perf(get,heal): fix GET hot-path overhead and heal checkpoint scaling (#4237)

perf(get,heal): land verified fixes for backlog #800-#804

Five fixes from the GET-path performance audit and scanner/heal
completeness audit (rustfs/backlog#800..#804), each verified locally:

- backlog#800 (heal checkpoint O(N^2)): ResumeCheckpoint object sets are
  now HashSet (Vec::contains was O(n) per healed object; 1.5ms at n=1M
  vs 11ns measured), and per-object checkpoint/resume-state persistence
  is batched (1000 mutations / 5s) instead of rewriting the whole file
  per object. complete_page() prunes the sets at page boundaries so
  memory stays bounded; positions still persist unconditionally and
  legacy Vec-format checkpoints still deserialize.

- backlog#801 (DiskInfo.healing never set): erasure-set heal now writes
  a healing marker (.rustfs.sys/healing.bin) on the disks it rebuilds
  (endpoints plumbed via HealRequest/HealTask.heal_endpoints from the
  auto disk scanner) and clears it on success. LocalDisk::disk_info
  surfaces the marker, so scanner heal coordination, lock selection and
  admin/metrics healing counts see the rebuild.

- backlog#802 (cache probe after data read): new GetObjectBodyCacheHook
  in ecstore lets the app-layer object data cache serve the body inside
  get_object_reader, after metadata quorum resolution (etag known) but
  before the erasure shard read/decode. Previously a hit still paid the
  full disk read. Hook is None/no-op when the cache is disabled.

- backlog#803 (GET hot-path redundant work): ObjectInfo is cloned for
  event notification only when an event will actually be built (GET and
  HEAD paths; events are currently suppressed so the clone was pure
  waste); get_opts/put_opts/del_opts resolve bucket versioning with one
  metadata-sys lookup instead of two; skip_verify_bitrot and
  get_lock_acquire_timeout env reads are cached via OnceLock; the
  io-priority metric is no longer double-counted; GetObject input fields
  are cloned selectively instead of cloning the whole input.

- backlog#804 (disk permit starvation): the disk-read permit wait is now
  bounded (RUSTFS_OBJECT_DISK_PERMIT_WAIT_TIMEOUT, default 5s, 0 =
  previous unbounded behavior); on timeout the GET proceeds without a
  permit and the bypass is counted. DiskReadPermitReader also releases
  the permit at body EOF instead of holding it until the client drops
  the stream.

Verification: make pre-commit; cargo clippy -D warnings on the four
changed crates; full rustfs lib suite (2096 tests) green; rustfs-heal
lib suite green with new unit tests for checkpoint pruning/legacy
format/throttle, permit EOF release, and the cache hook (hit + SSE
skip). The heal_integration_test and one set_disk listing test fail
identically on unmodified main (pre-existing global-state ordering
flakes, verified via git stash A/B).

Co-authored-by: houseme <housemecn@gmail.com>

crates/ecstore/src/object_api/body_cache_hook.rs

@@ -0,0 +1,49 @@
+// 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.
+
+//! Hook that lets the application layer serve a GET body from its object data
+//! cache after metadata resolution but before the erasure data read.
+//!
+//! The cache itself lives above ecstore (it needs app-level config, metrics
+//! and invalidation), but the lookup must happen inside `get_object_reader`:
+//! probing earlier would require a second metadata fan-out, and probing later
+//! (after the reader is built) means a hit no longer saves any disk I/O.
+
+use crate::object_api::ObjectInfo;
+use bytes::Bytes;
+use std::sync::{Arc, OnceLock};
+
+/// Serves full-object GET bodies from a cache keyed by object identity.
+///
+/// Implementations must validate identity (etag/version/size) against the
+/// provided `ObjectInfo`, which reflects the just-resolved metadata quorum,
+/// and must return `None` for anything they cannot serve byte-identically
+/// (encrypted objects, remote/transitioned objects, size mismatches, ...).
+#[async_trait::async_trait]
+pub trait GetObjectBodyCacheHook: Send + Sync + 'static {
+    async fn lookup(&self, bucket: &str, object: &str, info: &ObjectInfo) -> Option<Bytes>;
+}
+
+static GET_OBJECT_BODY_CACHE_HOOK: OnceLock<Arc<dyn GetObjectBodyCacheHook>> = OnceLock::new();
+
+/// Register the process-wide GET body cache hook. First registration wins;
+/// later calls are ignored so tests and re-inits cannot swap the hook midway.
+pub fn register_get_object_body_cache_hook(hook: Arc<dyn GetObjectBodyCacheHook>) {
+    let _ = GET_OBJECT_BODY_CACHE_HOOK.set(hook);
+}
+
+/// The registered hook, if any.
+pub(crate) fn get_object_body_cache_hook() -> Option<&'static Arc<dyn GetObjectBodyCacheHook>> {
+    GET_OBJECT_BODY_CACHE_HOOK.get()
+}

crates/ecstore/src/object_api/mod.rs

@@ -52,8 +52,11 @@ use uuid::Uuid;
 pub const ERASURE_ALGORITHM: &str = "rs-vandermonde";
 pub const BLOCK_SIZE_V2: usize = 1024 * 1024; // 1M
 
+mod body_cache_hook;
 mod readers;
 mod types;
 
+pub(crate) use body_cache_hook::get_object_body_cache_hook;
+pub use body_cache_hook::{GetObjectBodyCacheHook, register_get_object_body_cache_hook};
 pub use readers::*;
 pub use types::*;