feat: add scheduler workload admission contracts (#3602)

crates/concurrency/src/backpressure.rs

@@ -242,4 +242,19 @@ mod tests {
         assert_eq!(pipe.state(), BackpressureState::Normal);
         assert_eq!(pipe.meta().buffer_capacity, 1024);
     }
+
+    #[test]
+    fn test_backpressure_pipe_meta_is_read_only() {
+        let manager = BackpressureManager::new(2048, 80, 50);
+        let pipe = manager.create_pipe();
+        let first = pipe.meta();
+        let second = pipe.meta();
+
+        assert_eq!(first.buffer_capacity, 2048);
+        assert_eq!(first.state, BackpressureState::Normal);
+        assert_eq!(second.buffer_capacity, first.buffer_capacity);
+        assert_eq!(second.state, first.state);
+        assert!(second.age >= first.age);
+        assert_eq!(manager.state(), BackpressureState::Normal);
+    }
 }

crates/concurrency/src/lib.rs

@@ -125,6 +125,7 @@ mod backpressure;
 mod scheduler;
 
 pub mod workers;
+pub mod workload;
 
 // Public module exports with feature gates
 #[cfg(feature = "timeout")]
@@ -149,6 +150,10 @@ pub use config::{ConcurrencyConfig, ConcurrencyFeatures};
 // Manager
 mod manager;
 pub use manager::{ConcurrencyManager, GetObjectQueueSnapshot};
+pub use workload::{
+    AdmissionState, WorkloadAdmissionRegistrySnapshot, WorkloadAdmissionSnapshot, WorkloadAdmissionSnapshotProvider,
+    WorkloadClass,
+};
 
 // Prelude for convenient imports
 pub mod prelude {
@@ -169,5 +174,5 @@ pub mod prelude {
     #[cfg(feature = "scheduler")]
     pub use crate::scheduler::{IoStrategy, SchedulerManager, SchedulerPolicy};
 
-    pub use crate::{ConcurrencyConfig, ConcurrencyFeatures, ConcurrencyManager};
+    pub use crate::{AdmissionState, ConcurrencyConfig, ConcurrencyFeatures, ConcurrencyManager, WorkloadAdmissionSnapshot};
 }

crates/concurrency/src/manager.rs

@@ -281,6 +281,24 @@ mod tests {
         assert!(snapshot.is_congested(70.0));
     }
 
+    #[test]
+    fn test_queue_snapshot_clamps_over_available_permits() {
+        let snapshot = GetObjectQueueSnapshot::from_available_permits(64, 96);
+        assert_eq!(snapshot.permits_in_use, 0);
+        assert_eq!(snapshot.permits_available(), 64);
+        assert_eq!(snapshot.utilization_percent(), 0.0);
+        assert!(!snapshot.is_congested(0.0));
+    }
+
+    #[test]
+    fn test_queue_snapshot_handles_zero_total_permits() {
+        let snapshot = GetObjectQueueSnapshot::from_available_permits(0, 0);
+        assert_eq!(snapshot.permits_in_use, 0);
+        assert_eq!(snapshot.permits_available(), 0);
+        assert_eq!(snapshot.utilization_percent(), 0.0);
+        assert!(!snapshot.is_congested(0.0));
+    }
+
     #[test]
     fn test_manager_creation() {
         let manager = ConcurrencyManager::with_defaults();

crates/concurrency/src/scheduler.rs

@@ -239,6 +239,26 @@ mod tests {
         assert_eq!(core.low_priority_size_threshold, policy.low_priority_threshold);
     }
 
