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, 1380 insertions, 0 deletions

diff --git a/wsrep-lib/wsrep-API/v26/wsrep_api.h b/wsrep-lib/wsrep-API/v26/wsrep_api.h
new file mode 100644
index 00000000..59bb71da
--- /dev/null
+++ b/wsrep-lib/wsrep-API/v26/wsrep_api.h
@@ -0,0 +1,1380 @@
+/* Copyright (C) 2009-2013 Codership Oy <info@codership.com>
+
+   This program 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; version 2 of the License.
+
+   This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*!
+  @file wsrep API declaration.
+
+  HOW TO READ THIS FILE.
+
+  Due to C language rules this header layout doesn't lend itself to intuitive
+  reading. So here's the scoop: in the end this header declares two main types:
+
+  * struct wsrep_init_args
+
+  and
+
+  * struct wsrep
+
+  wsrep_init_args contains initialization parameters for wsrep provider like
+  names, addresses, etc. and pointers to callbacks. The callbacks will be called
+  by provider when it needs to do something application-specific, like log a
+  message or apply a writeset. It should be passed to init() call from
+  wsrep API. It is an application part of wsrep API contract.
+
+  struct wsrep is the interface to wsrep provider. It contains all wsrep API
+  calls. It is a provider part of wsrep API contract.
+
+  Finally, wsrep_load() method loads (dlopens) wsrep provider library. It is
+  defined in wsrep_loader.c unit and is part of libwsrep.a (which is not a
+  wsrep provider, but a convenience library).
+
+  wsrep_unload() does the reverse.
+
+*/
+#ifndef WSREP_H
+#define WSREP_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**************************************************************************
+ *                                                                        *
+ *                       wsrep replication API                            *
+ *                                                                        *
+ **************************************************************************/
+
+#define WSREP_INTERFACE_VERSION "26"
+
+/*! Empty backend spec */
+#define WSREP_NONE "none"
+
+
+/*!
+ * @brief log severity levels, passed as first argument to log handler
+ */
+typedef enum wsrep_log_level
+{
+    WSREP_LOG_FATAL, //!< Unrecoverable error, application must quit.
+    WSREP_LOG_ERROR, //!< Operation failed, must be repeated.
+    WSREP_LOG_WARN,  //!< Unexpected condition, but no operational failure.
+    WSREP_LOG_INFO,  //!< Informational message.
+    WSREP_LOG_DEBUG  //!< Debug message. Shows only of compiled with debug.
+} wsrep_log_level_t;
+
+/*!
+ * @brief error log handler
+ *
+ *        All messages from wsrep provider are directed to this
+ *        handler, if present.
+ *
+ * @param level   log level
+ * @param message log message
+ */
+typedef void (*wsrep_log_cb_t)(wsrep_log_level_t, const char *);
+
+
+/*!
+ *  Certain provider capabilities application may want to know about
+ */
+#define WSREP_CAP_MULTI_MASTER          ( 1ULL << 0 )
+#define WSREP_CAP_CERTIFICATION         ( 1ULL << 1 )
+#define WSREP_CAP_PARALLEL_APPLYING     ( 1ULL << 2 )
+#define WSREP_CAP_TRX_REPLAY            ( 1ULL << 3 )
+#define WSREP_CAP_ISOLATION             ( 1ULL << 4 )
+#define WSREP_CAP_PAUSE                 ( 1ULL << 5 )
+#define WSREP_CAP_CAUSAL_READS          ( 1ULL << 6 )
+#define WSREP_CAP_CAUSAL_TRX            ( 1ULL << 7 )
+#define WSREP_CAP_INCREMENTAL_WRITESET  ( 1ULL << 8 )
+#define WSREP_CAP_SESSION_LOCKS         ( 1ULL << 9 )
+#define WSREP_CAP_DISTRIBUTED_LOCKS     ( 1ULL << 10 )
+#define WSREP_CAP_CONSISTENCY_CHECK     ( 1ULL << 11 )
+#define WSREP_CAP_UNORDERED             ( 1ULL << 12 )
+#define WSREP_CAP_ANNOTATION            ( 1ULL << 13 )
+#define WSREP_CAP_PREORDERED            ( 1ULL << 14 )
+#define WSREP_CAP_STREAMING             ( 1ULL << 15 )
+#define WSREP_CAP_SNAPSHOT              ( 1ULL << 16 )
+#define WSREP_CAP_NBO                   ( 1ULL << 17 )
+
+typedef uint32_t wsrep_cap_t; //!< capabilities bitmask
+
+/*!
+ * Writeset flags
+ *
+ * TRX_END      the writeset and all preceding writesets must be committed
+ * ROLLBACK     all preceding writesets in a transaction must be rolled back
+ * ISOLATION    the writeset must be applied AND committed in isolation
+ * PA_UNSAFE    the writeset cannot be applied in parallel
+ * COMMUTATIVE  the order in which the writeset is applied does not matter
+ * NATIVE       the writeset contains another writeset in this provider format
+ *
+ * TRX_START    shall be set on the first trx fragment by provider
+ * TRX_PREPARE  shall be set on the fragment which prepares the transaction
+ *
+ * Note that some of the flags are mutually exclusive (e.g. TRX_END and
+ * ROLLBACK).
+ */
+#define WSREP_FLAG_TRX_END              ( 1ULL << 0 )
+#define WSREP_FLAG_ROLLBACK             ( 1ULL << 1 )
+#define WSREP_FLAG_ISOLATION            ( 1ULL << 2 )
+#define WSREP_FLAG_PA_UNSAFE            ( 1ULL << 3 )
+#define WSREP_FLAG_COMMUTATIVE          ( 1ULL << 4 )
+#define WSREP_FLAG_NATIVE               ( 1ULL << 5 )
+#define WSREP_FLAG_TRX_START            ( 1ULL << 6 )
+#define WSREP_FLAG_TRX_PREPARE          ( 1ULL << 7 )
+#define WSREP_FLAG_SNAPSHOT             ( 1ULL << 8 )
+#define WSREP_FLAG_IMPLICIT_DEPS        ( 1ULL << 9 )
+
+#define WSREP_FLAGS_LAST                WSREP_FLAG_IMPLICIT_DEPS
+#define WSREP_FLAGS_MASK                ((WSREP_FLAGS_LAST << 1) - 1)
+
+
+typedef uint64_t wsrep_trx_id_t;  //!< application transaction ID
+typedef uint64_t wsrep_conn_id_t; //!< application connection ID
+typedef int64_t  wsrep_seqno_t;   //!< sequence number of a writeset, etc.
