liaoxin01 commented on code in PR #68991:
URL: https://github.com/apache/doris/pull/68991#discussion_r4272783008


##########
be/src/io/cache/tablet_cache_policy_registry.cpp:
##########
@@ -0,0 +1,433 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#include "io/cache/tablet_cache_policy_registry.h"
+
+#include <bvar/bvar.h>
+
+#include <algorithm>
+#include <chrono>
+#include <limits>
+
+#include "common/config.h"
+#include "common/logging.h"
+#include "cpp/sync_point.h"
+#include "io/cache/cache_block_meta_store.h"
+#include "runtime/exec_env.h"
+#include "storage/tablet/tablet_meta.h"
+#include "util/thread.h"
+#include "util/time.h"
+
+namespace doris::io {
+
+bvar::Adder<uint64_t> 
g_tablet_cache_policy_fetch_num("file_cache_tablet_policy_fetch_num");
+bvar::Adder<uint64_t> g_tablet_cache_policy_fetch_failed_num(
+        "file_cache_tablet_policy_fetch_failed_num");
+bvar::PassiveStatus<size_t> g_tablet_cache_policy_num(
+        "file_cache_tablet_policy_num",
+        [](void*) { return TabletCachePolicyRegistry::instance()->size(); }, 
nullptr);
+
+namespace {
+
+// How often the record is scanned for policies nobody needs any more.
+constexpr int64_t kPruneIntervalS = 60;
+// How long a tablet whose policy could not be fetched is left alone.
+constexpr int64_t kFetchRetryIntervalS = 60;
+// How many reported tablets are looked up per hold of the exclusive lock.
+constexpr size_t kReportBatchSize = 1024;
+// How often the background refresh runs.
+constexpr std::chrono::seconds kRefreshInterval {1};
+
+Status fetch_from_tablet_meta(int64_t tablet_id, TabletCachePolicy* policy) {
+    TabletMetaSharedPtr tablet_meta;
+    RETURN_IF_ERROR(ExecEnv::get_tablet_meta(tablet_id, &tablet_meta, false));
+    DORIS_CHECK(tablet_meta != nullptr);
+    policy->ttl_seconds = tablet_meta->ttl_seconds();
+    policy->ctime = tablet_meta->creation_time();
+    return Status::OK();
+}
+
+} // namespace
+
+int64_t TabletCachePolicy::deadline() const {
+    if (ttl_seconds <= 0 || ctime <= 0) {
+        return 0;
+    }
+    // Same rule as TabletMeta::file_cache_ttl_expiration_time(): a huge ttl 
must not wrap into
+    // a deadline in the past.
+    if (ctime > std::numeric_limits<int64_t>::max() - ttl_seconds) {
+        return std::numeric_limits<int64_t>::max();
+    }
+    return ctime + ttl_seconds;
+}
+
+TabletCachePolicyRegistry* TabletCachePolicyRegistry::instance() {
+    // Never destroyed: a cache path may still be running when the process 
exits.
+    static auto* registry = new TabletCachePolicyRegistry();
+    return registry;
+}
+
+std::optional<int64_t> TabletCachePolicyRegistry::deadline(int64_t tablet_id) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    return it->second.policy.deadline();
+}
+
+int64_t TabletCachePolicyRegistry::protected_until(int64_t tablet_id, int64_t 
legacy_deadline,
+                                                   bool* legacy) {
+    // tablet_id 0 is data outside any Doris tablet (external tables, v2 cache 
files that never
+    // recorded one): it only has the deadline it was written with.
+    if (tablet_id > 0) {
+        if (const std::optional<int64_t> known = deadline(tablet_id); 
known.has_value()) {
+            *legacy = false;
+            return *known;
+        }
+        note_tablet(tablet_id);
+    }
+    *legacy = true;
+    return legacy_deadline;
+}
+
+bool TabletCachePolicyRegistry::is_protected(int64_t tablet_id, int64_t 
legacy_deadline,
+                                             int64_t now) {
+    bool legacy = false;
+    return protected_until(tablet_id, legacy_deadline, &legacy) > now;
+}
+
+std::optional<TabletCachePolicy> TabletCachePolicyRegistry::set_locked(
+        int64_t tablet_id, const TabletCachePolicy& policy, int64_t 
refreshed_at_s) {
+    auto [it, inserted] =
+            _entries.try_emplace(tablet_id, Entry {policy, refreshed_at_s, 
refreshed_at_s});
+    std::optional<TabletCachePolicy> before;
+    if (!inserted) {
+        before = it->second.policy;
+        if (const int64_t old_deadline = before->deadline(); old_deadline > 0) 
{
+            _deadlines.erase(_deadlines.find(old_deadline));
+        }
+        it->second.policy = policy;
+        it->second.refreshed_at_s = refreshed_at_s;
+    }
+    if (const int64_t new_deadline = policy.deadline(); new_deadline > 0) {
+        _deadlines.insert(new_deadline);
+    }
+    return before;
+}
+
+std::optional<TabletCachePolicy> 
TabletCachePolicyRegistry::erase_locked(int64_t tablet_id) {
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    const TabletCachePolicy before = it->second.policy;
+    if (const int64_t old_deadline = before.deadline(); old_deadline > 0) {
+        _deadlines.erase(_deadlines.find(old_deadline));
+    }
+    _entries.erase(it);
+    return before;
+}
+
+void TabletCachePolicyRegistry::bump_versions(const 
std::optional<TabletCachePolicy>& before,
+                                              const 
std::optional<TabletCachePolicy>& after) {
+    // An unknown tablet is judged by the deadline its blocks carry, so 
learning or forgetting a
+    // tablet can move its blocks either way.
+    const int64_t old_deadline = before.has_value() ? before->deadline() : -1;
+    const int64_t new_deadline = after.has_value() ? after->deadline() : -1;
+    if (!before.has_value() || !after.has_value() || new_deadline > 
old_deadline) {
+        _protection_gained_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+    if (!before.has_value() || !after.has_value() || new_deadline < 
old_deadline) {
+        _protection_lost_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+}
+
+void TabletCachePolicyRegistry::persist(int64_t tablet_id,
+                                        const 
std::optional<TabletCachePolicy>& policy) {
+    std::lock_guard lock(_stores_mutex);
+    for (auto* store : _stores) {
+        if (policy.has_value()) {
+            store->put_tablet_policy(tablet_id, *policy);
+        } else {
+            store->delete_tablet_policy(tablet_id);
+        }
+    }
+}
+
+void TabletCachePolicyRegistry::upsert(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    DORIS_CHECK(tablet_id > 0);
