fix(wdclient): prevent stale cache fallback for empty volume locations
## Problem
During Kubernetes pod restarts, volume servers temporarily disconnect and their
locations are removed from vidMap. The deleteLocation function leaves an empty
array [] in vid2Locations map instead of removing the key entirely.
GetLocations() was checking 'if found && len(locations) > 0', which would fail
for empty arrays and fall back to the cache chain, returning STALE locations
from before the restart. This caused S3 gateway to try connecting to old pod
IPs that no longer exist, resulting in connection timeouts and hanging registry
sync jobs.
Example timeline:
1. Volume pod at 10.131.1.28:8081 registers volumes 10,12
2. S3 gateway caches: vid2Locations[10] = [10.131.1.28:8081]
3. Pod restarts, gets new IP 10.131.1.65:8081
4. Master sends delete → vid2Locations[10] = [] (empty, but key exists)
5. BUG: GetLocations(10) sees found=true, len=0 → falls back to cache
6. Returns stale 10.131.1.28:8081 instead of waiting for new location
7. S3 requests timeout trying to reach unreachable old IP
## Solution
Distinguish between two cases:
- found=true, locations=[] : Volume explicitly has no locations (e.g. restart)
→ Return nil, false (no fallback to cache)
- found=false : Volume never seen in current map
→ Check cache (preserve cache benefits for unknown volumes)
An empty array explicitly means 'this volume currently has no locations',
which is semantically different from 'volume unknown'. Don't fall back to
stale cache for explicitly empty volumes.
## Testing
Added comprehensive tests:
- TestGetLocationsEmptyArrayNoFallback: Verifies empty arrays don't use cache
- TestGetLocationsUnknownVolumeUsesCache: Verifies unknown volumes still use cache
- All existing tests pass
## Impact
Fixes registry sync job hangs during SeaweedFS upgrades/restarts. S3 gateway
will now correctly wait for updated volume locations instead of using stale
cached IPs.
Related: OutSystems.SeaWeedfs Helm chart, vega cluster incident 2026-06-24
Ping previously dialled whatever host:port the caller asked for. Gate
each server's Ping handler on cluster membership: masters check the
topology, registered cluster nodes, and configured master peers; volume
servers only accept their seed/current masters; filers accept tracked
peer filers, the master-learned volume server set, and configured
masters.
Use address-indexed peer lookups to keep Ping target validation O(1):
- topology maintains a pb.ServerAddress -> *DataNode index alongside
the dc/rack/node tree, kept in sync from doLinkChildNode and
UnlinkChildNode plus the ip/port-rewrite branch in
GetOrCreateDataNode. GetTopology now returns nil on a detached
subtree instead of panicking, so the linkage hooks can no-op safely.
- vid_map tracks a refcount per volume-server address so
hasVolumeServer answers without scanning every vid location. The
add path skips empty-address entries the same way the delete path
already does, so a zero-value Location cannot leak a permanent
serverRefCount[""] bucket.
- masters reuse a cached master-address set from MasterClient instead
of walking the configured peer slice on every request.
- volume servers compare against a pre-built seed-master set and
protect currentMaster reads/writes with an RWMutex, fixing the
data race with the heartbeat goroutine. The seed slice is copied
on construction so external mutation cannot desync it from the
frozen lookup set.
- cluster.check drops the direct volume-to-volume sweep; volume
servers no longer carry a peer-volume list, and the note next to
the dropped probe is reworded to make clear that direct
volume-to-volume reachability is intentionally not validated by
this command.
Update the volume-server integration tests that drove Ping through the
new admission gate: success-path coverage now targets the master peer
(the only type a volume server tracks), and the unknown/unreachable
path asserts the InvalidArgument the gate now returns instead of the
old downstream dial error.
Mirror the same admission gate in the Rust volume server crate: a
seed-master HashSet built once at startup plus a tokio RwLock over the
heartbeat-tracked current master, both consulted in is_known_ping_target
on every Ping, with InvalidArgument returned for any target that isn't
a recognised master.
* chore(weed/wdclient): prune unused functions
* chore(weed/wdclient): prune test-only functions and associated tests
* chore(weed/wdclient): remove dead cursor field
The cursor field and its initialization are no longer used after
the removal of getLocationIndex.
