* fix(ec): gather shards from all disk locations before rebuild (#8631)
Fix "too few shards given" error during ec.rebuild on multi-disk volume
servers. The root cause has two parts:
1. VolumeEcShardsRebuild only looked at a single disk location for shard
files. On multi-disk servers, the existing local shards could be on one
disk while copied shards were placed on another, causing the rebuild to
see fewer shards than actually available.
2. VolumeEcShardsCopy had a DiskId condition (req.DiskId == 0 &&
len(vs.store.Locations) > 0) that was always true, making the
FindFreeLocation fallback dead code. This meant copies always went to
Locations[0] regardless of where existing shards were.
Changes:
- VolumeEcShardsRebuild now finds the location with the most shards,
then gathers shard files from other locations via hard links (or
symlinks for cross-device) before rebuilding. Gathered files are
cleaned up after rebuild.
- VolumeEcShardsCopy now only uses Locations[DiskId] when DiskId > 0
(explicitly set). Otherwise, it prefers the location that already has
the EC volume, falling back to HDD then any free location.
- generateMissingEcFiles now logs shard counts and provides a clear
error message when not enough shards are found, instead of passing
through to the opaque reedsolomon "too few shards given" error.
* fix(ec): update test to match skip behavior for unrepairable volumes
The test expected an error for volumes with insufficient shards, but
commit 5acb4578a changed unrepairable volumes to be skipped with a log
message instead of returning an error. Update the test to verify the
skip behavior and log output.
* fix(ec): address PR review comments
- Add comment clarifying DiskId=0 means "not specified" (protobuf default),
callers must use DiskId >= 1 to target a specific disk.
- Log warnings on cleanup failures for gathered shard links.
* fix(ec): read shard files from other disks directly instead of linking
Replace the hard link / symlink gathering approach with passing
additional search directories into RebuildEcFiles. The rebuild
function now opens shard files directly from whichever disk they
live on, avoiding filesystem link operations and cleanup.
RebuildEcFiles and RebuildEcFilesWithContext gain a variadic
additionalDirs parameter (backward compatible with existing callers).
* fix(ec): clarify DiskId selection semantics in VolumeEcShardsCopy comment
* fix(ec): avoid empty files on failed rebuild; don't skip ecx-only locations
- generateMissingEcFiles: two-pass approach — first discover present/missing
shards and check reconstructability, only then create output files. This
avoids leaving behind empty truncated shard files when there are too few
shards to rebuild.
- VolumeEcShardsRebuild: compute hasEcx before skipping zero-shard locations.
A location with an .ecx file but no shard files (all shards on other disks)
is now a valid rebuild candidate instead of being silently skipped.
* fix(ec): select ecx-only location as rebuildLocation when none chosen yet
When rebuildLocation is nil and a location has hasEcx=true but
existingShardCount=0 (all shards on other disks), the condition
0 > 0 was false so it was never promoted to rebuildLocation.
Add rebuildLocation == nil to the predicate so the first location
with an .ecx file is always selected as a candidate.
Chris Lu