+    const int64_t now = UnixSeconds();
+    {
+        // Unchanged and recently confirmed is the common case: every meta 
refresh reports the
+        // policy. Only take the exclusive lock to record a change, or to push 
the refresh time
+        // forward once it is half way to being due.
+        std::shared_lock lock(_mutex);
+        auto it = _entries.find(tablet_id);
+        if (it != _entries.end() && it->second.policy == policy &&
+            it->second.refreshed_at_s >
+                    now - config::file_cache_tablet_policy_refresh_interval_s 
/ 2) {
+            return;
+        }
+    }
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = set_locked(tablet_id, policy, now);
+    }
+    if (before == policy) {
+        return;
+    }
+    bump_versions(before, policy);
+    persist(tablet_id, policy);
+}
+
+void TabletCachePolicyRegistry::erase(int64_t tablet_id) {
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = erase_locked(tablet_id);
+    }
+    if (!before.has_value()) {
+        return;
+    }
+    bump_versions(before, std::nullopt);
+    persist(tablet_id, std::nullopt);
+}
+
+void TabletCachePolicyRegistry::restore(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        if (_entries.contains(tablet_id)) {
+            // Already known from the live meta or from another cache path's 
copy.
+            return;
+        }
+        // Never refreshed by this process, so it is due as soon as a cache 
path reports it;
+        // counted as reported now so that it is not forgotten before the 
cache has loaded.
+        before = set_locked(tablet_id, policy, 0);
+        _entries[tablet_id].reported_at_s = UnixSeconds();
+    }
+    bump_versions(before, policy);
+}
+
+void TabletCachePolicyRegistry::note_tablet(int64_t tablet_id) {
+    _noted_tablets.enqueue(tablet_id);
+}
+
+bool TabletCachePolicyRegistry::has_deadline_in(int64_t from, int64_t to) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _deadlines.upper_bound(from);
+    return it != _deadlines.end() && *it <= to;
+}
+
+void TabletCachePolicyRegistry::report_cached_tablets(const 
std::vector<int64_t>& tablet_ids) {
+    const int64_t now = UnixSeconds();
+    const int64_t stale_before = now - 
config::file_cache_tablet_policy_refresh_interval_s;
+    std::vector<int64_t> due;
+    // In batches: a path may hold blocks of many tablets, and the readers 
waiting on this lock
+    // hold their cache lock.
+    for (size_t begin = 0; begin < tablet_ids.size(); begin += 
kReportBatchSize) {
+        const size_t end = std::min(tablet_ids.size(), begin + 
kReportBatchSize);
+        std::unique_lock lock(_mutex);
+        for (size_t i = begin; i < end; ++i) {
+            const int64_t tablet_id = tablet_ids[i];
+            auto it = _entries.find(tablet_id);
+            if (it == _entries.end()) {
+                due.push_back(tablet_id);
+                continue;
+            }
+            it->second.reported_at_s = now;
+            if (it->second.refreshed_at_s <= stale_before) {
+                due.push_back(tablet_id);
+            }
+        }
+    }
+    std::lock_guard due_lock(_due_mutex);
+    _due.insert(due.begin(), due.end());
+}
+
+std::vector<int64_t> TabletCachePolicyRegistry::take_due(int64_t now, size_t 
budget) {
+    std::vector<int64_t> unknown;
+    int64_t tablet_id = 0;
+    while (_noted_tablets.try_dequeue(tablet_id)) {
+        if (!deadline(tablet_id).has_value()) {
+            unknown.push_back(tablet_id);
+        }
+    }
+    std::lock_guard due_lock(_due_mutex);
+    _due.insert(unknown.begin(), unknown.end());
+    std::vector<int64_t> batch;
+    for (auto it = _due.begin(); it != _due.end() && batch.size() < budget; it 
= _due.erase(it)) {
+        auto retry = _retry_at.find(*it);
+        if (retry == _retry_at.end() || retry->second <= now) {
+            batch.push_back(*it);
+        }
+    }
+    return batch;
+}
+
+void TabletCachePolicyRegistry::prune(int64_t now) {
+    if (now < _next_prune_s) {
+        return;
+    }
+    _next_prune_s = now + kPruneIntervalS;
+    std::erase_if(_retry_at, [now](const auto& retry) { return retry.second <= 
now; });
+    // A tablet no cache path holds and nothing refreshes (unloaded, or 
dropped) has no blocks
+    // to judge; it is learned again if its blocks come back.
+    const int64_t forget_before = now - 2 * 
config::file_cache_tablet_policy_refresh_interval_s;
+    auto is_unused = [forget_before](const Entry& entry) {
+        return std::max(entry.refreshed_at_s, entry.reported_at_s) < 
forget_before;
+    };
+    std::vector<int64_t> unused;
+    {
+        std::shared_lock lock(_mutex);
+        for (const auto& [id, entry] : _entries) {
+            if (is_unused(entry)) {
+                unused.push_back(id);
+            }
+        }
+    }
+    TEST_SYNC_POINT_CALLBACK("TabletCachePolicyRegistry::prune:collected", 
this, &unused);
+    for (int64_t id : unused) {
+        std::optional<TabletCachePolicy> before;
+        {
+            std::unique_lock lock(_mutex);
+            // Checked again: it may have been refreshed or reported since.
+            if (auto it = _entries.find(id); it != _entries.end() && 
is_unused(it->second)) {
+                before = erase_locked(id);
+            }
+        }
+        if (before.has_value()) {
+            bump_versions(before, std::nullopt);
+            persist(id, std::nullopt);
+        }
+    }
+}
+
+void TabletCachePolicyRegistry::refresh(size_t budget) {
+    std::lock_guard refresh_lock(_refresh_mutex);
+    const int64_t now = UnixSeconds();
+    const std::vector<int64_t> batch = take_due(now, budget);
+    prune(now);
+    const Fetcher& fetch = _fetcher ? _fetcher : 
Fetcher(fetch_from_tablet_meta);
+    for (size_t i = 0; i < batch.size(); ++i) {
+        const int64_t tablet_id = batch[i];
+        TabletCachePolicy policy;
+        Status st = fetch(tablet_id, &policy);
+        g_tablet_cache_policy_fetch_num << 1;
+        if (st.ok()) {
+            _retry_at.erase(tablet_id);
+            upsert(tablet_id, policy);

