Adding upstream version 1:10.11.6.upstream/1%10.11.6upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1075 insertions, 0 deletions

diff --git a/wsrep-lib/include/wsrep/client_state.hpp b/wsrep-lib/include/wsrep/client_state.hpp
new file mode 100644
index 00000000..d8449d7a
--- /dev/null
+++ b/wsrep-lib/include/wsrep/client_state.hpp
@@ -0,0 +1,1075 @@
+/*
+ * Copyright (C) 2018-2019 Codership Oy <info@codership.com>
+ *
+ * This file is part of wsrep-lib.
+ *
+ * Wsrep-lib is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Wsrep-lib is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with wsrep-lib.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/** @file client_state.hpp
+ *
+ *
+ * Return value conventions:
+ *
+ * The calls which may alter either client_state or associated
+ * transaction state will generally return zero on success and
+ * non-zero on failure. More detailed error information is stored
+ * into client state and persisted there until explicitly cleared.
+ */
+
+#ifndef WSREP_CLIENT_STATE_HPP
+#define WSREP_CLIENT_STATE_HPP
+
+#include "provider.hpp"
+#include "transaction.hpp"
+#include "client_id.hpp"
+#include "mutex.hpp"
+#include "lock.hpp"
+#include "buffer.hpp"
+#include "thread.hpp"
+#include "xid.hpp"
+#include "chrono.hpp"
+
+namespace wsrep
+{
+    class client_service;
+    class server_state;
+    class provider;
+    class condition_variable;
+
+    enum client_error
+    {
+        e_success,
+        e_error_during_commit,
+        e_deadlock_error,
+        e_interrupted_error,
+        e_size_exceeded_error,
+        e_append_fragment_error,
+        e_not_supported_error,
+        e_timeout_error
+    };
+
+    static inline const char* to_c_string(enum client_error error)
+    {
+        switch (error)
+        {
+        case e_success:               return "success";
+        case e_error_during_commit:   return "commit_error";
+        case e_deadlock_error:        return "deadlock_error";
+        case e_interrupted_error:     return "interrupted_error";
+        case e_size_exceeded_error:   return "size_exceeded_error";
+        case e_append_fragment_error: return "append_fragment_error";
+        case e_not_supported_error:   return "not_supported_error";
+        case e_timeout_error:         return "timeout_error";
+        }
+        return "unknown";
+    }
+
+    static inline std::string to_string(enum client_error error)
+    {
+        return to_c_string(error);
+    }
+    /**
+     * Client State
+     */
+    class client_state
+    {
+    public:
+        /**
+         * Client mode enumeration.
+         */
+        enum mode
+        {
+            /** undefined mode */
+            m_undefined,
+            /** Locally operating client session. */
+            m_local,
+            /** High priority mode */
+            m_high_priority,
+            /** Client is in total order isolation mode */
+            m_toi,
+            /** Client is executing rolling schema upgrade */
+            m_rsu,
+            /** Client is executing NBO */
+            m_nbo
+        };
+
+        static const int n_modes_ = m_nbo + 1;
+        /**
+         * Client state enumeration.
+         *
+         */
+        enum state
+        {
+            /**
+             * Client session has not been initialized yet.
+             */
+            s_none,
+            /**
+             * Client is idle, the control is in the application which
+             * uses the DBMS system.
+             */
+            s_idle,
+            /**
+             * The control of the client processing is inside the DBMS
+             * system.
+             */
+            s_exec,
+            /**
+             * Client handler is sending result to client.
+             */
+            s_result,
+            /**
+             * The client session is terminating.
+             */
+            s_quitting
+        };
+
+        static const int state_max_ = s_quitting + 1;
+
+        /**
+         * Aqcuire ownership on the thread.
+         *
+         * This method should be called every time the thread
+         * operating the client state changes. This method is called
+         * implicitly from before_command() and
+         * wait_rollback_complete_and_acquire_ownership().
