/* * Copyright (c) 2016 MariaDB Corporation Ab * * Use of this software is governed by the Business Source License included * in the LICENSE.TXT file and at www.mariadb.com/bsl. * * Change Date: 2019-07-01 * * On the date above, in accordance with the Business Source License, use * of this software will be governed by version 2 or later of the General * Public License. */ #include #include #include #include #include #include #include "readwritesplit.h" #include "rwsplit_internal.h" #include #include #include #include #include #include #include MODULE_INFO info = { MODULE_API_ROUTER, MODULE_GA, ROUTER_VERSION, "A Read/Write splitting router for enhancement read scalability" }; /** * @file readwritesplit.c The entry points for the read/write query splitting * router module. * * This file contains the entry points that comprise the API to the read write * query splitting router. It also contains functions that are directly called * by the entry point functions. Some of these are used by functions in other * modules of the read write split router, others are used only within this * module. * * @verbatim * Revision History * * Date Who Description * 01/07/2013 Vilho Raatikka Initial implementation * 15/07/2013 Massimiliano Pinto Added clientReply from master only in case * of session change * 17/07/2013 Massimiliano Pinto clientReply is now used by mysql_backend * for all reply situations * 18/07/2013 Massimiliano Pinto routeQuery now handles COM_QUIT * as QUERY_TYPE_SESSION_WRITE * 17/07/2014 Massimiliano Pinto Server connection counter is updated in * closeSession * 09/09/2015 Martin Brampton Modify error handler * 25/09/2015 Martin Brampton Block callback processing when no router * session in the DCB * 03/08/2016 Martin Brampton Extract the API functions, move the rest * * @endverbatim */ /** Maximum number of slaves */ #define MAX_SLAVE_COUNT 255 static char *version_str = "V1.1.0"; /* * The functions that implement the router module API */ static ROUTER *createInstance(SERVICE *service, char **options); static void *newSession(ROUTER *instance, SESSION *session); static void closeSession(ROUTER *instance, void *session); static void freeSession(ROUTER *instance, void *session); static int routeQuery(ROUTER *instance, void *session, GWBUF *queue); static void diagnostics(ROUTER *instance, DCB *dcb); static void clientReply(ROUTER *instance, void *router_session, GWBUF *queue, DCB *backend_dcb); static void handleError(ROUTER *instance, void *router_session, GWBUF *errmsgbuf, DCB *backend_dcb, error_action_t action, bool *succp); static uint64_t getCapabilities(void); /* * End of the API functions; now the module structure that links to them. * Note that the function names are chosen to exactly match the names used in * the definition of ROUTER_OBJECT. This is not obligatory, but is done to * make it easier to track the connection between calls and functions. */ static ROUTER_OBJECT MyObject = { createInstance, newSession, closeSession, freeSession, routeQuery, diagnostics, clientReply, handleError, getCapabilities }; /* * Declaration of functions that are used only within this module, and are * not part of the API. */ static void refreshInstance(ROUTER_INSTANCE *router, CONFIG_PARAMETER *singleparam); static void free_rwsplit_instance(ROUTER_INSTANCE *router); static bool rwsplit_process_router_options(ROUTER_INSTANCE *router, char **options); static void handle_error_reply_client(SESSION *ses, ROUTER_CLIENT_SES *rses, DCB *backend_dcb, GWBUF *errmsg); static bool handle_error_new_connection(ROUTER_INSTANCE *inst, ROUTER_CLIENT_SES **rses, DCB *backend_dcb, GWBUF *errmsg); static bool have_enough_servers(ROUTER_CLIENT_SES *rses, const int min_nsrv, int router_nsrv, ROUTER_INSTANCE *router); static bool create_backends(ROUTER_CLIENT_SES *rses, backend_ref_t** dest, int* n_backend); /** * Implementation of the mandatory version entry point * * @return version string of the module */ char *version() { return version_str; } /** * The module initialization routine, called when the module * is first loaded. */ void ModuleInit() { MXS_NOTICE("Initializing statement-based read/write split router module."); } /** * The module entry point routine. It is this routine that * must return the structure that is referred to as the * "module object", this is a structure with the set of * external entry points for this module. * * @return The module object */ ROUTER_OBJECT *GetModuleObject() { return &MyObject; } /* * Now we implement the API functions */ /** * @brief Create an instance of the read/write router (API). * * Create an instance of read/write statement router within the MaxScale. One * instance of the router is required for each service that is defined in the * configuration as using this router. One instance of the router will handle * multiple connections (or router sessions). * * @param service The service this router is being create for * @param options The options for this query router * @return NULL in failure, pointer to router in success. */ static ROUTER *createInstance(SERVICE *service, char **options) { ROUTER_INSTANCE *router; CONFIG_PARAMETER *param; if ((router = MXS_CALLOC(1, sizeof(ROUTER_INSTANCE))) == NULL) { return NULL; } router->service = service; spinlock_init(&router->lock); /* * Until we know otherwise assume we have some available slaves. */ router->available_slaves = true; /** Enable strict multistatement handling by default */ router->rwsplit_config.rw_strict_multi_stmt = true; /** By default, the client connection is closed immediately when a master * failure is detected */ router->rwsplit_config.rw_master_failure_mode = RW_FAIL_INSTANTLY; /** Call this before refreshInstance */ if (options && !rwsplit_process_router_options(router, options)) { free_rwsplit_instance(router); return NULL; } /** These options cancel each other out */ if (router->rwsplit_config.rw_disable_sescmd_hist && router->rwsplit_config.rw_max_sescmd_history_size > 0) { router->rwsplit_config.rw_max_sescmd_history_size = 0; } /** * Set default value for max_slave_connections as 100%. This way * LEAST_CURRENT_OPERATIONS allows us to balance evenly across all the * configured slaves. */ router->rwsplit_config.rw_max_slave_conn_count = MAX_SLAVE_COUNT; if (router->rwsplit_config.rw_slave_select_criteria == UNDEFINED_CRITERIA) { router->rwsplit_config.rw_slave_select_criteria = DEFAULT_CRITERIA; } /** * Copy all config parameters from service to router instance. * Finally, copy version number to indicate that configs match. */ param = config_get_param(service->svc_config_param, "max_slave_connections"); if (param != NULL) { refreshInstance(router, param); } /** * Read default value for slave replication lag upper limit and then * configured value if it exists. */ router->rwsplit_config.rw_max_slave_replication_lag = CONFIG_MAX_SLAVE_RLAG; param = config_get_param(service->svc_config_param, "max_slave_replication_lag"); if (param != NULL) { refreshInstance(router, param); } router->rwsplit_version = service->svc_config_version; /** Set default values */ router->rwsplit_config.rw_use_sql_variables_in = CONFIG_SQL_VARIABLES_IN; param = config_get_param(service->svc_config_param, "use_sql_variables_in"); if (param != NULL) { refreshInstance(router, param); } return (ROUTER *)router; } /** * @brief Associate a new session with this instance of the router (API). * * The session is used to store all the data required by the router for a * particular client connection. The instance of the router that relates to a * particular service is passed as the first parameter. The second parameter is * the session that has been created in response to the request from a client * for a connection. The passed session contains generic information; this * function creates the session structure that holds router specific data. * There is often a one to one relationship between sessions and router * sessions, although it is possible to create configurations where a * connection is handled by multiple routers, one after another. * * @param instance The router instance data * @param session The MaxScale session (generic connection data) * @return Session specific data for this session, i.e. a router session */ static void *newSession(ROUTER *router_inst, SESSION *session) { ROUTER_INSTANCE *router = (ROUTER_INSTANCE *)router_inst; ROUTER_CLIENT_SES *client_rses = (ROUTER_CLIENT_SES *)MXS_CALLOC(1, sizeof(ROUTER_CLIENT_SES)); if (client_rses == NULL) { return NULL; } #if defined(SS_DEBUG) client_rses->rses_chk_top = CHK_NUM_ROUTER_SES; client_rses->rses_chk_tail = CHK_NUM_ROUTER_SES; #endif client_rses->router = router; client_rses->client_dcb = session->client_dcb; client_rses->rses_autocommit_enabled = true; client_rses->rses_transaction_active = false; client_rses->have_tmp_tables = false; client_rses->forced_node = NULL; spinlock_init(&client_rses->rses_lock); memcpy(&client_rses->rses_config, &router->rwsplit_config, sizeof(client_rses->rses_config)); int router_nservers = router->service->n_dbref; const int min_nservers = 1; /*< hard-coded for now */ if (!have_enough_servers(client_rses, min_nservers, router_nservers, router)) { MXS_FREE(client_rses); return NULL; } /** * Create backend reference objects for this session. */ backend_ref_t *backend_ref; if (!create_backends(client_rses, &backend_ref, &router_nservers)) { MXS_FREE(client_rses); return NULL; } int max_nslaves = rses_get_max_slavecount(client_rses, router_nservers); int max_slave_rlag = rses_get_max_replication_lag(client_rses); client_rses->rses_backend_ref = backend_ref; client_rses->rses_nbackends = router_nservers; /*< # of backend servers */ backend_ref_t *master_ref = NULL; /*< pointer to selected master */ if (!select_connect_backend_servers(&master_ref, backend_ref, router_nservers, max_nslaves, max_slave_rlag, client_rses->rses_config.rw_slave_select_criteria, session, router)) { /** * Master and at least slaves must be found if the router is * in the strict mode. If sessions without master are allowed, only * slaves must be found. */ MXS_FREE(client_rses->rses_backend_ref); MXS_FREE(client_rses); return NULL; } /** Copy backend pointers to router session. */ client_rses->rses_master_ref = master_ref; if (client_rses->rses_config.rw_max_slave_conn_percent) { int n_conn = 0; double pct = (double)client_rses->rses_config.rw_max_slave_conn_percent / 100.0; n_conn = MXS_MAX(floor((double)client_rses->rses_nbackends * pct), 1); client_rses->rses_config.rw_max_slave_conn_count = n_conn; } router->stats.n_sessions += 1; return (void *)client_rses; } /** * @brief Close a router session (API). * * Close a session with the router, this is the mechanism by which a router * may cleanup data structure etc. The instance of the router that relates to * the relevant service is passed, along with the router session that is to * be closed. Typically the function is used in conjunction with freeSession * which will release the resources used by a router session (see below). * * @param instance The router instance data * @param session The router session being closed */ static void closeSession(ROUTER *instance, void *router_session) { ROUTER_CLIENT_SES *router_cli_ses = (ROUTER_CLIENT_SES *)router_session; CHK_CLIENT_RSES(router_cli_ses); if (!router_cli_ses->rses_closed && rses_begin_locked_router_action(router_cli_ses)) { /** * Mark router session as closed. @c rses_closed is checked at the start * of every API function to quickly stop the processing of closed sessions. */ router_cli_ses->rses_closed = true; for (int i = 0; i < router_cli_ses->rses_nbackends; i++) { backend_ref_t *bref = &router_cli_ses->rses_backend_ref[i]; if (BREF_IS_IN_USE(bref)) { /** This backend is in use and it needs to be closed */ DCB *dcb = bref->bref_dcb; CHK_DCB(dcb); ss_dassert(dcb->session->state == SESSION_STATE_STOPPING); if (BREF_IS_WAITING_RESULT(bref)) { /** This backend was executing a query when the session was closed */ bref_clear_state(bref, BREF_WAITING_RESULT); } bref_clear_state(bref, BREF_IN_USE); bref_set_state(bref, BREF_CLOSED); dcb_close(dcb); /** Decrease server reference connection count */ atomic_add(&bref->ref->connections, -1); } else { ss_dassert(!BREF_IS_WAITING_RESULT(bref)); /** This should never be true unless a backend reference is taken * out of use before clearing the BREF_WAITING_RESULT state */ if (BREF_IS_WAITING_RESULT(bref)) { MXS_WARNING("A closed backend was expecting a result, this should not be possible. " "Decrementing active operation counter for this backend."); bref_clear_state(bref, BREF_WAITING_RESULT); } } } rses_end_locked_router_action(router_cli_ses); } } /** * @brief Free a router session (API). * * When a router session has been closed, freeSession can be called to free * allocated resources. * * @param router_instance The router instance the session belongs to * @param router_client_session Client session * */ static void freeSession(ROUTER *router_instance, void *router_client_session) { ROUTER_CLIENT_SES *router_cli_ses = (ROUTER_CLIENT_SES *)router_client_session; /** * For each property type, walk through the list, finalize properties * and free the allocated memory. */ for (int i = RSES_PROP_TYPE_FIRST; i < RSES_PROP_TYPE_COUNT; i++) { rses_property_t *p = router_cli_ses->rses_properties[i]; rses_property_t *q = p; while (p != NULL) { q = p->rses_prop_next; rses_property_done(p); p = q; } } MXS_FREE(router_cli_ses->rses_backend_ref); MXS_FREE(router_cli_ses); return; } /** * @brief The main routing entry point for a query (API) * * The routeQuery function will make the routing decision based on the contents * of the instance, session and the query itself. The query always represents * a complete MariaDB/MySQL packet because we define the RCAP_TYPE_STMT_INPUT in * getCapabilities(). * * @param instance Router instance * @param router_session Router session associated with the client * @param querybuf Buffer containing the query * @return 1 on success, 0 on error */ static int routeQuery(ROUTER *instance, void *router_session, GWBUF *querybuf) { ROUTER_INSTANCE *inst = (ROUTER_INSTANCE *) instance; ROUTER_CLIENT_SES *rses = (ROUTER_CLIENT_SES *) router_session; int rval = 0; CHK_CLIENT_RSES(rses); if (rses->rses_closed) { closed_session_reply(querybuf); } else { live_session_reply(&querybuf, rses); if (route_single_stmt(inst, rses, querybuf)) { rval = 1; } } if (querybuf != NULL) { gwbuf_free(querybuf); } return rval; } /** * @brief Diagnostics routine (API) * * Print query router statistics to the DCB passed in * * @param instance The router instance * @param dcb The DCB for diagnostic output */ static void diagnostics(ROUTER *instance, DCB *dcb) { ROUTER_INSTANCE *router = (ROUTER_INSTANCE *)instance; char *weightby; double master_pct = 0.0, slave_pct = 0.0, all_pct = 0.0; if (router->stats.n_queries > 0) { master_pct = ((double)router->stats.n_master / (double)router->stats.n_queries) * 100.0; slave_pct = ((double)router->stats.n_slave / (double)router->stats.n_queries) * 100.0; all_pct = ((double)router->stats.n_all / (double)router->stats.n_queries) * 100.0; } dcb_printf(dcb, "\tNumber of router sessions: %d\n", router->stats.n_sessions); dcb_printf(dcb, "\tCurrent no. of router sessions: %d\n", router->service->stats.n_current); dcb_printf(dcb, "\tNumber of queries forwarded: %d\n", router->stats.n_queries); dcb_printf(dcb, "\tNumber of queries forwarded to master: %d (%.2f%%)\n", router->stats.n_master, master_pct); dcb_printf(dcb, "\tNumber of queries forwarded to slave: %d (%.2f%%)\n", router->stats.n_slave, slave_pct); dcb_printf(dcb, "\tNumber of queries forwarded to all: %d (%.2f%%)\n", router->stats.n_all, all_pct); if ((weightby = serviceGetWeightingParameter(router->service)) != NULL) { dcb_printf(dcb, "\tConnection distribution based on %s " "server parameter.\n", weightby); dcb_printf(dcb, "\t\tServer Target %% Connections " "Operations\n"); dcb_printf(dcb, "\t\t Global Router\n"); for (SERVER_REF *ref = router->service->dbref; ref; ref = ref->next) { dcb_printf(dcb, "\t\t%-20s %3.1f%% %-6d %-6d %d\n", ref->server->unique_name, (float)ref->weight / 10, ref->server->stats.n_current, ref->connections, ref->server->stats.n_current_ops); } } } /** * @brief Client Reply routine (API) * * The routine will reply to client for session change with master server data * * @param instance The router instance * @param router_session The router session * @param backend_dcb The backend DCB * @param queue The GWBUF with reply data */ static void clientReply(ROUTER *instance, void *router_session, GWBUF *writebuf, DCB *backend_dcb) { DCB *client_dcb; ROUTER_INSTANCE *router_inst; ROUTER_CLIENT_SES *router_cli_ses; sescmd_cursor_t *scur = NULL; backend_ref_t *bref; router_cli_ses = (ROUTER_CLIENT_SES *)router_session; router_inst = (ROUTER_INSTANCE *)instance; CHK_CLIENT_RSES(router_cli_ses); /** * Lock router client session