Review Comment:
   Not fixing: it needs a background fetch of the same tablet in flight exactly 
when an ALTER is synced, and the stale policy is corrected by the next meta 
sync or refresh.



##########
be/src/io/cache/tablet_cache_policy_registry.cpp:
##########
@@ -0,0 +1,433 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#include "io/cache/tablet_cache_policy_registry.h"
+
+#include <bvar/bvar.h>
+
+#include <algorithm>
+#include <chrono>
+#include <limits>
+
+#include "common/config.h"
+#include "common/logging.h"
+#include "cpp/sync_point.h"
+#include "io/cache/cache_block_meta_store.h"
+#include "runtime/exec_env.h"
+#include "storage/tablet/tablet_meta.h"
+#include "util/thread.h"
+#include "util/time.h"
+
+namespace doris::io {
+
+bvar::Adder<uint64_t> 
g_tablet_cache_policy_fetch_num("file_cache_tablet_policy_fetch_num");
+bvar::Adder<uint64_t> g_tablet_cache_policy_fetch_failed_num(
+        "file_cache_tablet_policy_fetch_failed_num");
+bvar::PassiveStatus<size_t> g_tablet_cache_policy_num(
+        "file_cache_tablet_policy_num",
+        [](void*) { return TabletCachePolicyRegistry::instance()->size(); }, 
nullptr);
+
+namespace {
+
+// How often the record is scanned for policies nobody needs any more.
+constexpr int64_t kPruneIntervalS = 60;
+// How long a tablet whose policy could not be fetched is left alone.
+constexpr int64_t kFetchRetryIntervalS = 60;
+// How many reported tablets are looked up per hold of the exclusive lock.
+constexpr size_t kReportBatchSize = 1024;
+// How often the background refresh runs.
+constexpr std::chrono::seconds kRefreshInterval {1};
+
+Status fetch_from_tablet_meta(int64_t tablet_id, TabletCachePolicy* policy) {
+    TabletMetaSharedPtr tablet_meta;
+    RETURN_IF_ERROR(ExecEnv::get_tablet_meta(tablet_id, &tablet_meta, false));
+    DORIS_CHECK(tablet_meta != nullptr);
+    policy->ttl_seconds = tablet_meta->ttl_seconds();
+    policy->ctime = tablet_meta->creation_time();
+    return Status::OK();
+}
+
+} // namespace
+
+int64_t TabletCachePolicy::deadline() const {
+    if (ttl_seconds <= 0 || ctime <= 0) {
+        return 0;
+    }
+    // Same rule as TabletMeta::file_cache_ttl_expiration_time(): a huge ttl 
must not wrap into
+    // a deadline in the past.
+    if (ctime > std::numeric_limits<int64_t>::max() - ttl_seconds) {
+        return std::numeric_limits<int64_t>::max();
+    }
+    return ctime + ttl_seconds;
+}
+
+TabletCachePolicyRegistry* TabletCachePolicyRegistry::instance() {
+    // Never destroyed: a cache path may still be running when the process 
exits.
+    static auto* registry = new TabletCachePolicyRegistry();
+    return registry;
+}
+
+std::optional<int64_t> TabletCachePolicyRegistry::deadline(int64_t tablet_id) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    return it->second.policy.deadline();
+}
+
+int64_t TabletCachePolicyRegistry::protected_until(int64_t tablet_id, int64_t 
legacy_deadline,
+                                                   bool* legacy) {
+    // tablet_id 0 is data outside any Doris tablet (external tables, v2 cache 
files that never
+    // recorded one): it only has the deadline it was written with.
+    if (tablet_id > 0) {
+        if (const std::optional<int64_t> known = deadline(tablet_id); 
known.has_value()) {
+            *legacy = false;
+            return *known;
+        }
+        note_tablet(tablet_id);
+    }
+    *legacy = true;
+    return legacy_deadline;
+}
+
+bool TabletCachePolicyRegistry::is_protected(int64_t tablet_id, int64_t 
legacy_deadline,
+                                             int64_t now) {
+    bool legacy = false;
+    return protected_until(tablet_id, legacy_deadline, &legacy) > now;
+}
+
+std::optional<TabletCachePolicy> TabletCachePolicyRegistry::set_locked(
+        int64_t tablet_id, const TabletCachePolicy& policy, int64_t 
refreshed_at_s) {
+    auto [it, inserted] =
+            _entries.try_emplace(tablet_id, Entry {policy, refreshed_at_s, 
refreshed_at_s});
+    std::optional<TabletCachePolicy> before;
+    if (!inserted) {
+        before = it->second.policy;
+        if (const int64_t old_deadline = before->deadline(); old_deadline > 0) 
{
+            _deadlines.erase(_deadlines.find(old_deadline));
+        }
+        it->second.policy = policy;
+        it->second.refreshed_at_s = refreshed_at_s;
+    }
+    if (const int64_t new_deadline = policy.deadline(); new_deadline > 0) {
+        _deadlines.insert(new_deadline);
+    }
+    return before;
+}
+
+std::optional<TabletCachePolicy> 
TabletCachePolicyRegistry::erase_locked(int64_t tablet_id) {
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    const TabletCachePolicy before = it->second.policy;
+    if (const int64_t old_deadline = before.deadline(); old_deadline > 0) {
+        _deadlines.erase(_deadlines.find(old_deadline));
+    }
+    _entries.erase(it);
+    return before;
+}
+
+void TabletCachePolicyRegistry::bump_versions(const 
std::optional<TabletCachePolicy>& before,
+                                              const 
std::optional<TabletCachePolicy>& after) {
+    // An unknown tablet is judged by the deadline its blocks carry, so 
learning or forgetting a
+    // tablet can move its blocks either way.
+    const int64_t old_deadline = before.has_value() ? before->deadline() : -1;
+    const int64_t new_deadline = after.has_value() ? after->deadline() : -1;
+    if (!before.has_value() || !after.has_value() || new_deadline > 
old_deadline) {
+        _protection_gained_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+    if (!before.has_value() || !after.has_value() || new_deadline < 
old_deadline) {
+        _protection_lost_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+}
+
+void TabletCachePolicyRegistry::persist(int64_t tablet_id,
+                                        const 
std::optional<TabletCachePolicy>& policy) {
+    std::lock_guard lock(_stores_mutex);
+    for (auto* store : _stores) {
+        if (policy.has_value()) {
+            store->put_tablet_policy(tablet_id, *policy);
+        } else {
+            store->delete_tablet_policy(tablet_id);
+        }
+    }
+}
+
+void TabletCachePolicyRegistry::upsert(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    DORIS_CHECK(tablet_id > 0);
+    const int64_t now = UnixSeconds();
+    {
+        // Unchanged and recently confirmed is the common case: every meta 
refresh reports the
+        // policy. Only take the exclusive lock to record a change, or to push 
the refresh time
+        // forward once it is half way to being due.
+        std::shared_lock lock(_mutex);
+        auto it = _entries.find(tablet_id);
+        if (it != _entries.end() && it->second.policy == policy &&
+            it->second.refreshed_at_s >
+                    now - config::file_cache_tablet_policy_refresh_interval_s 
/ 2) {
+            return;
+        }
+    }
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = set_locked(tablet_id, policy, now);
+    }
+    if (before == policy) {
+        return;
+    }
+    bump_versions(before, policy);
+    persist(tablet_id, policy);

Review Comment:
   The meta store queue is a FIFO under a lock now (a8294643a7b). The remaining 
window before the enqueue is microseconds and only matters after a restart, 
where the restored policy is refreshed soon. Not fixing further.



##########
be/src/io/cache/block_file_cache.cpp:
##########
@@ -2106,25 +2168,211 @@ std::string 
BlockFileCache::dump_single_cache_type_unlocked(const UInt128Wrapper
     return cache_type_to_string(cell->second.file_block->cache_type());
 }
 