+         */
+        void acquire_ownership()
+        {
+            wsrep::unique_lock<wsrep::mutex> lock(mutex_);
+            do_acquire_ownership(lock);
+        }
+
+        /**
+         * @deprecated Use acquire_ownership() instead.
+         */
+        void store_globals()
+        {
+            acquire_ownership();
+        }
+
+        /**
+         * Destructor.
+         */
+        virtual ~client_state();
+
+        /** @name Client session handling */
+        /** @{ */
+        /**
+         * This method should be called when opening the client session.
+         *
+         * Initializes client id and changes the state to s_idle.
+         */
+        void open(wsrep::client_id);
+
+        /**
+         * This method should be called before closing the client session.
+         *
+         * The state is changed to s_quitting and any open transactions
+         * are rolled back.
+         */
+        void close();
+
+        /**
+         * This method should be called after closing the client session
+         * to clean up.
+         *
+         * The state is changed to s_none.
+         */
+        void cleanup();
+
+        /**
+         * Overload of cleanup() method which takes lock as argument.
+         * This method does not release the lock during execution, but
+         * the lock is needed for debug build sanity checks.
+         */
+        void cleanup(wsrep::unique_lock<wsrep::mutex>& lock);
+        /** @} */
+
+        /** @name Client command handling */
+        /** @{ */
+        /**
+         * This mehod should be called before the processing of command
+         * received from DBMS client starts.
+         *
+         * This method will wait until the possible synchronous
+         * rollback for associated transaction has finished unless
+         * wait_rollback_complete_and_acquire_ownership() has been
+         * called before.
+         *
+         * The method has a side effect of changing the client
+         * context state to executing.
+         *
+         * The value set by keep_command_error has an effect on
+         * how before_command() behaves when it is entered after
+         * background rollback has been processed:
+         *
+         * - If keep_command_error is set true, the current error
+         *   is set and success will be returned.
+         * - If keep_command_error is set false, the transaction is
+         *   cleaned up and the return value will be non-zero to
+         *   indicate error.
+         *
+         * @param keep_command_error Make client state to preserve error
+         *        state in command hooks.
+         *        This is needed if a current command is not supposed to
+         *        return an error status to the client and the protocol must
+         *        advance until the next client command to return error status.
+         *
+         * @return Zero in case of success, non-zero in case of the
+         *         associated transaction was BF aborted.
+         */
+        int before_command(bool keep_command_error);
+
+        int before_command()
+        {
+            return before_command(false);
+        }
+
+        /**
+         * This method should be called before returning
+         * a result to DBMS client.
+         *
+         * The method will check if the transaction associated to
+         * the connection has been aborted. Rollback is performed
+         * if needed. After the call, current_error() will return an error
+         * code associated to the client state. If the error code is
+         * not success, the transaction associated to the client state
+         * has been aborted and rolled back.
+         */
+        void after_command_before_result();
+
+        /**
+         * Method which should be called after returning the
+         * control back to DBMS client..
+         *
+         * The method will do the check if the transaction associated
+         * to the connection has been aborted. If so, rollback is
+         * performed and the transaction is left to aborted state.
+         * The next call to before_command() will return an error and
+         * the error state can be examined after after_command_before_resul()
+         * is called.
+         *
+         * This method has a side effect of changing state to
+         * idle.
+         */
+        void after_command_after_result();
+        /** @} */
+
+        /** @name Statement level operations */
+        /** @{ */
+        /**
+         * Before statement execution operations.
+         *
+         * Check if server is synced and if dirty reads are allowed.
+         *
+         * @return Zero in case of success, non-zero if the statement
+         *         is not allowed to be executed due to read or write
+         *         isolation requirements.
+         */
+        int before_statement();
+
+        /**
+         * After statement execution operations.
+         *
+         * * Check for must_replay state
+         * * Do rollback if requested
+         */
+        int after_statement();
+        /** @} */
+
+        /**
+         * Perform cleanup after applying a transaction.