+    #[test]
+    fn test_scheduler_default_thresholds_remain_stable() {
+        let policy = SchedulerPolicy::default();
+        assert_eq!(policy.base_buffer_size, 64 * 1024);
+        assert_eq!(policy.max_buffer_size, 4 * 1024 * 1024);
+        assert_eq!(policy.high_priority_threshold, 1024 * 1024);
+        assert_eq!(policy.low_priority_threshold, 10 * 1024 * 1024);
+    }
+
+    #[test]
+    fn test_scheduler_priority_boundaries_remain_stable() {
+        let policy = SchedulerPolicy::default();
+        let manager = SchedulerManager::from_policy(policy);
+
+        assert_eq!(manager.get_priority(1_048_575), IoPriority::High);
+        assert_eq!(manager.get_priority(1_048_576), IoPriority::Normal);
+        assert_eq!(manager.get_priority(10_485_760), IoPriority::Normal);
+        assert_eq!(manager.get_priority(10_485_761), IoPriority::Low);
+    }
+
     #[test]
     fn test_scheduler_manager() {
         let manager = SchedulerManager::new(1024, 4096, 512, 2048);

crates/concurrency/src/workload.rs

@@ -0,0 +1,209 @@
+// Copyright 2024 RustFS Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Runtime workload admission contract types.
+
+/// Stable workload classes used by future runtime admission snapshots.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum WorkloadClass {
+    /// Foreground read requests.
+    ForegroundRead,
+    /// Foreground write requests.
+    ForegroundWrite,
+    /// Metadata and namespace operations.
+    Metadata,
+    /// Background scanner work.
+    Scanner,
+    /// Repair and heal work.
+    Repair,
+    /// Replication work.
+    Replication,
+}
+
+impl WorkloadClass {
+    /// Required workload classes covered by the runtime admission contract.
+    pub const REQUIRED: [Self; 6] = [
+        Self::ForegroundRead,
+        Self::ForegroundWrite,
+        Self::Metadata,
+        Self::Scanner,
+        Self::Repair,
+        Self::Replication,
+    ];
+
+    /// Return a stable label for logs, metrics, and snapshots.
+    pub const fn as_str(self) -> &'static str {
+        match self {
+            Self::ForegroundRead => "foreground_read",
+            Self::ForegroundWrite => "foreground_write",
+            Self::Metadata => "metadata",
+            Self::Scanner => "scanner",
+            Self::Repair => "repair",
+            Self::Replication => "replication",
+        }
+    }
+}
+
+impl std::fmt::Display for WorkloadClass {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+/// Read-only admission state for a workload class.
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum AdmissionState {
+    /// Admission is open for this workload class.
+    Open,
+    /// Admission is currently throttled.
+    Throttled,
+    /// Admission is saturated or queue-limited.
+    Saturated,
+    /// Admission is disabled by configuration or capability.
+    Disabled,
+    /// Admission state is not currently known.
+    #[default]
+    Unknown,
+}
+
+impl AdmissionState {
+    /// Return whether the state allows admission without throttling.
+    pub const fn is_open(self) -> bool {
+        matches!(self, Self::Open)
+    }
+}
+
+/// Read-only admission snapshot for one workload class.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct WorkloadAdmissionSnapshot {
+    /// Workload class described by this snapshot.
+    pub class: WorkloadClass,
+    /// Current admission state.
+    pub state: AdmissionState,
+    /// Active work count when the owner exposes it.
+    pub active: Option<usize>,
+    /// Queued work count when the owner exposes it.
+    pub queued: Option<usize>,
+    /// Admission limit when the owner exposes it.
