Implement DEBUG RELOAD option.

Fix c++ and openssl deprecation warnings.

src/core/dash.h

@@ -375,10 +375,11 @@ DashTable<_Key, _Value, Policy>::~DashTable() {
   Clear();
   auto* resource = segment_.get_allocator().resource();
   std::pmr::polymorphic_allocator<SegmentType> pa(resource);
+  using alloc_traits = std::allocator_traits<decltype(pa)>;
 
   IterateUnique([&](SegmentType* seg) {
-    pa.destroy(seg);
+    alloc_traits::destroy(pa, seg);
-    pa.deallocate(seg, 1);
+    alloc_traits::deallocate(pa, seg, 1);
     return false;
   });
 }
@@ -438,6 +439,8 @@ void DashTable<_Key, _Value, Policy>::Clear() {
   **********/
   if (global_depth_ > initial_depth_) {
     std::pmr::polymorphic_allocator<SegmentType> pa(segment_.get_allocator());
+    using alloc_traits = std::allocator_traits<decltype(pa)>;
+
     size_t dest = 0, src = 0;
     size_t new_size = (1 << initial_depth_);
 
@@ -448,8 +451,8 @@ void DashTable<_Key, _Value, Policy>::Clear() {
         seg->set_local_depth(initial_depth_);
         segment_[dest++] = seg;
       } else {
-        pa.destroy(seg);
+        alloc_traits::destroy(pa, seg);
-        pa.deallocate(seg, 1);
+        alloc_traits::deallocate(pa, seg, 1);
       }
 
       src = next_src;

src/core/interpreter.cc

@@ -5,7 +5,7 @@
 #include "core/interpreter.h"
 
 #include <absl/strings/str_cat.h>
-#include <openssl/sha.h>
+#include <openssl/evp.h>
 
 #include <cstring>
 #include <optional>
@@ -25,6 +25,16 @@ using namespace std;
 
 namespace {
 
+// EVP_Q_digest is not present in the older versions of OpenSSL.
+int EVPDigest(const void* data, size_t datalen, unsigned char* md, size_t* mdlen) {
+  unsigned int temp = 0;
+  int ret = EVP_Digest(data, datalen, md, &temp, EVP_sha1(), NULL);
+
+  if (mdlen != NULL)
+    *mdlen = temp;
+  return ret;
+}
+
 class RedisTranslator : public ObjectExplorer {
  public:
   RedisTranslator(lua_State* lua) : lua_(lua) {
@@ -155,7 +165,6 @@ void SetGlobalArrayInternal(lua_State* lua, const char* name, MutSliceSpan args)
   lua_setglobal(lua, name);
 }
 
-
 /* This function is used in order to push an error on the Lua stack in the
  * format used by redis.pcall to return errors, which is a lua table
  * with a single "err" field set to the error string. Note that this
@@ -247,6 +256,7 @@ debug = nil
   lua_setglobal(lua, "dofile");
 }
 
+// dest must have at least 41 chars.
 void ToHex(const uint8_t* src, char* dest) {
   const char cset[] = "0123456789abcdef";
   for (size_t j = 0; j < 20; j++) {
@@ -266,16 +276,13 @@ int RedisSha1Command(lua_State* lua) {
   size_t len;
   const char* s = lua_tolstring(lua, 1, &len);
 
-  SHA_CTX ctx;
+  uint8_t digest[EVP_MAX_MD_SIZE];
-  uint8_t buf[20];
+  EVPDigest(s, len, digest, NULL);
-  char digest[41];
 
-  SHA1_Init(&ctx);
+  char hex[41];
-  SHA1_Update(&ctx, s, len);
+  ToHex(digest, hex);
-  SHA1_Final(buf, &ctx);
-  ToHex(buf, digest);
 
-  lua_pushstring(lua, digest);
+  lua_pushstring(lua, hex);
   return 1;
 }
 
@@ -353,13 +360,10 @@ Interpreter::~Interpreter() {
 }
 
 void Interpreter::FuncSha1(string_view body, char* fp) {
-  SHA_CTX ctx;
+  uint8_t digest[EVP_MAX_MD_SIZE];
-  uint8_t buf[20];
+  EVPDigest(body.data(), body.size(), digest, NULL);
 
