Add parameter to specify checkpoint archive compression

The checkpoint archive compression was hardcoded to `archive.Gzip`.

There have been requests to make the used compression algorithm
selectable. There was especially the request to not compress the
checkpoint archive to be able to create faster checkpoints when not
compressing it.

This also changes the default from `gzip` to `zstd`. This change should
not break anything as the restore code path automatically handles
whatever compression the user provides during restore.

Signed-off-by: Adrian Reber <areber@redhat.com>

2 files changed, 31 insertions, 3 deletions

diff --git a/cmd/podman/common/completion.go b/cmd/podman/common/completion.go
index de5b2995a..c93f2017c 100644
--- a/cmd/podman/common/completion.go
+++ b/cmd/podman/common/completion.go
@@ -1211,3 +1211,10 @@ func AutocompleteVolumeFilters(cmd *cobra.Command, args []string, toComplete str
 	}
 	return completeKeyValues(toComplete, kv)
 }
+
+// AutocompleteCheckpointCompressType - Autocomplete checkpoint compress type options.
+// -> "gzip", "none", "zstd"
+func AutocompleteCheckpointCompressType(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+	types := []string{"gzip", "none", "zstd"}
+	return types, cobra.ShellCompDirectiveNoFileComp
+}
diff --git a/cmd/podman/containers/checkpoint.go b/cmd/podman/containers/checkpoint.go
index 47d60453b..4fa72d520 100644
--- a/cmd/podman/containers/checkpoint.go
+++ b/cmd/podman/containers/checkpoint.go
@@ -3,6 +3,7 @@ package containers
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/containers/common/pkg/completion"
 	"github.com/containers/podman/v3/cmd/podman/common"
@@ -11,6 +12,7 @@ import (
 	"github.com/containers/podman/v3/cmd/podman/validate"
 	"github.com/containers/podman/v3/pkg/domain/entities"
 	"github.com/containers/podman/v3/pkg/rootless"
+	"github.com/containers/storage/pkg/archive"
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 )
@@ -36,9 +38,7 @@ var (
 	}
 )
 
-var (
-	checkpointOptions entities.CheckpointOptions
-)
+var checkpointOptions entities.CheckpointOptions
 
 func init() {
 	registry.Commands = append(registry.Commands, registry.CliCommand{
@@ -60,11 +60,32 @@ func init() {
 	flags.BoolVarP(&checkpointOptions.PreCheckPoint, "pre-checkpoint", "P", false, "Dump container's memory information only, leave the container running")
 	flags.BoolVar(&checkpointOptions.WithPrevious, "with-previous", false, "Checkpoint container with pre-checkpoint images")
 
+	flags.StringP("compress", "c", "zstd", "Select compression algorithm (gzip, none, zstd) for checkpoint archive.")
+	_ = checkpointCommand.RegisterFlagCompletionFunc("compress", common.AutocompleteCheckpointCompressType)
+
 	validate.AddLatestFlag(checkpointCommand, &checkpointOptions.Latest)
 }
 
 func checkpoint(cmd *cobra.Command, args []string) error {
 	var errs utils.OutputErrors
+	if cmd.Flags().Changed("compress") {
+		if checkpointOptions.Export == "" {
+			return errors.Errorf("--compress can only be used with --export")
+		}
+		compress, _ := cmd.Flags().GetString("compress")
+		switch strings.ToLower(compress) {
+		case "none":
+			checkpointOptions.Compression = archive.Uncompressed
+		case "gzip":
+			checkpointOptions.Compression = archive.Gzip
+		case "zstd":
+			checkpointOptions.Compression = archive.Zstd
+		default:
+			return errors.Errorf("Selected compression algorithm (%q) not supported. Please select one from: gzip, none, zstd", compress)
+		}
+	} else {
+		checkpointOptions.Compression = archive.Zstd
+	}
 	if rootless.IsRootless() {
 		return errors.New("checkpointing a container requires root")
 	}