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Allow advertisement or entries chain truncation #132

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Allow advertisement or entries chain truncation #132

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8198186
Allow advertisement or entries chain truncation
gammazero Oct 10, 2023
9497457
chain truncation recognition for dtsync
gammazero Oct 12, 2023
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13 changes: 11 additions & 2 deletions dagsync/dtsync/syncer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package dtsync

import (
"context"
"errors"
"fmt"
"io"

Expand Down Expand Up @@ -110,9 +111,17 @@ func (s *Syncer) has(ctx context.Context, nextCid cid.Cid, sel ipld.Node) ([]cid
if err != nil {
return nil, false
}
if err := progress.WalkMatching(rootNode, csel, func(p traversal.Progress, n datamodel.Node) error {
err = progress.WalkMatching(rootNode, csel, func(p traversal.Progress, n datamodel.Node) error {
return nil
}); err != nil {
})
if err != nil {
// Advertisement or entries block, not at start of chain, was not
// found. Consider this to mean the chain was truncated at this point,
// and return what was found so far.
if errors.Is(err, ipld.ErrNotExists{}) {
log.Warnw("stopping ipld traversal due to content not found")
return traversed, true
}
return nil, false
}
return traversed, true
Expand Down
7 changes: 7 additions & 0 deletions dagsync/ipnisync/sync.go
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Original file line number Diff line number Diff line change
Expand Up @@ -276,6 +276,13 @@ func (s *Syncer) walkFetch(ctx context.Context, rootCid cid.Cid, sel selector.Se

err = progress.WalkMatching(rootNode, sel, func(_ traversal.Progress, _ datamodel.Node) error { return nil })
if err != nil {
// Advertisement or entries block, not at start of chain, was not
// found. Consider this to mean the chain was truncated at this point,
// and return what was found so far.
if errors.Is(err, ipld.ErrNotExists{}) {
log.Warnw("stopping ipld traversal due to content not found")
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it would be great to record these and be able to occasionally re-try?
it's easy to imagine mis-configured provider web servers that could get into states where a 404 is returned when the data is only temporarily unavailable.

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Right, this is certainly a desirable.
I imagine the bulk of the complexity in facilitating this is the semantics of retry: persisting the state of retriable CIDs while not blocking the ad ingestion. That would need to have some upper limit per provider per retry.

But first, a quick sanity check: @gammazero do we surface this error to providers at /providers endpoint?

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This is still an error if the first CID asked for is not found. It is only considered intentional if, at some point in chain traversal, a NotFound is returned. So, if a web server is misconfigured, then the first requested CID should result in error. So, I think it is safe to assume that a NotFound, if it occurs at a later point in traversal, is intentional.

return traversalOrder, nil
}
return nil, err
}
return traversalOrder, nil
Expand Down