-  SHA1_Init(&ctx);
+  ToHex(digest, fp);
-  SHA1_Update(&ctx, body.data(), body.size());
-  SHA1_Final(buf, &ctx);
-  ToHex(buf, fp);
 }
 
 auto Interpreter::AddFunction(string_view body, string* result) -> AddResult {
@@ -500,7 +504,7 @@ bool Interpreter::IsTableSafe() const {
         i = 0;
         len = lua_rawlen(lua_, -1);
       } else {
-        lua_pop(lua_, 1); // pop table element
+        lua_pop(lua_, 1);  // pop table element
         ++i;
       }
     }

src/server/debugcmd.cc

@@ -11,8 +11,10 @@
 #include "base/logging.h"
 #include "server/engine_shard_set.h"
 #include "server/error.h"
+#include "server/main_service.h"
 #include "server/rdb_load.h"
 #include "server/string_family.h"
+#include "server/transaction.h"
 #include "util/uring/uring_fiber_algo.h"
 #include "util/uring/uring_file.h"
 
@@ -24,6 +26,7 @@ namespace dfly {
 using namespace std;
 using namespace util;
 namespace this_fiber = ::boost::this_fiber;
+using boost::intrusive_ptr;
 using boost::fibers::fiber;
 using namespace facade;
 namespace fs = std::filesystem;
@@ -52,7 +55,7 @@ void DoPopulateBatch(std::string_view prefix, size_t val_size, const SetCmd::Set
   }
 }
 
-DebugCmd::DebugCmd(EngineShardSet* ess, ConnectionContext* cntx) : ess_(ess), cntx_(cntx) {
+DebugCmd::DebugCmd(ServerFamily* owner, ConnectionContext* cntx) : sf_(*owner), cntx_(cntx) {
 }
 
 void DebugCmd::Run(CmdArgList args) {
@@ -99,6 +102,7 @@ void DebugCmd::Run(CmdArgList args) {
 
 void DebugCmd::Reload(CmdArgList args) {
   bool save = true;
+
   for (size_t i = 2; i < args.size(); ++i) {
     ToUpper(&args[i]);
     std::string_view opt = ArgS(args, i);
@@ -110,18 +114,38 @@ void DebugCmd::Reload(CmdArgList args) {
       return (*cntx_)->SendError("DEBUG RELOAD only supports the NOSAVE options.");
     }
   }
+
+  error_code ec;
+
   if (save) {
-    return (*cntx_)->SendError("NOSAVE required (TBD).");
+    string err_details;
+    const CommandId* cid = sf_.service().FindCmd("SAVE");
+    CHECK_NOTNULL(cid);
+    intrusive_ptr<Transaction> trans(new Transaction{cid, &sf_.service().shard_set()});
+    trans->InitByArgs(0, {});
+    ec = sf_.DoSave(trans.get(), &err_details);
+    if (ec) {
+      return (*cntx_)->SendError(absl::StrCat(err_details, ec.message()));
+    }
   }
 
-  if (FLAGS_dbfilename.empty()) {
+  const CommandId* cid = sf_.service().FindCmd("FLUSHALL");
-    return (*cntx_)->SendError("dbfilename is not set");
+  intrusive_ptr<Transaction> flush_trans(new Transaction{cid, &sf_.service().shard_set()});
+  flush_trans->InitByArgs(0, {});
+  ec = sf_.DoFlush(flush_trans.get(), DbSlice::kDbAll);
+  if (ec) {
+    LOG(ERROR) << "Error flushing db " << ec.message();
   }
 
-  fs::path dir_path(FLAGS_dir);
+  string last_save_file = sf_.LastSaveFile();
-  string filename = FLAGS_dbfilename;
+  fs::path path(last_save_file);
-  fs::path path = dir_path;
+
-  path.append(filename);
+  if (last_save_file.empty()) {
+    fs::path dir_path(FLAGS_dir);
+    string filename = FLAGS_dbfilename;
+    dir_path.append(filename);
+    path = dir_path;
+  }
   auto res = uring::OpenRead(path.generic_string());
 
   if (!res) {
@@ -132,7 +156,7 @@ void DebugCmd::Reload(CmdArgList args) {
   io::FileSource fs(*res);
 
