MEDIUM: threads/lb: Make LB algorithms (lb_*.c) thread-safe
A lock for LB parameters has been added inside the proxy structure and atomic
operations have been used to update server variables releated to lb.
The only significant change is about lb_map. Because the servers status are
updated in the sync-point, we can call recalc_server_map function synchronously
in map_set_server_status_up/down function.
diff --git a/src/backend.c b/src/backend.c
index d17635f..23b85ce 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -99,6 +99,10 @@
* this.
* This functions is designed to be called before server's weight and state
* commit so it uses 'next' weight and states values.
+ *
+ * threads: this is the caller responsibility to lock data. For now, this
+ * function is called from lb modules, so it should be ok. But if you need to
+ * call it from another place, be careful (and update this comment).
*/
void recount_servers(struct proxy *px)
{
@@ -129,6 +133,10 @@
/* This function simply updates the backend's tot_weight and tot_used values
* after servers weights have been updated. It is designed to be used after
* recount_servers() or equivalent.
+ *
+ * threads: this is the caller responsibility to lock data. For now, this
+ * function is called from lb modules, so it should be ok. But if you need to
+ * call it from another place, be careful (and update this comment).
*/
void update_backend_weight(struct proxy *px)
{
@@ -233,7 +241,7 @@
return map_get_server_hash(px, hash);
}
-/*
+/*
* This function tries to find a running server for the proxy <px> following
* the URL parameter hash method. It looks for a specific parameter in the
* URL and hashes it to compute the server ID. This is useful to optimize
@@ -503,7 +511,7 @@
else
return map_get_server_hash(px, hash);
}
-
+
/*
* This function applies the load-balancing algorithm to the stream, as
* defined by the backend it is assigned to. The stream is then marked as
@@ -579,6 +587,7 @@
s->target = &srv->obj_type;
}
else if (s->be->lbprm.algo & BE_LB_KIND) {
+
/* we must check if we have at least one server available */
if (!s->be->lbprm.tot_weight) {
err = SRV_STATUS_NOSRV;