a4fadc596b
Now that we have most of the services required for use with containerd, it was found that common patterns were used throughout services. By defining a central `errdefs` package, we ensure that services will map errors to and from grpc consistently and cleanly. One can decorate an error with as much context as necessary, using `pkg/errors` and still have the error mapped correctly via grpc. We make a few sacrifices. At this point, the common errors we use across the repository all map directly to grpc error codes. While this seems positively crazy, it actually works out quite well. The error conditions that were specific weren't super necessary and the ones that were necessary now simply have better context information. We lose the ability to add new codes, but this constraint may not be a bad thing. Effectively, as long as one uses the errors defined in `errdefs`, the error class will be mapped correctly across the grpc boundary and everything will be good. If you don't use those definitions, the error maps to "unknown" and the error message is preserved. Signed-off-by: Stephen J Day <stephen.day@docker.com>
86 lines
2.4 KiB
Go
86 lines
2.4 KiB
Go
package rootfs
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import (
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"fmt"
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"github.com/containerd/containerd/errdefs"
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"github.com/containerd/containerd/log"
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"github.com/containerd/containerd/mount"
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"github.com/containerd/containerd/snapshot"
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"github.com/opencontainers/go-digest"
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"github.com/opencontainers/image-spec/identity"
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ocispec "github.com/opencontainers/image-spec/specs-go/v1"
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"github.com/pkg/errors"
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"golang.org/x/net/context"
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)
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type Applier interface {
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Apply(context.Context, ocispec.Descriptor, []mount.Mount) (ocispec.Descriptor, error)
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}
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type Layer struct {
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Diff ocispec.Descriptor
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Blob ocispec.Descriptor
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}
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func ApplyLayers(ctx context.Context, layers []Layer, sn snapshot.Snapshotter, a Applier) (digest.Digest, error) {
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var chain []digest.Digest
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for _, layer := range layers {
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if err := applyLayer(ctx, layer, chain, sn, a); err != nil {
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// TODO: possibly wait and retry if extraction of same chain id was in progress
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return "", err
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}
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chain = append(chain, layer.Diff.Digest)
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}
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return identity.ChainID(chain), nil
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}
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func applyLayer(ctx context.Context, layer Layer, chain []digest.Digest, sn snapshot.Snapshotter, a Applier) error {
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var (
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parent = identity.ChainID(chain)
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chainID = identity.ChainID(append(chain, layer.Diff.Digest))
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diff ocispec.Descriptor
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)
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_, err := sn.Stat(ctx, chainID.String())
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if err == nil {
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log.G(ctx).Debugf("Extraction not needed, layer snapshot exists")
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return nil
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} else if !errdefs.IsNotFound(err) {
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return errors.Wrap(err, "failed to stat snapshot")
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}
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key := fmt.Sprintf("extract %s", chainID)
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// Prepare snapshot with from parent
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mounts, err := sn.Prepare(ctx, key, parent.String())
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if err != nil {
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//TODO: If is snapshot exists error, retry
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return errors.Wrap(err, "failed to prepare extraction layer")
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}
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defer func() {
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if err != nil {
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log.G(ctx).WithError(err).WithField("key", key).Infof("Apply failure, attempting cleanup")
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if rerr := sn.Remove(ctx, key); rerr != nil {
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log.G(ctx).WithError(rerr).Warnf("Extraction snapshot %q removal failed: %v", key)
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}
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}
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}()
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diff, err = a.Apply(ctx, layer.Blob, mounts)
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if err != nil {
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return errors.Wrapf(err, "failed to extract layer %s", layer.Diff.Digest)
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}
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if diff.Digest != layer.Diff.Digest {
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err = errors.Errorf("wrong diff id calculated on extraction %q", diff.Digest)
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return err
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}
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if err = sn.Commit(ctx, chainID.String(), key); err != nil {
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return errors.Wrapf(err, "failed to commit snapshot %s", parent)
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}
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return nil
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}
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