for secure read of router session members. * Note that this could be done without lock by using version # */ if (!rses_begin_locked_router_action(router_cli_ses)) { gwbuf_free(writebuf); goto lock_failed; } /** Holding lock ensures that router session remains open */ ss_dassert(backend_dcb->session != NULL); client_dcb = backend_dcb->session->client_dcb; /** Unlock */ rses_end_locked_router_action(router_cli_ses); /** * 1. Check if backend received reply to sescmd. * 2. Check sescmd's state whether OK_PACKET has been * sent to client already and if not, lock property cursor, * reply to client, and move property cursor forward. Finally * release the lock. * 3. If reply for this sescmd is sent, lock property cursor * and */ if (client_dcb == NULL) { gwbuf_free(writebuf); /** Log that client was closed before reply */ goto lock_failed; } /** Lock router session */ if (!rses_begin_locked_router_action(router_cli_ses)) { /** Log to debug that router was closed */ goto lock_failed; } bref = get_bref_from_dcb(router_cli_ses, backend_dcb); #if !defined(FOR_BUG548_FIX_ONLY) /** This makes the issue becoming visible in poll.c */ if (bref == NULL) { /** Unlock router session */ rses_end_locked_router_action(router_cli_ses); goto lock_failed; } #endif CHK_BACKEND_REF(bref); scur = &bref->bref_sescmd_cur; /** * Active cursor means that reply is from session command * execution. */ if (sescmd_cursor_is_active(scur)) { check_session_command_reply(writebuf, scur, bref); if (GWBUF_IS_TYPE_SESCMD_RESPONSE(writebuf)) { /** * Discard all those responses that have already been sent to * the client. Return with buffer including response that * needs to be sent to client or NULL. */ bool rconn = false; writebuf = sescmd_cursor_process_replies(writebuf, bref, &rconn); if (rconn && !router_inst->rwsplit_config.rw_disable_sescmd_hist) { select_connect_backend_servers( &router_cli_ses->rses_master_ref, router_cli_ses->rses_backend_ref, router_cli_ses->rses_nbackends, router_cli_ses->rses_config.rw_max_slave_conn_count, router_cli_ses->rses_config.rw_max_slave_replication_lag, router_cli_ses->rses_config.rw_slave_select_criteria, router_cli_ses->rses_master_ref->bref_dcb->session, router_cli_ses->router); } } /** * If response will be sent to client, decrease waiter count. * This applies to session commands only. Counter decrement * for other type of queries is done outside this block. */ /** Set response status as replied */ bref_clear_state(bref, BREF_WAITING_RESULT); } /** * Clear BREF_QUERY_ACTIVE flag and decrease waiter counter. * This applies for queries other than session commands. */ else if (BREF_IS_QUERY_ACTIVE(bref)) { bref_clear_state(bref, BREF_QUERY_ACTIVE); /** Set response status as replied */ bref_clear_state(bref, BREF_WAITING_RESULT); } if (writebuf != NULL && client_dcb != NULL) { /** Write reply to client DCB */ SESSION_ROUTE_REPLY(backend_dcb->session, writebuf); } /** Unlock router session */ rses_end_locked_router_action(router_cli_ses); /** Lock router session */ if (!rses_begin_locked_router_action(router_cli_ses)) { /** Log to debug that router was closed */ goto lock_failed; } /** There is one pending session command to be executed. */ if (sescmd_cursor_is_active(scur)) { bool succp; MXS_INFO("Backend %s:%d processed reply and starts to execute active cursor.", bref->ref->server->name, bref->ref->server->port); succp = execute_sescmd_in_backend(bref); if (!succp) { MXS_INFO("Backend %s:%d failed to execute session command.", bref->ref->server->name, bref->ref->server->port); } } else if (bref->bref_pending_cmd != NULL) /*< non-sescmd is waiting to be routed */ { int ret; CHK_GWBUF(bref->bref_pending_cmd); if ((ret = bref->bref_dcb->func.write(bref->bref_dcb, gwbuf_clone(bref->bref_pending_cmd))) == 1) { ROUTER_INSTANCE* inst = (ROUTER_INSTANCE *)instance; atomic_add(&inst->stats.n_queries, 1); /** * Add one query response waiter to backend reference */ bref_set_state(bref, BREF_QUERY_ACTIVE); bref_set_state(bref, BREF_WAITING_RESULT); } else { char* sql = modutil_get_SQL(bref->bref_pending_cmd); if (sql) { MXS_ERROR("Routing query \"%s\" failed.", sql); MXS_FREE(sql); } else { MXS_ERROR("Failed to route query."); } } gwbuf_free(bref->bref_pending_cmd); bref->bref_pending_cmd = NULL; } /** Unlock router session */ rses_end_locked_router_action(router_cli_ses); lock_failed: return; } /** * @brief Get router capabilities (API) * * Return a bit map indicating the characteristics of this particular router. * In this case, the only bit set indicates that the router wants to receive * data for routing as whole SQL statements. * * @return RCAP_TYPE_STMT_INPUT. */ static uint64_t getCapabilities(void) { return RCAP_TYPE_STMT_INPUT; } /* * This is the end of the API functions, and the start of functions that are * used by the API functions and also used in other modules of the router * code. Their prototypes are included in rwsplit_internal.h since these * functions are not intended for use outside the read write split router. */ /** * @brief Acquires lock to router client session if it is not closed. * * Parameters: * @param rses - in, use * * * @return true if router session was not closed. If return value is true * it means that router is locked, and must be unlocked later. False, if * router was closed before lock was acquired. * */ bool rses_begin_locked_router_action(ROUTER_CLIENT_SES *rses) { bool succp = false; if (rses == NULL) { return false; } CHK_CLIENT_RSES(rses); if (rses->rses_closed) { goto return_succp; } spinlock_acquire(&rses->rses_lock); if (rses->rses_closed) { spinlock_release(&rses->rses_lock); goto return_succp; } succp = true; return_succp: return succp; } /** to be inline'd */ /** * @brief Releases router client session lock. * * Parameters: * @param rses - * * * @return void * */ void rses_end_locked_router_action(ROUTER_CLIENT_SES *rses) { CHK_CLIENT_RSES(rses); spinlock_release(&rses->rses_lock); } /* * @brief Clear one or more bits in the backend reference state * * The router session holds details of the backend servers that are * involved in the routing for this particular service. Each backend * server has a state bit string, and this function (along with * bref_set_state) is used to manage the state. * * @param bref The backend reference to be modified * @param state A bit string where the 1 bits indicate bits that should * be turned off in the bref state. */ void bref_clear_state(backend_ref_t *bref, bref_state_t state) { if (bref == NULL) { MXS_ERROR("[%s] Error: NULL parameter.", __FUNCTION__); return; } if ((state & BREF_WAITING_RESULT) && (bref->bref_state & BREF_WAITING_RESULT)) { int prev1; int prev2; /** Decrease waiter count */ prev1 = atomic_add(&bref->bref_num_result_wait, -1); if (prev1 <= 0) { atomic_add(&bref->bref_num_result_wait, 1); } else { /** Decrease global operation count */ prev2 = atomic_add(&bref->ref->server->stats.n_current_ops, -1); ss_dassert(prev2 > 0); if (prev2 <= 0) { MXS_ERROR("[%s] Error: negative current operation count in backend %s:%u", __FUNCTION__, bref->ref->server->name, bref->ref->server->port); } } } bref->bref_state &= ~state; } /* * @brief Set one or more bits in the backend reference state * * The router session holds details of the backend servers that are * involved in the routing for this particular service. Each backend * server has a state bit string, and this function (along with * bref_clear_state) is used to manage the state. * * @param bref The backend reference to be modified * @param state A bit string where the 1 bits indicate bits that should * be turned on in the bref state. */ void bref_set_state(backend_ref_t *bref, bref_state_t state) { if (bref == NULL) { MXS_ERROR("[%s] Error: NULL parameter.", __FUNCTION__); return; } if ((state & BREF_WAITING_RESULT) && (bref->bref_state & BREF_WAITING_RESULT) == 0) { int prev1; int prev2; /** Increase waiter count */ prev1 = atomic_add(&bref->bref_num_result_wait, 1); ss_dassert(prev1 >= 0); if (prev1 < 0) { MXS_ERROR("[%s] Error: negative number of connections waiting for " "results in backend %s:%u", __FUNCTION__, bref->ref->server->name, bref->ref->server->port); } /** Increase global operation count */ prev2 = atomic_add(&bref->ref->server->stats.n_current_ops, 1); ss_dassert(prev2 >= 0); if (prev2 < 0) { MXS_ERROR("[%s] Error: negative current operation count in backend %s:%u", __FUNCTION__, bref->ref->server->name, bref->ref->server->port); } } bref->bref_state |= state; } /** * @brief Free resources belonging to a property * * Property is freed at the end of router client session. * * @param prop The property whose resources are to be released */ void rses_property_done(rses_property_t *prop) { if (prop == NULL) { MXS_ERROR("[%s] Error: NULL parameter.", __FUNCTION__); return; } CHK_RSES_PROP(prop); switch (prop->rses_prop_type) { case RSES_PROP_TYPE_SESCMD: mysql_sescmd_done(&prop->rses_prop_data.sescmd); break; case RSES_PROP_TYPE_TMPTABLES: hashtable_free(prop->rses_prop_data.temp_tables); break; default: MXS_DEBUG("%lu [rses_property_done] Unknown property type %d " "in property %p", pthread_self(), prop->rses_prop_type, prop); ss_dassert(false); break; } MXS_FREE(prop); } /** * @brief Get count of backend servers that are slaves. * * Find out the number of read backend servers. * Depending on the configuration value type, either copy direct count * of slave connections or calculate the count from percentage value. * * @param rses Router client session * @param router_nservers The number of backend servers in total */ int rses_get_max_slavecount(ROUTER_CLIENT_SES *rses, int router_nservers) { int conf_max_nslaves; int max_nslaves; CHK_CLIENT_RSES(rses); if (rses->rses_config.rw_max_slave_conn_count > 0) { conf_max_nslaves = rses->rses_config.rw_max_slave_conn_count; } else { conf_max_nslaves = (router_nservers * rses->rses_config.rw_max_slave_conn_percent) / 100; } max_nslaves = MXS_MIN(router_nservers - 1, MXS_MAX(1, conf_max_nslaves)); return max_nslaves; } /* * @brief Get the maximum replication lag for this router * * @param rses Router client session * @return Replication lag from configuration or very large number */ int rses_get_max_replication_lag(ROUTER_CLIENT_SES *rses) { int conf_max_rlag; CHK_CLIENT_RSES(rses); /** if there is no configured value, then longest possible int is used */ if (rses->rses_config.rw_max_slave_replication_lag > 0) { conf_max_rlag = rses->rses_config.rw_max_slave_replication_lag; } else { conf_max_rlag = ~(1 << 31); } return conf_max_rlag; } /** * @brief Find a back end reference that matches the given DCB * * Finds out if there is a backend reference pointing at the DCB given as * parameter. * * @param rses router client session * @param dcb DCB * * @return backend reference pointer if succeed or NULL */ backend_ref_t *get_bref_from_dcb(ROUTER_CLIENT_SES *rses, DCB *dcb) { backend_ref_t *bref; int i = 0; CHK_DCB(dcb); CHK_CLIENT_RSES(rses); bref = rses->rses_backend_ref; while (i < rses->rses_nbackends) { if (bref->bref_dcb == dcb) { break; } bref++; i += 1; } if (i == rses->rses_nbackends) { bref = NULL; } return bref; } /** * @brief Call hang up function * * Calls hang-up function for DCB if it is not both running and in * master/slave/joined/ndb role. Called by DCB's callback