/** * Associate a new session with this instance of the router. * * @param instance The router instance data * @param session The session itself * @return Session specific data for this session */ static void * newSession(ROUTER *instance, SESSION *session) { ROUTER_INSTANCE *inst = (ROUTER_INSTANCE *)instance; ROUTER_CLIENT_SES *client_rses; BACKEND *candidate = NULL; int i; BACKEND *master_host = NULL; LOGIF(LD, (skygw_log_write_flush( LOGFILE_DEBUG, "%lu [newSession] new router session with session " "%p, and inst %p.", pthread_self(), session, inst))); client_rses = (ROUTER_CLIENT_SES *)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 /** * Find the Master host from available servers */ master_host = get_root_master(inst->servers); /** * Find a backend server to connect to. This is the extent of the * load balancing algorithm we need to implement for this simple * connection router. */ /* * Loop over all the servers and find any that have fewer connections * than the candidate server. * * If a server has less connections than the current candidate we mark this * as the new candidate to connect to. * * If a server has the same number of connections currently as the candidate * and has had less connections over time than the candidate it will also * become the new candidate. This has the effect of spreading the * connections over different servers during periods of very low load. */ for (i = 0; inst->servers[i]; i++) { if(inst->servers[i]) { LOGIF(LD, (skygw_log_write( LOGFILE_DEBUG, "%lu [newSession] Examine server in port %d with " "%d connections. Status is %s, " "inst->bitvalue is %d", pthread_self(), inst->servers[i]->server->port, inst->servers[i]->current_connection_count, STRSRVSTATUS(inst->servers[i]->server), inst->bitmask))); } if (SERVER_IN_MAINT(inst->servers[i]->server)) continue; if (inst->servers[i]->weight == 0) continue; /* Check server status bits against bitvalue from router_options */ if (inst->servers[i] && SERVER_IS_RUNNING(inst->servers[i]->server) && (inst->servers[i]->server->status & inst->bitmask & inst->bitvalue)) { if (master_host) { if (inst->servers[i] == master_host && (inst->bitvalue & SERVER_SLAVE)) { /* skip root Master here, as it could also be slave of an external server * that is not in the configuration. * Intermediate masters (Relay Servers) are also slave and will be selected * as Slave(s) */ continue; } if (inst->servers[i] == master_host && (inst->bitvalue & SERVER_MASTER)) { /* If option is "master" return only the root Master as there * could be intermediate masters (Relay Servers) * and they must not be selected. */ candidate = master_host; break; } } else { /* master_host is NULL, no master server. * If requested router_option is 'master' * candidate wll be NULL. */ if (inst->bitvalue & SERVER_MASTER) { candidate = NULL; break; } } /* If no candidate set, set first running server as our initial candidate server */ if (candidate == NULL) { candidate = inst->servers[i]; } else if ((inst->servers[i]->current_connection_count * 1000) / inst->servers[i]->weight < (candidate->current_connection_count * 1000) / candidate->weight) { /* This running server has fewer connections, set it as a new candidate */ candidate = inst->servers[i]; } else if ((inst->servers[i]->current_connection_count * 1000) / inst->servers[i]->weight == (candidate->current_connection_count * 1000) / candidate->weight && inst->servers[i]->server->stats.n_connections < candidate->server->stats.n_connections) { /* This running server has the same number of connections currently as the candidate but has had fewer connections over time than candidate, set this server to candidate*/ candidate = inst->servers[i]; } } } /* There is no candidate server here! * With router_option=slave a master_host could be set, so route traffic there. * Otherwise, just clean up and return NULL */ if (!candidate) { if (master_host) { candidate = master_host; } else { LOGIF(LE, (skygw_log_write_flush( LOGFILE_ERROR, "Error : Failed to create new routing session. " "Couldn't find eligible candidate server. Freeing " "allocated resources."))); free(client_rses); return NULL; } } client_rses->rses_capabilities = RCAP_TYPE_PACKET_INPUT; /* * We now have the server with the least connections. * Bump the connection count for this server */ atomic_add(&candidate->current_connection_count, 1); client_rses->backend = candidate; LOGIF(LD, (skygw_log_write( LOGFILE_DEBUG, "%lu [newSession] Selected server in port %d. " "Connections : %d\n", pthread_self(), candidate->server->port, candidate->current_connection_count))); /* * Open a backend connection, putting the DCB for this * connection in the client_rses->backend_dcb */ client_rses->backend_dcb = dcb_connect(candidate->server, session, candidate->server->protocol); if (client_rses->backend_dcb == NULL) { atomic_add(&candidate->current_connection_count, -1); free(client_rses); return NULL; } dcb_add_callback( client_rses->backend_dcb, DCB_REASON_NOT_RESPONDING, &handle_state_switch, client_rses); inst->stats.n_sessions++; /** * Add this session to the list of active sessions. */ spinlock_acquire(&inst->lock); client_rses->next = inst->connections; inst->connections = client_rses; spinlock_release(&inst->lock); CHK_CLIENT_RSES(client_rses); skygw_log_write( LOGFILE_TRACE, "Readconnroute: New session for server %s. " "Connections : %d", candidate->server->unique_name, candidate->current_connection_count); return (void *)client_rses; }
