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Compute diff from the upper directory of overlayfs-based snapshotter #2181

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Merged
tonistiigi merged 1 commit into from
Sep 2, 2021
Merged

Compute diff from the upper directory of overlayfs-based snapshotter #2181

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56 changes: 49 additions & 7 deletions cache/blobs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@ import (
"context"
"fmt"
"io"
"os"
"strconv"

"github.com/containerd/containerd/content"
"github.com/containerd/containerd/diff"
Expand All @@ -17,6 +19,7 @@ import (
imagespecidentity "github.com/opencontainers/image-spec/identity"
ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"golang.org/x/sync/errgroup"
)

Expand Down Expand Up @@ -106,13 +109,52 @@ func computeBlobChain(ctx context.Context, sr *immutableRef, createIfNeeded bool
if release != nil {
defer release()
}
desc, err := sr.cm.Differ.Compare(ctx, lower, upper,
diff.WithMediaType(mediaType),
diff.WithReference(sr.ID()),
diff.WithCompressor(compressorFunc),
)
if err != nil {
return nil, err
var desc ocispecs.Descriptor

// Determine differ and error/log handling according to the platform, envvar and the snapshotter.
var enableOverlay, fallback, logWarnOnErr bool
if forceOvlStr := os.Getenv("BUILDKIT_DEBUG_FORCE_OVERLAY_DIFF"); forceOvlStr != "" {
enableOverlay, err = strconv.ParseBool(forceOvlStr)
if err != nil {
return nil, errors.Wrapf(err, "invalid boolean in BUILDKIT_DEBUG_FORCE_OVERLAY_DIFF")
}
fallback = false // prohibit fallback on debug
} else if !isTypeWindows(sr) {
enableOverlay, fallback = true, true
switch sr.cm.ManagerOpt.Snapshotter.Name() {
case "overlayfs", "fuse-overlayfs", "stargz":
logWarnOnErr = true // snapshotter should support overlay diff. so print warn log on failure
}
}
if enableOverlay {
computed, ok, err := sr.tryComputeOverlayBlob(ctx, lower, upper, mediaType, sr.ID(), compressorFunc)
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@tonistiigi tonistiigi Sep 2, 2021

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the logic looks correct now but if you can, try to call tryComputeOverlayBlob only once. Even if it doesn't save lines, because env is(will be) used by the tests it is better if it doesn't go to a different code path. I can imagine a future change that modifies one branch only and we can't catch the error with tests. For the "overlay mounts not detected" case you can print the mount params, both for env and snapshotter case.

if !ok || err != nil {
if !fallback {
if !ok {
return nil, errors.Errorf("overlay mounts not detected (lower=%+v,upper=%+v)", lower, upper)
}
if err != nil {
return nil, errors.Wrapf(err, "failed to compute overlay diff")
}
}
if logWarnOnErr {
logrus.Warnf("failed to compute blob by overlay differ (ok=%v): %v", ok, err)
}
}
if ok {
desc = computed
}
}

if desc.Digest == "" {
desc, err = sr.cm.Differ.Compare(ctx, lower, upper,
diff.WithMediaType(mediaType),
diff.WithReference(sr.ID()),
diff.WithCompressor(compressorFunc),
)
if err != nil {
return nil, err
}
}

if desc.Annotations == nil {
Expand Down
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