---------
Co-authored-by: Chris Lu <chris.lu@gmail.com>
* fallback to check master
* clean up
* parsing
* refactor
* handle parse error
* return error
* avoid dup lookup
* use batch key
* dedup lookup logic
* address comments
* errors.Join(lookupErrors...)
* add a comment
* Fix: Critical data race in MasterClient vidMap
Fixes a critical data race where resetVidMap() was writing to the vidMap
pointer while other methods were reading it concurrently without synchronization.
Changes:
- Removed embedded *vidMap from MasterClient
- Added vidMapLock (sync.RWMutex) to protect vidMap pointer access
- Created safe accessor methods (GetLocations, GetDataCenter, etc.)
- Updated all direct vidMap accesses to use thread-safe methods
- Updated resetVidMap() to acquire write lock during pointer swap
The vidMap already has internal locking for its operations, but this fix
protects the vidMap pointer itself from concurrent read/write races.
Verified with: go test -race ./weed/wdclient/...
Impact:
- Prevents potential panics from concurrent pointer access
- No performance impact - uses RWMutex for read-heavy workloads
- Maintains backward compatibility through wrapper methods
* fmt
* Fix: Critical data race in MasterClient vidMap
Fixes a critical data race where resetVidMap() was writing to the vidMap
pointer while other methods were reading it concurrently without synchronization.
Changes:
- Removed embedded *vidMap from MasterClient struct
- Added vidMapLock (sync.RWMutex) to protect vidMap pointer access
- Created minimal public accessor methods for external packages:
* GetLocations, GetLocationsClone, GetVidLocations
* LookupFileId, LookupVolumeServerUrl
* GetDataCenter
- Internal code directly locks and accesses vidMap (no extra indirection)
- Updated resetVidMap() to acquire write lock during pointer swap
- Updated shell/commands.go to use GetDataCenter() method
Design Philosophy:
- vidMap already has internal locking for its map operations
- This fix specifically protects the vidMap *pointer* from concurrent access
- Public methods for external callers, direct locking for internal use
- Minimizes wrapper overhead while maintaining thread safety
Verified with: go test -race ./weed/wdclient/... (passes)
Impact:
- Prevents potential panics/crashes from data races
- Minimal performance impact (RWMutex for read-heavy workload)
- Maintains full backward compatibility
* fix more concurrent access
* reduce lock scope
* Optimize vidMap locking for better concurrency
Improved locking strategy based on the understanding that:
- vidMapLock protects the vidMap pointer from concurrent swaps
- vidMap has internal locks that protect its data structures
Changes:
1. Read operations: Grab pointer with RLock, release immediately, then operate
- Reduces lock hold time
- Allows resetVidMap to proceed sooner
- Methods: GetLocations, GetLocationsClone, GetVidLocations,
LookupVolumeServerUrl, GetDataCenter
2. Write operations: Changed from Lock() to RLock()
- RLock prevents pointer swap during operation
- Allows concurrent readers and other writers (serialized by vidMap's lock)
- Methods: addLocation, deleteLocation, addEcLocation, deleteEcLocation
Benefits:
- Significantly reduced lock contention
- Better concurrent performance under load
- Still prevents all race conditions
Verified with: go test -race ./weed/wdclient/... (passes)
* Further reduce lock contention in LookupVolumeIdsWithFallback
Optimized two loops that were holding RLock for extended periods:
Before:
- Held RLock during entire loop iteration
- Included string parsing and cache lookups
- Could block resetVidMap for significant time with large batches
After:
- Grab vidMap pointer with brief RLock
- Release lock immediately
- Perform all loop operations on local pointer
Impact:
- First loop: Cache check on initial volumeIds
- Second loop: Double-check after singleflight wait
Benefits:
- Minimal lock hold time (just pointer copy)
- resetVidMap no longer blocked by long loops
- Better concurrent performance with large volume ID lists
- Still thread-safe (vidMap methods have internal locks)
Verified with: go test -race ./weed/wdclient/... (passes)
* Add clarifying comments to vidMap helper functions
Added inline documentation to each helper function (addLocation, deleteLocation,
addEcLocation, deleteEcLocation) explaining the two-level locking strategy:
- RLock on vidMapLock prevents resetVidMap from swapping the pointer
- vidMap has internal locks that protect the actual map mutations
- This design provides optimal concurrency
The comments make it clear why RLock (not Lock) is correct and intentional,
preventing future confusion about the locking strategy.
