chore: Limit expiry value to 32 bits.

We use adaptive precision, where we keep "millis" precision if we can,
and switch to seconds precision if the deadline is too large.

This actually was before but now I reduced the cut-off to 4B ms,
or 49 days. Also, the ttl in seconds is now limited to 4B sec,
with larger values quietly rounded down to this limit.

Signed-off-by: Roman Gershman <[email protected]>

Author: BagritsevichStepan

src/core/expire_period.h

@@ -8,9 +8,13 @@
 
 namespace dfly {
 
+// ExpirePeriod encapsulates the expiration period of a key.
+// It can represent periods in milliseconds up to ~49 days and in seconds up to ~136 years.
+// If value in milliseconds is too high, it switches to seconds precision.
+// And if it's still too high, it silently clamps to the max value.
 class ExpirePeriod {
  public:
-  static constexpr size_t kMaxGenId = 15;
+  static constexpr uint32_t kMaxGenId = 15;
 
   ExpirePeriod() : val_(0), gen_(0), precision_(0) {
     static_assert(sizeof(ExpirePeriod) == 8);  // TODO
@@ -35,28 +39,30 @@ class ExpirePeriod {
 
   void Set(uint64_t ms);
 
-  bool is_second_precision() { return precision_ == 1;}
+  bool is_second_precision() const {
+    return precision_ == 1;
+  }
 
  private:
-  uint64_t val_ : 59;
-  uint64_t gen_ : 4;
-  uint64_t precision_ : 1;  // 0 - ms, 1 - sec.
+  uint32_t val_;
+  uint8_t gen_ : 2;        // generation id.
+  uint8_t precision_ : 1;  // 0 - ms, 1 - sec.
 };
 
 inline void ExpirePeriod::Set(uint64_t ms) {
-  constexpr uint64_t kBarrier = (1ULL << 48);
-
-  if (ms < kBarrier) {
-    val_ = ms;
-    precision_ = 0;   // ms
+  if (ms < UINT32_MAX) {
+    val_ = ms;       // about 49 days in ms.
+    precision_ = 0;  // ms
     return;
   }
 
-  precision_ = 1;
-  if (ms < kBarrier << 10) {
-    ms = (ms + 500) / 1000;   // seconds
+  precision_ = 1;  // seconds
+  if (ms < UINT64_MAX / 2) {
+    ms = (ms + 500) / 1000;
+    val_ = ms >= UINT32_MAX ? UINT32_MAX - 1 : ms;
+  } else {
+    val_ = UINT32_MAX - 1;
   }
-  val_ = ms >= kBarrier ? kBarrier - 1 : ms;
 }
 
 }  // namespace dfly

src/server/server_family.cc

@@ -1284,10 +1284,7 @@ void ServerFamily::FlushAll(Namespace* ns) {
   boost::intrusive_ptr<Transaction> flush_trans(new Transaction{cid});
   flush_trans->InitByArgs(ns, 0, {});
   VLOG(1) << "Performing flush";
-  error_code ec = Drakarys(flush_trans.get(), DbSlice::kDbAll);
-  if (ec) {
-    LOG(ERROR) << "Error flushing db " << ec.message();
-  }
+  Drakarys(flush_trans.get(), DbSlice::kDbAll);
 }
 
 // Load starts as many fibers as there are files to load each one separately.
@@ -2201,7 +2198,7 @@ bool ServerFamily::TEST_IsSaving() const {
   return is_saving.load(std::memory_order_relaxed);
 }
 
-error_code ServerFamily::Drakarys(Transaction* transaction, DbIndex db_ind) {
+void ServerFamily::Drakarys(Transaction* transaction, DbIndex db_ind) {
   VLOG(1) << "Drakarys";
 
   transaction->Execute(
@@ -2210,8 +2207,6 @@ error_code ServerFamily::Drakarys(Transaction* transaction, DbIndex db_ind) {
         return OpStatus::OK;
       },
       true);
-
-  return error_code{};
 }
 
 SaveInfoData ServerFamily::GetLastSaveInfo() const {

src/server/server_family.h

@@ -250,7 +250,7 @@ class ServerFamily {
 
   // Burns down and destroy all the data from the database.
   // if kDbAll is passed, burns all the databases to the ground.
-  std::error_code Drakarys(Transaction* transaction, DbIndex db_ind);
+  void Drakarys(Transaction* transaction, DbIndex db_ind);
 
   SaveInfoData GetLastSaveInfo() const;