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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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60
server/core/service.cc
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@ -72,9 +72,6 @@ using namespace maxscale;
using LockGuard = std::lock_guard<std::mutex>;
using UniqueLock = std::unique_lock<std::mutex>;
/** Base value for server weights */
#define SERVICE_BASE_SERVER_WEIGHT 1000
static struct
{
std::mutex lock;
@ -915,7 +912,8 @@ static SERVER_REF* server_ref_create(SERVER *server)
{
sref->next = NULL;
sref->server = server;
sref->weight = SERVICE_BASE_SERVER_WEIGHT;
// all servers have weight 1.0, when weights are not configured.
sref->inv_weight = 1.0;
sref->connections = 0;
sref->active = true;
}
@ -1628,7 +1626,6 @@ bool service_all_services_have_listeners()
return rval;
}
static void service_calculate_weights(SERVICE *service)
{
const char *weightby = serviceGetWeightingParameter(service);
@ -1637,31 +1634,25 @@ static void service_calculate_weights(SERVICE *service)
{
char buf[50]; // Enough to hold most numbers
/** Service has a weighting parameter and at least one server */
int total = 0;
double total {0};
bool weights_are_in_use = false;
/** Calculate total weight */
for (SERVER_REF *server = service->dbref; server; server = server->next)
{
server->weight = SERVICE_BASE_SERVER_WEIGHT;
if (server_get_parameter(server->server, weightby, buf, sizeof(buf)))
{
total += atoi(buf);
weights_are_in_use = true;
}
}
if (total == 0)
if (!weights_are_in_use)
{
MXS_WARNING("Weighting Parameter for service '%s' will be ignored as "
"no servers have values for the parameter '%s'.",
service->name, weightby);
}
else if (total < 0)
{
MXS_ERROR("Sum of weighting parameter '%s' for service '%s' exceeds "
"maximum value of %d. Weighting will be ignored.",
weightby, service->name, INT_MAX);
}
else
{
/** Calculate the relative weight of the servers */
@ -1669,34 +1660,27 @@ static void service_calculate_weights(SERVICE *service)
{
if (server_get_parameter(server->server, weightby, buf, sizeof(buf)))
{
int wght = atoi(buf);
int perc = (wght * SERVICE_BASE_SERVER_WEIGHT) / total;
if (perc == 0)
int config_weight = atoi(buf);
if (config_weight <= 0)
{
MXS_WARNING("Weighting parameter '%s' with a value of %d for"
" server '%s' rounds down to zero with total weight"
" of %d for service '%s'. No queries will be "
"routed to this server as long as a server with"
" positive weight is available.",
weightby, wght, server->server->name,
total, service->name);
MXS_WARNING("Weighting parameter '%s' is set to %d for server '%s'."
" The runtime weight will be set to 0, and the server"
" will only be used if no other servers are available.",
weightby,
config_weight,
server->server->name);
config_weight = 0;
}
else if (perc < 0)
{
MXS_ERROR("Weighting parameter '%s' for server '%s' is too large, "
"maximum value is %d. No weighting will be used for this "
"server.", weightby, server->server->name,
INT_MAX / SERVICE_BASE_SERVER_WEIGHT);
perc = SERVICE_BASE_SERVER_WEIGHT;
}
server->weight = perc;
server->inv_weight = 1.0 - config_weight / total;
}
else
{
MXS_WARNING("Server '%s' has no parameter '%s' used for weighting"
" for service '%s'.", server->server->name,
weightby, service->name);
MXS_WARNING("Weighting parameter '%s' is not set for server '%s'."
" The runtime weight will be set to 0, and the server"
" will only be used if no other servers are available.",
weightby,
server->server->name);
server->inv_weight = 1.0;
}
}
}