Remove unused DCB callback code

The highwater and lowwater callbacks were never registered for the client
DCBs in the binlogrouter.

The DCB hangup callbacks were never called by the core and were replaced
with fake hangup events in an earlier version.

server/modules/routing/binlogrouter/blr.c

@@ -192,8 +192,6 @@ MXS_MODULE* MXS_CREATE_MODULE()
             {"encrypt_binlog", MXS_MODULE_PARAM_BOOL, "false"},
             {"encryption_algorithm", MXS_MODULE_PARAM_ENUM, "aes_cbc", MXS_MODULE_OPT_NONE, enc_algo_values},
             {"encryption_key_file", MXS_MODULE_PARAM_PATH, NULL, MXS_MODULE_OPT_PATH_R_OK},
-            {"lowwater", MXS_MODULE_PARAM_COUNT, DEF_LOW_WATER},
-            {"highwater", MXS_MODULE_PARAM_COUNT, DEF_HIGH_WATER},
             {"shortburst", MXS_MODULE_PARAM_COUNT, DEF_SHORT_BURST},
             {"longburst", MXS_MODULE_PARAM_COUNT, DEF_LONG_BURST},
             {"burstsize", MXS_MODULE_PARAM_SIZE, DEF_BURST_SIZE},
@@ -321,8 +319,6 @@ createInstance(SERVICE *service, char **options)
 
     MXS_CONFIG_PARAMETER *params = service->svc_config_param;
 
-    inst->low_water = config_get_integer(params, "lowwater");
-    inst->high_water = config_get_integer(params, "highwater");
     inst->initbinlog = config_get_integer(params, "file");
 
     inst->short_burst = config_get_integer(params, "shortburst");
@@ -394,8 +390,6 @@ createInstance(SERVICE *service, char **options)
      *  password=
      *  master-id=
      *  filestem=
-     *  lowwater=
-     *  highwater=
      */
     if (options)
     {
@@ -535,14 +529,6 @@ createInstance(SERVICE *service, char **options)
                     MXS_FREE(inst->encryption.key_management_filename);
                     inst->encryption.key_management_filename = MXS_STRDUP_A(value);
                 }
-                else if (strcmp(options[i], "lowwater") == 0)
-                {
-                    inst->low_water = atoi(value);
-                }
-                else if (strcmp(options[i], "highwater") == 0)
-                {
-                    inst->high_water = atoi(value);
-                }
                 else if (strcmp(options[i], "shortburst") == 0)
                 {
                     inst->short_burst = atoi(value);

server/modules/routing/binlogrouter/blr.h

@@ -574,8 +574,6 @@ typedef struct router_instance
     int               rotating;     /*< Rotation in progress flag */
     BLFILE            *files;       /*< Files used by the slaves */
     SPINLOCK          fileslock;    /*< Lock for the files queue above */
-    unsigned int      low_water;    /*< Low water mark for client DCB */
-    unsigned int      high_water;   /*< High water mark for client DCB */
     unsigned int      short_burst;  /*< Short burst for slave catchup */
     unsigned int      long_burst;   /*< Long burst for slave catchup */
     unsigned long     burst_size;   /*< Maximum size of burst to send */

server/modules/routing/binlogrouter/blr_slave.c

@@ -2289,9 +2289,6 @@ blr_slave_binlog_dump(ROUTER_INSTANCE *router, ROUTER_SLAVE *slave, GWBUF *queue
         blr_slave_read_ste(router, slave, fde_end_pos);
     }
 
-    slave->dcb->low_water  = router->low_water;
-    slave->dcb->high_water = router->high_water;
-
     dcb_add_callback(slave->dcb, DCB_REASON_DRAINED, blr_slave_callback, slave);
 
     slave->state = BLRS_DUMPING;

server/modules/routing/readconnroute/readconnroute.c

@@ -423,11 +423,6 @@ newSession(MXS_ROUTER *instance, MXS_SESSION *session)
 
     atomic_add(&candidate->connections, 1);
 
-    // TODO: Remove this as it is never called
-    dcb_add_callback(client_rses->backend_dcb,
-                     DCB_REASON_NOT_RESPONDING,
-                     &handle_state_switch,
-                     client_rses);
     inst->stats.n_sessions++;
 
     CHK_CLIENT_RSES(client_rses);

server/modules/routing/readwritesplit/readwritesplit.c

@@ -1159,73 +1159,6 @@ backend_ref_t *get_bref_from_dcb(ROUTER_CLIENT_SES *rses, DCB *dcb)
     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(((MXS_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
  *

server/modules/routing/readwritesplit/rwsplit_select_backends.c

@@ -433,9 +433,6 @@ static bool connect_server(backend_ref_t *bref, MXS_SESSION *session, bool execu
 
         if (!execute_history || execute_sescmd_history(bref))
         {
-            /** Add a callback for unresponsive server */
-            dcb_add_callback(bref->bref_dcb, DCB_REASON_NOT_RESPONDING,
-                             &router_handle_state_switch, (void *) bref);
             bref->bref_state = 0;
             bref_set_state(bref, BREF_IN_USE);
             atomic_add(&bref->ref->connections, 1);

server/modules/routing/schemarouter/schemarouter.c

@@ -2772,11 +2772,6 @@ static bool connect_backend_servers(backend_ref_t*   backend_ref,
                      * of dcb_close.
                      */
                     atomic_add(&b->connections, 1);
-
-                    dcb_add_callback(backend_ref[i].bref_dcb,
-                                     DCB_REASON_NOT_RESPONDING,
-                                     &router_handle_state_switch,
-                                     (void *)&backend_ref[i]);
                 }
                 else
                 {
@@ -3750,15 +3745,6 @@ static bool handle_error_new_connection(ROUTER_INSTANCE*   inst,
         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);
 
     /**
      * Try to get replacement slave or at least the minimum
@@ -3815,59 +3801,6 @@ static backend_ref_t* get_bref_from_dcb(ROUTER_CLIENT_SES* rses,
     return bref;
 }
 
-/**
- * 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 Backend server DCB
- * @param reason The reason this DCB callback was called
- * @param data Data pointer assigned in the add_callback function call
- * @return Always 1
- */
-static 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->bref_backend->server;
-
-    if (SERVER_IS_RUNNING(srv))
-    {
-        goto return_rc;
-    }
-
-    switch (reason)
-    {
-    case DCB_REASON_NOT_RESPONDING:
-        atomic_add(&bref->bref_backend->connections, -1);
-        MXS_INFO("server %s not responding", srv->unique_name);
-        dcb->func.hangup(dcb);
-        break;
-
-    default:
-        break;
-    }
-
-return_rc:
-    return rc;
-}
-
-
 static sescmd_cursor_t* backend_ref_get_sescmd_cursor(backend_ref_t* bref)
 {
     sescmd_cursor_t* scur;