+         *
+         * @param err Applying error (empty for no error)
+         */
+        void after_applying();
+
+        /** @name Replication interface */
+        /** @{ */
+        /**
+         * Start a new transaction with a transaction id.
+         *
+         * @todo This method should
+         *       - Register the transaction on server level for bookkeeping
+         *       - Isolation levels? Or part of the transaction?
+         */
+        int start_transaction(const wsrep::transaction_id& id);
+
+        /**
+         * Establish read view ID of the transaction.
+         *
+         * This method should be preferably called immediately before any
+         * first read or write operation in the transaction is performed,
+         * Then it can be called with default NULL parameter and will use
+         * the current last committed GTID.
+         * Alternatively it can be called at any time before commit with an
+         * explicit GTID that corresponds to transaction read view.
+         *
+         * @param gtid optional explicit GTID of the transaction read view.
+         */
+        int assign_read_view(const wsrep::gtid* const gtid = NULL);
+
+        /**
+         * Append a key into transaction write set.
+         *
+         * @param key Key to be appended
+         *
+         * @return Zero on success, non-zero on failure.
+         */
+        int append_key(const wsrep::key& key);
+
+        /**
+         * Append keys in key_array into transaction write set.
+         *
+         * @param keys Array of keys to be appended
+         *
+         * @return Zero in case of success, non-zero on failure.
+         */
+        int append_keys(const wsrep::key_array& keys);
+
+        /**
+         * Append data into transaction write set.
+         */
+        int append_data(const wsrep::const_buffer& data);
+
+        /** @} */
+
+        /** @name Streaming replication interface */
+        /** @{ */
+        /**
+         * This method should be called after every row operation.
+         */
+        int after_row();
+
+        /**
+         * Set streaming parameters.
+         *
+         * @param fragment_unit Desired fragment unit
+         * @param fragment_size Desired fragment size
+         */
+        void streaming_params(enum wsrep::streaming_context::fragment_unit
+                              fragment_unit,
+                              size_t fragment_size);
+
+        /**
+         * Enable streaming replication.
+         *
+         * Currently it is not possible to change the fragment unit
+         * for active streaming transaction.
+         *
+         * @param fragment_unit Desired fragment unit
+         * @param fragment_size Desired fragment size
+         *
+         * @return Zero on success, non-zero if the streaming cannot be
+         *         enabled.
+         */
+        int enable_streaming(
+            enum wsrep::streaming_context::fragment_unit
+            fragment_unit,
+            size_t fragment_size);
+
+        /**
+         * Disable streaming for context.
+         */
+        void disable_streaming();
+
+        void fragment_applied(wsrep::seqno seqno);
+        /**
+         * Prepare write set meta data for ordering.
+         * This method should be called before ordered commit or
+         * rollback if the commit time meta data was not known
+         * at the time of the start of the transaction.
+         * This mostly applies to streaming replication.
+         *
+         * @param ws_handle Write set handle
+         * @param ws_meta Write set meta data
+         * @param is_commit Boolean to denote whether the operation
+         *                  is commit or rollback.
+         */
+        int prepare_for_ordering(const wsrep::ws_handle& ws_handle,
+                                 const wsrep::ws_meta& ws_meta,
+                                 bool is_commit);
+        /** @} */
+
+        /** @name Applying interface */
+        /** @{ */
+        int start_transaction(const wsrep::ws_handle& wsh,
+                              const wsrep::ws_meta& meta);
+
+        int next_fragment(const wsrep::ws_meta& meta);
+
+        /** @name Commit ordering interface */
+        /** @{ */
+        int before_prepare();
+
+        int after_prepare();
+
+        int before_commit();
+
+        int ordered_commit();
+
+        int after_commit();
+        /** @} */
+        int before_rollback();
+
+        int after_rollback();
+
+        /**
+         * This method should be called by the background rollbacker
+         * thread after the rollback is complete. This will allow
+         * the client to proceed through before_command() and
+         * wait_rollback_complete_and_acquire_ownership().