   RdbLoader loader;
-  error_code ec = loader.Load(&fs);
+  ec = loader.Load(&fs);
 
   if (ec) {
     (*cntx_)->SendError(ec.message());
@@ -162,7 +186,8 @@ void DebugCmd::Populate(CmdArgList args) {
       return (*cntx_)->SendError(kUintErr);
   }
 
-  size_t runners_count = ess_->pool()->size();
+  ProactorPool& pp = sf_.service().proactor_pool();
+  size_t runners_count = pp.size();
   vector<pair<uint64_t, uint64_t>> ranges(runners_count - 1);
   uint64_t batch_size = total_count / runners_count;
   size_t from = 0;
@@ -178,8 +203,8 @@ void DebugCmd::Populate(CmdArgList args) {
     auto range = ranges[i];
 
     // whatever we do, we should not capture i by reference.
-    fb_arr[i] = ess_->pool()->at(i)->LaunchFiber(
+    fb_arr[i] = pp.at(i)->LaunchFiber(
-        [=] { this->PopulateRangeFiber(range.first, range.second, prefix, val_size); });
+        [=, this] { this->PopulateRangeFiber(range.first, range.second, prefix, val_size); });
   }
   for (auto& fb : fb_arr)
     fb.join();
@@ -195,18 +220,19 @@ void DebugCmd::PopulateRangeFiber(uint64_t from, uint64_t len, std::string_view
   string key = absl::StrCat(prefix, ":");
   size_t prefsize = key.size();
   DbIndex db_indx = cntx_->db_index();
-  std::vector<PopulateBatch> ps(ess_->size(), PopulateBatch{db_indx});
+  EngineShardSet& ess = sf_.service().shard_set();
+  std::vector<PopulateBatch> ps(ess.size(), PopulateBatch{db_indx});
   SetCmd::SetParams params{db_indx};
 
   for (uint64_t i = from; i < from + len; ++i) {
     absl::StrAppend(&key, i);
-    ShardId sid = Shard(key, ess_->size());
+    ShardId sid = Shard(key, ess.size());
     key.resize(prefsize);
 
     auto& pops = ps[sid];
     pops.index[pops.sz++] = i;
     if (pops.sz == 32) {
-      ess_->Add(sid, [=, p = pops] {
+      ess.Add(sid, [=, p = pops] {
         DoPopulateBatch(prefix, value_len, params, p);
         if (i % 50 == 0) {
           this_fiber::yield();
@@ -218,13 +244,14 @@ void DebugCmd::PopulateRangeFiber(uint64_t from, uint64_t len, std::string_view
     }
   }
 
-  ess_->RunBriefInParallel([&](EngineShard* shard) {
+  ess.RunBriefInParallel([&](EngineShard* shard) {
     DoPopulateBatch(prefix, value_len, params, ps[shard->shard_id()]);
   });
 }
 
 void DebugCmd::Inspect(string_view key) {
-  ShardId sid = Shard(key, ess_->size());
+  EngineShardSet& ess = sf_.service().shard_set();
+  ShardId sid = Shard(key, ess.size());
   using ObjInfo = pair<unsigned, unsigned>;  // type, encoding.
 
   auto cb = [&]() -> facade::OpResult<ObjInfo> {
@@ -236,7 +263,7 @@ void DebugCmd::Inspect(string_view key) {
     return OpStatus::KEY_NOTFOUND;
   };
 
-  OpResult<ObjInfo> res = ess_->Await(sid, cb);
+  OpResult<ObjInfo> res = ess.Await(sid, cb);
   if (res) {
     string resp = absl::StrCat("Value encoding:", strEncoding(res->second));
     (*cntx_)->SendSimpleString(resp);

src/server/debugcmd.h

@@ -9,10 +9,11 @@
 namespace dfly {
 
 class EngineShardSet;
+class ServerFamily;
 
 class DebugCmd {
  public:
-  DebugCmd(EngineShardSet* ess, ConnectionContext* cntx);
+  DebugCmd(ServerFamily* owner, ConnectionContext* cntx);
 
   void Run(CmdArgList args);
 