+#ifdef __cplusplus
+typedef bool     wsrep_bool_t;
+#else
+typedef _Bool    wsrep_bool_t;    //!< should be the same as standard (C99) bool
+#endif /* __cplusplus */
+
+/*! undefined seqno */
+#define WSREP_SEQNO_UNDEFINED (-1)
+
+
+/*! wsrep provider status codes */
+typedef enum wsrep_status
+{
+    WSREP_OK = 0,          //!< success
+    WSREP_WARNING,         //!< minor warning, error logged
+    WSREP_TRX_MISSING,     //!< transaction is not known by wsrep
+    WSREP_TRX_FAIL,        //!< transaction aborted, server can continue
+    WSREP_BF_ABORT,        //!< trx was victim of brute force abort
+    WSREP_SIZE_EXCEEDED,   //!< data exceeded maximum supported size
+    WSREP_CONN_FAIL,       //!< error in client connection, must abort
+    WSREP_NODE_FAIL,       //!< error in node state, wsrep must reinit
+    WSREP_FATAL,           //!< fatal error, server must abort
+    WSREP_NOT_IMPLEMENTED, //!< feature not implemented
+    WSREP_NOT_ALLOWED      //!< operation not allowed
+} wsrep_status_t;
+
+
+/*! wsrep callbacks status codes */
+typedef enum wsrep_cb_status
+{
+    WSREP_CB_SUCCESS =  0, //!< success (as in "not critical failure")
+    WSREP_CB_FAILURE       //!< critical failure (consistency violation)
+    /* Technically, wsrep provider has no use for specific failure codes since
+     * there is nothing it can do about it but abort execution. Therefore any
+     * positive number shall indicate a critical failure. Optionally that value
+     * may be used by provider to come to a consensus about state consistency
+     * in a group of nodes. */
+} wsrep_cb_status_t;
+
+
+/*!
+ * UUID type - for all unique IDs
+ */
+typedef union wsrep_uuid {
+    uint8_t data[16];
+    size_t  alignment;
+} wsrep_uuid_t;
+
+/*! Undefined UUID */
+static const wsrep_uuid_t WSREP_UUID_UNDEFINED = {{0,}};
+
+/*! UUID string representation length, terminating '\0' not included */
+#define WSREP_UUID_STR_LEN 36
+
+/*!
+ * Scan UUID from string
+ * @return length of UUID string representation or negative error code
+ */
+extern int
+wsrep_uuid_scan (const char* str, size_t str_len, wsrep_uuid_t* uuid);
+
+/*!
+ * Print UUID to string
+ * @return length of UUID string representation or negative error code
+ */
+extern int
+wsrep_uuid_print (const wsrep_uuid_t* uuid, char* str, size_t str_len);
+
+/*!
+ * @brief Compare two UUIDs
+ *
+ * Performs a byte by byte comparison of lhs and rhs.
+ * Returns 0 if lhs and rhs match, otherwise -1 or 1 according to the
+ * difference of the first byte that differs in lsh and rhs.
+ *
+ * @return -1, 0, 1 if lhs is respectively smaller, equal, or greater than rhs
+ */
+extern int
+wsrep_uuid_compare (const wsrep_uuid_t* lhs, const wsrep_uuid_t* rhs);
+
+#define WSREP_MEMBER_NAME_LEN 32  //!< maximum logical member name length
+#define WSREP_INCOMING_LEN    256 //!< max Domain Name length + 0x00
+
+
+/*!
+ * Global transaction identifier
+ */
+typedef struct wsrep_gtid
+{
+    wsrep_uuid_t  uuid;  /*!< History UUID */
+    wsrep_seqno_t seqno; /*!< Sequence number */
+} wsrep_gtid_t;
+
+/*! Undefined GTID */
+static const wsrep_gtid_t WSREP_GTID_UNDEFINED = {{{0, }}, -1};
+
+/*! Minimum number of bytes guaranteed to store GTID string representation,
+ * terminating '\0' not included (36 + 1 + 20) */
+#define WSREP_GTID_STR_LEN 57
+
+
+/*!
+ * Scan GTID from string
+ * @return length of GTID string representation or negative error code
+ */
+extern int
+wsrep_gtid_scan(const char* str, size_t str_len, wsrep_gtid_t* gtid);
+
+/*!
+ * Print GTID to string
+ * @return length of GTID string representation or negative error code
+ */
+extern int
+wsrep_gtid_print(const wsrep_gtid_t* gtid, char* str, size_t str_len);
+
+/*!
+ * Source/server transaction ID (trx ID assigned at originating node)
+ */
+typedef struct wsrep_stid {
+    wsrep_uuid_t      node;    //!< source node ID
+    wsrep_trx_id_t    trx;     //!< local trx ID at source
+    wsrep_conn_id_t   conn;    //!< local connection ID at source
+} wsrep_stid_t;
+
+/*!
+ * Transaction meta data
+ */
+typedef struct wsrep_trx_meta
+{
+    wsrep_gtid_t  gtid;       /*!< Global transaction identifier */
+    wsrep_stid_t  stid;       /*!< Source transaction identifier */
+    wsrep_seqno_t depends_on; /*!< Sequence number of the last transaction
+                                   this transaction may depend on */
+} wsrep_trx_meta_t;
+
+/*! Abstract data buffer structure */
+typedef struct wsrep_buf
+{
+    const void* ptr; /*!< Pointer to data buffer */
+    size_t      len; /*!< Length of buffer */
+} wsrep_buf_t;
+
+/*! Transaction handle struct passed for wsrep transaction handling calls */
+typedef struct wsrep_ws_handle
+{
+    wsrep_trx_id_t trx_id; //!< transaction ID
+    void*          opaque; //!< opaque provider transaction context data
+} wsrep_ws_handle_t;
+
+/*!
+ * member status
+ */
+typedef enum wsrep_member_status {
+    WSREP_MEMBER_UNDEFINED, //!< undefined state
+    WSREP_MEMBER_JOINER,    //!< incomplete state, requested state transfer
+    WSREP_MEMBER_DONOR,     //!< complete state, donates state transfer
+    WSREP_MEMBER_JOINED,    //!< complete state
+    WSREP_MEMBER_SYNCED,    //!< complete state, synchronized with group
+    WSREP_MEMBER_ERROR,     //!< this and above is provider-specific error code
+    WSREP_MEMBER_MAX
+} wsrep_member_status_t;
+
+/*!