+         */
+        void sync_rollback_complete();
+
+        /**
+         * Wait for background rollback to complete. This method can
+         * be called before before_command() to verify that the
+         * background rollback has been finished. After the call returns,
+         * it is guaranteed that BF abort does not launch background
+         * rollback process before after_command_after_result() is called.
+         * This method is idempotent, it can be called many times
+         * by the same thread before before_command() is called.
+         */
+        void wait_rollback_complete_and_acquire_ownership();
+        /** @} */
+
+        //
+        // XA
+        //
+        /**
+         * Assign transaction external id.
+         *
+         * Other than storing the xid, the transaction is marked as XA.
+         * This should be called when XA transaction is started.
+         *
+         * @param xid transaction id
+         */
+        void assign_xid(const wsrep::xid& xid)
+        {
+            transaction_.assign_xid(xid);
+        }
+
+        /**
+         * Restores the client's transaction to prepared state
+         *
+         * The purpose of this method is to restore transaction state
+         * during recovery of a prepared XA transaction.
+         */
+        int restore_xid(const wsrep::xid& xid)
+        {
+            return transaction_.restore_to_prepared_state(xid);
+        }
+
+        /**
+         * Commit transaction with the given xid
+         *
+         * Sends a commit fragment to terminate the transaction with
+         * the given xid. For the fragment to be sent, a streaming
+         * applier for the transaction must exist, and the transaction
+         * must be in prepared state.
+         *
+         * @param xid the xid of the the transaction to commit
+         *
+         * @return Zero on success, non-zero on error. In case of error
+         *         the client_state's current_error is set
+         */
+        int commit_by_xid(const wsrep::xid& xid)
+        {
+            return transaction_.commit_or_rollback_by_xid(xid, true);
+        }
+
+        /**
+         * Rollback transaction with the given xid
+         *
+         * Sends a rollback fragment to terminate the transaction with
+         * the given xid. For the fragment to be sent, a streaming
+         * applier for the transaction must exist, and the transaction
+         * must be in prepared state.
+         *
+         * @param xid the xid of the the transaction to commit
+         *
+         * @return Zero on success, non-zero on error. In case of error
+         *         the client_state's current_error is set
+         */
+        int rollback_by_xid(const wsrep::xid& xid)
+        {
+            return transaction_.commit_or_rollback_by_xid(xid, false);
+        }
+
+        /**
+         * Detach a prepared XA transaction
+         *
+         * This method cleans up a local XA transaction in prepared state
+         * and converts it to high priority mode.
+         * This can be used to handle the case where the client of a XA
+         * transaction disconnects, and the transaction must not rollback.
+         * After this call, a different client may later attempt to terminate
+         * the transaction by calling method commit_by_xid() or rollback_by_xid().
+         */
+        void xa_detach();
+
+        /**
+         * Replay a XA transaction
+         *
+         * Replay a XA transaction that is in s_idle state.
+         * This may happen if the transaction is BF aborted
+         * between prepare and commit.
+         * Since the victim is idle, this method can be called
+         * by the BF aborter or the backround rollbacker.
+         */
+        void xa_replay();
+
+        //
+        // BF aborting
+        //
+        /**
+         * Brute force abort a transaction. This method should be
+         * called by a transaction which needs to BF abort a conflicting
+         * locally processing transaction.
+         *
+         * @param lock Lock to protect client state.
+         * @param bf_seqno Seqno of the BF aborter.
+         */
+        int bf_abort(wsrep::unique_lock<wsrep::mutex>& lock, wsrep::seqno bf_seqno);
+        /**
+         * Wrapper to bf_abort() call, grabs lock internally.
+         */
+        int bf_abort(wsrep::seqno bf_seqno);
+
+        /**
+         * Brute force abort a transaction in total order. This method
+         * should be called by the TOI operation which needs to
+         * BF abort a transaction.
