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MXS-1777 Turn server weights to their inverses, and make them doubles.

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The math becomes simpler when the weight is inverted, i.e. a simple multiplication
to get the (inverse) score. Inverse weights are normalized to the range [0..1] where a lower
number is a higher weight,
The enum select_criteria_t is used to provide a std::function that takes the backends
as vector  (rather than the prior pairwise compares) and returns the best backend.
This commit is contained in:
Niclas Antti
2018-08-28 11:01:11 +03:00
parent 105bd7195f
commit 91acbc0994
7 changed files with 278 additions and 289 deletions
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41
server/modules/routing/readwritesplit/readwritesplit.hh
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@ -25,6 +25,7 @@
#include <map>
#include <string>
#include <mutex>
#include <functional>
#include <maxscale/dcb.h>
#include <maxscale/log.h>
@ -61,22 +62,13 @@ typedef uint32_t route_target_t;
*/
enum select_criteria_t
{
UNDEFINED_CRITERIA = 0,
LEAST_GLOBAL_CONNECTIONS, /**< all connections established by MaxScale */
LEAST_ROUTER_CONNECTIONS, /**< connections established by this router */
LEAST_BEHIND_MASTER,
LEAST_CURRENT_OPERATIONS,
LOWEST_RESPONSE_TIME,
LAST_CRITERIA /**< not used except for an index */
LOWEST_RESPONSE_TIME
};
#define STRCRITERIA(c) ((c) == UNDEFINED_CRITERIA ? "UNDEFINED_CRITERIA" : \
((c) == LEAST_GLOBAL_CONNECTIONS ? "LEAST_GLOBAL_CONNECTIONS" : \
((c) == LEAST_ROUTER_CONNECTIONS ? "LEAST_ROUTER_CONNECTIONS" : \
((c) == LEAST_BEHIND_MASTER ? "LEAST_BEHIND_MASTER" : \
((c) == LEAST_CURRENT_OPERATIONS ? "LEAST_CURRENT_OPERATIONS" : \
"Unknown criteria")))))
/**
* Controls how master failure is handled
*/
@ -136,12 +128,21 @@ static const char gtid_wait_stmt[] =
"SET @maxscale_secret_variable=(SELECT CASE WHEN %s('%s', %s) = 0 "
"THEN 1 ELSE (SELECT 1 FROM INFORMATION_SCHEMA.ENGINES) END);";
/** Function that returns a "score" for a server to enable comparison.
* Smaller numbers are better.
*/
using SRWBackendVector = std::vector<mxs::SRWBackend*>;
using BackendSelectFunction = std::function
<SRWBackendVector::const_iterator (const SRWBackendVector& sBackends)>;
BackendSelectFunction get_backend_select_function(select_criteria_t);
struct Config
{
Config(MXS_CONFIG_PARAMETER* params):
slave_selection_criteria(
(select_criteria_t)config_get_enum(
params, "slave_selection_criteria", slave_selection_criteria_values)),
backend_select_fct(get_backend_select_function(slave_selection_criteria)),
use_sql_variables_in(
(mxs_target_t)config_get_enum(
params, "use_sql_variables_in", use_sql_variables_in_values)),
@ -173,7 +174,9 @@ struct Config
}
}
select_criteria_t slave_selection_criteria; /**< The slave selection criteria */
select_criteria_t slave_selection_criteria; /**< The slave selection criteria */
BackendSelectFunction backend_select_fct;
mxs_target_t use_sql_variables_in; /**< Whether to send user variables to
* master or all nodes */
failure_mode master_failure_mode; /**< Master server failure handling mode */
@ -370,24 +373,20 @@ mxs::SRWBackend get_root_master(const mxs::SRWBackendList& backends);
*/
std::pair<int, int> get_slave_counts(mxs::SRWBackendList& backends, mxs::SRWBackend& master);
/* TODO, hopefully temporary */
using BackendSPtrVec = std::vector<mxs::SRWBackend*>;
/**
* Find the best backend based on categorizing the servers, and then applying
* selection criteria to the best category.
* Find the best backend by grouping the servers by priority, and then applying
* selection criteria to the best group.
*
* @param backends: vector of SRWBackend
* @param sc: which select_criteria_t to use
* @param select: selection function
* @param master_accept_reads: NOTE: even if this is false, in some cases a master can
* still be selected for reads.
*
* @return Valid iterator into argument backends, or end(backends) if empty
*/
BackendSPtrVec::const_iterator find_best_backend(const BackendSPtrVec& backends,
select_criteria_t sc,
bool masters_accept_reads);
SRWBackendVector::const_iterator find_best_backend(const SRWBackendVector& backends,
BackendSelectFunction select,
bool masters_accepts_reads);
/*
* The following are implemented in rwsplit_tmp_table_multi.c