Adding upstream version 2.6.12.upstream/2.6.12upstream

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

1 files changed, 517 insertions, 0 deletions

diff --git a/src/lb_chash.c b/src/lb_chash.c
new file mode 100644
index 0000000..023219c
--- /dev/null
+++ b/src/lb_chash.c
@@ -0,0 +1,517 @@
+/*
+ * Consistent Hash implementation
+ * Please consult this very well detailed article for more information :
+ * http://www.spiteful.com/2008/03/17/programmers-toolbox-part-3-consistent-hashing/
+ *
+ * Our implementation has to support both weighted hashing and weighted round
+ * robin because we'll use it to replace the previous map-based implementation
+ * which offered both algorithms.
+ *
+ * Copyright 2000-2010 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/errors.h>
+#include <haproxy/queue.h>
+#include <haproxy/server-t.h>
+#include <haproxy/tools.h>
+
+/* Return next tree node after <node> which must still be in the tree, or be
+ * NULL. Lookup wraps around the end to the beginning. If the next node is the
+ * same node, return NULL. This is designed to find a valid next node before
+ * deleting one from the tree.
+ */
+static inline struct eb32_node *chash_skip_node(struct eb_root *root, struct eb32_node *node)
+{
+	struct eb32_node *stop = node;
+
+	if (!node)
+		return NULL;
+	node = eb32_next(node);
+	if (!node)
+		node = eb32_first(root);
+	if (node == stop)
+		return NULL;
+	return node;
+}
+
+/* Remove all of a server's entries from its tree. This may be used when
+ * setting a server down.
+ */
+static inline void chash_dequeue_srv(struct server *s)
+{
+	while (s->lb_nodes_now > 0) {
+		if (s->lb_nodes_now >= s->lb_nodes_tot) // should always be false anyway
+			s->lb_nodes_now = s->lb_nodes_tot;
+		s->lb_nodes_now--;
+		if (s->proxy->lbprm.chash.last == &s->lb_nodes[s->lb_nodes_now].node)
+			s->proxy->lbprm.chash.last = chash_skip_node(s->lb_tree, s->proxy->lbprm.chash.last);
+		eb32_delete(&s->lb_nodes[s->lb_nodes_now].node);
+	}
+}
+
+/* Adjust the number of entries of a server in its tree. The server must appear
+ * as many times as its weight indicates it. If it's there too often, we remove
+ * the last occurrences. If it's not there enough, we add more occurrences. To
+ * remove a server from the tree, normally call this with eweight=0.
+ *
+ * The server's lock and the lbprm's lock must be held.
+ */
+static inline void chash_queue_dequeue_srv(struct server *s)
+{
+	while (s->lb_nodes_now > s->next_eweight) {
+		if (s->lb_nodes_now >= s->lb_nodes_tot) // should always be false anyway
+			s->lb_nodes_now = s->lb_nodes_tot;
+		s->lb_nodes_now--;
+		if (s->proxy->lbprm.chash.last == &s->lb_nodes[s->lb_nodes_now].node)
+			s->proxy->lbprm.chash.last = chash_skip_node(s->lb_tree, s->proxy->lbprm.chash.last);
+		eb32_delete(&s->lb_nodes[s->lb_nodes_now].node);
+	}
+
+	/* Attempt to increase the total number of nodes, if the user
+	 * increased the weight beyond the original weight
+	 */
+	if (s->lb_nodes_tot < s->next_eweight) {
+		struct tree_occ *new_nodes;
+
+		/* First we need to remove all server's entries from its tree
+		 * because the realloc will change all nodes pointers */
+		chash_dequeue_srv(s);
+
+		new_nodes = realloc(s->lb_nodes, s->next_eweight * sizeof(*new_nodes));
+		if (new_nodes) {
+			unsigned int j;
+
+			s->lb_nodes = new_nodes;
+			memset(&s->lb_nodes[s->lb_nodes_tot], 0,
+			    (s->next_eweight - s->lb_nodes_tot) * sizeof(*s->lb_nodes));
+			for (j = s->lb_nodes_tot; j < s->next_eweight; j++) {
+				s->lb_nodes[j].server = s;
+				s->lb_nodes[j].node.key = full_hash(s->puid * SRV_EWGHT_RANGE + j);
+			}
+			s->lb_nodes_tot = s->next_eweight;
+		}
+	}
+	while (s->lb_nodes_now < s->next_eweight) {
+		if (s->lb_nodes_now >= s->lb_nodes_tot) // should always be false anyway
+			break;
+		if (s->proxy->lbprm.chash.last == &s->lb_nodes[s->lb_nodes_now].node)
+			s->proxy->lbprm.chash.last = chash_skip_node(s->lb_tree, s->proxy->lbprm.chash.last);
+		eb32_insert(s->lb_tree, &s->lb_nodes[s->lb_nodes_now].node);
+		s->lb_nodes_now++;
+	}
+}
+
+/* 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 lock will be used.
+ */
+static void chash_set_server_status_down(struct server *srv)
+{
+	struct proxy *p = srv->proxy;
+
+	if (!srv_lb_status_changed(srv))
+               return;
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	if (srv_willbe_usable(srv))
+		goto out_update_state;
+
+	if (!srv_currently_usable(srv))
+		/* server was already down */
+		goto out_update_backend;
+
+	if (srv->flags & SRV_F_BACKUP) {
+		p->lbprm.tot_wbck -= srv->cur_eweight;
+		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 -= srv->cur_eweight;