+         */
+        int total_order_bf_abort(wsrep::unique_lock<wsrep::mutex>& lock, wsrep::seqno bf_seqno);
+
+        /**
+         * Wrapper to total_order_bf_abort(), grabs lock internally.
+         */
+        int total_order_bf_abort(wsrep::seqno bf_seqno);
+
+        /**
+         * Adopt a streaming transaction state. This is must be
+         * called from high_priority_service::adopt_transaction()
+         * during streaming transaction rollback. The call will
+         * set up enough context for handling the rollback
+         * fragment.
+         */
+        void adopt_transaction(const wsrep::transaction& transaction);
+
+        /**
+         * Adopt (store) transaction applying error for further processing.
+         */
+        void adopt_apply_error(wsrep::mutable_buffer& err);
+
+        /**
+         * Clone enough state from another transaction so that replaing will
+         * be possible with a transaction contained in this client state.
+         *
+         * @param transaction Transaction which is to be replied in this
+         *                    client state
+         */
+        void clone_transaction_for_replay(const wsrep::transaction& transaction)
+        {
+            transaction_.clone_for_replay(transaction);
+        }
+
+        /** @name Non-transactional operations */
+        /** @{*/
+
+        /**
+         * Enter total order isolation critical section. If the wait_until
+         * is given non-default value, the operation is retried until
+         * successful, the given time point is reached or the client is
+         * interrupted.
+         *
+         * @param key_array Array of keys
+         * @param buffer Buffer containing the action to execute inside
+         *               total order isolation section
+         * @param flags  Provider flags for TOI operation
+         * @param wait_until Time point to wait until for successful
+         *                   certification.
+         *
+         * @return Zero on success, non-zero otherwise.
+         */
+        int enter_toi_local(
+            const wsrep::key_array& key_array,
+            const wsrep::const_buffer& buffer,
+            std::chrono::time_point<wsrep::clock>
+            wait_until =
+            std::chrono::time_point<wsrep::clock>());
+        /**
+         * Enter applier TOI mode
+         *
+         * @param ws_meta Write set meta data
+         */
+        void enter_toi_mode(const wsrep::ws_meta& ws_meta);
+
+        /**
+         * Return true if the client_state is under TOI operation.
+         */
+        bool in_toi() const
+        {
+            return (toi_meta_.seqno().is_undefined() == false);
+        }
+
+        /**
+         * Return the mode where client entered into TOI mode.
+         * The return value can be either m_local or
+         * m_high_priority.
+         */
+        enum mode toi_mode() const
+        {
+            return toi_mode_;
+        }
+
+        /**
+         * Leave total order isolation critical section.
+         * (for local mode clients)
+         *
+         * @param err definition of the error that happened during the
+         *            execution of TOI operation (empty for no error)
+         */
+        int leave_toi_local(const wsrep::mutable_buffer& err);
+
+        /**
+         * Leave applier TOI mode.
+         */
+        void leave_toi_mode();
+
+        /**
+         * Begin rolling schema upgrade operation.
+         *
+         * @param timeout Timeout in seconds to wait for committing
+         *        connections to finish.
+         */
+        int begin_rsu(int timeout);
+
+        /**
+         * End rolling schema upgrade operation.
+         */
+        int end_rsu();
+
+        /**
+         * Begin non-blocking operation.
+         *
+         * The NBO operation is started by grabbing TOI critical
+         * section. The keys and buffer are certifed as in TOI
+         * operation. If the call fails due to error returned by
+         * the provider, the provider error code can be retrieved
+         * by current_error_status() call.
+         *
+         * If the wait_until is given non-default value, the operation is
+         * retried until successful, the given time point is reached or the
+         * client is interrupted.
+         *
+         * @param keys Array of keys for NBO operation.
+         * @param buffer NBO write set
+         * @param wait_until Time point to wait until for successful certification.
+         * @return Zero in case of success, non-zero in case of failure.