routine. * * @param dcb DCB relating to a backend server * @param reason The reason for the state change * @param data Data is a backend reference structure belonging to this router * * @return 1 for success, 0 for failure */ int router_handle_state_switch(DCB *dcb, DCB_REASON reason, void *data) { backend_ref_t *bref; int rc = 1; SERVER *srv; CHK_DCB(dcb); if (NULL == dcb->session->router_session) { /* * The following processing will fail if there is no router session, * because the "data" parameter will not contain meaningful data, * so we have no choice but to stop here. */ return 0; } bref = (backend_ref_t *)data; CHK_BACKEND_REF(bref); srv = bref->ref->server; if (SERVER_IS_RUNNING(srv) && SERVER_IS_IN_CLUSTER(srv)) { goto return_rc; } MXS_DEBUG("%lu [router_handle_state_switch] %s %s:%d in state %s", pthread_self(), STRDCBREASON(reason), srv->name, srv->port, STRSRVSTATUS(srv)); CHK_SESSION(((SESSION *)dcb->session)); if (dcb->session->router_session) { CHK_CLIENT_RSES(((ROUTER_CLIENT_SES *)dcb->session->router_session)); } switch (reason) { case DCB_REASON_NOT_RESPONDING: dcb->func.hangup(dcb); break; default: break; } return_rc: return rc; } /* * The end of the functions used here and elsewhere in the router; start of * functions that are purely internal to this module, i.e. are called directly * or indirectly by the API functions and not used elsewhere. */ /** * @brief Process router options * * @param router Router instance * @param options Router options * @return True on success, false if a configuration error was found */ static bool rwsplit_process_router_options(ROUTER_INSTANCE *router, char **options) { int i; char *value; select_criteria_t c; if (options == NULL) { return true; } bool success = true; for (i = 0; options[i]; i++) { if ((value = strchr(options[i], '=')) == NULL) { MXS_ERROR("Unsupported router option \"%s\" for readwritesplit router.", options[i]); success = false; } else { *value = 0; value++; if (strcmp(options[i], "slave_selection_criteria") == 0) { c = GET_SELECT_CRITERIA(value); ss_dassert(c == LEAST_GLOBAL_CONNECTIONS || c == LEAST_ROUTER_CONNECTIONS || c == LEAST_BEHIND_MASTER || c == LEAST_CURRENT_OPERATIONS || c == UNDEFINED_CRITERIA); if (c == UNDEFINED_CRITERIA) { MXS_ERROR("Unknown slave selection criteria \"%s\". " "Allowed values are LEAST_GLOBAL_CONNECTIONS, " "LEAST_ROUTER_CONNECTIONS, LEAST_BEHIND_MASTER," "and LEAST_CURRENT_OPERATIONS.", STRCRITERIA(router->rwsplit_config.rw_slave_select_criteria)); success = false; } else { router->rwsplit_config.rw_slave_select_criteria = c; } } else if (strcmp(options[i], "max_sescmd_history") == 0) { router->rwsplit_config.rw_max_sescmd_history_size = atoi(value); } else if (strcmp(options[i], "disable_sescmd_history") == 0) { router->rwsplit_config.rw_disable_sescmd_hist = config_truth_value(value); } else if (strcmp(options[i], "master_accept_reads") == 0) { router->rwsplit_config.rw_master_reads = config_truth_value(value); } else if (strcmp(options[i], "strict_multi_stmt") == 0) { router->rwsplit_config.rw_strict_multi_stmt = config_truth_value(value); } else if (strcmp(options[i], "master_failure_mode") == 0) { if (strcasecmp(value, "fail_instantly") == 0) { router->rwsplit_config.rw_master_failure_mode = RW_FAIL_INSTANTLY; } else if (strcasecmp(value, "fail_on_write") == 0) { router->rwsplit_config.rw_master_failure_mode = RW_FAIL_ON_WRITE; } else if (strcasecmp(value, "error_on_write") == 0) { router->rwsplit_config.rw_master_failure_mode = RW_ERROR_ON_WRITE; } else { MXS_ERROR("Unknown value for 'master_failure_mode': %s", value); success = false; } } else { MXS_ERROR("Unknown router option \"%s=%s\" for readwritesplit router.", options[i], value); success = false; } } } /*< for */ return success; } /** * @brief Router error handling routine (API) * * Error Handler routine to resolve _backend_ failures. If it succeeds then * there are enough operative backends available and connected. Otherwise it * fails, and session is terminated. * * @param instance The router instance * @param router_session The router session * @param errmsgbuf The error message to reply * @param backend_dcb The backend DCB * @param action The action: ERRACT_NEW_CONNECTION or * ERRACT_REPLY_CLIENT * @param succp Result of action: true iff router can continue * * Even if succp == true connecting to new slave may have failed. succp is to * tell whether router has enough master/slave connections to continue work. */ static void handleError(ROUTER *instance, void *router_session, GWBUF *errmsgbuf, DCB *problem_dcb, error_action_t action, bool *succp) { SESSION *session; ROUTER_INSTANCE *inst = (ROUTER_INSTANCE *)instance; ROUTER_CLIENT_SES *rses = (ROUTER_CLIENT_SES *)router_session; CHK_DCB(problem_dcb); /** Don't handle same error twice on same DCB */ if (problem_dcb->dcb_errhandle_called) { /** we optimistically assume that previous call succeed */ /* * The return of true is potentially misleading, but appears to * be safe with the code as it stands on 9 Sept 2015 - MNB */ *succp = true; return; } else { problem_dcb->dcb_errhandle_called = true; } session = problem_dcb->session; bool close_dcb = true; if (session == NULL || rses == NULL) { *succp = false; } else if (DCB_ROLE_CLIENT_HANDLER == problem_dcb->dcb_role) { *succp = false; } else { CHK_SESSION(session); CHK_CLIENT_RSES(rses); switch (action) { case ERRACT_NEW_CONNECTION: { if (!rses_begin_locked_router_action(rses)) { close_dcb = false; /* With the assumption that if the router session is closed, * then so is the dcb. */ *succp = false; break; } /** * If master has lost its Master status error can't be * handled so that session could continue. */ if (rses->rses_master_ref && rses->rses_master_ref->bref_dcb == problem_dcb && !SERVER_IS_MASTER(rses->rses_master_ref->ref->server)) { SERVER *srv = rses->rses_master_ref->ref->server; backend_ref_t *bref; bref = get_bref_from_dcb(rses, problem_dcb); if (bref != NULL) { CHK_BACKEND_REF(bref); if (BREF_IS_WAITING_RESULT(bref)) { bref_clear_state(bref, BREF_WAITING_RESULT); } bref_clear_state(bref, BREF_IN_USE); bref_set_state(bref, BREF_CLOSED); } else { MXS_ERROR("server %s:%d lost the " "master status but could not locate the " "corresponding backend ref.", srv->name, srv->port); } if (rses->rses_config.rw_master_failure_mode != RW_FAIL_INSTANTLY && (bref == NULL || !BREF_IS_WAITING_RESULT(bref))) { /** The failure of a master is not considered a critical * failure as partial functionality still remains. Reads * are allowed as long as slave servers are available * and writes will cause an error to be returned. * * If we were waiting for a response from the master, we * can't be sure whether it was executed or not. In this * case the safest thing to do is to close the client * connection. */ *succp = true; } else { if (!srv->master_err_is_logged) { MXS_ERROR("server %s:%d lost the " "master status. Readwritesplit " "service can't locate the master. " "Client sessions will be closed.", srv->name, srv->port); srv->master_err_is_logged = true; } *succp = false; } } else { /** * This is called in hope of getting replacement for * failed slave(s). This call may free rses. */ *succp = handle_error_new_connection(inst, &rses, problem_dcb, errmsgbuf); } dcb_close(problem_dcb); close_dcb = false; /* Free the lock if rses still exists */ if (rses) { rses_end_locked_router_action(rses); } break; } case ERRACT_REPLY_CLIENT: { handle_error_reply_client(session, rses, problem_dcb, errmsgbuf); close_dcb = false; *succp = false; /*< no new backend servers were made available */ break; } default: ss_dassert(!true); *succp = false; break; } } if (close_dcb) { dcb_close(problem_dcb); } } /** * @brief Handle an error reply for a client * * @param ses Session * @param rses Router session * @param backend_dcb DCB for the backend server that has failed * @param errmsg GWBUF containing the error message */ static void handle_error_reply_client(SESSION *ses, ROUTER_CLIENT_SES *rses, DCB *backend_dcb, GWBUF *errmsg) { session_state_t sesstate; DCB *client_dcb; backend_ref_t *bref; spinlock_acquire(&ses->ses_lock); sesstate = ses->state; client_dcb = ses->client_dcb; spinlock_release(&ses->ses_lock); if (rses_begin_locked_router_action(rses)) { /** * If bref exists, mark it closed */ if ((bref = get_bref_from_dcb(rses, backend_dcb)) != NULL) { CHK_BACKEND_REF(bref); if (BREF_IS_IN_USE(bref)) { bref_clear_state(bref, BREF_IN_USE); bref_set_state(bref, BREF_CLOSED); if (BREF_IS_WAITING_RESULT(bref)) { bref_clear_state(bref, BREF_WAITING_RESULT); } dcb_close(backend_dcb); } } else { // All dcbs should be associated with a backend reference. ss_dassert(!true); } rses_end_locked_router_action(rses); } else { // The session has already been closed, hence the dcb has been // closed as well. } if (sesstate == SESSION_STATE_ROUTER_READY) { CHK_DCB(client_dcb); client_dcb->func.write(client_dcb, gwbuf_clone(errmsg)); } } /** * Check if there is backend reference pointing at failed DCB, and reset its * flags. Then clear DCB's callback and finally : try to find replacement(s) * for failed slave(s). * * This must be called with router lock. * * @param inst router instance * @param rses router client session * @param dcb failed DCB * @param errmsg error message which is sent to client if it is waiting * * @return true if there are enough backend connections to continue, false if * not */ static bool handle_error_new_connection(ROUTER_INSTANCE *inst, ROUTER_CLIENT_SES **rses, DCB *backend_dcb, GWBUF *errmsg) { ROUTER_CLIENT_SES *myrses; SESSION *ses; int max_nslaves; int max_slave_rlag; backend_ref_t *bref; bool succp; myrses = *rses; ss_dassert(SPINLOCK_IS_LOCKED(&myrses->rses_lock)); ses = backend_dcb->session; CHK_SESSION(ses); /** * If bref == NULL it has been replaced already with another one. */ if ((bref = get_bref_from_dcb(myrses, backend_dcb)) == NULL) { succp = true; goto return_succp; } CHK_BACKEND_REF(bref); /** * If query was sent through the bref and it is waiting for reply from * the backend server it is necessary to send an error to the client * because it is waiting for reply. */ if (BREF_IS_WAITING_RESULT(bref)) { DCB *client_dcb; client_dcb = ses->client_dcb; client_dcb->func.write(client_dcb, gwbuf_clone(errmsg)); bref_clear_state(bref, BREF_WAITING_RESULT); } bref_clear_state(bref, BREF_IN_USE); bref_set_state(bref, BREF_CLOSED); /** * Error handler is already called for this DCB because * it's not polling anymore. It can be assumed that * it succeed because rses isn't closed. */ if (backend_dcb->state != DCB_STATE_POLLING) { succp = true; goto return_succp; } /** * Remove callback because this DCB won't be used * unless it is reconnected later, and then the callback * is set again. */ dcb_remove_callback(backend_dcb, DCB_REASON_NOT_RESPONDING, &router_handle_state_switch, (void *)bref); max_nslaves = rses_get_max_slavecount(myrses, myrses->rses_nbackends); max_slave_rlag = rses_get_max_replication_lag(myrses); /** * Try to get replacement slave or at least the minimum * number of slave connections for router session. */ if (inst->rwsplit_config.rw_disable_sescmd_hist) { succp = have_enough_servers(myrses, 1, myrses->rses_nbackends, inst) ? true : false; } else { succp = select_connect_backend_servers(&myrses->rses_master_ref, myrses->rses_backend_ref, myrses->rses_nbackends, max_nslaves, max_slave_rlag, myrses->rses_config.rw_slave_select_criteria, ses, inst); } return_succp: return succp; } /** * @brief Calculate whether we have enough servers to route a query * * @param p_rses Router session * @param min_nsrv Minimum number of servers that is sufficient * @param nsrv Actual number of servers * @param router Router instance * * @return bool - whether enough, side effect is error logging */ static bool have_enough_servers(ROUTER_CLIENT_SES *rses, const int min_nsrv, int router_nsrv, ROUTER_INSTANCE *router) { bool succp; /** With too few servers session is not created */ if (router_nsrv < min_nsrv || MXS_MAX((rses)->rses_config.rw_max_slave_conn_count, (router_nsrv * (rses)->rses_config.rw_max_slave_conn_percent) / 100) < min_nsrv) { if (router_nsrv < min_nsrv) { MXS_ERROR("Unable to start %s service. There are " "too few backend servers available. Found %d " "when %d is required.", router->service->name, router_nsrv, min_nsrv); } else { int pct = (rses)->rses_config.rw_max_slave_conn_percent / 100; int nservers = router_nsrv * pct; if ((rses)->rses_config.rw_max_slave_conn_count < min_nsrv) { MXS_ERROR("Unable to start %s service. There are " "too few backend servers configured in " "MaxScale.cnf. Found %d when %d is required.", router->service->name, (rses)->rses_config.rw_max_slave_conn_count, min_nsrv); } if (nservers < min_nsrv) { double dbgpct = ((double)min_nsrv / (double)router_nsrv) * 100.0; MXS_ERROR("Unable to start %s service. There are " "too few backend servers configured in " "MaxScale.cnf. Found %d%% when at least %.0f%% " "would be required.", router->service->name, (rses)->rses_config.rw_max_slave_conn_percent, dbgpct); } } succp = false; } else { succp = true; } return succp; } /** * @brief Refresh the instance by the given parameter value. * * Used by createInstance and newSession * * @param router Router instance * @param singleparam Parameter fo be reloaded * * Note: this part is not done. Needs refactoring. */ static void refreshInstance(ROUTER_INSTANCE *router, CONFIG_PARAMETER *singleparam) { CONFIG_PARAMETER *param; bool refresh_single; config_param_type_t paramtype; if (singleparam != NULL) { param = singleparam; refresh_single = true; } else { param = router->service->svc_config_param; refresh_single = false; } paramtype = config_get_paramtype(param); while (param != NULL) { /** Catch unused parameter types */ ss_dassert(paramtype == COUNT_TYPE || paramtype == PERCENT_TYPE || paramtype == SQLVAR_TARGET_TYPE); if (paramtype == COUNT_TYPE) { if (strncmp(param->name, "max_slave_connections", MAX_PARAM_LEN) == 0) { int val; bool succp; router->rwsplit_config.rw_max_slave_conn_percent = 0; succp = config_get_valint(&val, param, NULL, paramtype); if (succp) { router->rwsplit_config.rw_max_slave_conn_count = val; } } else if (strncmp(param->name, "max_slave_replication_lag", MAX_PARAM_LEN) == 0) { int val; bool succp; succp = config_get_valint(&val, param, NULL, paramtype); if (succp) { router->rwsplit_config.rw_max_slave_replication_lag = val; } } } else if (paramtype == PERCENT_TYPE) { if (strncmp(param->name, "max_slave_connections", MAX_PARAM_LEN) == 0) { int val; bool succp; router->rwsplit_config.rw_max_slave_conn_count = 0; succp = config_get_valint(&val, param, NULL, paramtype); if (succp) { router->rwsplit_config.rw_max_slave_conn_percent = val; } } } else if (paramtype == SQLVAR_TARGET_TYPE) { if (strncmp(param->name, "use_sql_variables_in", MAX_PARAM_LEN) == 0) { target_t valtarget; bool succp; succp = config_get_valtarget(&valtarget, param, NULL, paramtype); if (succp) { router->rwsplit_config.rw_use_sql_variables_in = valtarget; } } } if (refresh_single) { break; } param = param->next; } } /* * @brief Release resources when createInstance fails to complete * * Internal to createInstance * * @param router Router instance * */ static void free_rwsplit_instance(ROUTER_INSTANCE *router) { if (router) { MXS_FREE(router); } } /** * @brief Create backend server references * * This creates a new set of backend references for the client session. Currently * this is only used on startup but it could be used to dynamically change the * set of used servers. * * @param rses Client router session * @param dest Destination where the array of backens is stored * @param n_backend Number of items in the array * @return True on success, false on error */ static bool create_backends(ROUTER_CLIENT_SES *rses, backend_ref_t** dest, int* n_backend) { backend_ref_t *backend_ref = (backend_ref_t *)MXS_CALLOC(1, *n_backend * sizeof(backend_ref_t)); if (backend_ref == NULL) { return false; } int i = 0; for (SERVER_REF *sref = rses->router->service->dbref; sref && i < *n_backend; sref = sref->next) { if (sref->active) { #if defined(SS_DEBUG) backend_ref[i].bref_chk_top = CHK_NUM_BACKEND_REF; backend_ref[i].bref_chk_tail = CHK_NUM_BACKEND_REF; backend_ref[i].bref_sescmd_cur.scmd_cur_chk_top = CHK_NUM_SESCMD_CUR; backend_ref[i].bref_sescmd_cur.scmd_cur_chk_tail = CHK_NUM_SESCMD_CUR; #endif backend_ref[i].bref_state = 0; backend_ref[i].ref = sref; /** store pointers to sescmd list to both cursors */ backend_ref[i].bref_sescmd_cur.scmd_cur_rses = rses; backend_ref[i].bref_sescmd_cur.scmd_cur_active = false; backend_ref[i].bref_sescmd_cur.scmd_cur_ptr_property = &rses->rses_properties[RSES_PROP_TYPE_SESCMD]; backend_ref[i].bref_sescmd_cur.scmd_cur_cmd = NULL; i++; } } if (i < *n_backend) { MXS_INFO("The service reported %d servers but only took %d into use.", *n_backend, i); *n_backend = i; } *dest = backend_ref; return true; }