@@ -22,7 +23,7 @@ class DebugCmd {
   void Reload(CmdArgList args);
   void Inspect(std::string_view key);
 
-  EngineShardSet* ess_;
+  ServerFamily& sf_;
   ConnectionContext* cntx_;
 };
 

src/server/main_service.h

@@ -67,6 +67,10 @@ class Service : public facade::ServiceInterface {
 
   absl::flat_hash_map<std::string, unsigned> UknownCmdMap() const;
 
+  const CommandId* FindCmd(std::string_view cmd) const {
+    return registry_.Find(cmd);
+  }
+
  private:
   static void Quit(CmdArgList args, ConnectionContext* cntx);
   static void Multi(CmdArgList args, ConnectionContext* cntx);

src/server/rdb_test.cc

@@ -106,6 +106,11 @@ TEST_F(RdbTest, Save) {
 }
 
 TEST_F(RdbTest, Load) {
+  Run({"set", "string_key", "val"});
+  Run({"set", "large_key", string(511, 'L')});
+  // Run({"zadd", "zs1", "1.1", "a", "-1.1", "b"});
+
+  Run({"debug", "reload"});
 }
 
 }  // namespace dfly

src/server/server_family.cc

@@ -47,9 +47,9 @@ using namespace std;
 using namespace util;
 namespace fibers = ::boost::fibers;
 namespace fs = std::filesystem;
+using absl::StrCat;
 using facade::MCReplyBuilder;
 using strings::HumanReadableNumBytes;
-using absl::StrCat;
 
 namespace {
 
@@ -77,7 +77,7 @@ error_code CreateDirs(fs::path dir_path) {
 
 ServerFamily::ServerFamily(Service* service) : service_(*service), ess_(service->shard_set()) {
   start_time_ = time(NULL);
-  last_save_.store(start_time_, memory_order_release);
+  last_save_ = start_time_;
   script_mgr_.reset(new ScriptMgr(&service->shard_set()));
 }
 
@@ -124,7 +124,7 @@ void ServerFamily::Shutdown() {
     pb_task_->CancelPeriodic(task_10ms_);
     task_10ms_ = 0;
 
-    unique_lock lk(replica_of_mu_);
+    unique_lock lk(replicaof_mu_);
     if (replica_) {
       replica_->Stop();
     }
@@ -177,6 +177,106 @@ void ServerFamily::StatsMC(std::string_view section, facade::ConnectionContext*
 #undef ADD_LINE
 }
 