* Improve encapsulation: Add shallowClone() method to vidMap
Added a shallowClone() method to vidMap to improve encapsulation and prevent
MasterClient from directly accessing vidMap's internal fields.
Changes:
1. Added vidMap.shallowClone() in vid_map.go
- Encapsulates the shallow copy logic within vidMap
- Makes vidMap responsible for its own state representation
- Documented that caller is responsible for thread safety
2. Simplified resetVidMap() in masterclient.go
- Uses tail := mc.vidMap.shallowClone() instead of manual field access
- Cleaner, more maintainable code
- Better adherence to encapsulation principles
Benefits:
- Improved code organization and maintainability
- vidMap internals are now properly encapsulated
- Easier to modify vidMap structure in the future
- More self-documenting code
Verified with: go test -race ./weed/wdclient/... (passes)
* Optimize locking: Reduce lock acquisitions and use helper methods
Two optimizations to further reduce lock contention and improve code consistency:
1. LookupFileIdWithFallback: Eliminated redundant lock acquisition
- Before: Two separate locks to get vidMap and dataCenter
- After: Single lock gets both values together
- Benefit: 50% reduction in lock/unlock overhead for this hot path
2. KeepConnected: Use GetDataCenter() helper for consistency
- Before: Manual lock/unlock to access DataCenter field
- After: Use existing GetDataCenter() helper method
- Benefit: Better encapsulation and code consistency
Impact:
- Reduced lock contention in high-traffic lookup path
- More consistent use of accessor methods throughout codebase
- Cleaner, more maintainable code
Verified with: go test -race ./weed/wdclient/... (passes)
* Refactor: Extract common locking patterns into helper methods
Eliminated code duplication by introducing two helper methods that encapsulate
the common locking patterns used throughout MasterClient:
1. getStableVidMap() - For read operations
- Acquires lock, gets pointer, releases immediately
- Returns stable snapshot for thread-safe reads
- Used by: GetLocations, GetLocationsClone, GetVidLocations,
LookupFileId, LookupVolumeServerUrl, GetDataCenter
2. withCurrentVidMap(f func(vm *vidMap)) - For write operations
- Holds RLock during callback execution
- Prevents pointer swap while allowing concurrent operations
- Used by: addLocation, deleteLocation, addEcLocation, deleteEcLocation
Benefits:
- Reduced code duplication (eliminated 48 lines of repetitive locking code)
- Centralized locking logic makes it easier to understand and maintain
- Self-documenting pattern through named helper methods
- Easier to modify locking strategy in the future (single point of change)
- Improved readability - accessor methods are now one-liners
Code size reduction: ~40% fewer lines for accessor/helper methods
Verified with: go test -race ./weed/wdclient/... (passes)
* consistent
* Fix cache pointer race condition with atomic.Pointer
Use atomic.Pointer for vidMap cache field to prevent data races
during cache trimming in resetVidMap. This addresses the race condition
where concurrent GetLocations calls could read the cache pointer while
resetVidMap is modifying it during cache chain trimming.
Changes:
- Changed cache field from *vidMap to atomic.Pointer[vidMap]
- Updated all cache access to use Load() and Store() atomic operations
- Updated shallowClone, GetLocations, deleteLocation, deleteEcLocation
- Updated resetVidMap to use atomic operations for cache trimming
* Merge: Resolve conflict in deleteEcLocation - keep atomic.Pointer and fix bug
Resolved merge conflict by combining:
1. Atomic pointer access pattern (from HEAD): cache.Load()
2. Correct method call (from fix): deleteEcLocation (not deleteLocation)
Resolution:
- Before (HEAD): cachedMap.deleteLocation() - WRONG, reintroduced bug
- Before (fix): vc.cache.deleteEcLocation() - RIGHT method, old pattern
- After (merged): cachedMap.deleteEcLocation() - RIGHT method, new pattern
This preserves both improvements:
✓ Thread-safe atomic.Pointer access pattern
✓ Correct recursive call to deleteEcLocation
Verified with: go test -race ./weed/wdclient/... (passes)
* Update vid_map.go
* remove shallow clone
* simplify
The vidMap structure is modified to a linked list structure (the length is limited to 5). When the vidMap is reset, the current vidMap is added to the new vidMap as a cache node. When the query locations is empty, the cache node is searched to avoid problems when the master switches leaders.
os-pradipbabar