+    pub limit: Option<usize>,
+    /// Optional state reason for disabled, throttled, saturated, or unknown states.
+    pub reason: Option<String>,
+}
+
+impl WorkloadAdmissionSnapshot {
+    /// Create a snapshot for a workload class and admission state.
+    pub const fn new(class: WorkloadClass, state: AdmissionState) -> Self {
+        Self {
+            class,
+            state,
+            active: None,
+            queued: None,
+            limit: None,
+            reason: None,
+        }
+    }
+
+    /// Add optional active, queued, and limit counters.
+    pub const fn with_counts(mut self, active: Option<usize>, queued: Option<usize>, limit: Option<usize>) -> Self {
+        self.active = active;
+        self.queued = queued;
+        self.limit = limit;
+        self
+    }
+
+    /// Add a human-readable reason.
+    pub fn with_reason(mut self, reason: impl Into<String>) -> Self {
+        self.reason = Some(reason.into());
+        self
+    }
+}
+
+/// Read-only admission registry snapshot.
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub struct WorkloadAdmissionRegistrySnapshot {
+    entries: Vec<WorkloadAdmissionSnapshot>,
+}
+
+impl WorkloadAdmissionRegistrySnapshot {
+    /// Create a registry snapshot from per-class entries.
+    pub fn new(entries: Vec<WorkloadAdmissionSnapshot>) -> Self {
+        Self { entries }
+    }
+
+    /// Borrow all entries in snapshot order.
+    pub fn entries(&self) -> &[WorkloadAdmissionSnapshot] {
+        &self.entries
+    }
+
+    /// Find the admission snapshot for a workload class.
+    pub fn get(&self, class: WorkloadClass) -> Option<&WorkloadAdmissionSnapshot> {
+        self.entries.iter().find(|entry| entry.class == class)
+    }
+}
+
+/// Provider boundary for future read-only workload admission snapshots.
+pub trait WorkloadAdmissionSnapshotProvider {
+    /// Return the current workload admission registry snapshot.
+    fn workload_admission_snapshot(&self) -> WorkloadAdmissionRegistrySnapshot;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn workload_contract_covers_required_classes() {
+        let labels: Vec<_> = WorkloadClass::REQUIRED.iter().map(|class| class.as_str()).collect();
+
+        assert_eq!(
+            labels,
+            vec![
+                "foreground_read",
+                "foreground_write",
+                "metadata",
+                "scanner",
+                "repair",
+                "replication"
+            ]
+        );
+        assert_eq!(WorkloadClass::Repair.to_string(), "repair");
+    }
+
+    #[test]
+    fn admission_snapshot_preserves_unknown_and_counted_states() {
+        let unknown = WorkloadAdmissionSnapshot::new(WorkloadClass::Scanner, AdmissionState::Unknown);
+        let open = WorkloadAdmissionSnapshot::new(WorkloadClass::ForegroundRead, AdmissionState::Open).with_counts(
+            Some(3),
+            Some(1),
+            Some(8),
+        );
+        let registry = WorkloadAdmissionRegistrySnapshot::new(vec![unknown.clone(), open.clone()]);
+
+        assert_eq!(registry.entries(), &[unknown, open]);
+        assert_eq!(
+            registry.get(WorkloadClass::Scanner).map(|snapshot| snapshot.state),
+            Some(AdmissionState::Unknown)
+        );
+        assert!(matches!(
+            registry.get(WorkloadClass::ForegroundRead).map(|snapshot| snapshot.state),
+            Some(state) if state.is_open()
+        ));
+        assert_eq!(
+            registry
+                .get(WorkloadClass::ForegroundRead)
+                .and_then(|snapshot| snapshot.limit),
+            Some(8)
+        );
+    }
+}

