merge branch 'cmd-umoci-stat'

Implements cyphar/umoci#38
Signed-off-by: Aleksa Sarai <[email protected]>

Author: cyphar

cmd/umoci/main.go

@@ -80,6 +80,7 @@ func main() {
 		gcCommand,
 		createCommand,
 		tagCommand,
+		statCommand,
 	}
 
 	// Actually run umoci.

cmd/umoci/stat.go

@@ -0,0 +1,109 @@
+/*
+ * umoci: Umoci Modifies Open Containers' Images
+ * Copyright (C) 2016 SUSE LLC.
+ *
+ * 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 main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/cyphar/umoci/image/cas"
+	"github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/urfave/cli"
+	"golang.org/x/net/context"
+)
+
+var statCommand = cli.Command{
+	Name:  "stat",
+	Usage: "displays status information of an image manifest",
+	ArgsUsage: `--image <image-path> --tag <reference>
+
+Where "<image-path>" is the path to the OCI image, and "<reference>" is the
+name of the reference descriptor to stat.
+
+WARNING: Do not depend on the output of this tool unless you're using --json.
+The intention of the default formatting of this tool is that it is easy for
+humans to read, and might change in future versions.`,
+
+	Flags: []cli.Flag{
+		// FIXME: This really should be a global option.
+		cli.StringFlag{
+			Name:  "image",
+			Usage: "path to OCI image bundle",
+		},
+		cli.StringFlag{
+			Name:  "tag",
+			Usage: "reference descriptor name to stat",
+		},
+		cli.BoolFlag{
+			Name:  "json",
+			Usage: "output the stat information as a JSON encoded blob",
+		},
+	},
+
+	Action: stat,
+}
+
+func stat(ctx *cli.Context) error {
+	// FIXME: Is there a nicer way of dealing with mandatory arguments?
+	imagePath := ctx.String("image")
+	if imagePath == "" {
+		return fmt.Errorf("image path cannot be empty")
+	}
+	tagName := ctx.String("tag")
+	if tagName == "" {
+		return fmt.Errorf("reference name cannot be empty")
+	}
+
+	// Get a reference to the CAS.
+	engine, err := cas.Open(imagePath)
+	if err != nil {
+		return err
+	}
+	defer engine.Close()
+
+	manifestDescriptor, err := engine.GetReference(context.TODO(), tagName)
+	if err != nil {
+		return err
+	}
+
+	// FIXME: Implement support for manifest lists.
+	if manifestDescriptor.MediaType != v1.MediaTypeImageManifest {
+		return fmt.Errorf("--from descriptor does not point to v1.MediaTypeImageManifest: not implemented: %s", manifestDescriptor.MediaType)
+	}
+
+	// Get stat information.
+	ms, err := Stat(context.TODO(), engine, *manifestDescriptor)
+	if err != nil {
+		return err
+	}
+
+	// Output the stat information.
+	if ctx.Bool("json") {
+		// Use JSON.
+		if err := json.NewEncoder(os.Stdout).Encode(ms); err != nil {
+			return err
+		}
+	} else {
+		if err := ms.Format(os.Stdout); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

cmd/umoci/utils.go

@@ -3,12 +3,18 @@ package main
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
+	"strings"
+	"text/tabwriter"
 
+	"github.com/cyphar/umoci/image/cas"
 	"github.com/cyphar/umoci/image/layer"
+	"github.com/docker/go-units"
 	ispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"golang.org/x/net/context"
 )
 