/** * Associate a new session with this instance of the router. * * @param instance The router instance data * @param session The session itself * @return Session specific data for this session */ static void * newSession(ROUTER *instance, SESSION *session) { ROUTER_INSTANCE *inst = (ROUTER_INSTANCE *)instance; ROUTER_CLIENT_SES *client_rses; BACKEND *candidate = NULL; int i; int master_host = -1; LOGIF(LD, (skygw_log_write_flush( LOGFILE_DEBUG, "%lu [newSession] new router session with session " "%p, and inst %p.", pthread_self(), session, inst))); client_rses = (ROUTER_CLIENT_SES *)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 /** * Find a backend server to connect to. This is the extent of the * load balancing algorithm we need to implement for this simple * connection router. */ /* * Loop over all the servers and find any that have fewer connections * than the candidate server. * * If a server has less connections than the current candidate we mark this * as the new candidate to connect to. * * If a server has the same number of connections currently as the candidate * and has had less connections over time than the candidate it will also * become the new candidate. This has the effect of spreading the * connections over different servers during periods of very low load. */ for (i = 0; inst->servers[i]; i++) { if(inst->servers[i]) { LOGIF(LD, (skygw_log_write( LOGFILE_DEBUG, "%lu [newSession] Examine server in port %d with " "%d connections. Status is %d, " "inst->bitvalue is %d", pthread_self(), inst->servers[i]->server->port, inst->servers[i]->current_connection_count, inst->servers[i]->server->status, inst->bitmask))); } /* * If router_options=slave, get the running master * It will be used if there are no running slaves at all */ if (inst->bitvalue == SERVER_SLAVE) { if (master_host < 0 && (SERVER_IS_MASTER(inst->servers[i]->server))) { master_host = i; } } if (inst->servers[i] && SERVER_IS_RUNNING(inst->servers[i]->server) && (inst->servers[i]->server->status & inst->bitmask) == inst->bitvalue) { /* If no candidate set, set first running server as our initial candidate server */ if (candidate == NULL) { candidate = inst->servers[i]; } else if (inst->servers[i]->current_connection_count < candidate->current_connection_count) { /* This running server has fewer connections, set it as a new candidate */ candidate = inst->servers[i]; } else if (inst->servers[i]->current_connection_count == candidate->current_connection_count && inst->servers[i]->server->stats.n_connections < candidate->server->stats.n_connections) { /* This running server has the same number of connections currently as the candidate but has had fewer connections over time than candidate, set this server to candidate*/ candidate = inst->servers[i]; } } } /* There is no candidate server here! * With router_option=slave a master_host could be set, so route traffic there. * Otherwise, just clean up and return NULL */ if (!candidate) { if (master_host >= 0) { candidate = inst->servers[master_host]; } else { LOGIF(LE, (skygw_log_write_flush( LOGFILE_ERROR, "Error : Failed to create new routing session. " "Couldn't find eligible candidate server. Freeing " "allocated resources."))); free(client_rses); return NULL; } } client_rses->rses_capabilities = RCAP_TYPE_PACKET_INPUT; /* * We now have the server with the least connections. * Bump the connection count for this server */ atomic_add(&candidate->current_connection_count, 1); client_rses->backend = candidate; LOGIF(LD, (skygw_log_write( LOGFILE_DEBUG, "%lu [newSession] Selected server in port %d. " "Connections : %d\n", pthread_self(), candidate->server->port, candidate->current_connection_count))); /* * Open a backend connection, putting the DCB for this * connection in the client_rses->backend_dcb */ client_rses->backend_dcb = dcb_connect(candidate->server, session, candidate->server->protocol); if (client_rses->backend_dcb == NULL) { atomic_add(&candidate->current_connection_count, -1); free(client_rses); return NULL; } inst->stats.n_sessions++; /** * Add this session to the list of active sessions. */ spinlock_acquire(&inst->lock); client_rses->next = inst->connections; inst->connections = client_rses; spinlock_release(&inst->lock); CHK_CLIENT_RSES(client_rses); return (void *)client_rses; }