Adding upstream version 2.6.12.upstream/2.6.12upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 623 insertions, 0 deletions

diff --git a/src/lb_fwrr.c b/src/lb_fwrr.c
new file mode 100644
index 0000000..a762623
--- /dev/null
+++ b/src/lb_fwrr.c
@@ -0,0 +1,623 @@
+/*
+ * Fast Weighted Round Robin load balancing algorithm.
+ *
+ * Copyright 2000-2009 Willy Tarreau <w@1wt.eu>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ */
+
+#include <import/eb32tree.h>
+#include <haproxy/api.h>
+#include <haproxy/backend.h>
+#include <haproxy/queue.h>
+#include <haproxy/server-t.h>
+
+
+static inline void fwrr_remove_from_tree(struct server *s);
+static inline void fwrr_queue_by_weight(struct eb_root *root, struct server *s);
+static inline void fwrr_dequeue_srv(struct server *s);
+static void fwrr_get_srv(struct server *s);
+static void fwrr_queue_srv(struct server *s);
+
+
+/* This function updates the server trees according to server <srv>'s new
+ * state. It should be called when server <srv>'s status changes to down.
+ * It is not important whether the server was already down or not. It is not
+ * important either that the new state is completely down (the caller may not
+ * know all the variables of a server's state).
+ *
+ * The server's lock must be held. The lbprm's lock will be used.
+ */
+static void fwrr_set_server_status_down(struct server *srv)
+{
+	struct proxy *p = srv->proxy;
+	struct fwrr_group *grp;
+
+	if (!srv_lb_status_changed(srv))
+		return;
+
+	if (srv_willbe_usable(srv))
+		goto out_update_state;
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	if (!srv_currently_usable(srv))
+		/* server was already down */
+		goto out_update_backend;
+
+	grp = (srv->flags & SRV_F_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+	grp->next_weight -= srv->cur_eweight;
+
+	if (srv->flags & SRV_F_BACKUP) {
+		p->lbprm.tot_wbck = p->lbprm.fwrr.bck.next_weight;
+		p->srv_bck--;
+
+		if (srv == p->lbprm.fbck) {
+			/* we lost the first backup server in a single-backup
+			 * configuration, we must search another one.
+			 */
+			struct server *srv2 = p->lbprm.fbck;
+			do {
+				srv2 = srv2->next;
+			} while (srv2 &&
+				 !((srv2->flags & SRV_F_BACKUP) &&
+				   srv_willbe_usable(srv2)));
+			p->lbprm.fbck = srv2;
+		}
+	} else {
+		p->lbprm.tot_wact = p->lbprm.fwrr.act.next_weight;
+		p->srv_act--;
+	}
+
+	fwrr_dequeue_srv(srv);
+	fwrr_remove_from_tree(srv);
+
+out_update_backend:
+	/* check/update tot_used, tot_weight */
+	update_backend_weight(p);
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+ out_update_state:
+	srv_lb_commit_status(srv);
+}
+
+/* This function updates the server trees according to server <srv>'s new
+ * state. It should be called when server <srv>'s status changes to up.
+ * It is not important whether the server was already down or not. It is not
+ * important either that the new state is completely UP (the caller may not
+ * know all the variables of a server's state). This function will not change
+ * the weight of a server which was already up.
+ *
+ * The server's lock must be held. The lbprm's lock will be used.
+ */
+static void fwrr_set_server_status_up(struct server *srv)
+{
+	struct proxy *p = srv->proxy;
+	struct fwrr_group *grp;
+
+	if (!srv_lb_status_changed(srv))
+		return;
+
+	if (!srv_willbe_usable(srv))
+		goto out_update_state;
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	if (srv_currently_usable(srv))
+		/* server was already up */
+		goto out_update_backend;
+
+	grp = (srv->flags & SRV_F_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+	grp->next_weight += srv->next_eweight;
+
+	if (srv->flags & SRV_F_BACKUP) {
+		p->lbprm.tot_wbck = p->lbprm.fwrr.bck.next_weight;
+		p->srv_bck++;
+
+		if (!(p->options & PR_O_USE_ALL_BK)) {
+			if (!p->lbprm.fbck) {
+				/* there was no backup server anymore */
+				p->lbprm.fbck = srv;
+			} else {
+				/* we may have restored a backup server prior to fbck,
+				 * in which case it should replace it.