+         */
+        int begin_nbo_phase_one(
+            const wsrep::key_array& keys,
+            const wsrep::const_buffer& buffer,
+            std::chrono::time_point<wsrep::clock>
+            wait_until =
+            std::chrono::time_point<wsrep::clock>());
+
+        /**
+         * End non-blocking operation phase after aquiring required
+         * resources for operation.
+         *
+         * @param err definition of the error that happened during the
+         *            execution of phase one (empty for no error)
+         */
+        int end_nbo_phase_one(const wsrep::mutable_buffer& err);
+
+        /**
+         * Enter in NBO mode. This method should be called when the
+         * applier launches the asynchronous process to perform the
+         * operation. The purpose of the call is to adjust
+         * the state and set write set meta data.
+         *
+         * @param ws_meta Write set meta data.
+         *
+         * @return Zero in case of success, non-zero on failure.
+         */
+        int enter_nbo_mode(const wsrep::ws_meta& ws_meta);
+
+        /**
+         * Begin non-blocking operation phase two. The keys argument
+         * passed to this call must contain the same keys which were
+         * passed to begin_nbo_phase_one().
+         *
+         * If the wait_until is given non-default value, the operation is
+         * retried until successful, the given time point is reached or the
+         * client is interrupted.
+         *
+         * @param keys Key array.
+         * @param wait_until Time point to wait until for entering TOI for
+         *                   phase two.
+         */
+        int begin_nbo_phase_two(const wsrep::key_array& keys,
+                                std::chrono::time_point<wsrep::clock>
+                                wait_until =
+                                std::chrono::time_point<wsrep::clock>());
+
+        /**
+         * End non-blocking operation phase two. This call will
+         * release TOI critical section and set the mode to m_local.
+         *
+         * @param err definition of the error that happened during the
+         *            execution of phase two (empty for no error)
+         */
+        int end_nbo_phase_two(const wsrep::mutable_buffer& err);
+
+        /**
+         * Get reference to the client mutex.
+         *
+         * @return Reference to the client mutex.
+         */
+        wsrep::mutex& mutex() { return mutex_; }
+
+        /**
+         * Get server context associated the the client session.
+         *
+         * @return Reference to server context.
+         */
+        wsrep::server_state& server_state() const
+        { return server_state_; }
+
+        wsrep::client_service& client_service() const
+        { return client_service_; }
+        /**
+         * Get reference to the Provider which is associated
+         * with the client context.
+         *
+         * @return Reference to the provider.
+         * @throw wsrep::runtime_error if no providers are associated
+         *        with the client context.
+         *
+         * @todo Should be removed.
+         */
+        wsrep::provider& provider() const;
+
+        /**
+         * Get Client identifier.
+         *
+         * @return Client Identifier
+         */
+        client_id id() const { return id_; }
+
+        /**
+         * Get Client mode.
+         *
+         * @todo Enforce mutex protection if called from other threads.
+         *
+         * @return Client mode.
+         */
+        enum mode mode() const { return mode_; }
+
+        /**
+         * Get Client state.
+         *
+         * @todo Enforce mutex protection if called from other threads.
+         *
+         * @return Client state
+         */
+        enum state state() const { return state_; }
+
+        /**
+         * Return a const reference to the transaction associated
+         * with the client state.
+         */
+        const wsrep::transaction& transaction() const
+        {
+            return transaction_;
+        }
+
+        /**
+         * Mark the transaction associated with the client state
+         * (if any), as unsafe for parallel applying
+         *
+         * @return Zero on success, non-zero on error.
+         */
+        int mark_transaction_pa_unsafe()
+        {
+          if (transaction_.active())
+          {
+            transaction_.pa_unsafe(true);
+            return 0;
+          }
+          return 1;
+        }
+
+        const wsrep::ws_meta& toi_meta() const
+        {
+            return toi_meta_;
+        }
+
+        /**
+         * Do sync wait operation. If the method fails, current_error()
+         * can be inspected about the reason of error.
