/**
* 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;
}
/**
* Process a COM_BINLOG_DUMP message from the slave. This is the
* final step in the process of registration. The new master, MaxScale
* must send a response packet and generate a fake BINLOG_ROTATE event
* with the binlog file requested by the slave. And then send a
* FORMAT_DESCRIPTION_EVENT that has been saved from the real master.
*
* Once send MaxScale must continue to send binlog events to the slave.
*
* @param router The router instance
* @param slave The slave server
* @param queue The BINLOG_DUMP packet
* @return The number of bytes written to the slave
*/
static int
blr_slave_binlog_dump(ROUTER_INSTANCE *router, ROUTER_SLAVE *slave, GWBUF *queue)
{
GWBUF *resp;
uint8_t *ptr;
int len, flags, serverid, rval, binlognamelen;
REP_HEADER hdr;
uint32_t chksum;
ptr = GWBUF_DATA(queue);
len = extract_field(ptr, 24);
binlognamelen = len - 11;
ptr += 4; // Skip length and sequence number
if (*ptr++ != COM_BINLOG_DUMP)
{
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"blr_slave_binlog_dump expected a COM_BINLOG_DUMP but received %d",
*(ptr-1))));
return 0;
}
slave->binlog_pos = extract_field(ptr, 32);
ptr += 4;
flags = extract_field(ptr, 16);
ptr += 2;
serverid = extract_field(ptr, 32);
ptr += 4;
strncpy(slave->binlogfile, (char *)ptr, binlognamelen);
slave->binlogfile[binlognamelen] = 0;
slave->seqno = 1;
if (slave->nocrc)
len = 19 + 8 + binlognamelen;
else
len = 19 + 8 + 4 + binlognamelen;
// Build a fake rotate event
resp = gwbuf_alloc(len + 5);
hdr.payload_len = len + 1;
hdr.seqno = slave->seqno++;
hdr.ok = 0;
hdr.timestamp = 0L;
hdr.event_type = ROTATE_EVENT;
hdr.serverid = router->masterid;
hdr.event_size = len;
hdr.next_pos = 0;
hdr.flags = 0x20;
ptr = blr_build_header(resp, &hdr);
encode_value(ptr, slave->binlog_pos, 64);
ptr += 8;
memcpy(ptr, slave->binlogfile, binlognamelen);
ptr += binlognamelen;
if (!slave->nocrc)
{
/*
* Now add the CRC to the fake binlog rotate event.
*
* The algorithm is first to compute the checksum of an empty buffer
* and then the checksum of the event portion of the message, ie we do not
* include the length, sequence number and ok byte that makes up the first
* 5 bytes of the message. We also do not include the 4 byte checksum itself.
*/
chksum = crc32(0L, NULL, 0);
chksum = crc32(chksum, GWBUF_DATA(resp) + 5, hdr.event_size - 4);
encode_value(ptr, chksum, 32);
}
rval = slave->dcb->func.write(slave->dcb, resp);
/* Send the FORMAT_DESCRIPTION_EVENT */
if (slave->binlog_pos != 4)
blr_slave_send_fde(router, slave);
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;
LOGIF(LM, (skygw_log_write(
LOGFILE_MESSAGE,
"%s: New slave %s, server id %d, requested binlog file %s from position %lu",
router->service->name, slave->dcb->remote,
slave->serverid,
slave->binlogfile, slave->binlog_pos)));
if (slave->binlog_pos != router->binlog_position ||
strcmp(slave->binlogfile, router->binlog_name) != 0)
{
spinlock_acquire(&slave->catch_lock);
slave->cstate &= ~CS_UPTODATE;
slave->cstate |= CS_EXPECTCB;
spinlock_release(&slave->catch_lock);
poll_fake_write_event(slave->dcb);
}
return rval;
}