+ * static information about a group member (some fields are tentative yet)
+ */
+typedef struct wsrep_member_info {
+    wsrep_uuid_t id;                           //!< group-wide unique member ID
+    char         name[WSREP_MEMBER_NAME_LEN];  //!< human-readable name
+    char         incoming[WSREP_INCOMING_LEN]; //!< address for client requests
+} wsrep_member_info_t;
+
+/*!
+ * group status
+ */
+typedef enum wsrep_view_status {
+    WSREP_VIEW_PRIMARY,      //!< primary group configuration (quorum present)
+    WSREP_VIEW_NON_PRIMARY,  //!< non-primary group configuration (quorum lost)
+    WSREP_VIEW_DISCONNECTED, //!< not connected to group, retrying.
+    WSREP_VIEW_MAX
+} wsrep_view_status_t;
+
+/*!
+ * view of the group
+ */
+typedef struct wsrep_view_info {
+    wsrep_gtid_t        state_id;  //!< global state ID
+    wsrep_seqno_t       view;      //!< global view number
+    wsrep_view_status_t status;    //!< view status
+    wsrep_cap_t         capabilities;//!< capabilities available in the view
+    int                 my_idx;    //!< index of this member in the view
+    int                 memb_num;  //!< number of members in the view
+    int                 proto_ver; //!< application protocol agreed on the view
+    wsrep_member_info_t members[1];//!< array of member information
+} wsrep_view_info_t;
+
+
+/*!
+ * @brief connected to group
+ *
+ * This handler is called once the first primary view is seen.
+ * The purpose of this call is to provide basic information only,
+ * like node UUID and group UUID.
+ */
+typedef enum wsrep_cb_status (*wsrep_connected_cb_t) (
+    void*                    app_ctx,
+    const wsrep_view_info_t* view
+);
+
+
+/*!
+ * @brief group view handler
+ *
+ * This handler is called in *total order* corresponding to the group
+ * configuration change. It is to provide a vital information about
+ * new group view.
+ *
+ * @param app_ctx     application context
+ * @param recv_ctx    receiver context
+ * @param view        new view on the group
+ * @param state       current state
+ * @param state_len   length of current state
+ */
+typedef enum wsrep_cb_status (*wsrep_view_cb_t) (
+    void*                     app_ctx,
+    void*                     recv_ctx,
+    const wsrep_view_info_t*  view,
+    const char*               state,
+    size_t                    state_len
+);
+
+
+/*!
+ * Magic string to tell provider to engage into trivial (empty) state transfer.
+ * No data will be passed, but the node shall be considered JOINED.
+ * Should be passed in sst_req parameter of wsrep_sst_cb_t.
+ */
+#define WSREP_STATE_TRANSFER_TRIVIAL "trivial"
+
+/*!
+ * Magic string to tell provider not to engage in state transfer at all.
+ * The member will stay in WSREP_MEMBER_UNDEFINED state but will keep on
+ * receiving all writesets.
+ * Should be passed in sst_req parameter of wsrep_sst_cb_t.
+ */
+#define WSREP_STATE_TRANSFER_NONE "none"
+
+
+/*!
+ * @brief Creates and returns State Snapshot Transfer request for provider.
+ *
+ * This handler is called whenever the node is found to miss some of events
+ * from the cluster history (e.g. fresh node joining the cluster).
+ * SST will be used if it is impossible (or impractically long) to replay
+ * missing events, which may be not known in advance, so the node must always
+ * be ready to accept full SST or abort in case event replay is impossible.
+ *
+ * Normally SST request is an opaque buffer that is passed to the
+ * chosen SST donor node and must contain information sufficient for
+ * donor to deliver SST (typically SST method and delivery address).
+ * See above macros WSREP_STATE_TRANSFER_TRIVIAL and WSREP_STATE_TRANSFER_NONE
+ * to modify the standard provider behavior.
+ *
+ * @note Currently it is assumed that sst_req is allocated using
+ *       malloc()/calloc()/realloc() and it will be freed by
+ *       wsrep provider.
+ *
+ * @param app_ctx     application context
+ * @param sst_req     location to store SST request
+ * @param sst_req_len location to store SST request length or error code,
+ *                    value of 0 means no SST.
+ */
+typedef enum wsrep_cb_status (*wsrep_sst_request_cb_t) (
+    void*                     app_ctx,
+    void**                    sst_req,
+    size_t*                   sst_req_len
+);
+
+
+/*!
+ * @brief apply callback
+ *
+ * This handler is called from wsrep library to apply replicated writeset
+ * Must support brute force applying for multi-master operation
+ *
+ * @param recv_ctx  receiver context pointer provided by the application
+ * @param ws_handle internal provider writeset handle
+ * @param flags     WSREP_FLAG_... flags
+ * @param data      data buffer containing the writeset
+ * @param meta      transaction meta data of the writeset to be applied
+ * @param exit_loop set to true to exit receive loop
+ *
+ * @return error code:
+ * @retval 0 - success
+ * @retval non-0 - application-specific error code
+ */
+typedef enum wsrep_cb_status (*wsrep_apply_cb_t) (
+    void*                    recv_ctx,
+    const wsrep_ws_handle_t* ws_handle,
+    uint32_t                 flags,
+    const wsrep_buf_t*       data,
+    const wsrep_trx_meta_t*  meta,
+    wsrep_bool_t*            exit_loop
+);
+
+
+/*!
+ * @brief unordered callback
+ *
+ * This handler is called to execute unordered actions (actions that need not
+ * to be executed in any particular order) attached to writeset.
+ *
+ * @param recv_ctx receiver context pointer provided by the application
+ * @param data     data buffer containing the writeset
+ */
+typedef enum wsrep_cb_status (*wsrep_unordered_cb_t) (
+    void*              recv_ctx,
+    const wsrep_buf_t* data
+);
+
+
+/*!
+ * @brief a callback to donate state snapshot
+ *
+ * This handler is called from wsrep library when it needs this node
+ * to deliver state to a new cluster member.
+ * No state changes will be committed for the duration of this call.
+ * Wsrep implementation may provide internal state to be transmitted
+ * to new cluster member for initial state.
+ *
+ * @param app_ctx   application context
+ * @param recv_ctx  receiver context
+ * @param str_msg   state transfer request message
+ * @param gtid      current state ID on this node
+ * @param state     current wsrep internal state buffer
+ * @param bypass    bypass snapshot transfer, only transfer uuid:seqno pair
+ */
+typedef enum wsrep_cb_status (*wsrep_sst_donate_cb_t) (
+    void*               app_ctx,
+    void*               recv_ctx,
+    const wsrep_buf_t*  str_msg,
+    const wsrep_gtid_t* state_id,
+    const wsrep_buf_t*  state,
+    wsrep_bool_t        bypass
+);
+
+
+/*!
+ * @brief a callback to signal application that wsrep state is synced
+ *        with cluster
+ *
+ * This callback is called after wsrep library has got in sync with
+ * rest of the cluster.
+ *
+ * @param app_ctx application context
+ *
+ * @return wsrep_cb_status enum
+ */
+typedef enum wsrep_cb_status (*wsrep_synced_cb_t) (void* app_ctx);
+
+
+/*
+ * An opaque encryption key of arbitrary size - provided by the application
+ * May contain not only the key, but also algorithm specification and the like.
+ */
+typedef wsrep_buf_t wsrep_enc_key_t;
+
+/*
+ * Initialization vector/nonce. Given that most symmetric ciphers use 16 byte
+ * blocks this can be made 32 bytes without much loss of generality.
+ * Must be set by provider to start an encryption/decrytpion operation.
+ */
+typedef char wsrep_enc_iv_t[32];
+
+/*
+ * Encryption context that should be sufficient to deterministically encrypt/
+ * decrypt a data buffer either standalone or as part of a stream. May be used
+ * passed in apply_cb() along with the encrypted replication events to
+ * application as well.
+ *
+ * @param key    [in] can be a pointer to const since provider will have to keep
+ *               the keys until the last writeset that uses the key is in the
+ *               cache
+ * @param iv     [in] initialization vector for the beginning of the new
+ *               operation.
+ * @param ctx    [in/out] ongoing operation context
+ *               To initialize a new context the encrypt_cb() caller sets it to
+ *               NULL, which signals the encryption of a new continuous buffer.
+ *               In that case the callback allocates the new context (using
+ *               supplied key and iv) and stores the pointer to it for
+ *               processing subsequent data.
+ *               The end of the operation is signaled by passing TRUE in the
+ *               parameter `last` to the encryption callback, the callback then
+ *               finishes any pending encryption and deallocates the context.
+ */
+typedef struct
+{
+    const wsrep_enc_key_t* key;
+    const wsrep_enc_iv_t*  iv;
+    void*                  ctx;
+}
+wsrep_enc_ctx_t;
+
+/*
+ * Encryption direction
+ */
+typedef enum
+{
+    WSREP_ENC = 0, /* encryption */
+    WSREP_DEC = 1  /* decryption */
+}
+wsrep_enc_direction_t;
+
+/*
+ * Encryption/decryption callback. Must be used by both provider and the
+ * application to obtain identical results. Can be NULL for no encryption.
+ *
+ * @param app_ctx   application context
+ * @param enc_ctx   current operation context
+ * @param input     input data buffer
+ * @param output    an output buffer, must be at least the size of the input
+ *                  data plus unwritten bytes from the previous call(s). E.g. in
+ *                  block mode, encryption/decryption operation will write data
+ *                  to output in multiples of the algoritm block size. So a call
+ *                  to encrypt a single byte won't normally write anything to
+ *                  output waiting for the next input chunk. So on the next call
+ *                  it may write one byte more than was given in the input.
+ * @param direction of the operation (encryption/decryption)
+ * @param last      true if this is the last buffer to encrypt in the stream.
+ *                  In that case the callback shall write the remaining bytes of
+ *                  the stream to output (if any) and deallocate ctx->ctx if
+ *                  allocated previously
+ *
+ * @return          a number of bytes written to output or a negative error code.
+ */
+typedef int (*wsrep_encrypt_cb_t)
+(
+    void*                 app_ctx,
+    wsrep_enc_ctx_t*      enc_ctx,
+    const wsrep_buf_t*    input,
+    void*                 output,
+    wsrep_enc_direction_t direction,
+    bool                  last
+);
+
+
+/*!
+ * Initialization parameters for wsrep provider.
+ */
+struct wsrep_init_args
+{
+    void* app_ctx;             //!< Application context for callbacks
+
+    /* Configuration parameters */
+    const char* node_name;     //!< Symbolic name of this node (e.g. hostname)
+    const char* node_address;  //!< Address to be used by wsrep provider
+    const char* node_incoming; //!< Address for incoming client connections
+    const char* data_dir;      //!< Directory where wsrep files are kept if any
+    const char* options;       //!< Provider-specific configuration string
+    int         proto_ver;     //!< Max supported application protocol version
+
+    /* Application initial state information. */
+    const wsrep_gtid_t* state_id;    //!< Application state GTID
+    const wsrep_buf_t*  state;       //!< Initial state for wsrep provider
+
+    /* Application callbacks */
+    wsrep_log_cb_t         logger_cb;       //!< logging handler
+    wsrep_connected_cb_t   connected_cb;    //!< connected to group
+    wsrep_view_cb_t        view_cb;         //!< group view change handler
+    wsrep_sst_request_cb_t sst_request_cb;  //!< SST request creator
+    wsrep_encrypt_cb_t     encrypt_cb;      //!< Encryption callback
+
+    /* Applier callbacks */
+    wsrep_apply_cb_t       apply_cb;        //!< apply  callback
+    wsrep_unordered_cb_t   unordered_cb;    //!< callback for unordered actions
+
+    /* State Snapshot Transfer callbacks */
+    wsrep_sst_donate_cb_t  sst_donate_cb;   //!< donate SST
+    wsrep_synced_cb_t      synced_cb;       //!< synced with group
+};
+
+
+/*! Type of the stats variable value in struct wsrep_status_var */
+typedef enum wsrep_var_type
+{
+    WSREP_VAR_STRING, //!< pointer to null-terminated string
+    WSREP_VAR_INT64,  //!< int64_t
+    WSREP_VAR_DOUBLE  //!< double
+}
+wsrep_var_type_t;
+
+/*! Generalized stats variable representation */
+struct wsrep_stats_var
+{
+    const char*      name;     //!< variable name
+    wsrep_var_type_t type;     //!< variable value type
+    union {
+        int64_t     _int64;
+        double      _double;
+        const char* _string;
+    } value;                   //!< variable value
+};
+
+
+/*! Key struct used to pass certification keys for transaction handling calls.