-void BlockFileCache::change_cache_type(const UInt128Wrapper& hash, size_t 
offset,
-                                       FileCacheType new_type,
-                                       std::lock_guard<std::mutex>& 
cache_lock) {
-    if (auto iter = _files.find(hash); iter != _files.end()) {
-        auto& file_blocks = iter->second;
-        if (auto cell_it = file_blocks.find(offset); cell_it != 
file_blocks.end()) {
-            FileBlockCell& cell = cell_it->second;
-            auto& cur_queue = get_queue(cell.file_block->cache_type());
-            DCHECK(cell.queue_iterator.has_value());
-            cur_queue.remove(*cell.queue_iterator, cache_lock);
-            _lru_recorder->record_queue_event(
-                    cell.file_block->cache_type(), CacheLRULogType::REMOVE,
-                    cell.file_block->get_hash_value(), 
cell.file_block->offset(), cell.size());
-            auto& new_queue = get_queue(new_type);
-            cell.queue_iterator =
-                    new_queue.add(hash, offset, 
cell.file_block->range().size(), cache_lock);
-            _lru_recorder->record_queue_event(new_type, CacheLRULogType::ADD,
-                                              
cell.file_block->get_hash_value(),
-                                              cell.file_block->offset(), 
cell.size());
+bool BlockFileCache::is_protected(const FileBlock& block, int64_t now) {
+    return is_protected(block.tablet_id(), 
static_cast<int64_t>(block.expiration_time()), now);
+}
+
+bool BlockFileCache::is_protected(int64_t tablet_id, int64_t legacy_deadline, 
int64_t now) {
+    bool legacy = false;
+    const int64_t deadline = _policy_registry->protected_until(tablet_id, 
legacy_deadline, &legacy);
+    if (deadline <= now) {
+        return false;
+    }
+    if (legacy) {
+        int64_t next = _next_legacy_deadline.load(std::memory_order_relaxed);
+        while (deadline < next && !_next_legacy_deadline.compare_exchange_weak(
+                                          next, deadline, 
std::memory_order_relaxed)) {
+        }
+    }
+    return true;
+}
+
+FileCacheType BlockFileCache::queue_type_for(int64_t tablet_id, int64_t 
legacy_deadline,
+                                             FileCacheType cache_class, 
int64_t now) {
+    DCHECK(cache_class != FileCacheType::TTL);
+    return is_protected(tablet_id, legacy_deadline, now) ? FileCacheType::TTL 
: cache_class;
+}
+
+void BlockFileCache::move_cell_to_queue(FileBlockCell& cell, FileCacheType 
new_type,
+                                        std::lock_guard<std::mutex>& 
cache_lock) {
+    auto& file_block = *cell.file_block;
+    const FileCacheType old_type = file_block.cache_type();
+    DCHECK(old_type != new_type);
+    DCHECK(cell.queue_iterator.has_value());
+    get_queue(old_type).remove(*cell.queue_iterator, cache_lock);
+    _lru_recorder->record_queue_event(old_type, CacheLRULogType::REMOVE,
+                                      file_block.get_hash_value(), 
file_block.offset(),
+                                      cell.size());
+    cell.queue_iterator = get_queue(new_type).add_front(
+            file_block.get_hash_value(), file_block.offset(), cell.size(), 
cache_lock);
+    _lru_recorder->record_queue_event(new_type, CacheLRULogType::ADDTOFRONT,
+                                      file_block.get_hash_value(), 
file_block.offset(),
+                                      cell.size());
+    file_block._key.meta.type = new_type;

Review Comment:
   Not fixing: the only reader without the cache lock is get_info_for_log(), so 
at worst a log line shows the previous queue. Taking the block lock here would 
wait under the cache lock for a finalize, which holds it across file I/O.



##########
be/src/io/cache/block_file_cache.cpp:
##########
@@ -2106,25 +2168,211 @@ std::string 
BlockFileCache::dump_single_cache_type_unlocked(const UInt128Wrapper
     return cache_type_to_string(cell->second.file_block->cache_type());
 }
 
-void BlockFileCache::change_cache_type(const UInt128Wrapper& hash, size_t 
offset,
-                                       FileCacheType new_type,
-                                       std::lock_guard<std::mutex>& 
cache_lock) {
-    if (auto iter = _files.find(hash); iter != _files.end()) {
-        auto& file_blocks = iter->second;
-        if (auto cell_it = file_blocks.find(offset); cell_it != 
file_blocks.end()) {
-            FileBlockCell& cell = cell_it->second;
-            auto& cur_queue = get_queue(cell.file_block->cache_type());
-            DCHECK(cell.queue_iterator.has_value());
-            cur_queue.remove(*cell.queue_iterator, cache_lock);
-            _lru_recorder->record_queue_event(
-                    cell.file_block->cache_type(), CacheLRULogType::REMOVE,
-                    cell.file_block->get_hash_value(), 
cell.file_block->offset(), cell.size());
-            auto& new_queue = get_queue(new_type);
-            cell.queue_iterator =
-                    new_queue.add(hash, offset, 
cell.file_block->range().size(), cache_lock);
-            _lru_recorder->record_queue_event(new_type, CacheLRULogType::ADD,
-                                              
cell.file_block->get_hash_value(),
-                                              cell.file_block->offset(), 
cell.size());
+bool BlockFileCache::is_protected(const FileBlock& block, int64_t now) {
+    return is_protected(block.tablet_id(), 
static_cast<int64_t>(block.expiration_time()), now);
+}
+
+bool BlockFileCache::is_protected(int64_t tablet_id, int64_t legacy_deadline, 
int64_t now) {
+    bool legacy = false;
+    const int64_t deadline = _policy_registry->protected_until(tablet_id, 
legacy_deadline, &legacy);
+    if (deadline <= now) {
+        return false;
+    }
+    if (legacy) {
+        int64_t next = _next_legacy_deadline.load(std::memory_order_relaxed);
+        while (deadline < next && !_next_legacy_deadline.compare_exchange_weak(
+                                          next, deadline, 
std::memory_order_relaxed)) {
+        }
+    }
+    return true;
+}
+
+FileCacheType BlockFileCache::queue_type_for(int64_t tablet_id, int64_t 
legacy_deadline,
+                                             FileCacheType cache_class, 
int64_t now) {
+    DCHECK(cache_class != FileCacheType::TTL);
+    return is_protected(tablet_id, legacy_deadline, now) ? FileCacheType::TTL 
: cache_class;
+}
+
+void BlockFileCache::move_cell_to_queue(FileBlockCell& cell, FileCacheType 
new_type,
+                                        std::lock_guard<std::mutex>& 
cache_lock) {
+    auto& file_block = *cell.file_block;
+    const FileCacheType old_type = file_block.cache_type();
+    DCHECK(old_type != new_type);
+    DCHECK(cell.queue_iterator.has_value());
+    get_queue(old_type).remove(*cell.queue_iterator, cache_lock);
+    _lru_recorder->record_queue_event(old_type, CacheLRULogType::REMOVE,
+                                      file_block.get_hash_value(), 
file_block.offset(),
+                                      cell.size());
+    cell.queue_iterator = get_queue(new_type).add_front(
+            file_block.get_hash_value(), file_block.offset(), cell.size(), 
cache_lock);
+    _lru_recorder->record_queue_event(new_type, CacheLRULogType::ADDTOFRONT,
+                                      file_block.get_hash_value(), 
file_block.offset(),
+                                      cell.size());
+    file_block._key.meta.type = new_type;
+    *_ttl_relocated_blocks << 1;
+}
+
+void BlockFileCache::add_cached_tablet(int64_t tablet_id) {
+    if (tablet_id > 0) {
+        ++_cached_tablets[tablet_id];
+    }
+}
+
+void BlockFileCache::remove_cached_tablet(int64_t tablet_id) {
+    if (tablet_id > 0) {
+        auto it = _cached_tablets.find(tablet_id);
+        DCHECK(it != _cached_tablets.end());
+        if (--it->second == 0) {
+            _cached_tablets.erase(it);
+        }
+    }
+}
+
+void BlockFileCache::relocate_to_ttl_queue(const std::vector<FileBlockCell*>& 
cells,
+                                           std::lock_guard<std::mutex>& 
cache_lock) {
+    for (auto* cell : cells) {
+        move_cell_to_queue(*cell, FileCacheType::TTL, cache_lock);
+    }
+}
+
+void BlockFileCache::complete_loaded_cell(FileBlockCell& cell, int64_t 
tablet_id,
+                                          FileCacheType cache_class, uint64_t 
legacy_deadline,
+                                          std::lock_guard<std::mutex>& 
cache_lock) {
+    auto& meta = cell.file_block->_key.meta;
+    remove_cached_tablet(meta.tablet_id);
+    add_cached_tablet(tablet_id);
+    meta.tablet_id = tablet_id;
+    meta.cache_class = cache_class_of(cache_class);
+    meta.expiration_time = legacy_deadline;
+    const FileCacheType queue_type = queue_type_for(
+            tablet_id, static_cast<int64_t>(legacy_deadline), 
meta.cache_class, UnixSeconds());
+    if (queue_type != meta.type) {
+        move_cell_to_queue(cell, queue_type, cache_lock);
+    }
+}
+
+void BlockFileCache::start_queue_sweeps(int64_t now) {
+    auto& state = _queue_sweep;
+    auto is_active = [&](FileCacheType type) { return 
state.active[file_cache_type_index(type)]; };
+    const bool backstop_due =
+            now - state.last_backstop_at >= 
config::file_cache_queue_sweep_backstop_interval_s;
+    // A pass over the TTL queue picks up blocks whose tablet lost its TTL, or 
whose deadline
+    // passed, since the previous pass started.
+    if (!is_active(FileCacheType::TTL)) {
+        const uint64_t lost_version = 
_policy_registry->protection_lost_version();
+        if (backstop_due || lost_version != state.ttl_pass_lost_version ||
+            _policy_registry->has_deadline_in(state.ttl_pass_started_at, now) 
||
+            _next_legacy_deadline.load(std::memory_order_relaxed) <= now) {
+            state.active[file_cache_type_index(FileCacheType::TTL)] = true;
+            state.ttl_pass_lost_version = lost_version;
+            state.ttl_pass_started_at = now;
+            state.ttl_pass_legacy_bytes = 0;
+            // The pass finds again those still ahead.
+            _next_legacy_deadline.store(std::numeric_limits<int64_t>::max(),
+                                        std::memory_order_relaxed);
+        }
+    }
+    // A pass over the class queues picks up blocks whose tablet gained a TTL. 
The three queues
+    // start together so that the version they record holds for all of them.
+    constexpr std::array<FileCacheType, 3> class_types {FileCacheType::INDEX, 
FileCacheType::NORMAL,
+                                                        
FileCacheType::DISPOSABLE};
+    if (std::none_of(class_types.begin(), class_types.end(), is_active)) {
+        const uint64_t gained_version = 
_policy_registry->protection_gained_version();
+        if (backstop_due || gained_version != state.class_pass_gained_version) 
{
+            for (auto type : class_types) {
+                state.active[file_cache_type_index(type)] = true;
+            }
+            state.class_pass_gained_version = gained_version;
+        }
+    }
+    if (backstop_due &&
+        std::all_of(state.active.begin(), state.active.end(), [](bool active) 
{ return active; })) {
+        state.last_backstop_at = now;
+    }
+}
+
+size_t BlockFileCache::sweep_queue(FileCacheType type, size_t budget, int64_t 
now,
+                                   std::lock_guard<std::mutex>& cache_lock) {
+    auto& active = _queue_sweep.active[file_cache_type_index(type)];
+    if (!active) {
+        return 0;
+    }
+    auto& queue = get_queue(type);
+    auto& pass_left = _queue_sweep.pass_left[file_cache_type_index(type)];
+    if (!queue.sweep_cursor.has_value()) {
+        // A pass walks at most as many blocks as the queue holds when it 
starts: blocks touched
+        // or added meanwhile go to the hot end, and must not keep the pass 
from ending. A block
+        // touched before the cursor reached it may be left for the next pass.
+        queue.sweep_cursor = queue.begin();
+        pass_left = queue.queue.size();
+    }
+    auto& cursor = *queue.sweep_cursor;
+    size_t walked = 0;
+    std::vector<std::pair<FileBlockCell*, FileCacheType>> moves;
+    for (; walked < budget && pass_left > 0 && cursor != queue.end(); 
++walked, --pass_left) {
+        auto& entry = *cursor;
+        ++cursor;
+        auto* cell = get_cell(entry.hash, entry.offset, cache_lock);
+        DCHECK(cell != nullptr);
+        const auto& block = *cell->file_block;
+        const FileCacheType want =
+                is_protected(block, now) ? FileCacheType::TTL : 
block.cache_class();
+        if (want != type) {
+            moves.emplace_back(cell, want);
+        } else if (type == FileCacheType::TTL && block.tablet_id() <= 0) {
+            _queue_sweep.ttl_pass_legacy_bytes += cell->size();
+        }
+    }
+    for (auto& [cell, want] : moves) {
+        move_cell_to_queue(*cell, want, cache_lock);
+    }
+    if (pass_left == 0 || queue.sweep_cursor == queue.end()) {

