fix: Reconstruct slave sync thread model

conf/pika.conf

@@ -34,10 +34,17 @@ slow-cmd-thread-pool-size : 1
 # Slow cmd list e.g. hgetall, mset
 slow-cmd-list :
 
-# The number of sync-thread for data replication from master, those are the threads work on slave nodes
-# and are used to execute commands sent from master node when replicating.
+# The number of threads to write DB in slaveNode when replicating.
+# It's preferable to set slave's sync-thread-num value close to master's thread-pool-size.
 sync-thread-num : 6
 
+# The num of threads to write binlog in slaveNode when replicating,
+# each DB cloud only bind to one sync-binlog-thread to write binlog in maximum
+#[NOTICE] It's highly recommended to set sync_binlog_thread_num_ equal to database_(then each DB cloud have a exclusive thread to write binlog),
+# eg. if you use 8 DBs(databases_ is 8), sync-binlog-thread-num is preferable to be 8
+# Valid range of sync-binlog-thread-num is [1, databases], the final value of it is Min(sync-binlog-thread-num, databases)
+sync-binlog-thread-num : 1
+
 # Directory to store log files of Pika, which contains multiple types of logs,
 # Including: INFO, WARNING, ERROR log, as well as binglog(write2fine) file which
 # is used for replication.
@@ -101,6 +108,8 @@ instance-mode : classic
 # The default database id is DB 0. You can select a different one on
 # a per-connection by using SELECT. The db id range is [0, 'databases' value -1].
 # The value range of this parameter is [1, 8].
+# [NOTICE] It's RECOMMENDED to set sync-binlog-thread-num equal to DB num(databases),
+# if you've changed the value of databases, remember to check if the value of sync-binlog-thread-num is proper.
 databases : 1
 
 # The number of followers of a master. Only [0, 1, 2, 3, 4] is valid at present.

include/pika_conf.h

@@ -65,6 +65,10 @@ class PikaConf : public pstd::BaseConf {
     std::shared_lock l(rwlock_);
     return sync_thread_num_;
   }
+  int sync_binlog_thread_num() {
+    std::shared_lock l(rwlock_);
+    return sync_binlog_thread_num_;
+  }
   std::string log_path() {
     std::shared_lock l(rwlock_);
     return log_path_;
@@ -793,6 +797,7 @@ class PikaConf : public pstd::BaseConf {
   int slow_cmd_thread_pool_size_ = 0;
   std::unordered_set<std::string> slow_cmd_set_;
   int sync_thread_num_ = 0;
+  int sync_binlog_thread_num_ = 0;
   int expire_dump_days_ = 3;
   int db_sync_speed_ = 0;
   std::string slaveof_;

include/pika_repl_client.h

@@ -65,6 +65,7 @@ class PikaReplClient {
   pstd::Status Close(const std::string& ip, int port);
 
   void Schedule(net::TaskFunc func, void* arg);
+  void ScheduleByDBName(net::TaskFunc func, void* arg, const std::string& db_name);
   void ScheduleWriteBinlogTask(const std::string& db_name, const std::shared_ptr<InnerMessage::InnerResponse>& res,
                                const std::shared_ptr<net::PbConn>& conn, void* res_private_data);
   void ScheduleWriteDBTask(const std::shared_ptr<Cmd>& cmd_ptr, const LogOffset& offset, const std::string& db_name);
@@ -80,13 +81,15 @@ class PikaReplClient {
   pstd::Status SendRemoveSlaveNode(const std::string& ip, uint32_t port, const std::string& db_name, const std::string& local_ip);
 
  private:
-  size_t GetHashIndex(const std::string& key, bool upper_half);
-  void UpdateNextAvail() { next_avail_ = (next_avail_ + 1) % static_cast<int32_t>(bg_workers_.size()); }
+  size_t GetBinlogWorkerIndexByDBName(const std::string &db_name);
+  size_t GetHashIndexByKey(const std::string& key);
+  void UpdateNextAvail() { next_avail_ = (next_avail_ + 1) % static_cast<int32_t>(write_binlog_workers_.size()); }
 