+         *
+         * @param Sync wait timeout in seconds.
+         *
+         * @return Zero on success, non-zero on error.
+         */
+        int sync_wait(int timeout);
+
+        /**
+         * Return the current sync wait GTID.
+         *
+         * Sync wait GTID is updated on each sync_wait() call and
+         * reset to wsrep::gtid::undefined() in after_command_after_result()
+         * method. The variable can thus be used to check if a sync wait
+         * has been performend for the current client command.
+         */
+        const wsrep::gtid& sync_wait_gtid() const
+        {
+            return sync_wait_gtid_;
+        }
+        /**
+         * Return the last written GTID.
+         */
+        const wsrep::gtid& last_written_gtid() const
+        {
+            return last_written_gtid_;
+        }
+
+        /**
+         * Set debug logging level.
+         *
+         * Levels:
+         * 0 - Debug logging is disabled
+         * 1..n - Debug logging with increasing verbosity.
+         */
+        void debug_log_level(int level) { debug_log_level_ = level; }
+
+        /**
+         * Return current debug logging level. The return value
+         * is a maximum of client state and server state debug log
+         * levels.
+         *
+         * @return Current debug log level.
+         */
+        int debug_log_level() const
+        {
+            return std::max(debug_log_level_,
+                            wsrep::log::debug_log_level());
+        }
+
+        //
+        // Error handling
+        //
+
+        /**
+         * Reset the current error state.
+         *
+         * @todo There should be some protection about when this can
+         *       be done.
+         */
+        void reset_error()
+        {
+            current_error_ = wsrep::e_success;
+        }
+
+        /**
+         * Return current error code.
+         *
+         * @return Current error code.
+         */
+        enum wsrep::client_error current_error() const
+        {
+            return current_error_;
+        }
+
+        enum wsrep::provider::status current_error_status() const
+        {
+            return current_error_status_;
+        }
+
+        /**
+         * Return true if rollbacker is active. The caller should
+         * hold the mutex protecting client_state.
+         */
+        bool is_rollbacker_active()
+        {
+            return rollbacker_active_;
+        }
+    protected:
+        /**
+         * Client context constuctor. This is protected so that it
+         * can be called from derived class constructors only.
+         */
+        client_state(wsrep::mutex& mutex,
+                     wsrep::condition_variable& cond,
+                     wsrep::server_state& server_state,
+                     wsrep::client_service& client_service,
+                     const client_id& id,
+                     enum mode mode)
+            : owning_thread_id_(wsrep::this_thread::get_id())
+            , rollbacker_active_(false)
+            , mutex_(mutex)
+            , cond_(cond)
+            , server_state_(server_state)
+            , client_service_(client_service)
+            , id_(id)
+            , mode_(mode)
+            , toi_mode_(m_undefined)
+            , state_(s_none)
+            , state_hist_()
+            , transaction_(*this)
+            , toi_meta_()
+            , nbo_meta_()
+            , allow_dirty_reads_()
+            , sync_wait_gtid_()
+            , last_written_gtid_()
+            , debug_log_level_(0)
+            , current_error_(wsrep::e_success)
+            , current_error_status_(wsrep::provider::success)
+            , keep_command_error_()
+        { }
+
+    private:
+        client_state(const client_state&);
+        client_state& operator=(client_state&);
+
+        friend class client_state_switch;
+        friend class high_priority_context;
+        friend class transaction;
+
+        void do_acquire_ownership(wsrep::unique_lock<wsrep::mutex>& lock);
+        // Wait for sync rollbacker to finish, with lock. Changes state
+        // to exec.
+        void do_wait_rollback_complete_and_acquire_ownership(
+            wsrep::unique_lock<wsrep::mutex>& lock);
+        void update_last_written_gtid(const wsrep::gtid&);
+        void debug_log_state(const char*) const;
+        void debug_log_keys(const wsrep::key_array& keys) const;
+        void state(wsrep::unique_lock<wsrep::mutex>& lock, enum state state);
+        void mode(wsrep::unique_lock<wsrep::mutex>& lock, enum mode mode);
+
+        // Override current client error status. Optionally provide
+        // an error status from the provider if the error was caused
+        // by the provider call.