+ *  A key consists of zero or more key parts. */
+typedef struct wsrep_key
+{
+    const wsrep_buf_t* key_parts;     /*!< Array of key parts  */
+    size_t             key_parts_num; /*!< Number of key parts */
+} wsrep_key_t;
+
+/*! Key type:
+ *  SHARED    - higher level resource shared between clients, e.g. SQL table
+ *  REFERENCE - resource referenced but not modified, e.g. parent row
+ *  UPDATE    - resource is modified
+ *  EXCLUSIVE - resource is either created or deleted */
+typedef enum wsrep_key_type
+{
+    WSREP_KEY_SHARED = 0,
+    WSREP_KEY_REFERENCE,
+    WSREP_KEY_UPDATE,
+    WSREP_KEY_EXCLUSIVE
+} wsrep_key_type_t;
+
+/*! Data type:
+ *  ORDERED    state modification event that should be applied and committed
+ *             in order.
+ *  UNORDERED  some action that does not modify state and execution of which is
+ *             optional and does not need to happen in order.
+ *  ANNOTATION (human readable) writeset annotation. */
+typedef enum wsrep_data_type
+{
+    WSREP_DATA_ORDERED = 0,
+    WSREP_DATA_UNORDERED,
+    WSREP_DATA_ANNOTATION
+} wsrep_data_type_t;
+
+
+/*!
+ * @brief Helper method to reset trx writeset handle state when trx id changes
+ *
+ * Instead of passing wsrep_ws_handle_t directly to wsrep calls,
+ * wrapping handle with this call offloads bookkeeping from
+ * application.
+ */
+static inline wsrep_ws_handle_t* wsrep_ws_handle_for_trx(
+    wsrep_ws_handle_t* ws_handle,
+    wsrep_trx_id_t     trx_id)
+{
+    if (ws_handle->trx_id != trx_id)
+    {
+        ws_handle->trx_id = trx_id;
+        ws_handle->opaque = NULL;
+    }
+    return ws_handle;
+}
+
+
+/*!
+ *  A handle for processing preordered actions.
+ *  Must be initialized to WSREP_PO_INITIALIZER before use.
+ */
+typedef struct wsrep_po_handle { void* opaque; } wsrep_po_handle_t;
+
+static const wsrep_po_handle_t WSREP_PO_INITIALIZER = { NULL };
+
+
+typedef struct wsrep_st wsrep_t;
+/*!
+ * wsrep interface for dynamically loadable libraries
+ */
+struct wsrep_st {
+
+    const char *version; //!< interface version string
+
+  /*!
+   * @brief Initializes wsrep provider
+   *
+   * @param wsrep provider handle
+   * @param args  wsrep initialization parameters
+   */
+    wsrep_status_t (*init)   (wsrep_t*                      wsrep,
+                              const struct wsrep_init_args* args);
+
+  /*!
+   * @brief Returns provider capabilities bitmap
+   *
+   * Note that these are potential provider capabilities. Provider will
+   * offer only capabilities supported by all members in the view
+   * (see wsrep_view_info).
+   *
+   * @param wsrep provider handle
+   */
+    wsrep_cap_t    (*capabilities) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Passes provider-specific configuration string to provider.
+   *
+   * @param wsrep provider handle
+   * @param conf  configuration string
+   *
+   * @retval WSREP_OK      configuration string was parsed successfully
+   * @retval WSREP_WARNING could not parse configuration string, no action taken
+   */
+    wsrep_status_t (*options_set) (wsrep_t* wsrep, const char* conf);
+
+  /*!
+   * @brief Returns provider-specific string with current configuration values.
+   *
+   * @param wsrep provider handle
+   *
+   * @return a dynamically allocated string with current configuration
+   *         parameter values
+   */
+    char*          (*options_get) (wsrep_t* wsrep);
+
+  /*!
+   * @brief A call to set/rotate the key in provider.
+   *
+   * This may happen asynchronously and so is a best effort operation.
+   * Some buffers may still be encrypted with a previous key.
+   *
+   * @param a key object for the encryption callback
+   *
+   * return success or an error code
+   */
+    wsrep_status_t (*enc_set_key)(wsrep_t* wsrep, const wsrep_enc_key_t* key);
+
+  /*!
+   * @brief Opens connection to cluster
+   *
+   * Returns when either node is ready to operate as a part of the cluster
+   * or fails to reach operating status.
+   *
+   * @param wsrep        provider handle
+   * @param cluster_name unique symbolic cluster name
+   * @param cluster_url  URL-like cluster address (backend://address)
+   * @param state_donor  name of the node to be asked for state transfer.
+   * @param bootstrap    a flag to request initialization of a new wsrep
+   *                     service rather then a connection to the existing one.
+   *                     cluster_url may still carry important initialization
+   *                     parameters, like backend spec and/or listen address.
+   */
+    wsrep_status_t (*connect) (wsrep_t*     wsrep,
+                               const char*  cluster_name,
+                               const char*  cluster_url,
+                               const char*  state_donor,
+                               wsrep_bool_t bootstrap);
+
+  /*!
+   * @brief Closes connection to cluster.
+   *
+   * @param wsrep this  wsrep handler
+   */
+    wsrep_status_t (*disconnect)(wsrep_t* wsrep);
+
+  /*!
+   * @brief start receiving replication events
+   *
+   * This function does not return until provider is closed or \p exit_loop
+   * parameter to wsrep_apply_cb_t() is set to true.
+   *
+   * @param wsrep provider handle
+   * @param recv_ctx receiver context
+   */
+    wsrep_status_t (*recv)(wsrep_t* wsrep, void* recv_ctx);
+
+  /*!
+   * @brief Tells provider that a given writeset has a read view associated
+   *        with it.
+   *
+   * @param wsrep  provider handle
+   * @param handle writeset handle
+   * @param rv     read view GTID established by the caller or if NULL,
+   *               provider will infer it internally.
+   */
+    wsrep_status_t (*assign_read_view)(wsrep_t*            wsrep,
+                                       wsrep_ws_handle_t*  handle,
+                                       const wsrep_gtid_t* rv);
+
+  /*!
+   * @brief Certifies transaction with provider.
+   *
+   * Must be called before transaction commit. Returns success code, which
+   * caller must check.
+   *
+   * In case of WSREP_OK, transaction can proceed to commit.
+   * Otherwise transaction must rollback.
+   *
+   * In case of a failure there are two conceptually different situations:
+   * - the writeset was not ordered. In that case meta struct shall contain
+   *   undefined GTID: WSREP_UUID_UNDEFINED:WSREP_SEQNO_UNDEFINED.
