[MEDIUM] hash: add support for an 'avalanche' hash-type
When the number of servers is a multiple of the size of the input set,
map-based hash can be inefficient. This typically happens with 64
servers when doing URI hashing. The "avalanche" hash-type applies an
avalanche hash before performing a map lookup in order to smooth the
distribution. The result is slightly less smooth than the map for small
numbers of servers, but still better than the consistent hashing.
diff --git a/include/types/backend.h b/include/types/backend.h
index 91d95b1..a3237ff 100644
--- a/include/types/backend.h
+++ b/include/types/backend.h
@@ -94,7 +94,8 @@
/* hash types */
#define BE_LB_HASH_MAP 0x000000 /* map-based hash (default) */
#define BE_LB_HASH_CONS 0x100000 /* consistent hashbit to indicate a dynamic algorithm */
-#define BE_LB_HASH_TYPE 0x100000 /* get/clear hash types */
+#define BE_LB_HASH_AVAL 0x200000 /* run an avalanche hash before a map */
+#define BE_LB_HASH_TYPE 0x300000 /* get/clear hash types */
/* various constants */