yuqi1129 commented on code in PR #10696:
URL: https://github.com/apache/gravitino/pull/10696#discussion_r3057340584
##########
design-docs/cache-improvement-design.md:
##########
@@ -0,0 +1,686 @@
+# Gravitino Cache Improvement Design
+
+---
+
+## 1. Background
+
+### 1.1 System Overview
+
+Gravitino is a unified metadata management control plane. Compute engines
(Spark, Flink, Trino)
+call it during query planning to resolve catalog, schema, and table metadata,
and to verify
+user permissions. The access pattern is distinctly **read-heavy,
write-light**: DDL operations
+are infrequent, and metadata is resolved once per job.
+
+Gravitino is evolving from single-node to multi-node active-active HA
deployment. Each node
+currently maintains its own independent in-process Caffeine cache with no
cross-node
+synchronisation. Under HA, any write on one node leaves other nodes' caches
stale until TTL
+expiry.
+
+---
+
+### 1.2 Current Cache Architecture Overview
+
+Gravitino maintains three distinct caching layers for the authorization path:
+
+```
+┌──────────────────────────────────────────────────────┐
+│ Layer 3: Per-request cache (AuthorizationRequestContext) │
+│ Scope: one HTTP request; prevents duplicate auth calls │
+├──────────────────────────────────────────────────────┤
+│ Layer 2: Auth policy caches (JcasbinAuthorizer) │
+│ loadedRoles Cache<Long, Boolean> hook update/TTL │
+│ ownerRel Cache<Long, Optional<Long>> hook update/TTL │
+├──────────────────────────────────────────────────────┤
+│ Layer 1: Entity store cache (RelationalEntityStore) │
+│ CaffeineEntityCache — or NoOpsCache when disabled │
+│ Caches entity reads and relation queries for all modules │
+│ Controlled by Configs.CACHE_ENABLED │
+└──────────────────────────────────────────────────────┘
+```
+
+**JCasbin is the core of the auth cache system.** It maintains an in-memory
policy table:
+
+```
+(roleId, objectType, metadataId, privilege) → ALLOW | DENY
+```
+
+The Layer 2 caches exist solely to manage JCasbin's policy loading lifecycle:
+
+| Cache | Role
|
+|-----------------------------------------|----------------------------------------------------------------------------------------------------------------|
+| `loadedRoles: Cache<Long, Boolean>` | Tracks which roles are already
loaded into JCasbin — prevents repeated [C2]+[C3] queries on every auth request
|
+| `ownerRel: Cache<Long, Optional<Long>>` | Caches owner lookups for
OWNER-privilege checks — prevents [D1] on every ownership check
|
+
+Without `loadedRoles`, every auth request would re-execute N DB queries to
reload all of a
+user's role policies into JCasbin. These two caches are the reason the auth
path is fast on
+the warm path. Layer 1 (entity cache) additionally accelerates the name→ID
resolution calls
+([A], [B], [C1]) that feed into JCasbin's enforce call.
+
+---
+
+#### 1.2.1 Problems with the Current Entity Cache
+
+**The entity cache (Layer 1) has accumulated significant complexity and is not
well-suited to
+serve as a general-purpose or auth-dedicated caching layer.**
+
+##### Mixed responsibilities make it hard to maintain
+
+`CaffeineEntityCache` uses a single `Cache<EntityCacheRelationKey,
List<Entity>>` to store
+three semantically different kinds of data:
+
+| Stored data | Key form |
Example relation types |
+|-------------------------|--------------------------------------------------|-----------------------------------------------------------|
+| Direct entity | `(nameIdentifier, entityType, null)` |
any entity: catalog, schema, table, user, role, ... |
+| Relation result set | `(nameIdentifier, entityType, relType)` |
`ROLE_USER_REL`, `TAG_METADATA_OBJECT_REL`, ... |
+| Reverse index entries | `ReverseIndexCache` (separate radix tree) |
entity → list of cache keys that reference it |
+
+On top of this, a `cacheIndex` (radix tree) keeps a prefix-indexed view of all
keys to
+support cascading invalidation. The resulting invalidation logic
(`invalidateEntities`) is a
+BFS traversal that walks both the forward index and the reverse index, making
it difficult to
+reason about correctness and hard to extend safely.
+
+The five relation types currently tracked (`METADATA_OBJECT_ROLE_REL`,
`ROLE_USER_REL`,
+`ROLE_GROUP_REL`, `POLICY_METADATA_OBJECT_REL`, `TAG_METADATA_OBJECT_REL`) are
all
+auth-related, which reflects the original design intent: **the entity cache
was built
+primarily to serve the auth path.** Over time it accumulated relation types
and reverse-index
+logic without a clear ownership model, making it harder to maintain and evolve.
+
+##### Limited benefit for non-auth interfaces
+
+For general metadata API calls (list catalogs, list schemas, list tables), the
entity cache
+provides minimal benefit:
+
+| Operation | Goes through cache? | Notes
|
+|------------------------------------|---------------------|---------------------------------------------------|
+| `list(namespace, type)` | **No** | Bypasses cache
entirely; always hits DB |
+| `get(ident, type)` (single entity) | Yes | Cache helps on
repeated reads of the same entity |
+| `update(ident, type)` | Invalidate only | Invalidates
entry, write always goes to DB |
+| `listEntitiesByRelation(...)` | Yes | Only for the five
auth-centric relation types |
+
+In practice, the most common metadata browsing operations (`LIST` endpoints)
are not cached
+at the entity store level. The cache's real workload is the auth path, where
the same user
+entity, role assignments, and resource IDs are resolved on every single
authorization check.
+
+**Conclusion:** The entity cache is a de-facto auth cache dressed up as a
general-purpose
+cache. Its complexity is unjustified for the non-auth use case, and its
TTL-based consistency
+model is insufficient for the auth use case (see §1.8). A purpose-built auth
cache layer —
+separate from the entity store — is the cleaner path forward.
+
+---
+
+### 1.3 JCasbin Authorization — Deep Dive
+
+#### 1.3.1 Call Graph for a Single `authorize()` Check
+
+```
+JcasbinAuthorizer.authorize(principal, metalake, metadataObject, privilege)
+│
+├─ [A] getUserEntity(username, metalake)
+│ entityStore.get(USER by NameIdentifier)
+│ → Needed to obtain integer userId for JCasbin enforce()
+│
+├─ [B] MetadataIdConverter.getID(metadataObject, metalake) ← TARGET
RESOURCE
+│ entityStore.get(entity by NameIdentifier)
+│ → Needed to get integer metadataId for JCasbin enforce()
+│ → Called on every auth request
+│
+├─ [C] loadRolePrivilege(metalake, username, userId, requestContext)
+│ │ (guarded by requestContext.hasLoadRole — runs once per HTTP request)
+│ │
+│ ├─ [C1] entityStore.listEntitiesByRelation(ROLE_USER_REL, userIdentifier)
+│ │ → Get all roles assigned to this user
+│ │
+│ └─ For each role NOT already in loadedRoles cache:
+│ ├─ [C2] entityStore.get(RoleEntity by name) ← async, thread pool
+│ └─ loadPolicyByRoleEntity(roleEntity)
+│ └─ For each securableObject in role.securableObjects():
+│ ├─ [C3] MetadataIdConverter.getID(securableObject, metalake)
+│ └─ enforcer.addPolicy(roleId, objType, metadataId, privilege,
effect)
+│
+│ loadedRoles.put(roleId, true) ← mark role as loaded
+│
+├─ [D] loadOwnerPolicy(...) ← only called when privilege == OWNER
+│ ├─ Check ownerRel cache → if HIT, return
+│ └─ [D1] entityStore.listEntitiesByRelation(OWNER_REL, ...)
+│ ownerRel.put(metadataId, Optional.of(ownerId))
+│
+└─ [E] enforcer.enforce(userId, objectType, metadataId, privilege) ←
in-memory, O(1)
+```
+
+#### 1.3.2 What Each Cache Protects
+
+`loadedRoles: Cache<Long, Boolean>` — answers "is this role's policy already
in JCasbin?"
+Without it, every request re-executes [C2]+[C3] for all roles the user has
(N+1 queries).
+With it, [C2]+[C3] only run on first load per role. **This is the most
critical cache.**
+
+`ownerRel: Cache<Long, Optional<Long>>` — caches [D1] results. Only consulted
when
+`privilege == OWNER`; regular privilege checks (SELECT, CREATE, ALTER, ...)
never touch it.
+
+**What these caches do NOT protect** (hit DB on every auth request without
entity cache):
+
+| Call | Description
| Protected by |
+|----------------------------------------------|-------------------------------------------|-------------------|
+| [A] `getUserEntity()` | Fetch User entity → get
integer userId | Entity cache only |
+| [B] `MetadataIdConverter.getID()` target | Resolve target resource name
→ integer ID | Entity cache only |
+| [C1] `listEntitiesByRelation(ROLE_USER_REL)` | Get user's role list
| Entity cache only |
+
+---
+
+### 1.4 Impact of Disabling Entity Cache
+
+Layer 2 sits **on top of** Layer 1. When Layer 1 is disabled (NoOpsCache),
calls [A], [B],
+[C1] hit DB on every auth request.