+   * - the writeset was successfully ordered, but failed certification.
+   *   In this case meta struct shall contain a valid GTID.
+   *
+   * Regardless of the return code, if meta struct contains a valid GTID
+   * the commit order critical section must be entered with that GTID.
+   *
+   * @param wsrep      provider handle
+   * @param conn_id    connection ID
+   * @param ws_handle  writeset of committing transaction
+   * @param flags      fine tuning the replication WSREP_FLAG_*
+   * @param meta       transaction meta data
+   *
+   * @retval WSREP_OK         writeset successfully certified, can commit
+   * @retval WSREP_TRX_FAIL   must rollback transaction
+   * @retval WSREP_CONN_FAIL  must close client connection
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*certify)(wsrep_t*                wsrep,
+                              wsrep_conn_id_t         conn_id,
+                              wsrep_ws_handle_t*      ws_handle,
+                              uint32_t                flags,
+                              wsrep_trx_meta_t*       meta);
+
+  /*!
+   * @brief Enters commit order critical section.
+   *
+   * Anything executed between this call and commit_order_leave() will be
+   * executed in provider enforced order.
+   *
+   * @param wsrep      provider handle
+   * @param ws_handle  internal provider writeset handle
+   * @param meta       transaction meta data
+   *
+   * @retval WSREP_OK         commit order entered successfully
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*commit_order_enter)(wsrep_t*                 wsrep,
+                                         const wsrep_ws_handle_t* ws_handle,
+                                         const wsrep_trx_meta_t*  meta);
+
+  /*!
+   * @brief Leaves commit order critical section
+   *
+   * Anything executed between commit_order_enter() and this call will be
+   * executed in provider enforced order.
+   *
+   * @param wsrep      provider handle
+   * @param ws_handle  internal provider writeset handle
+   * @param meta       transaction meta data
+   * @param error      buffer containing error info (null/empty for no error)
+   *
+   * @retval WSREP_OK         commit order left successfully
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*commit_order_leave)(wsrep_t*                 wsrep,
+                                         const wsrep_ws_handle_t* ws_handle,
+                                         const wsrep_trx_meta_t*  meta,
+                                         const wsrep_buf_t*       error);
+
+  /*!
+   * @brief Releases resources after transaction commit/rollback.
+   *
+   * Ends total order critical section.
+   *
+   * @param wsrep      provider handle
+   * @param ws_handle  writeset of committing transaction
+   * @retval WSREP_OK  release succeeded
+   */
+    wsrep_status_t (*release) (wsrep_t*            wsrep,
+                               wsrep_ws_handle_t*  ws_handle);
+
+  /*!
+   * @brief Replay trx as a slave writeset
+   *
+   * If local trx has been aborted by brute force, and it has already
+   * replicated before this abort, we must try if we can apply it as
+   * slave trx. Note that slave nodes see only trx writesets and certification
+   * test based on write set content can be different to DBMS lock conflicts.
+   *
+   * @param wsrep      provider handle
+   * @param ws_handle  writeset of committing transaction
+   * @param trx_ctx    transaction context
+   *
+   * @retval WSREP_OK         cluster commit succeeded
+   * @retval WSREP_TRX_FAIL   must rollback transaction
+   * @retval WSREP_BF_ABORT   brute force abort happened after trx replicated
+   *                          must rollback transaction and try to replay
+   * @retval WSREP_CONN_FAIL  must close client connection
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*replay_trx)(wsrep_t*                  wsrep,
+                                 const wsrep_ws_handle_t*  ws_handle,
+                                 void*                     trx_ctx);
+
+  /*!
+   * @brief Abort certify() call of another thread.
+   *
+   * It is possible, that some high-priority transaction needs to abort
+   * another transaction which is in certify() call waiting for resources.
+   *
+   * The kill routine checks that abort is not attempted against a transaction
+   * which is front of the caller (in total order).
+   *
+   * If the abort was successful, the victim sequence number is stored
+   * into location pointed by the victim_seqno.
+   *
+   * @param wsrep      provider handle
+   * @param bf_seqno   seqno of brute force trx, running this cancel
+   * @param victim_trx transaction to be aborted, and which is committing
+   * @param victim_seqno seqno of the victim transaction if assigned
+   *
+   * @retval WSREP_OK          abort succeeded
+   * @retval WSREP_NOT_ALLOWED the provider declined the abort request
+   * @retval WSREP_TRX_MISSING the victim_trx was missing
+   * @retval WSREP_WARNING     abort failed
+   */
+    wsrep_status_t (*abort_certification)(wsrep_t*       wsrep,
+                                          wsrep_seqno_t  bf_seqno,
+                                          wsrep_trx_id_t victim_trx,
+                                          wsrep_seqno_t* victim_seqno);
+
+  /*!
+   * @brief Send a rollback fragment on behalf of trx
+   *
+   * @param wsrep  provider handle
+   * @param trx    transaction to be rolled back
+   * @param data   data to append to the fragment
+   *
+   * @retval WSREP_OK rollback fragment sent successfully
+   */
+    wsrep_status_t (*rollback)(wsrep_t*           wsrep,
+                               wsrep_trx_id_t     trx,
+                               const wsrep_buf_t* data);
+
+  /*!
+   * @brief Appends a row reference to transaction writeset
+   *
+   * Both copy flag and key_type can be ignored by provider (key type
+   * interpreted as WSREP_KEY_EXCLUSIVE).
+   *
+   * @param wsrep      provider handle
+   * @param ws_handle  writeset handle
+   * @param keys       array of keys
+   * @param count      length of the array of keys
+   * @param type       type of the key
+   * @param copy       can be set to FALSE if keys persist through commit.
+   */
+    wsrep_status_t (*append_key)(wsrep_t*            wsrep,
+                                 wsrep_ws_handle_t*  ws_handle,
+                                 const wsrep_key_t*  keys,
+                                 size_t              count,
+                                 enum wsrep_key_type type,
+                                 wsrep_bool_t        copy);
+
+  /*!
+   * @brief Appends data to transaction writeset
+   *
+   * This method can be called any time before certify() call and it appends
+   * a data buffer to the transaction writeset.
+   * Repeated calls of the method will result in direct buffer concatenation
+   * and all data will be passed as a single buffer to the apply callback.
+   *
+   * Both copy and unordered flags can be ignored by provider.