+				 */
+				struct server *srv2 = srv;
+				do {
+					srv2 = srv2->next;
+				} while (srv2 && (srv2 != p->lbprm.fbck));
+				if (srv2)
+					p->lbprm.fbck = srv;
+			}
+		}
+	} else {
+		p->lbprm.tot_wact = p->lbprm.fwrr.act.next_weight;
+		p->srv_act++;
+	}
+
+	/* note that eweight cannot be 0 here */
+	fwrr_get_srv(srv);
+	srv->npos = grp->curr_pos + (grp->next_weight + grp->curr_weight - grp->curr_pos) / srv->next_eweight;
+	fwrr_queue_srv(srv);
+
+out_update_backend:
+	/* check/update tot_used, tot_weight */
+	update_backend_weight(p);
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+ out_update_state:
+	srv_lb_commit_status(srv);
+}
+
+/* This function must be called after an update to server <srv>'s effective
+ * weight. It may be called after a state change too.
+ *
+ * The server's lock must be held. The lbprm's lock will be used.
+ */
+static void fwrr_update_server_weight(struct server *srv)
+{
+	int old_state, new_state;
+	struct proxy *p = srv->proxy;
+	struct fwrr_group *grp;
+
+	if (!srv_lb_status_changed(srv))
+		return;
+
+	/* If changing the server's weight changes its state, we simply apply
+	 * the procedures we already have for status change. If the state
+	 * remains down, the server is not in any tree, so it's as easy as
+	 * updating its values. If the state remains up with different weights,
+	 * there are some computations to perform to find a new place and
+	 * possibly a new tree for this server.
+	 */
+	 
+	old_state = srv_currently_usable(srv);
+	new_state = srv_willbe_usable(srv);
+
+	if (!old_state && !new_state) {
+		srv_lb_commit_status(srv);
+		return;
+	}
+	else if (!old_state && new_state) {
+		fwrr_set_server_status_up(srv);
+		return;
+	}
+	else if (old_state && !new_state) {
+		fwrr_set_server_status_down(srv);
+		return;
+	}
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	grp = (srv->flags & SRV_F_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+	grp->next_weight = grp->next_weight - srv->cur_eweight + srv->next_eweight;
+
+	p->lbprm.tot_wact = p->lbprm.fwrr.act.next_weight;
+	p->lbprm.tot_wbck = p->lbprm.fwrr.bck.next_weight;
+
+	if (srv->lb_tree == grp->init) {
+		fwrr_dequeue_srv(srv);
+		fwrr_queue_by_weight(grp->init, srv);
+	}
+	else if (!srv->lb_tree) {
+		/* FIXME: server was down. This is not possible right now but
+		 * may be needed soon for slowstart or graceful shutdown.
+		 */
+		fwrr_dequeue_srv(srv);
+		fwrr_get_srv(srv);
+		srv->npos = grp->curr_pos + (grp->next_weight + grp->curr_weight - grp->curr_pos) / srv->next_eweight;
+		fwrr_queue_srv(srv);
+	} else {
+		/* The server is either active or in the next queue. If it's
+		 * still in the active queue and it has not consumed all of its
+		 * places, let's adjust its next position.
+		 */
+		fwrr_get_srv(srv);
+
+		if (srv->next_eweight > 0) {
+			int prev_next = srv->npos;
+			int step = grp->next_weight / srv->next_eweight;
+
+			srv->npos = srv->lpos + step;
+			srv->rweight = 0;
+
+			if (srv->npos > prev_next)
+				srv->npos = prev_next;
+			if (srv->npos < grp->curr_pos + 2)
+				srv->npos = grp->curr_pos + step;
+		} else {
+			/* push it into the next tree */
+			srv->npos = grp->curr_pos + grp->curr_weight;
+		}
+
+		fwrr_dequeue_srv(srv);
+		fwrr_queue_srv(srv);
+	}
+
+	update_backend_weight(p);
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	srv_lb_commit_status(srv);
+}
+
+/* Remove a server from a tree. It must have previously been dequeued. This
+ * function is meant to be called when a server is going down or has its
+ * weight disabled.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_remove_from_tree(struct server *s)
+{
+	s->lb_tree = NULL;
+}
+
+/* Queue a server in the weight tree <root>, assuming the weight is >0.
