MINOR: http: add option prefer-last-server
When the load balancing algorithm in use is not deterministic, and a previous
request was sent to a server to which haproxy still holds a connection, it is
sometimes desirable that subsequent requests on a same session go to the same
server as much as possible. Note that this is different from persistence, as
we only indicate a preference which haproxy tries to apply without any form
of warranty. The real use is for keep-alive connections sent to servers. When
this option is used, haproxy will try to reuse the same connection that is
attached to the server instead of rebalancing to another server, causing a
close of the connection. This can make sense for static file servers. It does
not make much sense to use this in combination with hashing algorithms.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index de5c337..6c6cc0b 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -76,7 +76,8 @@
/* bits for proxy->options */
#define PR_O_REDISP 0x00000001 /* allow reconnection to dispatch in case of errors */
#define PR_O_TRANSP 0x00000002 /* transparent mode : use original DEST as dispatch */
-/* unused: 0x04, 0x08, 0x10, 0x20 */
+/* unused: 0x04, 0x08, 0x10 */
+#define PR_O_PREF_LAST 0x00000020 /* prefer last server */
#define PR_O_DISPATCH 0x00000040 /* use dispatch mode */
#define PR_O_KEEPALIVE 0x00000080 /* follow keep-alive sessions */
#define PR_O_FWDFOR 0x00000100 /* conditionally insert x-forwarded-for with client address */