 // FIXME: This should be moved to a library. Too much of this code is in the
@@ -74,3 +80,121 @@ func ReadBundleMeta(bundle string) (UmociMeta, error) {
 	err = json.NewDecoder(fh).Decode(&meta)
 	return meta, err
 }
+
+// ManifestStat has information about a given OCI manifest.
+// TODO: Implement support for manifest lists, this should also be able to
+//       contain stat information for a list of manifests.
+type ManifestStat struct {
+	// TODO: Flesh this out. Currently it's only really being used to get an
+	//       equivalent of docker-history(1). We really need to add more
+	//       information about it.
+
+	// History stores the history information for the manifest.
+	History []historyStat `json:"history"`
+}
+
+// Format formats a ManifestStat using the default formatting, and writes the
+// result to the given writer.
+// TODO: This should really be implemented in a way that allows for users to
+//       define their own custom templates for different blocks (meaning that
+//       this should use text/template rather than using tabwriters manually.
+func (ms ManifestStat) Format(w io.Writer) error {
+	// Output history information.
+	tw := tabwriter.NewWriter(w, 4, 2, 1, ' ', 0)
+	fmt.Fprintf(tw, "LAYER\tCREATED\tCREATED BY\tSIZE\tCOMMENT\n")
+	for _, histEntry := range ms.History {
+		var (
+			created   = strings.Replace(histEntry.Created, "\t", " ", -1)
+			createdBy = strings.Replace(histEntry.CreatedBy, "\t", " ", -1)
+			comment   = strings.Replace(histEntry.Comment, "\t", " ", -1)
+			layerID   = "<none>"
+			size      = "<none>"
+		)
+
+		if !histEntry.EmptyLayer {
+			layerID = histEntry.Layer.Digest
+			size = units.HumanSize(float64(histEntry.Layer.Size))
+		}
+
+		// TODO: We need to truncate some of the fields.
+
+		fmt.Fprintf(tw, "%s\t%s\t%s\t%s\t%s\n", layerID, created, createdBy, size, comment)
+	}
+	tw.Flush()
+	return nil
+}
+
+// historyStat contains information about a single entry in the history of a
+// manifest. This is essentially equivalent to a single record from
+// docker-history(1).
+type historyStat struct {
+	// Layer is the descriptor referencing where the layer is stored. If it is
+	// nil, then this entry is an empty_layer (and thus doesn't have a backing
+	// diff layer).
+	Layer *ispec.Descriptor `json:"layer"`
+
+	// DiffID is an additional piece of information to Layer. It stores the
+	// DiffID of the given layer corresponding to the history entry. If DiffID
+	// is "", then this entry is an empty_layer.
+	DiffID string `json:"diff_id"`
+
+	// History is embedded in the stat information.
+	ispec.History
+}
+
+// Stat computes the ManifestStat for a given manifest blob. The provided
+// descriptor must refer to an OCI Manifest.
+func Stat(ctx context.Context, engine cas.Engine, manifestDescriptor ispec.Descriptor) (ManifestStat, error) {
+	var stat ManifestStat
+
+	if manifestDescriptor.MediaType != ispec.MediaTypeImageManifest {
+		return stat, fmt.Errorf("stat: cannot stat a non-manifest descriptor: invalid media type '%s'", manifestDescriptor.MediaType)
+	}
+
+	// We have to get the actual manifest.
+	manifestBlob, err := cas.FromDescriptor(ctx, engine, &manifestDescriptor)
+	if err != nil {
+		return stat, err
+	}
+	manifest, ok := manifestBlob.Data.(*ispec.Manifest)
+	if !ok {
+		return stat, fmt.Errorf("stat: cannot convert manifestBlob to manifest")
+	}
+
+	// Now get the config.
+	configBlob, err := cas.FromDescriptor(ctx, engine, &manifest.Config)
+	if err != nil {
+		return stat, err
+	}
+	config, ok := configBlob.Data.(*ispec.Image)
+	if !ok {
+		return stat, fmt.Errorf("stat: cannot convert configBlob to config")
+	}
+
+	// TODO: This should probably be moved into separate functions.
+
+	// Generate the history of the image. Because the config.History entries
+	// are in the same order as the manifest.Layer entries this is fairly
+	// simple. However, we only increment the layer index if a layer was
+	// actually generated by a history entry.
+	layerIdx := 0
+	for _, histEntry := range config.History {
+		info := historyStat{
+			History: histEntry,
+			DiffID:  "",
+			Layer:   nil,
+		}
+
+		// Only fill the other information and increment layerIdx if it's a
+		// non-empty layer.
+		if !histEntry.EmptyLayer {
+			info.DiffID = config.RootFS.DiffIDs[layerIdx]
+			info.Layer = &manifest.Layers[layerIdx]
+			layerIdx++
+		}
+
+		stat.History = append(stat.History, info)
+	}
+
+	return stat, nil
+}

glide.lock

@@ -1,5 +1,7 @@
 package: umoci
 import:
+- package: github.com/docker/go-units
+  version: ~0.3.1
 - package: github.com/Sirupsen/logrus
   version: ~0.11.0
 - package: github.com/urfave/cli

glide.yaml

@@ -0,0 +1,47 @@
+#!/usr/bin/env bats -t
+# umoci: Umoci Modifies Open Containers' Images
+# Copyright (C) 2016 SUSE LLC.
+#
+# 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.
+
+load helpers
+
+function setup() {
+	setup_image
+}
+
+function teardown() {
+	teardown_image
+}
+
+@test "umoci stat --json" {
+	# Make sure that stat looks about right.
+	umoci stat --image "$IMAGE" --tag "$TAG" --json
+	[ "$status" -eq 0 ]
+
+	statFile="$(mktemp --tmpdir="$BATS_TMPDIR" umoci-stat.XXXXXX)"
+	echo "$output" > "$statFile"
+
+	# .history should have at least one entry.
+	sane_run jq -SMr '.history | length' "$statFile"
+	[ "$status" -eq 0 ]
+	[ "$output" -ge 1 ]
+
+	# There should be at least one non-empty_layer.
+	sane_run jq -SMr '[.history[] | .empty_layer == false] | any' "$statFile"
+	[ "$status" -eq 0 ]
+	[[ "$output" == "true" ]]
+}
+
+# TODO: Add a test to make sure that empty_layer and layer are mutually
+#       exclusive. Unfortunately, jq doesn't provide an XOR operator...