   std::unique_ptr<PikaReplClientThread> client_thread_;
   int next_avail_ = 0;
   std::hash<std::string> str_hash;
-  std::vector<std::unique_ptr<PikaReplBgWorker>> bg_workers_;
+  std::vector<std::unique_ptr<PikaReplBgWorker>> write_binlog_workers_;
+  std::vector<std::unique_ptr<PikaReplBgWorker>> write_db_workers_;
 };
 
 #endif

include/pika_rm.h

@@ -182,6 +182,7 @@ class PikaReplicaManager {
                                const std::shared_ptr<InnerMessage::InnerResponse>& res,
                                const std::shared_ptr<net::PbConn>& conn, void* res_private_data);
   void ScheduleWriteDBTask(const std::shared_ptr<Cmd>& cmd_ptr, const LogOffset& offset, const std::string& db_name);
+  void ScheduleReplClientBGTaskByDBName(net::TaskFunc , void* arg, const std::string &db_name);
   void ReplServerRemoveClientConn(int fd);
   void ReplServerUpdateClientConnMap(const std::string& ip_port, int fd);
 

src/pika_admin.cc

@@ -942,6 +942,7 @@ void InfoCmd::InfoServer(std::string& info) {
   tmp_stream << "tcp_port:" << g_pika_conf->port() << "\r\n";
   tmp_stream << "thread_num:" << g_pika_conf->thread_num() << "\r\n";
   tmp_stream << "sync_thread_num:" << g_pika_conf->sync_thread_num() << "\r\n";
+  tmp_stream << "sync_binlog_thread_num:" << g_pika_conf->sync_binlog_thread_num() << "\r\n";
   tmp_stream << "uptime_in_seconds:" << (current_time_s - g_pika_server->start_time_s()) << "\r\n";
   tmp_stream << "uptime_in_days:" << (current_time_s / (24 * 3600) - g_pika_server->start_time_s() / (24 * 3600) + 1)
              << "\r\n";
@@ -1501,6 +1502,12 @@ void ConfigCmd::ConfigGet(std::string& ret) {
     EncodeNumber(&config_body, g_pika_conf->sync_thread_num());
   }
 
+  if (pstd::stringmatch(pattern.data(), "sync-binlog-thread-num", 1) != 0) {
+     elements += 2;
+     EncodeString(&config_body, "sync-binlog-thread-num");
+     EncodeNumber(&config_body, g_pika_conf->sync_binlog_thread_num());
+    }
+
   if (pstd::stringmatch(pattern.data(), "log-path", 1) != 0) {
     elements += 2;
     EncodeString(&config_body, "log-path");

src/pika_conf.cc

@@ -185,6 +185,15 @@ int PikaConf::Load() {
   }
   default_db_ = db_structs_[0].db_name;
 
+  // sync_binlog_thread_num_ must be set after the setting of databases_
+  GetConfInt("sync-binlog-thread-num", &sync_binlog_thread_num_);
+  if (sync_binlog_thread_num_ <= 0){
+      sync_binlog_thread_num_ = databases_;
+  }else {
+      // final value is MIN(sync_binlog_thread_num, databases_)
+      sync_binlog_thread_num_ = sync_binlog_thread_num_ > databases_ ?  databases_ : sync_binlog_thread_num_;
+  }
+
   int tmp_replication_num = 0;
   GetConfInt("replication-num", &tmp_replication_num);
   if (tmp_replication_num > 4 || tmp_replication_num < 0) {