Review Comment:
   Not fixing: only blocks touched during a pass can be missed. Eviction judges 
every block itself, and the next pass or the daily backstop moves them.



##########
be/src/io/cache/tablet_cache_policy_registry.cpp:
##########
@@ -0,0 +1,433 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#include "io/cache/tablet_cache_policy_registry.h"
+
+#include <bvar/bvar.h>
+
+#include <algorithm>
+#include <chrono>
+#include <limits>
+
+#include "common/config.h"
+#include "common/logging.h"
+#include "cpp/sync_point.h"
+#include "io/cache/cache_block_meta_store.h"
+#include "runtime/exec_env.h"
+#include "storage/tablet/tablet_meta.h"
+#include "util/thread.h"
+#include "util/time.h"
+
+namespace doris::io {
+
+bvar::Adder<uint64_t> 
g_tablet_cache_policy_fetch_num("file_cache_tablet_policy_fetch_num");
+bvar::Adder<uint64_t> g_tablet_cache_policy_fetch_failed_num(
+        "file_cache_tablet_policy_fetch_failed_num");
+bvar::PassiveStatus<size_t> g_tablet_cache_policy_num(
+        "file_cache_tablet_policy_num",
+        [](void*) { return TabletCachePolicyRegistry::instance()->size(); }, 
nullptr);
+
+namespace {
+
+// How often the record is scanned for policies nobody needs any more.
+constexpr int64_t kPruneIntervalS = 60;
+// How long a tablet whose policy could not be fetched is left alone.
+constexpr int64_t kFetchRetryIntervalS = 60;
+// How many reported tablets are looked up per hold of the exclusive lock.
+constexpr size_t kReportBatchSize = 1024;
+// How often the background refresh runs.
+constexpr std::chrono::seconds kRefreshInterval {1};
+
+Status fetch_from_tablet_meta(int64_t tablet_id, TabletCachePolicy* policy) {
+    TabletMetaSharedPtr tablet_meta;
+    RETURN_IF_ERROR(ExecEnv::get_tablet_meta(tablet_id, &tablet_meta, false));
+    DORIS_CHECK(tablet_meta != nullptr);
+    policy->ttl_seconds = tablet_meta->ttl_seconds();
+    policy->ctime = tablet_meta->creation_time();
+    return Status::OK();
+}
+
+} // namespace
+
+int64_t TabletCachePolicy::deadline() const {
+    if (ttl_seconds <= 0 || ctime <= 0) {
+        return 0;
+    }
+    // Same rule as TabletMeta::file_cache_ttl_expiration_time(): a huge ttl 
must not wrap into
+    // a deadline in the past.
+    if (ctime > std::numeric_limits<int64_t>::max() - ttl_seconds) {
+        return std::numeric_limits<int64_t>::max();
+    }
+    return ctime + ttl_seconds;
+}
+
+TabletCachePolicyRegistry* TabletCachePolicyRegistry::instance() {
+    // Never destroyed: a cache path may still be running when the process 
exits.
+    static auto* registry = new TabletCachePolicyRegistry();
+    return registry;
+}
+
+std::optional<int64_t> TabletCachePolicyRegistry::deadline(int64_t tablet_id) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    return it->second.policy.deadline();
+}
+
+int64_t TabletCachePolicyRegistry::protected_until(int64_t tablet_id, int64_t 
legacy_deadline,
+                                                   bool* legacy) {
+    // tablet_id 0 is data outside any Doris tablet (external tables, v2 cache 
files that never
+    // recorded one): it only has the deadline it was written with.
+    if (tablet_id > 0) {
+        if (const std::optional<int64_t> known = deadline(tablet_id); 
known.has_value()) {
+            *legacy = false;
+            return *known;
+        }
+        note_tablet(tablet_id);
+    }
+    *legacy = true;
+    return legacy_deadline;
+}
+
+bool TabletCachePolicyRegistry::is_protected(int64_t tablet_id, int64_t 
legacy_deadline,
+                                             int64_t now) {
+    bool legacy = false;
+    return protected_until(tablet_id, legacy_deadline, &legacy) > now;
+}
+
+std::optional<TabletCachePolicy> TabletCachePolicyRegistry::set_locked(
+        int64_t tablet_id, const TabletCachePolicy& policy, int64_t 
refreshed_at_s) {
+    auto [it, inserted] =
+            _entries.try_emplace(tablet_id, Entry {policy, refreshed_at_s, 
refreshed_at_s});
+    std::optional<TabletCachePolicy> before;
+    if (!inserted) {
+        before = it->second.policy;
+        if (const int64_t old_deadline = before->deadline(); old_deadline > 0) 
{
+            _deadlines.erase(_deadlines.find(old_deadline));
+        }
+        it->second.policy = policy;
+        it->second.refreshed_at_s = refreshed_at_s;
+    }
+    if (const int64_t new_deadline = policy.deadline(); new_deadline > 0) {
+        _deadlines.insert(new_deadline);
+    }
+    return before;
+}
+
+std::optional<TabletCachePolicy> 
TabletCachePolicyRegistry::erase_locked(int64_t tablet_id) {
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    const TabletCachePolicy before = it->second.policy;
+    if (const int64_t old_deadline = before.deadline(); old_deadline > 0) {
+        _deadlines.erase(_deadlines.find(old_deadline));
+    }
+    _entries.erase(it);
+    return before;
+}
+
+void TabletCachePolicyRegistry::bump_versions(const 
std::optional<TabletCachePolicy>& before,
+                                              const 
std::optional<TabletCachePolicy>& after) {
+    // An unknown tablet is judged by the deadline its blocks carry, so 
learning or forgetting a
+    // tablet can move its blocks either way.
+    const int64_t old_deadline = before.has_value() ? before->deadline() : -1;
+    const int64_t new_deadline = after.has_value() ? after->deadline() : -1;
+    if (!before.has_value() || !after.has_value() || new_deadline > 
old_deadline) {
+        _protection_gained_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+    if (!before.has_value() || !after.has_value() || new_deadline < 
old_deadline) {
+        _protection_lost_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+}
+
+void TabletCachePolicyRegistry::persist(int64_t tablet_id,
+                                        const 
std::optional<TabletCachePolicy>& policy) {
+    std::lock_guard lock(_stores_mutex);
+    for (auto* store : _stores) {
+        if (policy.has_value()) {
+            store->put_tablet_policy(tablet_id, *policy);
+        } else {
+            store->delete_tablet_policy(tablet_id);
+        }
+    }
+}
+
+void TabletCachePolicyRegistry::upsert(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    DORIS_CHECK(tablet_id > 0);
+    const int64_t now = UnixSeconds();
+    {
+        // Unchanged and recently confirmed is the common case: every meta 
refresh reports the
+        // policy. Only take the exclusive lock to record a change, or to push 
the refresh time
+        // forward once it is half way to being due.
+        std::shared_lock lock(_mutex);
+        auto it = _entries.find(tablet_id);
+        if (it != _entries.end() && it->second.policy == policy &&
+            it->second.refreshed_at_s >
+                    now - config::file_cache_tablet_policy_refresh_interval_s 
/ 2) {
+            return;
+        }
+    }
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = set_locked(tablet_id, policy, now);
+    }
+    if (before == policy) {
+        return;
+    }
+    bump_versions(before, policy);
+    persist(tablet_id, policy);
+}
+
+void TabletCachePolicyRegistry::erase(int64_t tablet_id) {
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = erase_locked(tablet_id);
+    }