+error_code ServerFamily::DoSave(Transaction* trans, string* err_details) {
+  static unsigned fl_index = 1;
+
+  auto [current, switched] = global_state_.Next(GlobalState::SAVING);
+  if (!switched) {
+    *err_details = StrCat(GlobalState::Name(current), " - can not save database");
+    return make_error_code(errc::operation_in_progress);
+  }
+
+  absl::Cleanup rev_state = [this] { global_state_.Clear(); };
+
+  fs::path dir_path(FLAGS_dir);
+  error_code ec;
+
+  if (!dir_path.empty()) {
+    ec = CreateDirs(dir_path);
+    if (ec) {
+      *err_details = "create-dir ";
+      return ec;
+    }
+  }
+
+  string filename = FLAGS_dbfilename.empty() ? "dump_save.rdb" : FLAGS_dbfilename;
+  fs::path path = dir_path;
+  path.append(filename);
+  path.concat(StrCat("_", fl_index++));
+  VLOG(1) << "Saving to " << path;
+
+  auto res = uring::OpenWrite(path.generic_string());
+  if (!res) {
+    return res.error();
+  }
+
+  auto& pool = service_.proactor_pool();
+  pool.Await([](auto*) { ServerState::tlocal()->set_gstate(GlobalState::SAVING); });
+
+  unique_ptr<::io::WriteFile> wf(*res);
+  auto start = absl::Now();
+
+  RdbSaver saver{&ess_, wf.get()};
+
+  ec = saver.SaveHeader();
+  if (!ec) {
+    auto cb = [&saver](Transaction* t, EngineShard* shard) {
+      saver.StartSnapshotInShard(shard);
+      return OpStatus::OK;
+    };
+    trans->ScheduleSingleHop(std::move(cb));
+
+    // perform snapshot serialization, block the current fiber until it completes.
+    RdbTypeFreqMap freq_map;
+    ec = saver.SaveBody(&freq_map);
+
+    // TODO: needs protection from reads.
+    last_save_freq_map_.clear();
+    for (const auto& k_v : freq_map) {
+      last_save_freq_map_.push_back(k_v);
+    }
+  }
+
+  pool.Await([](auto*) { ServerState::tlocal()->set_gstate(GlobalState::IDLE); });
+  CHECK_EQ(GlobalState::SAVING, global_state_.Clear());
+
+  absl::Duration dur = absl::Now() - start;
+  double seconds = double(absl::ToInt64Milliseconds(dur)) / 1000;
+  LOG(INFO) << "Saving " << path << " finished after "
+            << strings::HumanReadableElapsedTime(seconds);
+
+  auto close_ec = wf->Close();
+
+  if (!ec)
+    ec = close_ec;
+
+  if (!ec) {
+    lock_guard lk(save_mu_);
+    last_save_ = time(NULL);
+    last_save_file_ = path.generic_string();
+  }
+
+  return ec;
+}
+
+error_code ServerFamily::DoFlush(Transaction* transaction, DbIndex db_ind) {
+  transaction->Schedule();  // TODO: to convert to ScheduleSingleHop ?
+
+  transaction->Execute(
+      [db_ind](Transaction* t, EngineShard* shard) {
+        shard->db_slice().FlushDb(db_ind);
+        return OpStatus::OK;
+      },
+      true);
+
+  return error_code{};
+}
+
+string ServerFamily::LastSaveFile() const {
+  lock_guard lk(save_mu_);
+  return last_save_file_;
+}
+
 void ServerFamily::DbSize(CmdArgList args, ConnectionContext* cntx) {
   atomic_ulong num_keys{0};
 
@@ -192,16 +292,7 @@ void ServerFamily::DbSize(CmdArgList args, ConnectionContext* cntx) {
 
 void ServerFamily::FlushDb(CmdArgList args, ConnectionContext* cntx) {
   DCHECK(cntx->transaction);
-  Transaction* transaction = cntx->transaction;
+  DoFlush(cntx->transaction, cntx->transaction->db_index());
-  transaction->Schedule();  // TODO: to convert to ScheduleSingleHop ?
-
-  transaction->Execute(
-      [](Transaction* t, EngineShard* shard) {
-        shard->db_slice().FlushDb(t->db_index());
-        return OpStatus::OK;
-      },
-      true);
-
   cntx->reply_builder()->SendOk();
 }
 
@@ -212,16 +303,7 @@ void ServerFamily::FlushAll(CmdArgList args, ConnectionContext* cntx) {
   }
 
   DCHECK(cntx->transaction);
-  Transaction* transaction = cntx->transaction;
+  DoFlush(cntx->transaction, DbSlice::kDbAll);
-  transaction->Schedule();
-
-  transaction->Execute(
-      [](Transaction* t, EngineShard* shard) {
-        shard->db_slice().FlushDb(DbSlice::kDbAll);
-        return OpStatus::OK;
-      },
-      true);
-
   (*cntx)->SendOk();
 }
 
@@ -262,7 +344,7 @@ void ServerFamily::Config(CmdArgList args, ConnectionContext* cntx) {
     return (*cntx)->SendStringArr(res);
   } else {
     string err = StrCat("Unknown subcommand or wrong number of arguments for '", sub_cmd,
-                              "'. Try CONFIG HELP.");
+                        "'. Try CONFIG HELP.");
     return (*cntx)->SendError(err, kSyntaxErr);
   }
 }
@@ -270,7 +352,7 @@ void ServerFamily::Config(CmdArgList args, ConnectionContext* cntx) {
 void ServerFamily::Debug(CmdArgList args, ConnectionContext* cntx) {
   ToUpper(&args[1]);
 