+ * We want to sort them by inverted weights, because we need to place
+ * heavy servers first in order to get a smooth distribution.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_queue_by_weight(struct eb_root *root, struct server *s)
+{
+	s->lb_node.key = SRV_EWGHT_MAX - s->next_eweight;
+	eb32_insert(root, &s->lb_node);
+	s->lb_tree = root;
+}
+
+/* This function is responsible for building the weight trees in case of fast
+ * weighted round-robin. It also sets p->lbprm.wdiv to the eweight to uweight
+ * ratio. Both active and backup groups are initialized.
+ */
+void fwrr_init_server_groups(struct proxy *p)
+{
+	struct server *srv;
+	struct eb_root init_head = EB_ROOT;
+
+	p->lbprm.set_server_status_up   = fwrr_set_server_status_up;
+	p->lbprm.set_server_status_down = fwrr_set_server_status_down;
+	p->lbprm.update_server_eweight  = fwrr_update_server_weight;
+
+	p->lbprm.wdiv = BE_WEIGHT_SCALE;
+	for (srv = p->srv; srv; srv = srv->next) {
+		srv->next_eweight = (srv->uweight * p->lbprm.wdiv + p->lbprm.wmult - 1) / p->lbprm.wmult;
+		srv_lb_commit_status(srv);
+	}
+
+	recount_servers(p);
+	update_backend_weight(p);
+
+	/* prepare the active servers group */
+	p->lbprm.fwrr.act.curr_pos = p->lbprm.fwrr.act.curr_weight =
+		p->lbprm.fwrr.act.next_weight = p->lbprm.tot_wact;
+	p->lbprm.fwrr.act.curr = p->lbprm.fwrr.act.t0 =
+		p->lbprm.fwrr.act.t1 = init_head;
+	p->lbprm.fwrr.act.init = &p->lbprm.fwrr.act.t0;
+	p->lbprm.fwrr.act.next = &p->lbprm.fwrr.act.t1;
+
+	/* prepare the backup servers group */
+	p->lbprm.fwrr.bck.curr_pos = p->lbprm.fwrr.bck.curr_weight =
+		p->lbprm.fwrr.bck.next_weight = p->lbprm.tot_wbck;
+	p->lbprm.fwrr.bck.curr = p->lbprm.fwrr.bck.t0 =
+		p->lbprm.fwrr.bck.t1 = init_head;
+	p->lbprm.fwrr.bck.init = &p->lbprm.fwrr.bck.t0;
+	p->lbprm.fwrr.bck.next = &p->lbprm.fwrr.bck.t1;
+
+	/* queue active and backup servers in two distinct groups */
+	for (srv = p->srv; srv; srv = srv->next) {
+		if (!srv_currently_usable(srv))
+			continue;
+		fwrr_queue_by_weight((srv->flags & SRV_F_BACKUP) ?
+				p->lbprm.fwrr.bck.init :
+				p->lbprm.fwrr.act.init,
+				srv);
+	}
+}
+
+/* simply removes a server from a weight tree.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_dequeue_srv(struct server *s)
+{
+	eb32_delete(&s->lb_node);
+}
+
+/* queues a server into the appropriate group and tree depending on its
+ * backup status, and ->npos. If the server is disabled, simply assign
+ * it to the NULL tree.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static void fwrr_queue_srv(struct server *s)
+{
+	struct proxy *p = s->proxy;
+	struct fwrr_group *grp;
+
+	grp = (s->flags & SRV_F_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+
+	/* Delay everything which does not fit into the window and everything
+	 * which does not fit into the theoretical new window.
