BUG/MEDIUM: server: set the macro for server's max weight SRV_UWGHT_MAX to SRV_UWGHT_RANGE
The max weight of server is 256 now, but SRV_UWGHT_MAX is still 255. As a result,
FWRR will not work well when server's weight is 256. The description is as below:
There are some macros related to server's weight in include/types/server.h:
#define SRV_UWGHT_RANGE 256
#define SRV_UWGHT_MAX (SRV_UWGHT_RANGE - 1)
#define SRV_EWGHT_MAX (SRV_UWGHT_MAX * BE_WEIGHT_SCALE)
Since weight of server can be reach to 256 and BE_WEIGHT_SCALE equals to 16,
the max eweight of server should be 256*16 = 4096, it will exceed SRV_EWGHT_MAX
which equals to SRV_UWGHT_MAX*BE_WEIGHT_SCALE = 255*16 = 4080. When a server
with weight 256 is insterted into FWRR tree during initialization, the key value
of this server should be SRV_EWGHT_MAX - s->eweight = 4080 - 4096 = -16 which
is closed to UINT_MAX in unsigned type, so the server with highest weight will
be not elected as the first server to process request.
In addition, it is a better choice to compare with SRV_UWGHT_MAX than a magic
number 256 while doing check for the weight. The max number of servers for
round-robin algorithm is also updated.
Signed-off-by: Godbach <nylzhaowei@gmail.com>
diff --git a/src/lb_fwrr.c b/src/lb_fwrr.c
index d92b6eb..7f5c8a9 100644
--- a/src/lb_fwrr.c
+++ b/src/lb_fwrr.c
@@ -343,7 +343,7 @@
* lower the scale, the rougher the weights modulation, and the
* higher the scale, the lower the number of servers without
* overflow. With this formula, the result is always positive,
- * so we can use eb3é_insert().
+ * so we can use eb32_insert().
*/
s->lb_node.key = SRV_UWGHT_RANGE * s->npos +
(unsigned)(SRV_EWGHT_MAX + s->rweight - s->eweight) / BE_WEIGHT_SCALE;