+    if (!before.has_value()) {
+        return;
+    }
+    bump_versions(before, std::nullopt);
+    persist(tablet_id, std::nullopt);
+}
+
+void TabletCachePolicyRegistry::restore(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        if (_entries.contains(tablet_id)) {
+            // Already known from the live meta or from another cache path's 
copy.
+            return;
+        }
+        // Never refreshed by this process, so it is due as soon as a cache 
path reports it;
+        // counted as reported now so that it is not forgotten before the 
cache has loaded.
+        before = set_locked(tablet_id, policy, 0);
+        _entries[tablet_id].reported_at_s = UnixSeconds();
+    }
+    bump_versions(before, policy);
+}
+
+void TabletCachePolicyRegistry::note_tablet(int64_t tablet_id) {
+    _noted_tablets.enqueue(tablet_id);
+}
+
+bool TabletCachePolicyRegistry::has_deadline_in(int64_t from, int64_t to) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _deadlines.upper_bound(from);
+    return it != _deadlines.end() && *it <= to;
+}
+
+void TabletCachePolicyRegistry::report_cached_tablets(const 
std::vector<int64_t>& tablet_ids) {
+    const int64_t now = UnixSeconds();
+    const int64_t stale_before = now - 
config::file_cache_tablet_policy_refresh_interval_s;
+    std::vector<int64_t> due;
+    // In batches: a path may hold blocks of many tablets, and the readers 
waiting on this lock
+    // hold their cache lock.
+    for (size_t begin = 0; begin < tablet_ids.size(); begin += 
kReportBatchSize) {
+        const size_t end = std::min(tablet_ids.size(), begin + 
kReportBatchSize);
+        std::unique_lock lock(_mutex);
+        for (size_t i = begin; i < end; ++i) {
+            const int64_t tablet_id = tablet_ids[i];
+            auto it = _entries.find(tablet_id);
+            if (it == _entries.end()) {
+                due.push_back(tablet_id);
+                continue;
+            }
+            it->second.reported_at_s = now;
+            if (it->second.refreshed_at_s <= stale_before) {
+                due.push_back(tablet_id);
+            }
+        }
+    }
+    std::lock_guard due_lock(_due_mutex);
+    _due.insert(due.begin(), due.end());
+}
+
+std::vector<int64_t> TabletCachePolicyRegistry::take_due(int64_t now, size_t 
budget) {
+    std::vector<int64_t> unknown;
+    int64_t tablet_id = 0;
+    while (_noted_tablets.try_dequeue(tablet_id)) {
+        if (!deadline(tablet_id).has_value()) {
+            unknown.push_back(tablet_id);
+        }
+    }
+    std::lock_guard due_lock(_due_mutex);
+    _due.insert(unknown.begin(), unknown.end());
+    std::vector<int64_t> batch;
+    for (auto it = _due.begin(); it != _due.end() && batch.size() < budget; it 
= _due.erase(it)) {
+        auto retry = _retry_at.find(*it);
+        if (retry == _retry_at.end() || retry->second <= now) {
+            batch.push_back(*it);
+        }
+    }
+    return batch;
+}
+
+void TabletCachePolicyRegistry::prune(int64_t now) {
+    if (now < _next_prune_s) {
+        return;
+    }
+    _next_prune_s = now + kPruneIntervalS;
+    std::erase_if(_retry_at, [now](const auto& retry) { return retry.second <= 
now; });
+    // A tablet no cache path holds and nothing refreshes (unloaded, or 
dropped) has no blocks
+    // to judge; it is learned again if its blocks come back.
+    const int64_t forget_before = now - 2 * 
config::file_cache_tablet_policy_refresh_interval_s;
+    auto is_unused = [forget_before](const Entry& entry) {
+        return std::max(entry.refreshed_at_s, entry.reported_at_s) < 
forget_before;
+    };
+    std::vector<int64_t> unused;
+    {
+        std::shared_lock lock(_mutex);
+        for (const auto& [id, entry] : _entries) {
+            if (is_unused(entry)) {
+                unused.push_back(id);
+            }
+        }
+    }
+    TEST_SYNC_POINT_CALLBACK("TabletCachePolicyRegistry::prune:collected", 
this, &unused);
+    for (int64_t id : unused) {
+        std::optional<TabletCachePolicy> before;
+        {
+            std::unique_lock lock(_mutex);
+            // Checked again: it may have been refreshed or reported since.
+            if (auto it = _entries.find(id); it != _entries.end() && 
is_unused(it->second)) {
+                before = erase_locked(id);
+            }
+        }
+        if (before.has_value()) {
+            bump_versions(before, std::nullopt);
+            persist(id, std::nullopt);
+        }
+    }
+}
+
+void TabletCachePolicyRegistry::refresh(size_t budget) {
+    std::lock_guard refresh_lock(_refresh_mutex);
+    const int64_t now = UnixSeconds();
+    const std::vector<int64_t> batch = take_due(now, budget);
+    prune(now);
+    const Fetcher& fetch = _fetcher ? _fetcher : 
Fetcher(fetch_from_tablet_meta);
+    for (size_t i = 0; i < batch.size(); ++i) {
+        const int64_t tablet_id = batch[i];
+        TabletCachePolicy policy;
+        Status st = fetch(tablet_id, &policy);
+        g_tablet_cache_policy_fetch_num << 1;
+        if (st.ok()) {
+            _retry_at.erase(tablet_id);
+            upsert(tablet_id, policy);
+            continue;
+        }
+        if (st.is<ErrorCode::NOT_FOUND>()) {
+            _retry_at.erase(tablet_id);
+            erase(tablet_id);
+            continue;
+        }
+        // Most likely the meta service is unavailable: the rest waits for the 
next round rather
+        // than for one failed call after another. Meanwhile a known tablet 
keeps being judged by
+        // its last known policy, an unknown one by the deadline its blocks 
were written with.
+        g_tablet_cache_policy_fetch_failed_num << 1;
+        LOG_EVERY_N(WARNING, 100) << "failed to fetch file cache ttl policy of 
tablet " << tablet_id
+                                  << ": " << st;
+        _retry_at[tablet_id] = UnixSeconds() + kFetchRetryIntervalS;
+        std::lock_guard due_lock(_due_mutex);
+        _due.insert(batch.begin() + i + 1, batch.end());
+        break;
+    }
+}
+
+void TabletCachePolicyRegistry::register_cache() {
+    std::lock_guard lock(_thread_mutex);
+    if (_open_caches++ > 0) {
+        return;
+    }
+    {
+        std::lock_guard stop_lock(_stop_mutex);
+        _stop_refresh = false;
+    }
+    _refresh_thread = std::thread(&TabletCachePolicyRegistry::refresh_loop, 
this);
+}
+
+void TabletCachePolicyRegistry::unregister_cache() {
+    std::lock_guard lock(_thread_mutex);
+    DCHECK_GT(_open_caches, 0);
+    if (--_open_caches > 0) {
+        return;
+    }
+    {
+        std::lock_guard stop_lock(_stop_mutex);
+        _stop_refresh = true;
+    }
+    _stop_cv.notify_all();
+    _refresh_thread.join();
+}
+
+void TabletCachePolicyRegistry::refresh_loop() {
+    Thread::set_self_name("file_cache_tablet_policy_refresh");
+    while (true) {
+        {
+            std::unique_lock stop_lock(_stop_mutex);
+            if (_stop_cv.wait_for(stop_lock, kRefreshInterval, [this] { return 
_stop_refresh; })) {
+                return;
+            }
+        }
+        
refresh(static_cast<size_t>(config::file_cache_tablet_policy_refresh_batch));
+    }
+}
+
+void TabletCachePolicyRegistry::add_store(CacheBlockMetaStore* store) {
+    std::lock_guard lock(_stores_mutex);
+    _stores.push_back(store);

