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Added code to correctly identify the initial candidate for load balancing,

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taking into account the status of the candidate.

Also made the balancing such that if two servers have the same number of
current connections the one that has had least connections since startup
will be used.
This commit is contained in:
Mark Riddoch 2013-06-26 09:10:31 +02:00
parent c7a424cdab
commit 9e2a41c2b7
1 changed files with 35 additions and 5 deletions
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40
modules/routing/readconnroute.c
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@ -178,7 +178,7 @@ newSession(ROUTER *instance, SESSION *session)
{
INSTANCE *inst = (INSTANCE *)instance;
CLIENT_SESSION *client;
BACKEND *candidate;
BACKEND *candidate = NULL;
int i;
if ((client = (CLIENT_SESSION *)malloc(sizeof(CLIENT_SESSION))) == NULL)
@ -190,13 +190,43 @@ int i;
* load balancing algorithm we need to implement for this simple
* connection router.
*/
candidate = inst->servers[0];
for (i = 1; inst->servers[i]; i++)
/* First find a running server to set as our initial candidate server */
for (i = 0; inst->servers[i]; i++)
{
if (inst->servers[i] && SERVER_IS_RUNNING(inst->servers[i]->server)
&& inst->servers[i]->count < candidate->count)
if (inst->servers[i] && SERVER_IS_RUNNING(inst->servers[i]->server))
{
candidate = inst->servers[i];
break;
}
}
/*
* Loop over all the servers and find any that have fewer connections than our
* 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 = 1; inst->servers[i]; i++)
{
if (inst->servers[i] && SERVER_IS_RUNNING(inst->servers[i]->server))
{
if (inst->servers[i]->count < candidate->count)
{
candidate = inst->servers[i];
}
else if (inst->servers[i]->count == candidate->count &&
inst->servers[i]->server->stats.n_connections
< candidate->server->stats.n_connections)
{
candidate = inst->servers[i];
}
}
}