+	 */
+	if (!srv_willbe_usable(s)) {
+		fwrr_remove_from_tree(s);
+	}
+	else if (s->next_eweight <= 0 ||
+		 s->npos >= 2 * grp->curr_weight ||
+		 s->npos >= grp->curr_weight + grp->next_weight) {
+		/* put into next tree, and readjust npos in case we could
+		 * finally take this back to current. */
+		s->npos -= grp->curr_weight;
+		fwrr_queue_by_weight(grp->next, s);
+	}
+	else {
+		/* The sorting key is stored in units of s->npos * user_weight
+		 * in order to avoid overflows. As stated in backend.h, the
+		 * 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 eb32_insert().
+		 */
+		s->lb_node.key = SRV_UWGHT_RANGE * s->npos +
+			(unsigned)(SRV_EWGHT_MAX + s->rweight - s->next_eweight) / BE_WEIGHT_SCALE;
+
+		eb32_insert(&grp->curr, &s->lb_node);
+		s->lb_tree = &grp->curr;
+	}
+}
+
+/* prepares a server when extracting it from the "init" tree.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_get_srv_init(struct server *s)
+{
+	s->npos = s->rweight = 0;
+}
+
+/* prepares a server when extracting it from the "next" tree.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_get_srv_next(struct server *s)
+{
+	struct fwrr_group *grp = (s->flags & SRV_F_BACKUP) ?
+		&s->proxy->lbprm.fwrr.bck :
+		&s->proxy->lbprm.fwrr.act;
+
+	s->npos += grp->curr_weight;
+}
+
+/* prepares a server when it was marked down.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_get_srv_down(struct server *s)
+{
+	struct fwrr_group *grp = (s->flags & SRV_F_BACKUP) ?
+		&s->proxy->lbprm.fwrr.bck :
+		&s->proxy->lbprm.fwrr.act;
+
+	s->npos = grp->curr_pos;
+}
+
+/* prepares a server when extracting it from its tree.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static void fwrr_get_srv(struct server *s)
+{
+	struct proxy *p = s->proxy;
+	struct fwrr_group *grp = (s->flags & SRV_F_BACKUP) ?
+		&p->lbprm.fwrr.bck :
+		&p->lbprm.fwrr.act;
+
+	if (s->lb_tree == grp->init) {
+		fwrr_get_srv_init(s);
+	}
+	else if (s->lb_tree == grp->next) {
+		fwrr_get_srv_next(s);
+	}
+	else if (s->lb_tree == NULL) {
+		fwrr_get_srv_down(s);
+	}
+}
+
+/* switches trees "init" and "next" for FWRR group <grp>. "init" should be empty
+ * when this happens, and "next" filled with servers sorted by weights.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static inline void fwrr_switch_trees(struct fwrr_group *grp)
+{
+	struct eb_root *swap;
+	swap = grp->init;
+	grp->init = grp->next;
+	grp->next = swap;
+	grp->curr_weight = grp->next_weight;
+	grp->curr_pos = grp->curr_weight;
+}
+
+/* return next server from the current tree in FWRR group <grp>, or a server
+ * from the "init" tree if appropriate. If both trees are empty, return NULL.
+ *
+ * The lbprm's lock must be held. The server's lock is not used.
+ */
+static struct server *fwrr_get_server_from_group(struct fwrr_group *grp)
+{
+	struct eb32_node *node1;
+	struct eb32_node *node2;
+	struct server *s1 = NULL;
+	struct server *s2 = NULL;
+
+	node1 = eb32_first(&grp->curr);
+	if (node1) {
+		s1 = eb32_entry(node1, struct server, lb_node);
+		if (s1->cur_eweight && s1->npos <= grp->curr_pos)
+			return s1;
+	}
+
+	/* Either we have no server left, or we have a hole. We'll look in the
+	 * init tree or a better proposal. At this point, if <s1> is non-null,
+	 * it is guaranteed to remain available as the tree is locked.
+	 */
+	node2 = eb32_first(grp->init);
+	if (node2) {
+		s2 = eb32_entry(node2, struct server, lb_node);
+		if (s2->cur_eweight) {
+			fwrr_get_srv_init(s2);
+			return s2;
+		}
+	}
+	return s1;
+}
+
+/* Computes next position of server <s> in the group. Nothing is done if <s>
+ * has a zero weight. 
+ *
+ * The lbprm's lock must be held to protect lpos/npos/rweight.