+
+| Call | With entity cache
| Without entity cache |
+|--------------------------------------------------|-------------------------------|---------------------------------|
+| [A] `getUserEntity()` | Cache hit after first
request | **DB query every auth request** |
+| [B] `MetadataIdConverter.getID()` target | Cache hit after first
request | **DB query every auth request** |
+| [C1] `listEntitiesByRelation(ROLE_USER_REL)` | Cache hit after first
request | **DB query every auth request** |
+| [C2] `entityStore.get(RoleEntity)` | Protected by
`loadedRoles` | DB only on cold role load |
+| [C3] `MetadataIdConverter.getID()` per privilege | Protected by
`loadedRoles` | DB only on cold role load |
+| [D1] `listEntitiesByRelation(OWNER_REL)` | Protected by `ownerRel`
| DB only on first owner check |
+
+---
+
+
+## 2. Goals
+
+### 2.1 The Two Problems to Solve
+
+**Problem 1 — Performance:** With entity cache disabled, [A] and [C1] hit DB
on every auth
+request. The new auth cache layer must protect these without relying on entity
store cache.
+([B] also hits DB, but this is correct and acceptable — see §1.5.)
+
+**Problem 2 — Consistency:** `loadedRoles` is TTL-bounded (1 hour staleness)
and updated by hook with in a instance. Permission
+changes must take effect at the next auth request, not after TTL expiry.
+
+Both problems are solved by the same mechanism: a version-validated cache for
the user's role
+list (userId comes for free from the same query).
+
+### 2.2 Requirements
+
+| Goal | Requirement
|
+|---------------------------------|---------------------------------------------------------------------------------------------------------------|
+| HA auth consistency | Privilege revocations visible on all nodes
at the next auth request |
+| Auth self-sufficiency | [A] and [C1] protected without relying on
entity store cache |
+| Auth performance | Hot path: ≤ 3 lightweight DB queries
|
+| No new mandatory infrastructure | Solution requires only the existing DB
|
+| Incremental delivery | Phase 1 independently shippable
|
+
+---
+
+## 3. Industry Reference
+
+### 3.1 Apache Polaris — Per-Entity Version Tracking
+
+Polaris achieves strong consistency by embedding two version counters on every
entity
+(`entityVersion` and `grantRecordsVersion`) and validating them on each cache
access:
+
+| Path | Condition | DB queries
|
+|-------------------------|-----------------------|---------------------------------------|
+| Cache hit | Both versions current | **0**
|
+| Stale, targeted refresh | Either version behind | **1** — returns only the
changed part |
+| Cache miss | Not in cache | **1** — full load
|
+
+`loadEntitiesChangeTracking(ids)` issues one lightweight query returning only
integer version
+columns for a batch of IDs — the same pattern used in §4.1 Step 3 below.
+
+**Key difference from Gravitino:** Polaris bundles entity + grants in one
cached object, so
+one batch query validates both dimensions. Gravitino separates user→role from
role→privilege,
+requiring 2 version-check queries on a warm hit. Both achieve strong
consistency.
+
+### 3.2 Other References
+
+**Nessie** — HTTP fan-out invalidation: async POST to peer nodes on write,
convergence < 200 ms.
+
+**Keycloak** — JGroups embedded cluster messaging: in-JVM broadcast, no
separate service.
+Recommended future direction if Gravitino needs stronger delivery guarantees.
+
+**DB version polling** — monotonic counters incremented in write transaction;
a background
+thread polls for version changes and proactively invalidates caches.
Considered but not
+adopted; per-request validation (§4.1) achieves strong consistency without
background threads.
+
+---
+
+## 4. Design
+
+### 4.1 Per-Request Version Check (Polaris Style)
+
+Every auth request executes two lightweight version-check queries before
serving from cache.
+If any version has advanced, only the stale portion is reloaded. Staleness
window: **zero**.
+
+#### 4.1.1 Schema Changes
+
+Three new version columns, all `DEFAULT 1` — fully backward compatible.
Existing rows get
+version 1; first auth check after migration populates caches normally.
