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MXS-1503: Clean up connection creation function

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The select_connect_backend_servers function is the main connection
creation function. Cleaned it up and split it into smaller, reusable
parts.
This commit is contained in:
Markus Mäkelä
2018-03-27 20:32:35 +03:00
parent a0a37bf793
commit a1b5fcd4ff
1 changed files with 60 additions and 59 deletions
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119
server/modules/routing/readwritesplit/rwsplit_select_backends.cc
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@ -36,10 +36,10 @@
* *
* @return True if this server is a valid slave candidate * @return True if this server is a valid slave candidate
*/ */
static bool valid_for_slave(const SERVER *server, const SERVER *master) static bool valid_for_slave(const SRWBackend& backend, const SERVER_REF *master)
{ {
return (SERVER_IS_SLAVE(server) || SERVER_IS_RELAY_SERVER(server)) && return (backend->is_slave() || backend->is_relay()) &&
(master == NULL || (server != master)); (master == NULL || (backend->server() != master->server));
} }
/** /**
@ -54,8 +54,8 @@ static bool valid_for_slave(const SERVER *server, const SERVER *master)
* *
* @return The best slave backend reference or NULL if no candidates could be found * @return The best slave backend reference or NULL if no candidates could be found
*/ */
SRWBackend get_slave_candidate(const SRWBackendList& backends, const SERVER *master, static SRWBackend get_slave_candidate(const SRWBackendList& backends, const SERVER_REF *master,
int (*cmpfun)(const SRWBackend&, const SRWBackend&)) int (*cmpfun)(const SRWBackend&, const SRWBackend&))
{ {
SRWBackend candidate; SRWBackend candidate;
@ -65,7 +65,7 @@ SRWBackend get_slave_candidate(const SRWBackendList& backends, const SERVER *mas
const SRWBackend& backend = *it; const SRWBackend& backend = *it;
if (!backend->in_use() && backend->can_connect() && if (!backend->in_use() && backend->can_connect() &&
valid_for_slave(backend->server(), master)) valid_for_slave(backend, master))
{ {
if (candidate) if (candidate)
{ {
@ -268,6 +268,38 @@ static SERVER_REF* get_root_master(const SRWBackendList& backends)
return master_host; return master_host;
} }
/**
* Get the total number of slaves and number of connected slaves
*
* @param backends List of backend servers
* @param master The master server or NULL for no master
*
* @return the total number of slaves and the connected slave count
*/
std::pair<int, int> get_slave_counts(SRWBackendList& backends, SERVER_REF* master)
{
int slaves_found = 0;
int slaves_connected = 0;
/** Calculate how many connections we already have */
for (SRWBackendList::const_iterator it = backends.begin(); it != backends.end(); it++)
{
const SRWBackend& backend = *it;
if (backend->can_connect() && valid_for_slave(backend, master))
{
slaves_found += 1;
if (backend->in_use())
{
slaves_connected += 1;
}
}
}
return std::make_pair(slaves_found, slaves_connected);
}
/** /**
* @brief Search suitable backend servers from those of router instance * @brief Search suitable backend servers from those of router instance
* *
@ -296,12 +328,9 @@ bool select_connect_backend_servers(int router_nservers,
int* expected_responses, int* expected_responses,
connection_type type) connection_type type)
{ {
/* get the root Master */ SERVER_REF *master = get_root_master(backends);
SERVER_REF *master_backend = get_root_master(backends);
SERVER *master_host = master_backend ? master_backend->server : NULL;
if (config.master_failure_mode == RW_FAIL_INSTANTLY && if (!master && config.master_failure_mode == RW_FAIL_INSTANTLY)
(master_host == NULL || SERVER_IS_DOWN(master_host)))
{ {
MXS_ERROR("Couldn't find suitable Master from %d candidates.", router_nservers); MXS_ERROR("Couldn't find suitable Master from %d candidates.", router_nservers);
return false; return false;
@ -329,11 +358,6 @@ bool select_connect_backend_servers(int router_nservers,
log_server_connections(select_criteria, backends); log_server_connections(select_criteria, backends);
} }
int slaves_found = 0;
int slaves_connected = 0;
const int min_nslaves = 0; /*< not configurable at the time */
bool succp = false;
if (!master_connected) if (!master_connected)
{ {
/** Find a master server */ /** Find a master server */
@ -341,38 +365,27 @@ bool select_connect_backend_servers(int router_nservers,
{ {
const SRWBackend& backend = *it; const SRWBackend& backend = *it;
if (backend->can_connect() && master_host && backend->server() == master_host) if (backend->can_connect() && master && backend->server() == master->server)
{ {
if (backend->connect(session)) if (backend->connect(session))
{ {
current_master = backend; current_master = backend;
} }
break;
} }
} }
} }
/** Calculate how many connections we already have */ auto counts = get_slave_counts(backends, master);
for (SRWBackendList::const_iterator it = backends.begin(); it != backends.end(); it++) int slaves_found = counts.first;
{ int slaves_connected = counts.second;
const SRWBackend& backend = *it;
if (backend->can_connect() && valid_for_slave(backend->server(), master_host))
{
slaves_found += 1;
if (backend->in_use())
{
slaves_connected += 1;
}
}
}
ss_dassert(slaves_connected < max_nslaves || max_nslaves == 0); ss_dassert(slaves_connected < max_nslaves || max_nslaves == 0);
/** Connect to all possible slaves */ /** Connect to all possible slaves */
for (SRWBackend backend(get_slave_candidate(backends, master_host, cmpfun)); for (SRWBackend backend(get_slave_candidate(backends, master, cmpfun));
backend && slaves_connected < max_nslaves; backend && slaves_connected < max_nslaves;
backend = get_slave_candidate(backends, master_host, cmpfun)) backend = get_slave_candidate(backends, master, cmpfun))
{ {
if (backend->can_connect() && backend->connect(session)) if (backend->can_connect() && backend->connect(session))
{ {
@ -396,37 +409,25 @@ bool select_connect_backend_servers(int router_nservers,
} }
} }
if (slaves_connected >= min_nslaves && slaves_connected <= max_nslaves) if (MXS_LOG_PRIORITY_IS_ENABLED(LOG_INFO))
{ {
succp = true; if (slaves_connected < max_nslaves)
if (MXS_LOG_PRIORITY_IS_ENABLED(LOG_INFO))
{ {
if (slaves_connected < max_nslaves) MXS_INFO("Couldn't connect to maximum number of "
{ "slaves. Connected successfully to %d slaves "
MXS_INFO("Couldn't connect to maximum number of " "of %d of them.", slaves_connected, slaves_found);
"slaves. Connected successfully to %d slaves " }
"of %d of them.", slaves_connected, slaves_found);
}
for (SRWBackendList::const_iterator it = backends.begin(); it != backends.end(); it++) for (SRWBackendList::const_iterator it = backends.begin(); it != backends.end(); it++)
{
const SRWBackend& backend = *it;
if (backend->in_use())
{ {
const SRWBackend& backend = *it; MXS_INFO("Selected %s in \t%s", STRSRVSTATUS(backend->server()),
if (backend->in_use()) backend->uri());
{
MXS_INFO("Selected %s in \t%s", STRSRVSTATUS(backend->server()),
backend->uri());
}
} }
} }
} }
else
{
MXS_ERROR("Couldn't establish required amount of slave connections for "
"router session. Would need between %d and %d slaves but only have %d.",
min_nslaves, max_nslaves, slaves_connected);
close_all_connections(backends);
}
return succp; return true;
} }