+ */
+static inline void fwrr_update_position(struct fwrr_group *grp, struct server *s)
+{
+	unsigned int eweight = *(volatile unsigned int *)&s->cur_eweight;
+
+	if (!eweight)
+		return;
+
+	if (!s->npos) {
+		/* first time ever for this server */
+		s->npos     = grp->curr_pos;
+	}
+
+	s->lpos     = s->npos;
+	s->npos    += grp->next_weight / eweight;
+	s->rweight += grp->next_weight % eweight;
+
+	if (s->rweight >= eweight) {
+		s->rweight -= eweight;
+		s->npos++;
+	}
+}
+
+/* Return next server from the current tree in backend <p>, or a server from
+ * the init tree if appropriate. If both trees are empty, return NULL.
+ * Saturated servers are skipped and requeued.
+ *
+ * The lbprm's lock will be used in R/W mode. The server's lock is not used.
+ */
+struct server *fwrr_get_next_server(struct proxy *p, struct server *srvtoavoid)
+{
+	struct server *srv, *full, *avoided;
+	struct fwrr_group *grp;
+	int switched;
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+	if (p->srv_act)
+		grp = &p->lbprm.fwrr.act;
+	else if (p->lbprm.fbck) {
+		srv = p->lbprm.fbck;
+		goto out;
+	}
+	else if (p->srv_bck)
+		grp = &p->lbprm.fwrr.bck;
+	else {
+		srv = NULL;
+		goto out;
+	}
+
+	switched = 0;
+	avoided = NULL;
+	full = NULL; /* NULL-terminated list of saturated servers */
+	while (1) {
+		/* if we see an empty group, let's first try to collect weights
+		 * which might have recently changed.
+		 */
+		if (!grp->curr_weight)
+			grp->curr_pos = grp->curr_weight = grp->next_weight;
+
+		/* get first server from the "current" tree. When the end of
+		 * the tree is reached, we may have to switch, but only once.
+		 */
+		while (1) {
+			srv = fwrr_get_server_from_group(grp);
+			if (srv)
+				break;
+			if (switched) {
+				if (avoided) {
+					srv = avoided;
+					goto take_this_one;
+				}
+				goto requeue_servers;
+			}
+			switched = 1;
+			fwrr_switch_trees(grp);
+		}
+
+		/* OK, we have a server. However, it may be saturated, in which
+		 * case we don't want to reconsider it for now. We'll update
+		 * its position and dequeue it anyway, so that we can move it
+		 * to a better place afterwards.
+		 */
+		fwrr_update_position(grp, srv);
+		fwrr_dequeue_srv(srv);
+		grp->curr_pos++;
+		if (!srv->maxconn || (!srv->queue.length && srv->served < srv_dynamic_maxconn(srv))) {
+			/* make sure it is not the server we are trying to exclude... */
+			if (srv != srvtoavoid || avoided)
+				break;
+
+			avoided = srv; /* ...but remember that is was selected yet avoided */
+		}
+
+		/* the server is saturated or avoided, let's chain it for later reinsertion.
+		 */
+		srv->next_full = full;
+		full = srv;
+	}
+
+ take_this_one:
+	/* OK, we got the best server, let's update it */
+	fwrr_queue_srv(srv);
+
+ requeue_servers:
+	/* Requeue all extracted servers. If full==srv then it was
+	 * avoided (unsuccessfully) and chained, omit it now. The
+	 * only way to get there is by having <avoided>==NULL or
+	 * <avoided>==<srv>.
+	 */
+	if (unlikely(full != NULL)) {
+		if (switched) {
+			/* the tree has switched, requeue all extracted servers
+			 * into "init", because their place was lost, and only
+			 * their weight matters.
+			 */
+			do {
+				if (likely(full != srv))
+					fwrr_queue_by_weight(grp->init, full);
+				full = full->next_full;
+			} while (full);
+		} else {
+			/* requeue all extracted servers just as if they were consumed
+			 * so that they regain their expected place.
+			 */
+			do {
+				if (likely(full != srv))
+					fwrr_queue_srv(full);
+				full = full->next_full;
+			} while (full);
+		}
+	}
+ out:
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+	return srv;
+}
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */