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Don't cache truncated package downloads in xpkg - #1189
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CachedClient.Get copies the package stream into the package cache through a pipe while it parses it. The parser closes its reader even when parsing fails, and closing the tee reader closed the pipe cleanly. So when a download failed partway, FsPackageCache.Store saw a normal EOF and cached a valid gzip that held only a prefix of package.yaml. The next Get hit the cache, parsed the prefix without error, and returned a package that was missing most of its objects. Give the parser only the package content to close, and close the pipe with the parse error once Parse returns, so Store fails instead of caching a prefix. Get now waits for Store to finish before returning. Also make Store write to a temporary file and rename it into place only after the content has been written and synced, removing the temporary file on any error. The cache then never holds a partially written package under its real name. Signed-off-by: ezgidemirel <ezgidemirel91@gmail.com>
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. 📝 WalkthroughWalkthroughPackage caching now writes compressed content through a temporary file before renaming it into place. Package parsing passes errors to the cache writer and waits for storage to finish. Tests cover failed reads and truncated package streams. ChangesPackage cache integrity
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~20 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant Client.Get
participant Parser
participant Pipe
participant FsPackageCache.Store
Client.Get->>Pipe: Create cache stream
Client.Get->>FsPackageCache.Store: Start storage goroutine with pipe reader
Client.Get->>Parser: Parse size-limited tee
Parser-->>Client.Get: Return parse result
Client.Get->>Pipe: Close with parse error
FsPackageCache.Store-->>Client.Get: Return storage result
Merge Risk: 🔵 Low · up to This change prevents truncated package downloads from becoming cached entries. One narrow concern remains: two cache instances writing the same package in a shared directory would use the same temporary filename. Using a unique temporary file per write would close this gap. It does not need to block merging unless deployments run multiple cache writers on one directory. Security Architecture ReviewSecurity architecture risk: 🔵 Low · up to The change strengthens package-cache integrity by preventing parse failures from publishing partial downloads. No introduced security regression was established, but safe sharing of a cache directory and recovery of previously truncated entries remain uncertain. Retained concerns Security review detailsSecurity Blast Radius
Trust Boundaries and Controls
Resilience and Maintainability Implications
Hardening Proposals
Important Pre-merge checks failedPlease resolve all errors before merging. Addressing warnings is optional. ❌ Failed checks (1 error)
✅ Passed checks (4 passed)
Full details: Breaking ChangesExplanation
Resolution If the new filesystem requirements are intentional, add the
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Inline comments:
Review comments at @pkg/xpkg/cache.go:
- Around line 90-92: Update FsPackageCache.Store to create an exclusive, unique
temporary file in the cache directory for each call, then rename that call’s own
temporary path into place. Preserve the existing cache-write behavior while
ensuring concurrent instances cannot truncate or expose each other’s in-progress
writes.
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pkg/xpkg/cache.gopkg/xpkg/cache_test.gopkg/xpkg/client.gopkg/xpkg/client_test.go
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| tmp := path + ".tmp" | ||
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| cf, err := c.fs.Create(tmp) |
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🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win
Use a unique temporary file for each Store call.
When two FsPackageCache instances share a directory and cache ID, their instance-local mutexes do not coordinate writes. Both calls use the same .tmp path. The second Create can truncate the first write, and a rename can expose a file while the other call still writes to it. Could we create each temporary file exclusively under the cache directory and rename its own path? Thanks for addressing the single-writer failure path.
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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Review comment at @pkg/xpkg/cache.go around lines 90 - 92:
Update FsPackageCache.Store to create an exclusive, unique temporary file in the
cache directory for each call, then rename that call’s own temporary path into
place. Preserve the existing cache-write behavior while ensuring concurrent
instances cannot truncate or expose each other’s in-progress writes.
After applying the fix, consider running `coderabbit review --agent` for local
review. Visit https://docs.coderabbit.ai/cli?utm_source=ghpr
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Eyh, I found this PR because we were hit with the same issue. Fun troubleshooting, awful cache sanity :D 3 different prod clusters with v2.2.0: download died at the first TLS record boundary, the cached prefix cut inside a 50 KB block scalar, so it parsed fine and was applied as a Composition missing the write side fix is good, but can I'm looking into what could cause the network issue in the first place... |
Thanks, that's exactly the case this PR fixes: the download failed, but the cache saw a clean EOF and kept the prefix. On hashing: the cache key holds the image manifest digest, not the layer digest, and the cache stores You're right that the download side doesn't verify a digest either. |
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Backport failed for Please cherry-pick the changes locally and resolve any conflicts. git fetch origin release-2.2
git worktree add -d .worktree/backport-1189-to-release-2.2 origin/release-2.2
cd .worktree/backport-1189-to-release-2.2
git switch --create backport-1189-to-release-2.2
git cherry-pick -x 6ccb301b8a4644cb2016f968b909f1ec1c998d2e |
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Successfully created backport PR for |
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Successfully created backport PR for |
3 participants
Description of your changes
A package download that fails partway can get cached as a valid, truncated
package.yaml. After that, every reconcile parses the truncated copy without error. The package revision records only some of its objects instatus.objectRefs, reportsHealthy=True, and rbac-manager renders the provider's:systemClusterRole from that short list. Then a provider whose CRDs are still in the cluster from an earlier healthy install crash-loops on the first kind it isn't allowed to watch.This matches the reports in crossplane/crossplane#7536 and crossplane/crossplane#7712: partial
objectRefs, a different count after each delete and restart, and the missing kinds being the last ones in the package.Root cause. On a cache miss,
CachedClient.Getcopies the download intoFsPackageCache.Storethrough anio.Pipewhile the parser reads it. The parser always closes its reader on the way out, error or not, and closingteeReadClosercalledpipeW.Close(). The comment on that line already noted that it would only error if we calledpipeW.CloseWithError(), and we never did. So when the stream failed withunexpected EOF,Storesaw a clean EOF, wrote a complete gzip trailer around the prefix, and saved it under the final cache path. The nextGethit the cache and parsed the prefix. A cut between YAML documents is a valid stream, and in practice so are many cuts in the middle of a document.Changes
pkg/xpkg/client.go: the parser now closes only the package content. AfterParsereturns,GetcallspipeW.CloseWithError(err), which closes cleanly when the error is nil, so a failed parse makesStorefail instead of caching a prefix.Getnow also waits forStoreto finish before it returns. Before, the write was fire-and-forget.pkg/xpkg/cache.go:Storewrites to<id>.gz.tmp, syncs and closes it, then renames it to<id>.gz. It removes the temporary file on any error.HasandGetonly look at<id>.gz, so they never see a partially written file. This also covers a process killed mid-write.Each change is needed on its own: reverting either one makes the new tests fail.
Tests
TestClientGetCachesOnlyCompletePackages(new) runs a real parser and a realFsPackageCacheagainst a layer stream that fails withio.ErrUnexpectedEOFpartway through. It then callsGeta second time with the registry unavailable, so the call can only succeed from the cache. There are three cases:CompletePackage,TruncatedAtDocumentBoundaryandTruncatedMidString. Without this change,TruncatedAtDocumentBoundaryreturns 2 of 4 objects from the cache with a nil error.TestStoregains anErrFailedReadLeavesNoFilecase and now checks which files are left in the cache directory. Each case gets its own filesystem so the cases don't depend on map iteration order.End-to-end verification. I built Crossplane core v2.3.3 against this change backported to
v2.3.3, and tested it on kind withprovider-azureadv2.3.0. The package came from an in-cluster registry.Notes for reviewers
TeeReadCloseris no longer used in this repo. It's exported, so I left it in place.objectRefslist and reportsHealthy=True. #7537 would only restore the provider's RBAC while the missing MRDs are still controlled by the current revision, which is the case when the revision is kept, for example after a core restart. It wouldn't help when the revision is replaced.Refs crossplane/crossplane#7536, crossplane/crossplane#7712. Those issues are fixed once crossplane/crossplane picks up this change.
I have:
./nix.sh flake checkto ensure this PR is ready for review.Linked a PR or a docs tracking issue to document this change.Internal behaviour only, no user-facing change to document.AddedI will cherry-pick to release-2.3 and release-2.4 manually.backport release-x.ylabels to auto-backport this PR.