + return err + } + (*l.l)[i] = buf.String() + } + buf.Reset() + return nil +} diff --git a/container_test.go b/container_test.go index 726ff0daf..dd88e627d 100644 --- a/container_test.go +++ b/container_test.go @@ -22,6 +22,7 @@ import ( "io" "io/ioutil" "os" + "os/exec" "runtime" "strings" "syscall" @@ -34,6 +35,7 @@ import ( "github.com/containerd/containerd/oci" _ "github.com/containerd/containerd/runtime" "github.com/containerd/typeurl" + specs "github.com/opencontainers/runtime-spec/specs-go" "github.com/containerd/containerd/errdefs" "github.com/containerd/containerd/windows/hcsshimtypes" @@ -1469,3 +1471,61 @@ func TestContainerLabels(t *testing.T) { t.Fatalf("expected label \"test\" to be \"no\"") } } + +func TestContainerHook(t *testing.T) { + t.Parallel() + + client, err := newClient(t, address) + if err != nil { + t.Fatal(err) + } + defer client.Close() + + var ( + image Image + ctx, cancel = testContext() + id = t.Name() + ) + defer cancel() + + image, err = client.GetImage(ctx, testImage) + if err != nil { + t.Fatal(err) + } + hook := func(_ context.Context, _ oci.Client, _ *containers.Container, s *specs.Spec) error { + if s.Hooks == nil { + s.Hooks = &specs.Hooks{} + } + path, err := exec.LookPath("containerd") + if err != nil { + return err + } + psPath, err := exec.LookPath("ps") + if err != nil { + return err + } + s.Hooks.Prestart = []specs.Hook{ + { + Path: path, + Args: []string{ + "containerd", + "oci-hook", "--", + psPath, "--pid", "{{pid}}", + }, + Env: os.Environ(), + }, + } + return nil + } + container, err := client.NewContainer(ctx, id, WithNewSpec(oci.WithImageConfig(image), hook), WithNewSnapshot(id, image)) + if err != nil { + t.Fatal(err) + } + defer container.Delete(ctx, WithSnapshotCleanup) + + task, err := container.NewTask(ctx, empty()) + if err != nil { + t.Fatal(err) + } + defer task.Delete(ctx, WithProcessKill) +}