src/pika_repl_client.cc

@@ -27,8 +27,11 @@ extern std::unique_ptr<PikaReplicaManager> g_pika_rm;
 PikaReplClient::PikaReplClient(int cron_interval, int keepalive_timeout)  {
   client_thread_ = std::make_unique<PikaReplClientThread>(cron_interval, keepalive_timeout);
   client_thread_->set_thread_name("PikaReplClient");
-  for (int i = 0; i < 2 * g_pika_conf->sync_thread_num(); ++i) {
-    bg_workers_.push_back(std::make_unique<PikaReplBgWorker>(PIKA_SYNC_BUFFER_SIZE));
+  for(int i = 0; i < g_pika_conf->sync_binlog_thread_num(); i++){
+      write_binlog_workers_.push_back(std::make_unique<PikaReplBgWorker>(PIKA_SYNC_BUFFER_SIZE));
+  }
+  for (int i = 0; i < g_pika_conf->sync_thread_num(); ++i) {
+    write_db_workers_.push_back(std::make_unique<PikaReplBgWorker>(PIKA_SYNC_BUFFER_SIZE));
   }
 }
 
@@ -43,49 +46,74 @@ int PikaReplClient::Start() {
     LOG(FATAL) << "Start ReplClient ClientThread Error: " << res
                << (res == net::kCreateThreadError ? ": create thread error " : ": other error");
   }
-  for (auto & bg_worker : bg_workers_) {
-    res = bg_worker->StartThread();
+  for (auto & binlog_worker : write_binlog_workers_) {
+    res = binlog_worker->StartThread();
     if (res != net::kSuccess) {
-      LOG(FATAL) << "Start Pika Repl Worker Thread Error: " << res
+      LOG(FATAL) << "Start Pika Repl Write Binlog Worker Thread Error: " << res
                  << (res == net::kCreateThreadError ? ": create thread error " : ": other error");
     }
   }
+  for (auto & db_worker : write_db_workers_) {
+        res = db_worker->StartThread();
+        if (res != net::kSuccess) {
+            LOG(FATAL) << "Start Pika Repl Write DB Worker Thread Error: " << res
+                       << (res == net::kCreateThreadError ? ": create thread error " : ": other error");
+        }
+    }
   return res;
 }
 
 int PikaReplClient::Stop() {
   client_thread_->StopThread();
-  for (auto & bg_worker : bg_workers_) {
-    bg_worker->StopThread();
+  for (auto & binlog_worker : write_binlog_workers_) {
+    binlog_worker->StopThread();
+  }
+  for (auto &db_worker: write_db_workers_) {
+    db_worker->StopThread();
   }
   return 0;
 }
 
 void PikaReplClient::Schedule(net::TaskFunc func, void* arg) {
-  bg_workers_[next_avail_]->Schedule(func, arg);
+  write_binlog_workers_[next_avail_]->Schedule(func, arg);
   UpdateNextAvail();
 }
 
+void PikaReplClient::ScheduleByDBName(net::TaskFunc func, void* arg, const std::string& db_name) {
+  size_t index = GetBinlogWorkerIndexByDBName(db_name);
+  write_binlog_workers_[index]->Schedule(func, arg);
+};
+
 void PikaReplClient::ScheduleWriteBinlogTask(const std::string& db_name,
                                              const std::shared_ptr<InnerMessage::InnerResponse>& res,
                                              const std::shared_ptr<net::PbConn>& conn, void* res_private_data) {
-  size_t index = GetHashIndex(db_name, true);
-  auto task_arg = new ReplClientWriteBinlogTaskArg(res, conn, res_private_data, bg_workers_[index].get());
-  bg_workers_[index]->Schedule(&PikaReplBgWorker::HandleBGWorkerWriteBinlog, static_cast<void*>(task_arg));
+  size_t index = GetBinlogWorkerIndexByDBName(db_name);
+  auto task_arg = new ReplClientWriteBinlogTaskArg(res, conn, res_private_data, write_binlog_workers_[index].get());
+  write_binlog_workers_[index]->Schedule(&PikaReplBgWorker::HandleBGWorkerWriteBinlog, static_cast<void*>(task_arg));
 }
 