-  DebugCmd dbg_cmd{&ess_, cntx};
+  DebugCmd dbg_cmd{this, cntx};
 
   return dbg_cmd.Run(args);
 }
@@ -283,86 +365,18 @@ void ServerFamily::Memory(CmdArgList args, ConnectionContext* cntx) {
   }
 
   string err = StrCat("Unknown subcommand or wrong number of arguments for '", sub_cmd,
-                            "'. Try MEMORY HELP.");
+                      "'. Try MEMORY HELP.");
   return (*cntx)->SendError(err, kSyntaxErr);
 }
 
 void ServerFamily::Save(CmdArgList args, ConnectionContext* cntx) {
-  static unsigned fl_index = 1;
+  string err_detail;
 
-  auto [current, switched] = global_state_.Next(GlobalState::SAVING);
+  error_code ec = DoSave(cntx->transaction, &err_detail);
-  if (!switched) {
-    string error = StrCat(GlobalState::Name(current), " - can not save database");
-    return (*cntx)->SendError(error);
-  }
-
-  absl::Cleanup rev_state = [this] { global_state_.Clear(); };
-
-  fs::path dir_path(FLAGS_dir);
-  error_code ec;
-
-  if (!dir_path.empty()) {
-    ec = CreateDirs(dir_path);
-    if (ec)
-      return (*cntx)->SendError(StrCat("create dir ", ec.message()));
-  }
-
-  string filename = FLAGS_dbfilename.empty() ? "dump_save.rdb" : FLAGS_dbfilename;
-  fs::path path = dir_path;
-  path.append(filename);
-  path.concat(StrCat("_", fl_index++));
-  VLOG(1) << "Saving to " << path;
-
-  auto res = uring::OpenWrite(path.generic_string());
-  if (!res) {
-    (*cntx)->SendError(res.error().message());
-    return;
-  }
-
-  auto& pool = service_.proactor_pool();
-  pool.Await([](auto*) { ServerState::tlocal()->set_gstate(GlobalState::SAVING); });
-
-  unique_ptr<::io::WriteFile> wf(*res);
-  auto start = absl::Now();
-
-  RdbSaver saver{&ess_, wf.get()};
-
-  ec = saver.SaveHeader();
-  if (!ec) {
-    auto cb = [&saver](Transaction* t, EngineShard* shard) {
-      saver.StartSnapshotInShard(shard);
-      return OpStatus::OK;
-    };
-    cntx->transaction->ScheduleSingleHop(std::move(cb));
-
-    // perform snapshot serialization, block the current fiber until it completes.
-    RdbTypeFreqMap freq_map;
-    ec = saver.SaveBody(&freq_map);
-
-    // TODO: needs protection from reads.
-    last_save_freq_map_.clear();
-    for (const auto& k_v : freq_map) {
-      last_save_freq_map_.push_back(k_v);
-    }
-  }
-
-  pool.Await([](auto*) { ServerState::tlocal()->set_gstate(GlobalState::IDLE); });
-  CHECK_EQ(GlobalState::SAVING, global_state_.Clear());
-
-  absl::Duration dur = absl::Now() - start;
-  double seconds = double(absl::ToInt64Milliseconds(dur)) / 1000;
-  LOG(INFO) << "Saving " << path << " finished after "
-            << strings::HumanReadableElapsedTime(seconds);
-
-  auto close_ec = wf->Close();
-
-  if (!ec)
-    ec = close_ec;
 
   if (ec) {
-    (*cntx)->SendError(ec.message());
+    (*cntx)->SendError(absl::StrCat(err_detail, ec.message()));
   } else {
-    last_save_.store(time(NULL), memory_order_release);
     (*cntx)->SendOk();
   }
 }
@@ -430,7 +444,7 @@ tcp_port:)";
     absl::StrAppend(&info, a1, a2, "\r\n");
   };
 