+   *
+   * @param wsrep      provider handle
+   * @param ws_handle  writeset handle
+   * @param data       array of data buffers
+   * @param count      buffer count
+   * @param type       type of data
+   * @param copy       can be set to FALSE if data persists through commit.
+   */
+    wsrep_status_t (*append_data)(wsrep_t*             wsrep,
+                                  wsrep_ws_handle_t*   ws_handle,
+                                  const wsrep_buf_t*   data,
+                                  size_t               count,
+                                  enum wsrep_data_type type,
+                                  wsrep_bool_t         copy);
+
+  /*!
+   * @brief Blocks until the given GTID is committed
+   *
+   * This call will block the caller until the given GTID
+   * is guaranteed to be committed, or until a timeout occurs.
+   * The timeout value is given in parameter tout, if tout is -1,
+   * then the global causal read timeout applies.
+   *
+   * If no pointer upto is provided the call will block until
+   * causal ordering with all possible preceding writes in the
+   * cluster is guaranteed.
+   *
+   * If pointer to gtid is non-null, the call stores the global
+   * transaction ID of the last transaction which is guaranteed
+   * to be committed when the call returns.
+   *
+   * @param wsrep  provider handle
+   * @param upto   gtid to wait upto
+   * @param tout   timeout in seconds
+   *               -1 wait for global causal read timeout
+   * @param gtid   location to store GTID
+   */
+    wsrep_status_t (*sync_wait)(wsrep_t*      wsrep,
+                                wsrep_gtid_t* upto,
+                                int           tout,
+                                wsrep_gtid_t* gtid);
+
+  /*!
+   * @brief Returns the last committed gtid
+   *
+   * @param gtid location to store GTID
+   */
+    wsrep_status_t (*last_committed_id)(wsrep_t*      wsrep,
+                                        wsrep_gtid_t* gtid);
+
+  /*!
+   * @brief Clears allocated connection context.
+   *
+   * Whenever a new connection ID is passed to wsrep provider through
+   * any of the API calls, a connection context is allocated for this
+   * connection. This call is to explicitly notify provider of connection
+   * closing.
+   *
+   * @param wsrep       provider handle
+   * @param conn_id     connection ID
+   * @param query       the 'set database' query
+   * @param query_len   length of query (does not end with 0)
+   */
+    wsrep_status_t (*free_connection)(wsrep_t*        wsrep,
+                                      wsrep_conn_id_t conn_id);
+
+  /*!
+   * @brief Replicates a query and starts "total order isolation" section.
+   *
+   * Regular mode:
+   *
+   * Replicates the action spec and returns success code, which caller must
+   * check. Total order isolation continues until to_execute_end() is called.
+   * Regular "total order isolation" is achieved by calling to_execute_start()
+   * with WSREP_FLAG_TRX_START and WSREP_FLAG_TRX_END set.
+   *
+   * Two-phase mode:
+   *
+   * In this mode a query execution is split in two phases. The first phase is
+   * acquiring total order isolation to access critical section and the
+   * second phase is to release acquired resources in total order.
+   *
+   * To start the first phase the call is made with WSREP_FLAG_TRX_START set.
+   * The action is replicated and success code is returned. The total order
+   * isolation continues until to_execute_end() is called. However, the provider
+   * will keep the reference to the operation for conflict resolution purposes.
+   *
+   * The second phase is started with WSREP_FLAG_TRX_END set. Provider
+   * returns once it has achieved total ordering isolation for second phase.
+   * Total order isolation continues until to_execute_end() is called.
+   * All references to the operation are cleared by provider before
+   * call to to_execute_end() returns.
+   *
+   * @param wsrep       provider handle
+   * @param conn_id     connection ID
+   * @param keys        array of keys
+   * @param keys_num    length of the array of keys
+   * @param action      action buffer array to be executed
+   * @param count       action buffer count
+   * @param flags       flags
+   * @param meta        transaction meta data
+   *
+   * @retval WSREP_OK         cluster commit succeeded
+   * @retval WSREP_CONN_FAIL  must close client connection
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*to_execute_start)(wsrep_t*           wsrep,
+                                       wsrep_conn_id_t    conn_id,
+                                       const wsrep_key_t* keys,
+                                       size_t             keys_num,
+                                       const wsrep_buf_t* action,
+                                       size_t             count,
+                                       uint32_t           flags,
+                                       wsrep_trx_meta_t*  meta);
+
+  /*!
+   * @brief Ends the total order isolation section.
+   *
+   * Marks the end of total order isolation. TO locks are freed
+   * and other transactions are free to commit from this point on.
+   *
+   * @param wsrep   provider handle
+   * @param conn_id connection ID
+   * @param error   error information about TOI operation (empty for no error)
+   *
+   * @retval WSREP_OK         cluster commit succeeded
+   * @retval WSREP_CONN_FAIL  must close client connection
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*to_execute_end)(wsrep_t*           wsrep,
+                                     wsrep_conn_id_t    conn_id,
+                                     const wsrep_buf_t* error);
+
+
+  /*!
+   * @brief Collects preordered replication events into a writeset.
+   *
+   * @param wsrep   wsrep provider handle
+   * @param handle  a handle associated with a given writeset
+   * @param data    an array of data buffers.
+   * @param count   length of data buffer array.
+   * @param copy    whether provider needs to make a copy of events.
+   *
+   * @retval WSREP_OK         cluster-wide commit succeeded
+   * @retval WSREP_TRX_FAIL   operation failed (e.g. trx size exceeded limit)
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*preordered_collect) (wsrep_t*           wsrep,
+                                          wsrep_po_handle_t* handle,
+                                          const wsrep_buf_t* data,
+                                          size_t             count,
+                                          wsrep_bool_t       copy);
+
+  /*!
+   * @brief "Commits" preordered writeset to cluster.
+   *
+   * The contract is that the writeset will be committed in the same (partial)
+   * order this method was called. Frees resources associated with the writeset
+   * handle and reinitializes the handle.
+   *
+   * @param wsrep     wsrep provider handle
+   * @param po_handle a handle associated with a given writeset
+   * @param source_id ID of the event producer, also serves as the partial order
+   *                  or stream ID - events with different source_ids won't be
+   *                  ordered with respect to each other.
+   * @param flags     WSREP_FLAG_... flags
+   * @param pa_range  the number of preceding events this event can be processed
+   *                  in parallel with. A value of 0 means strict serial
+   *                  processing. Note: commits always happen in wsrep order.