docs/architecture/crate-boundaries.md

@@ -104,6 +104,10 @@ Required `rustfs-storage-api` public re-exports:
 - `pub use object::{VersionMarker, WalkOptions, WalkVersionsSortOrder};`
 - `pub use topology::{DiskCapabilities, TopologyCapabilities, TopologyDisk, TopologyLabels, TopologyPool, TopologySet, TopologySnapshot, TopologySnapshotProvider};`
 
+Required `rustfs-concurrency` public workload admission contract re-exports:
+
+- `pub use workload::{AdmissionState, WorkloadAdmissionRegistrySnapshot, WorkloadAdmissionSnapshot, WorkloadAdmissionSnapshotProvider, WorkloadClass};`
+
 ECStore must keep compile-time coverage for `StorageAdminApi`, `HealOperations`,
 and the separate `NamespaceLocking` operation group.
 

docs/architecture/migration-progress.md

@@ -5,19 +5,19 @@ Status values: `[ ]` not started, `[~]` in progress, `[x]` complete, `[!]` block
 ## Current Context
 
 - Issue: [`rustfs/backlog#660`](https://github.com/rustfs/backlog/issues/660)
-- Branch: `overtrue/arch-observability-topology-contracts`
+- Branch: `overtrue/arch-scheduler-workload-contracts`
 - Baseline: stacked on `origin/overtrue/arch-test-harness-compat-aliases`
-  after `rustfs/rustfs#3600`
-  (`ae6a5befcf60f2f2ebce9799ba93649032234273`).
-- PR type for this branch: `contract`
+  after `rustfs/rustfs#3601`
+  (`dc099f415670d94c0f79a7f9015653a08cdf458f`).
+- PR type for this branch: `test-only` plus `contract`
 - Runtime behavior changes: none.
-- Rust code changes: add observability and topology capability DTO/trait
-  contracts to `rustfs-storage-api`.
-- CI/script changes: extend migration re-export guard coverage for the new
-  contract exports.
+- Rust code changes: add scheduler preservation tests and workload admission
+  contract types to `rustfs-concurrency`.
+- CI/script changes: extend migration re-export guard coverage for workload
+  admission contract exports.
 - Docs changes: add
-  [`runtime-capability-contracts.md`](runtime-capability-contracts.md) and
-  record the combined PR-08/API-013 plus PR-09/API-014 contract slice.
+  [`workload-admission-contracts.md`](workload-admission-contracts.md) and
+  record the combined PR-05/TEST-SCH-001 plus PR-07/R-015 slice.
 
 ## Phase 0 Tasks
 
@@ -119,6 +119,31 @@ Status values: `[ ]` not started, `[~]` in progress, `[x]` complete, `[!]` block
     plus supported, unsupported, unknown, and disabled capability states;
     focused storage-api check; migration guard; formatting; diff hygiene; and
     three-expert review.
+
+- [x] `PR-05/TEST-SCH-001` Add scheduler preservation tests.
+  - Completed slice: pin worker over-release clamping, reusable scheduler
+    default thresholds and priority boundaries, backpressure pipe metadata
+    reads, and get-object queue snapshot saturation/zero-total semantics.
+  - Acceptance: current reusable scheduling and admission-facing behavior is
+    covered before later read-only snapshot extraction.
+  - Must preserve: scheduler algorithm, queue capacity, threshold defaults,
+    Tokio runtime settings, request admission, scanner admission, heal
+    admission, replication admission, and background task admission behavior.
+  - Verification: focused concurrency tests, focused concurrency check,
+    migration guard, formatting, diff hygiene, and three-expert review.
+
+- [x] `PR-07/R-015` Add runtime workload class contract.
+  - Completed slice: add `WorkloadClass`, `AdmissionState`,
+    `WorkloadAdmissionSnapshot`, `WorkloadAdmissionRegistrySnapshot`, and
+    `WorkloadAdmissionSnapshotProvider` to `rustfs-concurrency`.
+  - Acceptance: foreground read, foreground write, metadata, scanner, repair,
+    and replication workload classes are representable through read-only
+    admission registry snapshots without ECStore dependency.
+  - Must preserve: no SchedulerManager decision logic, Tokio worker defaults,
+    scanner/heal admission behavior, replication admission behavior, cluster
+    scheduling, placement, membership, or business call-site migration.
+  - Verification: workload contract unit tests, focused concurrency check,
+    migration guard, formatting, diff hygiene, and three-expert review.
 - [x] `TEST-PRTYPE-001` Check PR type enum consistency.
   - Acceptance: `./scripts/check_architecture_migration_rules.sh` parses the
     allowed PR types from [`crate-boundaries.md`](crate-boundaries.md) and fails
@@ -1704,7 +1729,9 @@ Status values: `[ ]` not started, `[~]` in progress, `[x]` complete, `[!]` block
 1. `contract`/`consumer-migration`: wire read-only observability and topology
    snapshots to implementation owners without changing runtime, profiling,
    placement, or admin route behavior.
-2. `pure-move`/`consumer-migration`: continue larger cleanup slices with the
+2. `api-extraction`: expose the set-local scheduler snapshot after the
+   TEST-SCH-001 and R-015 protection/contract slice.
+3. `pure-move`/`consumer-migration`: continue larger cleanup slices with the
    loss-prevention guards active for remaining ECStore compatibility contracts
    now that broad compatibility passthroughs are fully closed.
 