+
+```sql
+ALTER TABLE `role_meta`
+ ADD COLUMN `securable_objects_version` INT UNSIGNED NOT NULL DEFAULT 1
+ COMMENT 'Incremented atomically with any privilege grant/revoke for this
role';
+
+ALTER TABLE `user_meta`
+ ADD COLUMN `role_grants_version` INT UNSIGNED NOT NULL DEFAULT 1
+ COMMENT 'Incremented atomically with any role assignment/revocation for
this user';
+
+ALTER TABLE `group_meta`
+ ADD COLUMN `role_grants_version` INT UNSIGNED NOT NULL DEFAULT 1
+ COMMENT 'Incremented atomically with any role assignment/revocation for
this group';
+```
+
+Write paths that must bump the version **in the same DB transaction**:
+
+| Operation | Column
| Location |
+|------------------------------------|---------------------------------------------------------|--------------------|
+| Grant / revoke privilege on role R | `role_meta.securable_objects_version
WHERE role_id = R` | `RoleMetaService` |
+| Assign / revoke role for user U | `user_meta.role_grants_version WHERE
user_id = U` | `UserMetaService` |
+| Assign / revoke role for group G | `group_meta.role_grants_version WHERE
group_id = G` | `GroupMetaService` |
+
+Version comparison uses `!=` (not `<`) to safely handle theoretical INT
wrap-around.
+
+**Ownership transfers** do not require a version column. The `ownerRel` cache
is removed;
+Step 2.5 queries `owner_meta` directly on every `OWNER`-privilege check,
providing strong
+consistency without caching. The soft-delete pattern of `owner_meta` (old row
deleted, new
+row inserted with `current_version = 1`) makes version-based cache validation
unreliable
+for this table. Direct query is simpler and always correct. See §7.2.
+
+#### 4.1.2 Cache Data Structures (Changes in JcasbinAuthorizer)
+
+```java
+// ─── BEFORE ──────────────────────────────────────────────────────────
+private Cache<Long, Boolean> loadedRoles; // roleId → loaded?
+private Cache<Long, Optional<Long>> ownerRel;
+
+// ─── AFTER ───────────────────────────────────────────────────────────
+
+// NEW: replaces entity cache dependency for [A] (userId) and [C1] (role list).
+// Step 1 query returns both user_id and role_grants_version in one shot.
+// metalakeName→metalakeId resolved inline via JOIN — no dedicated cache
needed.
+private GravitinoCache<String, CachedUserRoles> userRoleCache;
+// key = metalakeName + ":" + userName
+
+record CachedUserRoles(
+ long userId, // integer userId for JCasbin enforce()
+ int roleGrantsVersion, // user_meta.role_grants_version at load time
+ List<Long> roleIds // role ID list at load time
+) {}
+
+// NEW: mirrors userRoleCache for groups (group can also hold role
assignments).
+private GravitinoCache<String, CachedGroupRoles> groupRoleCache;
+// key = metalakeName + ":" + groupName
+
+record CachedGroupRoles(
+ long groupId,
+ int roleGrantsVersion, // group_meta.role_grants_version at load
time
+ List<Long> roleIds
+) {}
+
+// TYPE CHANGE: was Cache<Long, Boolean>, now stores securable_objects_version.
+// Enables version-based staleness detection rather than TTL expiry.
+private GravitinoCache<Long, Integer> loadedRoles;
+// roleId → securable_objects_version at the time JCasbin policies were loaded
+
+// REMOVED: ownerRel cache eliminated (see §7.2).
+// OWNER privilege checks query owner_meta directly (Step 2.5 below).
+// private Cache<Long, Optional<Long>> ownerRel;
+```
+
+**Why no cache for [B] (target resource name→ID):**
+Adding a `metadataIdCache` would require invalidation on every entity rename,
drop, or
+recreate across all entity types. Since JCasbin uses integer IDs (not names),
the DB lookup
+for [B] is always correct (~1 ms indexed). Simpler and more correct to hit DB
every request.
+
+**Why `ownerRel` is removed:**
+`ownerRel` has the same HA staleness problem as `loadedRoles` but cannot be
easily
+version-validated (`owner_meta` uses soft-delete; new rows always start at
version 1).
+`ownerRel` is only consulted for `privilege == OWNER`. Since Step 2 already
resolves
+`metadataId`, one direct indexed query on `owner_meta` (Step 2.5) gives strong
consistency
+for OWNER checks at the cost of 1 extra query, only on OWNER checks. See §7.2.
+
+#### 4.1.3 Auth Check Flow
+
+```
+authorize(metalakeName, username, resource, operation)
+│
+├─ STEP 1 — User version check (1 query, metalake resolved via JOIN):
+│
+│ SELECT um.user_id, um.role_grants_version
+│ FROM user_meta um
+│ JOIN metalake_meta mm ON um.metalake_id = mm.metalake_id AND mm.deleted_at
= 0
+│ WHERE mm.metalake_name = ? AND um.user_name = ? AND um.deleted_at = 0
+│ ↑ returns only 2 integer columns — no JSON, no audit fields
+│
+│ userRoleCache HIT and role_grants_version matches:
+│ → use cached userId and roleIds [A] and [C1] avoided
+│
+│ MISS or version mismatch:
+│ → SELECT role_id FROM user_role_rel WHERE user_id = ? AND deleted_at = 0
+│ → re-associate userId ↔ roleIds in JCasbin enforcers
+│ → userRoleCache.put(key, new CachedUserRoles(userId, version, roleIds))
+│
+├─ STEP 2 — Resolve target resource ID (always DB, no cache):
+│
+│ metadataId = MetadataIdConverter.getID(resource, metalake) ← 1 indexed DB
query
+│ Always correct: rename does not change ID; drop+recreate returns the new
ID.