 void PikaReplClient::ScheduleWriteDBTask(const std::shared_ptr<Cmd>& cmd_ptr, const LogOffset& offset,
                                          const std::string& db_name) {
   const PikaCmdArgsType& argv = cmd_ptr->argv();
   std::string dispatch_key = argv.size() >= 2 ? argv[1] : argv[0];
-  size_t index = GetHashIndex(dispatch_key, false);
+  size_t index = GetHashIndexByKey(dispatch_key);
   auto task_arg = new ReplClientWriteDBTaskArg(cmd_ptr, offset, db_name);
-  bg_workers_[index]->Schedule(&PikaReplBgWorker::HandleBGWorkerWriteDB, static_cast<void*>(task_arg));
+  write_db_workers_[index]->Schedule(&PikaReplBgWorker::HandleBGWorkerWriteDB, static_cast<void*>(task_arg));
+}
+
+size_t PikaReplClient::GetBinlogWorkerIndexByDBName(const std::string &db_name) {
+    char db_num = db_name.back();
+    if (db_num < '0' || db_num > '8') {
+        LOG(ERROR)
+                << "Corruption in consuming binlog: the last char of the db_name(extracted from binlog) is not a valid db num, the extracted db_num is "
+                << db_num << " while write_binlog_workers.size() is " << write_binlog_workers_.size();
+    }
+    return (db_num - '0') % write_binlog_workers_.size();
 }
 
-size_t PikaReplClient::GetHashIndex(const std::string& key, bool upper_half) {
-  size_t hash_base = bg_workers_.size() / 2;
-  return (str_hash(key) % hash_base) + (upper_half ? 0 : hash_base);
+size_t PikaReplClient::GetHashIndexByKey(const std::string& key) {
+  size_t hash_base = write_db_workers_.size();
+  return (str_hash(key) % hash_base);
 }
 
 Status PikaReplClient::Write(const std::string& ip, const int port, const std::string& msg) {

src/pika_repl_client_conn.cc

@@ -63,9 +63,12 @@ int PikaReplClientConn::DealMessage() {
       break;
     }
     case InnerMessage::kTrySync: {
+      const std::string& db_name = response->try_sync().slot().db_name();
+      //TrySync resp must contain db_name
+      assert(!db_name.empty());
       auto task_arg =
           new ReplClientTaskArg(response, std::dynamic_pointer_cast<PikaReplClientConn>(shared_from_this()));
-      g_pika_rm->ScheduleReplClientBGTask(&PikaReplClientConn::HandleTrySyncResponse, static_cast<void*>(task_arg));
+      g_pika_rm->ScheduleReplClientBGTaskByDBName(&PikaReplClientConn::HandleTrySyncResponse, static_cast<void*>(task_arg), db_name);
       break;
     }
     case InnerMessage::kBinlogSync: {
@@ -193,7 +196,6 @@ void PikaReplClientConn::HandleTrySyncResponse(void* arg) {
     LOG(WARNING) << "TrySync Failed: " << reply;
     return;
   }
-
   const InnerMessage::InnerResponse_TrySync& try_sync_response = response->try_sync();
   const InnerMessage::Slot& db_response = try_sync_response.slot();
   std::string db_name = db_response.db_name();

src/pika_rm.cc

@@ -659,6 +659,10 @@ void PikaReplicaManager::ScheduleReplClientBGTask(net::TaskFunc func, void* arg)
   pika_repl_client_->Schedule(func, arg);
 }
 
+void PikaReplicaManager::ScheduleReplClientBGTaskByDBName(net::TaskFunc func, void* arg, const std::string &db_name) {
+  pika_repl_client_->ScheduleByDBName(func, arg, db_name);
+}
+
 void PikaReplicaManager::ScheduleWriteBinlogTask(const std::string& db,
                                                  const std::shared_ptr<InnerMessage::InnerResponse>& res,
                                                  const std::shared_ptr<net::PbConn>& conn, void* res_private_data) {