+   * @param commit    'true'  to commit writeset to cluster (replicate) or
+   *                  'false' to rollback (cancel) the writeset.
+   *
+   * @retval WSREP_OK         cluster-wide commit succeeded
+   * @retval WSREP_TRX_FAIL   operation failed (e.g. NON-PRIMARY component)
+   * @retval WSREP_NODE_FAIL  must close all connections and reinit
+   */
+    wsrep_status_t (*preordered_commit)  (wsrep_t*             wsrep,
+                                          wsrep_po_handle_t*   handle,
+                                          const wsrep_uuid_t*  source_id,
+                                          uint32_t             flags,
+                                          int                  pa_range,
+                                          wsrep_bool_t         commit);
+
+  /*!
+   * @brief Signals to wsrep provider that state snapshot has been sent to
+   *        joiner.
+   *
+   * @param wsrep    provider handle
+   * @param state_id state ID
+   * @param rcode    0 or negative error code of the operation.
+   */
+    wsrep_status_t (*sst_sent)(wsrep_t*            wsrep,
+                               const wsrep_gtid_t* state_id,
+                               int                 rcode);
+
+  /*!
+   * @brief Signals to wsrep provider that new state snapshot has been received.
+   *        May deadlock if called from sst_prepare_cb.
+   *
+   * @param wsrep     provider handle
+   * @param state_id  state ID
+   * @param state     initial state provided by SST donor
+   * @param rcode     0 or negative error code of the operation.
+   */
+    wsrep_status_t (*sst_received)(wsrep_t*            wsrep,
+                                   const wsrep_gtid_t* state_id,
+                                   const wsrep_buf_t*  state,
+                                   int                 rcode);
+
+
+  /*!
+   * @brief Generate request for consistent snapshot.
+   *
+   * If successful, this call will generate internally SST request
+   * which in turn triggers calling SST donate callback on the nodes
+   * specified in donor_spec. If donor_spec is null, callback is
+   * called only locally. This call will block until sst_sent is called
+   * from callback.
+   *
+   * @param wsrep      provider handle
+   * @param msg        context message for SST donate callback
+   * @param msg_len    length of context message
+   * @param donor_spec list of snapshot donors
+   */
+    wsrep_status_t (*snapshot)(wsrep_t*           wsrep,
+                               const wsrep_buf_t* msg,
+                               const char*        donor_spec);
+
+  /*!
+   * @brief Returns an array of status variables.
+   *        Array is terminated by Null variable name.
+   *
+   * @param wsrep provider handle
+   * @return array of struct wsrep_status_var.
+   */
+    struct wsrep_stats_var* (*stats_get) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Release resources that might be associated with the array.
+   *
+   * @param wsrep     provider handle.
+   * @param var_array array returned by stats_get().
+   */
+    void (*stats_free) (wsrep_t* wsrep, struct wsrep_stats_var* var_array);
+
+  /*!
+   * @brief Reset some stats variables to initial value, provider-dependent.
+   *
+   * @param wsrep provider handle.
+   */
+    void (*stats_reset) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Pauses writeset applying/committing.
+   *
+   * @return global sequence number of the paused state or negative error code.
+   */
+    wsrep_seqno_t (*pause) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Resumes writeset applying/committing.
+   */
+    wsrep_status_t (*resume) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Desynchronize from cluster
+   *
+   * Effectively turns off flow control for this node, allowing it
+   * to fall behind the cluster.
+   */
+    wsrep_status_t (*desync) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Request to resynchronize with cluster.
+   *
+   * Effectively turns on flow control. Asynchronous - actual synchronization
+   * event to be delivered via sync_cb.
+   */
+    wsrep_status_t (*resync) (wsrep_t* wsrep);
+
+  /*!
+   * @brief Acquire global named lock
+   *
+   * @param wsrep  wsrep provider handle
+   * @param name   lock name
+   * @param shared shared or exclusive lock
+   * @param owner  64-bit owner ID
+   * @param tout   timeout in nanoseconds.
+   *               0 - return immediately, -1 wait forever.
+   * @return          wsrep status or negative error code
+   * @retval -EDEADLK lock was already acquired by this thread
+   * @retval -EBUSY   lock was busy
+   */
+    wsrep_status_t (*lock) (wsrep_t* wsrep,
+                            const char* name, wsrep_bool_t shared,
+                            uint64_t owner, int64_t tout);
+
+  /*!
+   * @brief Release global named lock
+   *
+   * @param wsrep   wsrep provider handle
+   * @param name    lock name
+   * @param owner   64-bit owner ID
+   * @return        wsrep status or negative error code
+   * @retval -EPERM lock does not belong to this owner
+   */
+    wsrep_status_t (*unlock) (wsrep_t* wsrep, const char* name, uint64_t owner);
+
+  /*!
+   * @brief Check if global named lock is locked
+   *
+   * @param wsrep wsrep provider handle
+   * @param name  lock name
+   * @param owner if not NULL will contain 64-bit owner ID
+   * @param node  if not NULL will contain owner's node UUID
+   * @return true if lock is locked
+   */
+    wsrep_bool_t (*is_locked) (wsrep_t* wsrep, const char* name, uint64_t* conn,
+                               wsrep_uuid_t* node);
+
+  /*!
+   * wsrep provider name
+   */
+    const char* provider_name;
+
+  /*!
+   * wsrep provider version
+   */
+    const char* provider_version;
+
+  /*!
+   * wsrep provider vendor name
+   */
+    const char* provider_vendor;
+
+  /*!
+   * @brief Frees allocated resources before unloading the library.
+   * @param wsrep provider handle
+   */
+    void (*free)(wsrep_t* wsrep);
+
+    void *dlh;    //!< reserved for future use
+    void *ctx;    //!< reserved for implementation private context
+};
+
+
+/*!
+ *
+ * @brief Loads wsrep library
+ *
+ * @param spec   path to wsrep library. If NULL or WSREP_NONE initializes dummy
+ *               pass-through implementation.
+ * @param hptr   wsrep handle
+ * @param log_cb callback to handle loader messages. Otherwise writes to stderr.
+ *
+ * @return zero on success, errno on failure
+ */
+int wsrep_load(const char* spec, wsrep_t** hptr, wsrep_log_cb_t log_cb);
+
+/*!
+ * @brief Unloads the wsrep library. The application must call
+ * wsrep->free() before unload to release library side resources.
+ *
+ * @param hptr wsrep handler pointer
+ */
+void wsrep_unload(wsrep_t* hptr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* WSREP_H */