+        void override_error(enum wsrep::client_error error,
+                            enum wsrep::provider::status status =
+                            wsrep::provider::success);
+
+        // Poll provider::enter_toi() until return status from provider
+        // does not indicate certification failure, timeout expires
+        // or client is interrupted.
+        enum wsrep::provider::status
+        poll_enter_toi(wsrep::unique_lock<wsrep::mutex>& lock,
+                       const wsrep::key_array& keys,
+                       const wsrep::const_buffer& buffer,
+                       wsrep::ws_meta& meta,
+                       int flags,
+                       std::chrono::time_point<wsrep::clock> wait_until,
+                       bool& timed_out);
+        void enter_toi_common(wsrep::unique_lock<wsrep::mutex>&);
+        void leave_toi_common();
+
+        wsrep::thread::id owning_thread_id_;
+        bool rollbacker_active_;
+        wsrep::mutex& mutex_;
+        wsrep::condition_variable& cond_;
+        wsrep::server_state& server_state_;
+        wsrep::client_service& client_service_;
+        wsrep::client_id id_;
+        enum mode mode_;
+        enum mode toi_mode_;
+        enum state state_;
+        std::vector<enum state> state_hist_;
+        wsrep::transaction transaction_;
+        wsrep::ws_meta toi_meta_;
+        wsrep::ws_meta nbo_meta_;
+        bool allow_dirty_reads_;
+        wsrep::gtid sync_wait_gtid_;
+        wsrep::gtid last_written_gtid_;
+        int debug_log_level_;
+        enum wsrep::client_error current_error_;
+        enum wsrep::provider::status current_error_status_;
+        bool keep_command_error_;
+
+        /**
+         * Marks external rollbacker thread for the client
+         * as active. This will block client in before_command(), until
+         * rolbacker has released the client.
+         */
+        void set_rollbacker_active(bool value)
+        {
+            rollbacker_active_ = value;
+        }
+    };
+
+    static inline const char* to_c_string(
+        enum wsrep::client_state::state state)
+    {
+        switch (state)
+        {
+        case wsrep::client_state::s_none: return "none";
+        case wsrep::client_state::s_idle: return "idle";
+        case wsrep::client_state::s_exec: return "exec";
+        case wsrep::client_state::s_result: return "result";
+        case wsrep::client_state::s_quitting: return "quit";
+        }
+        return "unknown";
+    }
+
+    static inline std::string to_string(enum wsrep::client_state::state state)
+    {
+        return to_c_string(state);
+    }
+
+    static inline const char* to_c_string(enum wsrep::client_state::mode mode)
+    {
+        switch (mode)
+        {
+        case wsrep::client_state::m_undefined: return "undefined";
+        case wsrep::client_state::m_local: return "local";
+        case wsrep::client_state::m_high_priority: return "high priority";
+        case wsrep::client_state::m_toi: return "toi";
+        case wsrep::client_state::m_rsu: return "rsu";
+        case wsrep::client_state::m_nbo: return "nbo";
+        }
+        return "unknown";
+    }
+
+    static inline std::string to_string(enum wsrep::client_state::mode mode)
+    {
+        return to_c_string(mode);
+    }
+
+    /**
+     * Utility class to switch the client state to high priority
+     * mode. The client is switched back to the original mode
+     * when the high priority context goes out of scope.
+     */
+    class high_priority_context
+    {
+    public:
+        high_priority_context(wsrep::client_state& client);
+        virtual ~high_priority_context();
+    private:
+        wsrep::client_state& client_;
+        enum wsrep::client_state::mode orig_mode_;
+    };
+}
+
+#endif // WSREP_CLIENT_STATE_HPP