@@ -1712,14 +1739,24 @@ Status values: `[ ]` not started, `[~]` in progress, `[x]` complete, `[!]` block
 
 | Expert | Status | Notes |
 |---|---|---|
-| Quality/architecture | passed | S-015 removes obsolete KMS admin policy action variants after the handler fallback cleanup; API-042/API-043/API-044/API-045/API-046/API-047/API-048/API-049/API-050/API-051/API-052/API-053/API-054 narrow notify, S3 Select, OBS, IAM, Swift, heal, scanner, RustFS runtime, test, fuzz, lifecycle helper, harness, and RustFS runtime compatibility contracts without moving ECStore storage metadata ownership; G-011/G-012/G-013 add docs-only baselines for scheduler, placement/repair, and profiling/NUMA work; Issue #660 PR-08/PR-09 add read-only observability and topology contracts in rustfs-storage-api only. |
-| Migration preservation | passed | KMS endpoint URLs, query aliases, request bodies, response contracts, and dedicated `kms:*` authorization behavior are preserved; event builder call sites, ECStore event bridge conversion, restore event data, version IDs, metadata filtering, config read/save semantics, S3 Select store/error/buffer semantics, OBS metrics state reads, IAM config/notification/error semantics, Swift bucket metadata access, heal disk/resume/task behavior, scanner lifecycle/replication/data-usage behavior, RustFS startup/admin/app/storage runtime access, e2e/test/fuzz import behavior, lifecycle expiration/transition helper DTO field contracts, flattened harness and RustFS runtime scalar/secondary alias behavior, unchanged no-op handling, remove-event behavior, scheduler/readiness/placement/profiling runtime behavior, platform gates, missing/unknown capability states, and placement/topology labels are preserved. |
-| Testing/verification | passed | Focused compiles/tests, fuzz target compile, guards, formatting, diff hygiene, risk scan, and full `make pre-commit` passed for prior code slices; current Issue #660 PR-08/PR-09 contract slice uses storage-api tests/checks, migration guard, formatting, diff hygiene, and three-expert review. |
+| Quality/architecture | passed | S-015 removes obsolete KMS admin policy action variants after the handler fallback cleanup; API-042/API-043/API-044/API-045/API-046/API-047/API-048/API-049/API-050/API-051/API-052/API-053/API-054 narrow notify, S3 Select, OBS, IAM, Swift, heal, scanner, RustFS runtime, test, fuzz, lifecycle helper, harness, and RustFS runtime compatibility contracts without moving ECStore storage metadata ownership; G-011/G-012/G-013 add docs-only baselines for scheduler, placement/repair, and profiling/NUMA work; Issue #660 PR-08/PR-09 add read-only observability and topology contracts in storage-api only; current PR-05/PR-07 slice adds scheduler preservation tests and a small workload admission contract in concurrency only. |
+| Migration preservation | passed | KMS endpoint URLs, query aliases, request bodies, response contracts, and dedicated `kms:*` authorization behavior are preserved; event builder call sites, ECStore event bridge conversion, restore event data, version IDs, metadata filtering, config read/save semantics, S3 Select store/error/buffer semantics, OBS metrics state reads, IAM config/notification/error semantics, Swift bucket metadata access, heal disk/resume/task behavior, scanner lifecycle/replication/data-usage behavior, RustFS startup/admin/app/storage runtime access, e2e/test/fuzz import behavior, lifecycle expiration/transition helper DTO field contracts, flattened harness and RustFS runtime scalar/secondary alias behavior, unchanged no-op handling, remove-event behavior, scheduler/readiness/placement/profiling runtime behavior, platform gates, missing/unknown capability states, placement/topology labels, scheduler thresholds, queue snapshot semantics, and admission behavior are preserved. |
+| Testing/verification | passed | Focused compiles/tests, fuzz target compile, guards, formatting, diff hygiene, risk scan, and full `make pre-commit` passed for prior code slices; current Issue #660 PR-05/PR-07 slice uses concurrency tests/checks, migration guard, formatting, diff hygiene, and three-expert review. |
 