Review Comment:
   Not fixing: it only matters when a restart drops every old cache path, and 
those tablets are fetched again within minutes.



##########
be/src/io/cache/tablet_cache_policy_registry.cpp:
##########
@@ -0,0 +1,433 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#include "io/cache/tablet_cache_policy_registry.h"
+
+#include <bvar/bvar.h>
+
+#include <algorithm>
+#include <chrono>
+#include <limits>
+
+#include "common/config.h"
+#include "common/logging.h"
+#include "cpp/sync_point.h"
+#include "io/cache/cache_block_meta_store.h"
+#include "runtime/exec_env.h"
+#include "storage/tablet/tablet_meta.h"
+#include "util/thread.h"
+#include "util/time.h"
+
+namespace doris::io {
+
+bvar::Adder<uint64_t> 
g_tablet_cache_policy_fetch_num("file_cache_tablet_policy_fetch_num");
+bvar::Adder<uint64_t> g_tablet_cache_policy_fetch_failed_num(
+        "file_cache_tablet_policy_fetch_failed_num");
+bvar::PassiveStatus<size_t> g_tablet_cache_policy_num(
+        "file_cache_tablet_policy_num",
+        [](void*) { return TabletCachePolicyRegistry::instance()->size(); }, 
nullptr);
+
+namespace {
+
+// How often the record is scanned for policies nobody needs any more.
+constexpr int64_t kPruneIntervalS = 60;
+// How long a tablet whose policy could not be fetched is left alone.
+constexpr int64_t kFetchRetryIntervalS = 60;
+// How many reported tablets are looked up per hold of the exclusive lock.
+constexpr size_t kReportBatchSize = 1024;
+// How often the background refresh runs.
+constexpr std::chrono::seconds kRefreshInterval {1};
+
+Status fetch_from_tablet_meta(int64_t tablet_id, TabletCachePolicy* policy) {
+    TabletMetaSharedPtr tablet_meta;
+    RETURN_IF_ERROR(ExecEnv::get_tablet_meta(tablet_id, &tablet_meta, false));
+    DORIS_CHECK(tablet_meta != nullptr);
+    policy->ttl_seconds = tablet_meta->ttl_seconds();
+    policy->ctime = tablet_meta->creation_time();
+    return Status::OK();
+}
+
+} // namespace
+
+int64_t TabletCachePolicy::deadline() const {
+    if (ttl_seconds <= 0 || ctime <= 0) {
+        return 0;
+    }
+    // Same rule as TabletMeta::file_cache_ttl_expiration_time(): a huge ttl 
must not wrap into
+    // a deadline in the past.
+    if (ctime > std::numeric_limits<int64_t>::max() - ttl_seconds) {
+        return std::numeric_limits<int64_t>::max();
+    }
+    return ctime + ttl_seconds;
+}
+
+TabletCachePolicyRegistry* TabletCachePolicyRegistry::instance() {
+    // Never destroyed: a cache path may still be running when the process 
exits.
+    static auto* registry = new TabletCachePolicyRegistry();
+    return registry;
+}
+
+std::optional<int64_t> TabletCachePolicyRegistry::deadline(int64_t tablet_id) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    return it->second.policy.deadline();
+}
+
+int64_t TabletCachePolicyRegistry::protected_until(int64_t tablet_id, int64_t 
legacy_deadline,
+                                                   bool* legacy) {
+    // tablet_id 0 is data outside any Doris tablet (external tables, v2 cache 
files that never
+    // recorded one): it only has the deadline it was written with.
+    if (tablet_id > 0) {
+        if (const std::optional<int64_t> known = deadline(tablet_id); 
known.has_value()) {
+            *legacy = false;
+            return *known;
+        }
+        note_tablet(tablet_id);
+    }
+    *legacy = true;
+    return legacy_deadline;
+}
+
+bool TabletCachePolicyRegistry::is_protected(int64_t tablet_id, int64_t 
legacy_deadline,
+                                             int64_t now) {
+    bool legacy = false;
+    return protected_until(tablet_id, legacy_deadline, &legacy) > now;
+}
+
+std::optional<TabletCachePolicy> TabletCachePolicyRegistry::set_locked(
+        int64_t tablet_id, const TabletCachePolicy& policy, int64_t 
refreshed_at_s) {
+    auto [it, inserted] =
+            _entries.try_emplace(tablet_id, Entry {policy, refreshed_at_s, 
refreshed_at_s});
+    std::optional<TabletCachePolicy> before;
+    if (!inserted) {
+        before = it->second.policy;
+        if (const int64_t old_deadline = before->deadline(); old_deadline > 0) 
{
+            _deadlines.erase(_deadlines.find(old_deadline));
+        }
+        it->second.policy = policy;
+        it->second.refreshed_at_s = refreshed_at_s;
+    }
+    if (const int64_t new_deadline = policy.deadline(); new_deadline > 0) {
+        _deadlines.insert(new_deadline);
+    }
+    return before;
+}
+
+std::optional<TabletCachePolicy> 
TabletCachePolicyRegistry::erase_locked(int64_t tablet_id) {
+    auto it = _entries.find(tablet_id);
+    if (it == _entries.end()) {
+        return std::nullopt;
+    }
+    const TabletCachePolicy before = it->second.policy;
+    if (const int64_t old_deadline = before.deadline(); old_deadline > 0) {
+        _deadlines.erase(_deadlines.find(old_deadline));
+    }
+    _entries.erase(it);
+    return before;
+}
+
+void TabletCachePolicyRegistry::bump_versions(const 
std::optional<TabletCachePolicy>& before,
+                                              const 
std::optional<TabletCachePolicy>& after) {
+    // An unknown tablet is judged by the deadline its blocks carry, so 
learning or forgetting a
+    // tablet can move its blocks either way.
+    const int64_t old_deadline = before.has_value() ? before->deadline() : -1;
+    const int64_t new_deadline = after.has_value() ? after->deadline() : -1;
+    if (!before.has_value() || !after.has_value() || new_deadline > 
old_deadline) {
+        _protection_gained_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+    if (!before.has_value() || !after.has_value() || new_deadline < 
old_deadline) {
+        _protection_lost_version.fetch_add(1, std::memory_order_acq_rel);
+    }
+}
+
+void TabletCachePolicyRegistry::persist(int64_t tablet_id,
+                                        const 
std::optional<TabletCachePolicy>& policy) {
+    std::lock_guard lock(_stores_mutex);
+    for (auto* store : _stores) {
+        if (policy.has_value()) {
+            store->put_tablet_policy(tablet_id, *policy);
+        } else {
+            store->delete_tablet_policy(tablet_id);
+        }
+    }
+}
+
+void TabletCachePolicyRegistry::upsert(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    DORIS_CHECK(tablet_id > 0);
+    const int64_t now = UnixSeconds();
+    {
+        // Unchanged and recently confirmed is the common case: every meta 
refresh reports the
+        // policy. Only take the exclusive lock to record a change, or to push 
the refresh time
+        // forward once it is half way to being due.
+        std::shared_lock lock(_mutex);
+        auto it = _entries.find(tablet_id);
+        if (it != _entries.end() && it->second.policy == policy &&
+            it->second.refreshed_at_s >
+                    now - config::file_cache_tablet_policy_refresh_interval_s 
/ 2) {
+            return;
+        }
+    }
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = set_locked(tablet_id, policy, now);
+    }
+    if (before == policy) {
+        return;
+    }
+    bump_versions(before, policy);
+    persist(tablet_id, policy);
+}
+
+void TabletCachePolicyRegistry::erase(int64_t tablet_id) {
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        before = erase_locked(tablet_id);
+    }
+    if (!before.has_value()) {
+        return;
+    }
+    bump_versions(before, std::nullopt);
+    persist(tablet_id, std::nullopt);
+}
+
+void TabletCachePolicyRegistry::restore(int64_t tablet_id, const 
TabletCachePolicy& policy) {
+    std::optional<TabletCachePolicy> before;
+    {
+        std::unique_lock lock(_mutex);
+        if (_entries.contains(tablet_id)) {
+            // Already known from the live meta or from another cache path's 
copy.
+            return;
+        }
+        // Never refreshed by this process, so it is due as soon as a cache 
path reports it;
+        // counted as reported now so that it is not forgotten before the 
cache has loaded.
+        before = set_locked(tablet_id, policy, 0);
+        _entries[tablet_id].reported_at_s = UnixSeconds();
+    }
+    bump_versions(before, policy);
+}
+
+void TabletCachePolicyRegistry::note_tablet(int64_t tablet_id) {
+    _noted_tablets.enqueue(tablet_id);
+}
+
+bool TabletCachePolicyRegistry::has_deadline_in(int64_t from, int64_t to) 
const {
+    std::shared_lock lock(_mutex);
+    auto it = _deadlines.upper_bound(from);
+    return it != _deadlines.end() && *it <= to;
+}
+
+void TabletCachePolicyRegistry::report_cached_tablets(const 
std::vector<int64_t>& tablet_ids) {
+    const int64_t now = UnixSeconds();
+    const int64_t stale_before = now - 
config::file_cache_tablet_policy_refresh_interval_s;
+    std::vector<int64_t> due;
+    // In batches: a path may hold blocks of many tablets, and the readers 
waiting on this lock
+    // hold their cache lock.
+    for (size_t begin = 0; begin < tablet_ids.size(); begin += 
kReportBatchSize) {
+        const size_t end = std::min(tablet_ids.size(), begin + 
kReportBatchSize);
+        std::unique_lock lock(_mutex);
+        for (size_t i = begin; i < end; ++i) {
+            const int64_t tablet_id = tablet_ids[i];
+            auto it = _entries.find(tablet_id);
+            if (it == _entries.end()) {
+                due.push_back(tablet_id);
+                continue;
+            }
+            it->second.reported_at_s = now;
+            if (it->second.refreshed_at_s <= stale_before) {
+                due.push_back(tablet_id);
+            }
+        }
+    }
+    std::lock_guard due_lock(_due_mutex);
+    _due.insert(due.begin(), due.end());
+}
+
+std::vector<int64_t> TabletCachePolicyRegistry::take_due(int64_t now, size_t 
budget) {
+    std::vector<int64_t> unknown;
+    int64_t tablet_id = 0;
+    while (_noted_tablets.try_dequeue(tablet_id)) {

Review Comment:
   Fixed in 6484c43b61e: noted tablets are kept in a set, each once.



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