Hi Willy,
I have done a test for haproxy on latest snapshot which has two servers
with such key configuration
lb algo is roundrobin
server A: weight 128
server B: weight 256
I sent 9 requests and the order for getting responses from server is
expected as:
BBABBABBA
But I got the unexpected order as below:
ABBAAAAAA
Indeed, I have noticed that there is a problem for the implentation of
roundrobin yesterday before this test, and this test verified the
problem. The description is as below:
srv->eweight will exceed SRV_EWGHT_MAX in accordance with the fromula:
srv->eweight = srv->uweight * BE_WEIGHT_SCALE;
Since uweight can be reach to 256 and BE_WEIGHT_SCALE equals to 16. So
the max vaule of eweight should be 256*16. But there is a macro named
SRV_EWGHT_MAX, it equals to 255*16(SRV_UWGHT_MAX*BE_WEIGHT_SCALE). And
when a server is insterted into round robin tree during initialization,
fwrr_queue_by_weight() is called:
static inline void fwrr_queue_by_weight(struct eb_root *root, struct
server *s)
{
s->lb_node.key = SRV_EWGHT_MAX - s->eweight;
eb32_insert(root, &s->lb_node);
s->lb_tree = root;
}
When server's weight is 256, eweight is 256*16. The eweight will larger
than SRV_EWGHT_MAX. As a result, the key value in lb tree will be closed
to UNIT_MAX in unsigned type, and it will be not elected as the first
server to process request. Furthermore, roundrobin can not work well in
my test.
Since there is a macro SRV_UWGHT_MAX equals to 255 as below:
#define SRV_UWGHT_RANGE 256
#define SRV_UWGHT_MAX (SRV_UWGHT_RANGE - 1)
I want to know whether the server's weight should not larger than
SRV_UWGHT_MAX(255), but the max value is 256 now in cfgparse.c as below:
else if (!strcmp(args[cur_arg], "weight")) {
int w;
w = atol(args[cur_arg + 1]);
if (w < 0 || w > 256) {
If so, I will give a patch to fix it, or it should be fixed in other way.
--
Best Regards,
Godbach
