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Fixed readwritesplit server weight calculations

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The server weights were ignored for the first connection and servers with a
weight of 0 would get connections if the connection count was high enough.

This fixes the weighting behavior so that when connections are created,
servers with a weight of 0 will be ignored as long as there is a server
with a positive weight available.

With this change, three servers configured with weights 2, 1 and 0 would
get connections balanced in the following way:

weight = 2, 66% of connections
weight = 1, 33% of connections
weight = 0, 0% of connections

If the server with the weight of 2 would go down, the server with the weight
of 1 would get 100% of the connections. If both servers with positive weights
go down, the server with the weight of 0 would be used.
This commit is contained in:
Markus Makela 2016-03-03 23:22:16 +02:00
parent 75eea82fe3
commit 609912ae90
1 changed files with 47 additions and 14 deletions
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61
server/modules/routing/readwritesplit/readwritesplit.c
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@ -660,11 +660,11 @@ createInstance(SERVICE *service, char **options)
if (perc == 0)
{
perc = 1;
MXS_ERROR("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.", weightby, wght,
"routed to this server as long as a server with"
" positive weight is available.", weightby, wght,
backend->backend_server->unique_name, total,
service->name);
}
@ -2964,8 +2964,21 @@ int bref_cmp_router_conn(
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
return ((1000 * b1->backend_conn_count) / b1->weight)
- ((1000 * b2->backend_conn_count) / b2->weight);
if (b1->weight == 0 && b2->weight == 0)
{
return b1->backend_server->stats.n_current - b2->backend_server->stats.n_current;
}
else if (b1->weight == 0)
{
return 1;
}
else if (b2->weight == 0)
{
return -1;
}
return ((1000 + 1000 * b1->backend_conn_count) / b1->weight)
- ((1000 + 1000 * b2->backend_conn_count) / b2->weight);
}
/** Compare nunmber of global connections in backend servers */
@ -2975,11 +2988,23 @@ int bref_cmp_global_conn(
{
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
return ((1000 * b1->backend_server->stats.n_current) / b1->weight)
- ((1000 * b2->backend_server->stats.n_current) / b2->weight);
}
if (b1->weight == 0 && b2->weight == 0)
{
return b1->backend_server->stats.n_current - b2->backend_server->stats.n_current;
}
else if (b1->weight == 0)
{
return 1;
}
else if (b2->weight == 0)
{
return -1;
}
return ((1000 + 1000 * b1->backend_server->stats.n_current) / b1->weight)
- ((1000 + 1000 * b2->backend_server->stats.n_current) / b2->weight);
}
/** Compare relication lag between backend servers */
int bref_cmp_behind_master(
@ -3002,7 +3027,20 @@ int bref_cmp_current_load(
SERVER* s2 = ((backend_ref_t *)bref2)->bref_backend->backend_server;
BACKEND* b1 = ((backend_ref_t *)bref1)->bref_backend;
BACKEND* b2 = ((backend_ref_t *)bref2)->bref_backend;
if (b1->weight == 0 && b2->weight == 0)
{
return b1->backend_server->stats.n_current - b2->backend_server->stats.n_current;
}
else if (b1->weight == 0)
{
return 1;
}
else if (b2->weight == 0)
{
return -1;
}
return ((1000 * s1->stats.n_current_ops) - b1->weight)
- ((1000 * s2->stats.n_current_ops) - b2->weight);
}
@ -3291,11 +3329,6 @@ static bool select_connect_backend_servers(
{
BACKEND* b = backend_ref[i].bref_backend;
if (router->servers[i]->weight == 0)
{
continue;
}
if (SERVER_IS_RUNNING(b->backend_server) &&
((b->backend_server->status & router->bitmask) ==
router->bitvalue))