+│
+│ TODO: A strong-consistency name→id cache could eliminate this DB query on
the warm
+│ path. Version-based validation does not apply here (checking the version
requires
+│ the same query that returns the ID). A viable approach would require an
+│ entity_mutation_log for cross-node invalidation plus write-path eviction
on the
+│ local node. Not implemented in this phase.
+│
+├─ [Only when privilege == OWNER] STEP 2.5 — Query ownership directly (no
cache):
+│
+│ SELECT owner_id, owner_type FROM owner_meta
+│ WHERE metadata_object_id = ? AND deleted_at = 0
+│ (metadataId already known from Step 2; indexed on metadata_object_id)
+│ → Compare owner_id with userId; return ALLOW/DENY immediately.
+│ Non-OWNER privilege checks skip Step 2.5 entirely.
+│
+├─ STEP 3 — Role batch version check (1 query):
+│
+│ SELECT role_id, securable_objects_version
+│ FROM role_meta WHERE role_id IN (?, ?, ...) AND deleted_at = 0
+│ ↑ one query validates all of the user's roles simultaneously
+│
+│ For each role where loadedRoles.get(roleId) == dbVersion:
+│ → policy current; skip [C2][C3] avoided
+│
+│ For stale/cold roles:
+│ → allowEnforcer.deleteRole(roleId); denyEnforcer.deleteRole(roleId)
+│ → batchListSecurableObjectsByRoleIds(staleRoleIds) (1 query for all
stale roles)
+│ → loadPoliciesForRoles(staleObjects)
+│ → loadedRoles.put(roleId, dbVersion)
+│
+└─ STEP 4 — enforce() (in-memory, O(1))
+ allowEnforcer.enforce(userId, objectType, metadataId, privilege)
+ denyEnforcer.enforce(userId, objectType, metadataId, privilege)
+```
+
+#### 4.1.4 Properties
+
+| Dimension | Value
|
+|--------------------------|--------------------------------------------------------------------------|
+| Staleness window | **0** — every request validates against DB
|
+| Hot path DB queries | **3** (Step 1 + Step 2 + Step 3; Steps 1 and 3
return integer cols only) |
+| OWNER privilege hot path | **4** (+ Step 2.5 indexed owner_meta query)
|
+| Cold/stale path | **4–5** queries
|
+| Background threads | **None**
|
+| Failure mode | DB unavailable → auth blocked (same as today)
|
+| HA correctness | **Fixed** — every node checks DB version on every
request |
+
+#### 4.1.5 Correctness Under Rename and Drop
+
+| Scenario | Analysis
|
+|-----------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| **User / Group rename** | `userRoleCache` is keyed on
`metalakeName:userName`. A rename produces a cache miss → Step 1 queries DB and
returns the correct result. The old key has no traffic and expires via TTL.
**Safe.** |
+| **User / Group drop** | Step 1 returns zero rows →
auth denied. The old cache entry expires harmlessly. **Safe.**
|
+| **User / Group drop + same-name recreate** | The new entity gets a new
auto-increment `user_id` and `role_grants_version = 1`. The cached entry holds
the old `user_id` and an older version → **version mismatch on the next Step 1
forces a cache refresh.** ✅ |
+| **SecurableObject rename** | JCasbin stores integer
`metadataId`. Rename does not change the ID. Step 2 resolves the new name to
the same ID via DB. `enforce()` matches the existing policy. **No action
needed.** ✅ |
+| **SecurableObject drop** | Step 2 returns "not found" →
auth denied. Orphan JCasbin policies remain in memory but can never be matched
(no ID resolves to the dropped object). **Safe.**
|
+| **SecurableObject drop + same-name recreate** | The new object gets a new
`metadataId`. No JCasbin policy covers it → DENY until a new privilege grant
bumps `securable_objects_version` in the same transaction and Step 3 detects
the version change to reload policies. **Correct.** |
+
+#### 4.1.6 Concurrent Mutation During Auth (TOCTOU)
Review Comment:
Add a description of the concurrent problem and its effect.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