 ## Verification Notes
 
 Passed before push:
 
+- Issue #660 PR-05/PR-07 current slice:
+  - `cargo test -p rustfs-concurrency --no-fail-fast`: passed.
+  - `cargo check -p rustfs-concurrency`: passed.
+  - `./scripts/check_architecture_migration_rules.sh`: passed.
+  - `./scripts/check_layer_dependencies.sh`: passed.
+  - `cargo fmt --all --check`: passed.
+  - `git diff --check`: passed.
+  - `make pre-commit`: passed.
+  - Three-expert review: passed.
+
 - Issue #660 PR-08/PR-09 current slice:
   - `cargo test -p rustfs-storage-api`: passed.
   - `cargo check -p rustfs-storage-api`: passed.

docs/architecture/workload-admission-contracts.md

@@ -0,0 +1,43 @@
+# Workload Admission Contracts
+
+This document records the `rustfs/backlog#660` PR-05 and PR-07 scheduler
+preservation and runtime workload-class contract slice.
+
+## Preservation Coverage
+
+The `rustfs-concurrency` tests pin the current reusable scheduler and
+admission-facing behavior before later snapshot extraction:
+
+- Worker slot over-release remains clamped by the configured worker limit.
+- Scheduler default buffer and priority thresholds remain unchanged.
+- Scheduler priority boundaries remain high below the high threshold, normal at
+  both thresholds, and low above the low threshold.
+- Backpressure pipe metadata reads preserve buffer capacity and state without
+  mutating the manager state.
+- `GetObjectQueueSnapshot` preserves saturated, over-available, and zero-total
+  permit semantics.
+
+## Workload Class Contract
+
+`WorkloadClass` defines the required future admission categories:
+
+- Foreground read.
+- Foreground write.
+- Metadata.
+- Scanner.
+- Repair.
+- Replication.
+
+`AdmissionState`, `WorkloadAdmissionSnapshot`, and
+`WorkloadAdmissionRegistrySnapshot` define read-only status shapes for later
+runtime owners. They do not replace the current scheduler, request guard,
+scanner, heal, replication, or ECStore placement behavior.
+
+## Boundary Rules
+
+- `rustfs-concurrency` owns this reusable contract surface.
+- The contract does not depend on `rustfs-ecstore` or RustFS binary runtime
+  state.
+- No scheduler decision logic, queue capacity, Tokio runtime default, scanner
+  admission, heal admission, replication admission, placement, membership, or
+  NUMA behavior changes are part of this slice.

scripts/check_architecture_migration_rules.sh

@@ -212,6 +212,18 @@ require_source_line \
   "crates/storage-api/src/lib.rs" \
   "pub use capability::{CapabilitySnapshotError, CapabilityState, CapabilityStatus};" \
   "storage-api public capability contract re-export"
+require_source_contains \
+  "crates/concurrency/src/lib.rs" \
+  "pub use workload::{" \
+  "concurrency public workload admission contract re-export"
+require_source_contains \
+  "crates/concurrency/src/lib.rs" \
+  "AdmissionState, WorkloadAdmissionRegistrySnapshot, WorkloadAdmissionSnapshot, WorkloadAdmissionSnapshotProvider," \
+  "concurrency public workload admission contract status re-exports"
+require_source_contains \
+  "crates/concurrency/src/lib.rs" \
+  "WorkloadClass," \
+  "concurrency public workload class re-export"
 require_source_line \
   "crates/storage-api/src/lib.rs" \
   "pub use multipart::{CompletePart, ListMultipartsInfo, ListPartsInfo, MultipartInfo, MultipartUploadResult, PartInfo};" \