YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

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#ifndef YB_MASTER_SCOPED_LEADER_SHARED_LOCK_H

#define YB_MASTER_SCOPED_LEADER_SHARED_LOCK_H

#include <chrono>

#include <string>

#include <unordered_map>

#include <glog/logging.h>

#include "yb/master/master_fwd.h"

#include "yb/rpc/service_if.h"

#include "yb/util/status_fwd.h"

#include "yb/util/rw_mutex.h"

#include "yb/util/shared_lock.h"

namespace yb {

namespace master {

// This is how we should instantiate ScopedLeaderSharedLock. Captures context information so we can

// use it in logging and debugging.

#define SCOPED_LEADER_SHARED_LOCK(lock_name, catalog_manager) \

    ::yb::master::ScopedLeaderSharedLock lock_name( \

        (catalog_manager), __FILE__, __LINE__, __func__)

// Scoped "shared lock" to serialize master leader elections.

//

// While in scope, blocks the catalog manager in the event that it becomes

// the leader of its Raft configuration and needs to reload its persistent

// metadata. Once destroyed, the catalog manager is unblocked.

//

// Usage:

//

// void MasterServiceImpl::CreateTable(const CreateTableRequestPB* req,

//                                     CreateTableResponsePB* resp,

//                                     rpc::RpcContext* rpc) {

//   ScopedLeaderSharedLock l(server_->catalog_manager());

//   if (!l.CheckIsInitializedAndIsLeaderOrRespond(resp, rpc)) {

//     return;

//   }

//

//   Status s = server_->catalog_manager()->CreateTable(req, resp, rpc);

//   CheckRespErrorOrSetUnknown(s, resp);

//   rpc.RespondSuccess();

// }

//

class ScopedLeaderSharedLock {

 public:

  // Creates a new shared lock, acquiring the catalog manager's leader_lock_

  // for reading in the process. The lock is released when this object is

  // destroyed.

  //

  // 'catalog' must outlive this object.

  explicit ScopedLeaderSharedLock(

      CatalogManager* catalog,

      const char* file_name,

      int line_number,

      const char* function_name);

  explicit ScopedLeaderSharedLock(

      enterprise::CatalogManager* catalog,

      const char* file_name,

      int line_number,

      const char* function_name);

  ~ScopedLeaderSharedLock();

  void Unlock();

  // General status of the catalog manager. If not OK (e.g. the catalog

  // manager is still being initialized), all operations are illegal and

  // leader_status() should not be trusted.

  const Status& catalog_status() const { return catalog_status_; }

  // Leadership status of the catalog manager. If not OK, the catalog

  // manager is not the leader, but some operations may still be legal.

  const Status& leader_status() const {

    DCHECK(catalog_status_.ok());

    return leader_status_;

  }

  // First non-OK status of the catalog manager, adhering to the checking

  // order specified above.

  const Status& first_failed_status() const {

    if (!catalog_status_.ok()) {

      return catalog_status_;

    }

    return leader_status_;

  }

  // Check that the catalog manager is initialized. It may or may not be the

  // leader of its Raft configuration.

  //

  // If not initialized, writes the corresponding error to 'resp',

  // responds to 'rpc', and returns false.

  template<typename RespClass>

  bool CheckIsInitializedOrRespond(RespClass* resp, rpc::RpcContext* rpc);

  // Check that the catalog manager is initialized and that it is the leader

  // of its Raft configuration. Initialization status takes precedence over

  // leadership status.

  //

  // If not initialized or if not the leader, writes the corresponding error

  // to 'resp', responds to 'rpc', and returns false.

  template<typename RespClass>

  bool CheckIsInitializedAndIsLeaderOrRespond(RespClass* resp, rpc::RpcContext* rpc);

  // TServer API variant of above class to set appropriate error codes.

  template<typename RespClass>

  bool CheckIsInitializedAndIsLeaderOrRespondTServer(RespClass* resp, rpc::RpcContext* rpc);

  // If set_error is false, then the error field of resp should not be set.

  template<typename RespClass>

  bool CheckIsInitializedOrRespondTServer(RespClass* resp, rpc::RpcContext* rpc,

                                          bool set_error = true);

 private:

  template<typename RespClass, typename ErrorClass>

  bool CheckIsInitializedAndIsLeaderOrRespondInternal(RespClass* resp, rpc::RpcContext* rpc);

  template<typename RespClass, typename ErrorClass>

  bool CheckIsInitializedOrRespondInternal(RespClass* resp, rpc::RpcContext* rpc,

                                           bool set_error = true);

  CatalogManager* catalog_;

  shared_lock<RWMutex> leader_shared_lock_;

  Status catalog_status_;

  Status leader_status_;

  std::chrono::steady_clock::time_point start_;

  const char* file_name_;

  int line_number_;

  const char* function_name_;

};

}  // namespace master

}  // namespace yb

#endif  // YB_MASTER_SCOPED_LEADER_SHARED_LOCK_H