rustfs/docs/operations/tier-ilm-debugging.md

Tier / ILM Transition Debugging Guide

How to debug lifecycle tiering (hot → cold transition) issues: inspecting xl.meta, tracing the versionId sent to the remote tier, and known pitfalls.

Code map (post #3929 layout):

Concern	Location
ILM actions (transition_object, expire_transitioned_object, get_transitioned_object_reader, gen_transition_objname)	crates/ecstore/src/bucket/lifecycle/bucket_lifecycle_ops.rs
Erasure-set transition/restore entry points	crates/ecstore/src/set_disk/ and crates/ecstore/src/store/
WarmBackend trait (put/get/remove/in_use)	crates/ecstore/src/services/tier/warm_backend.rs
Per-provider tier backends (S3, MinIO, GCS, Azure, …)	crates/ecstore/src/services/tier/warm_backend_*.rs
Remote-tier sweep (delete_object_from_remote_tier)	crates/ecstore/src/bucket/lifecycle/tier_sweeper.rs
ObjectInfo / TransitionedObject types	crates/ecstore/src/object_api/types.rs
FileMeta / FileInfo / version metadata	crates/filemeta/src/
Dual-key internal metadata helpers (insert_bytes / get_bytes)	crates/utils/src/http/metadata_compat.rs

Metadata key conventions

Internal metadata is stored under both x-rustfs-internal-<suffix> and x-minio-internal-<suffix> for MinIO interoperability. get_bytes prefers the RustFS key and falls back to the MinIO key.

Suffix	Meaning
transition-status	"complete" when tiered
transitioned-object	tier key path (stored without the tier prefix; get_dest adds it)
transitioned-versionID	S3 version_id returned by tier PUT (16 raw UUID bytes, or absent)
transition-tier	tier name
tier-free-versionID	delete-marker version for free-version sweep

Reading binary values must reject empty/malformed/nil values (regression covered in crates/filemeta/src/filemeta/version.rs tests):

get_bytes(&self.meta_sys, SUFFIX_TRANSITIONED_VERSION_ID)
    .and_then(|v| Uuid::from_slice(v.as_slice()).ok())
    .filter(|u| !u.is_nil())
// None for: absent key, wrong-length bytes, nil UUID

transition_version_id == None means the tier bucket is unversioned; the GET/DELETE against the tier must then send no versionId parameter. A nil UUID (00000000-…) sent as ?versionId= causes NoSuchVersion.

Inspect xl.meta directly

cargo build -p rustfs-filemeta --example dump_fileinfo
./target/debug/examples/dump_fileinfo /srv/rustfs/data/disk0/{bucket}/{object}/xl.meta
# Shows: transition_status, transition_tier, transitioned_obj, transition_ver_id

• transition_ver_id: <none> → no versionId will be sent to the tier (correct for a non-versioned tier bucket).
• transition_ver_id: <uuid> → that UUID will be sent as ?versionId=<uuid>.

There is one xl.meta per erasure shard disk ({disk}/{bucket}/{object}/xl.meta); all shards of a healthy object should be identical. dump_versions (same crate) lists every version in a file.

Trace the versionId at runtime

RUST_LOG=rustfs_ecstore::bucket::lifecycle=debug rustfs …

• fetching transitioned object from tier — DEBUG, before the tier request.
• tier GET failed — ERROR, includes tier_version_id.

If both x-rustfs-internal-transitioned-versionID and x-minio-internal-transitioned-versionID are the empty string, the object was transitioned to a non-versioned tier bucket and no versionId must be sent.

Known open issue: expire/GET race

expire_transitioned_object deletes the remote tier version before deleting local metadata. A concurrent GET between those two steps reads a valid stored version_id whose remote version is already gone → NoSuchVersion. The proper fix is to delete local metadata first (making the object unreachable), then the remote tier version.

Historical fixes (for context, already merged)

• Nil-UUID versionId sent to tier (NoSuchVersion): reading code used Uuid::from_slice(..).unwrap_or_default(), converting an empty metadata value into Uuid::nil(). Fixed by the and_then/filter pattern above.
• warm_backend_s3sdk ignored the remote version and range options on GET/DELETE.
• copy_object returned 501 (NotImplemented) for tiered objects on self-copy with --storage-class, blocking de-tiering via mc cp --storage-class STANDARD obj obj. Fixed by writing the tier-fetched put_object_reader back through put_object.