-  #define ADD_HEADER(x) absl::StrAppend(&info, x "\r\n")
+#define ADD_HEADER(x) absl::StrAppend(&info, x "\r\n")
 
   if (should_enter("SERVER")) {
     append(kInfo1, FLAGS_port);
@@ -566,7 +580,7 @@ void ServerFamily::ReplicaOf(CmdArgList args, ConnectionContext* cntx) {
 
   if (absl::EqualsIgnoreCase(host, "no") && absl::EqualsIgnoreCase(port_s, "one")) {
     // use this lock as critical section to prevent concurrent replicaof commands running.
-    unique_lock lk(replica_of_mu_);
+    unique_lock lk(replicaof_mu_);
 
     // Switch to primary mode.
     if (!ServerState::tlocal()->is_master) {
@@ -591,7 +605,7 @@ void ServerFamily::ReplicaOf(CmdArgList args, ConnectionContext* cntx) {
 
   auto new_replica = make_shared<Replica>(string(host), port, &service_);
 
-  unique_lock lk(replica_of_mu_);
+  unique_lock lk(replicaof_mu_);
   if (replica_) {
     replica_->Stop();  // NOTE: consider introducing update API flow.
   }
@@ -637,8 +651,10 @@ void ServerFamily::Sync(CmdArgList args, ConnectionContext* cntx) {
 void ServerFamily::Psync(CmdArgList args, ConnectionContext* cntx) {
   SyncGeneric("?", 0, cntx);  // full sync, ignore the request.
 }
+
 void ServerFamily::LastSave(CmdArgList args, ConnectionContext* cntx) {
-  (*cntx)->SendLong(last_save_.load(memory_order_relaxed));
+  lock_guard lk(save_mu_);
+  (*cntx)->SendLong(last_save_);
 }
 
 void ServerFamily::_Shutdown(CmdArgList args, ConnectionContext* cntx) {

src/server/server_family.h

@@ -35,13 +35,15 @@ struct Metrics {
 
 class ServerFamily {
  public:
-  ServerFamily(Service* engine);
+  ServerFamily(Service* service);
   ~ServerFamily();
 
   void Init(util::AcceptServer* acceptor);
   void Register(CommandRegistry* registry);
   void Shutdown();
 
+  Service& service() { return service_;}
+
   Metrics GetMetrics() const;
 
   GlobalState* global_state() {
@@ -54,6 +56,11 @@ class ServerFamily {
 
   void StatsMC(std::string_view section, facade::ConnectionContext* cntx);
 
+  std::error_code DoSave(Transaction* transaction, std::string* err_details);
+  std::error_code DoFlush(Transaction* transaction, DbIndex db_ind);
+
+  std::string LastSaveFile() const;
+
  private:
   uint32_t shard_count() const {
     return ess_.size();
@@ -86,12 +93,16 @@ class ServerFamily {
 
   util::AcceptServer* acceptor_ = nullptr;
   util::ProactorBase* pb_task_ = nullptr;
-  ::boost::fibers::mutex replica_of_mu_;
+
+  mutable ::boost::fibers::mutex replicaof_mu_, save_mu_;
   std::shared_ptr<Replica> replica_;  // protected by replica_of_mu_
 
   std::unique_ptr<ScriptMgr> script_mgr_;
 
-  std::atomic<int64_t> last_save_;  // in seconds.
+
+  int64_t last_save_;  // in seconds. protected by save_mu_.
+  std::string last_save_file_;   // protected by save_mu_.
+
   GlobalState global_state_;
   time_t start_time_ = 0;  // in seconds, epoch time.
 

src/server/transaction.cc

@@ -452,6 +452,7 @@ void Transaction::RunNoop(EngineShard* shard) {
 }
 
 void Transaction::ScheduleInternal() {
+  DCHECK(!shard_data_.empty());
   DCHECK_EQ(0u, txid_);
   DCHECK_EQ(0, coordinator_state_ & (COORD_SCHED | COORD_OOO));
 
@@ -886,6 +887,8 @@ bool Transaction::ScheduleUniqueShard(EngineShard* shard) {
 
 // This function should not block since it's run via RunBriefInParallel.
 pair<bool, bool> Transaction::ScheduleInShard(EngineShard* shard) {
+  DCHECK(!shard_data_.empty());
+
   // schedule_success, lock_granted.
   pair<bool, bool> result{false, false};