+		p->srv_act--;
+	}
+
+	chash_dequeue_srv(srv);
+
+out_update_backend:
+	/* check/update tot_used, tot_weight */
+	update_backend_weight(p);
+ out_update_state:
+	srv_lb_commit_status(srv);
+
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+}
+
+/* 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 lock will be used.
+ */
+static void chash_set_server_status_up(struct server *srv)
+{
+	struct proxy *p = srv->proxy;
+
+	if (!srv_lb_status_changed(srv))
+               return;
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	if (!srv_willbe_usable(srv))
+		goto out_update_state;
+
+	if (srv_currently_usable(srv))
+		/* server was already up */
+		goto out_update_backend;
+
+	if (srv->flags & SRV_F_BACKUP) {
+		p->lbprm.tot_wbck += srv->next_eweight;
+		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 += srv->next_eweight;
+		p->srv_act++;
+	}
+
+	/* note that eweight cannot be 0 here */
+	chash_queue_dequeue_srv(srv);
+
+ out_update_backend:
+	/* check/update tot_used, tot_weight */
+	update_backend_weight(p);
+ out_update_state:
+	srv_lb_commit_status(srv);
+
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+}
+
+/* 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 lock may be used.
+ */
+static void chash_update_server_weight(struct server *srv)
+{
+	int old_state, new_state;
+	struct proxy *p = srv->proxy;
+
+	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) {
+		chash_set_server_status_up(srv);
+		return;
+	}
+	else if (old_state && !new_state) {
+		chash_set_server_status_down(srv);
+		return;
+	}
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	/* only adjust the server's presence in the tree */
+	chash_queue_dequeue_srv(srv);
+
+	if (srv->flags & SRV_F_BACKUP)
+		p->lbprm.tot_wbck += srv->next_eweight - srv->cur_eweight;
+	else
+		p->lbprm.tot_wact += srv->next_eweight - srv->cur_eweight;
+
+	update_backend_weight(p);
+	srv_lb_commit_status(srv);
+
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+}
+
+/*
+ * This function implements the "Consistent Hashing with Bounded Loads" algorithm
+ * of Mirrokni, Thorup, and Zadimoghaddam (arxiv:1608.01350), adapted for use with
+ * unequal server weights.
+ */
+int chash_server_is_eligible(struct server *s)
+{
+	/* The total number of slots to allocate is the total number of outstanding requests
+	 * (including the one we're about to make) times the load-balance-factor, rounded up.
+	 */
+	unsigned tot_slots = ((s->proxy->served + 1) * s->proxy->lbprm.hash_balance_factor + 99) / 100;
+	unsigned slots_per_weight = tot_slots / s->proxy->lbprm.tot_weight;
+	unsigned remainder = tot_slots % s->proxy->lbprm.tot_weight;
+
+	/* Allocate a whole number of slots per weight unit... */
+	unsigned slots = s->cur_eweight * slots_per_weight;
+
+	/* And then distribute the rest among servers proportionally to their weight. */
+	slots += ((s->cumulative_weight + s->cur_eweight) * remainder) / s->proxy->lbprm.tot_weight
+		- (s->cumulative_weight * remainder) / s->proxy->lbprm.tot_weight;
+
+	/* But never leave a server with 0. */
+	if (slots == 0)
+		slots = 1;
+
+	return s->served < slots;
+}
+
+/*
+ * This function returns the running server from the CHASH tree, which is at
+ * the closest distance from the value of <hash>. Doing so ensures that even
+ * with a well imbalanced hash, if some servers are close to each other, they
+ * will still both receive traffic. If any server is found, it will be returned.
+ * It will also skip server <avoid> if the hash result ends on this one.
+ * If no valid server is found, NULL is returned.
+ *
+ * The lbprm's lock will be used in R/O mode. The server's lock is not used.
+ */
+struct server *chash_get_server_hash(struct proxy *p, unsigned int hash, const struct server *avoid)
+{
+	struct eb32_node *next, *prev;
+	struct server *nsrv, *psrv;
+	struct eb_root *root;
+	unsigned int dn, dp;
+	int loop;
+
+	HA_RWLOCK_RDLOCK(LBPRM_LOCK, &p->lbprm.lock);
+
+	if (p->srv_act)
+		root = &p->lbprm.chash.act;
+	else if (p->lbprm.fbck) {
+		nsrv = p->lbprm.fbck;
+		goto out;
+	}
+	else if (p->srv_bck)
+		root = &p->lbprm.chash.bck;
+	else {
+		nsrv = NULL;
+		goto out;
+	}
+
+	/* find the node after and the node before */
+	next = eb32_lookup_ge(root, hash);
+	if (!next)
+		next = eb32_first(root);
+	if (!next) {
+		nsrv = NULL; /* tree is empty */
+		goto out;
+	}
+
+	prev = eb32_prev(next);
+	if (!prev)
+		prev = eb32_last(root);
+
+	nsrv = eb32_entry(next, struct tree_occ, node)->server;
+	psrv = eb32_entry(prev, struct tree_occ, node)->server;
+
+	/* OK we're located between two servers, let's
+	 * compare distances between hash and the two servers
+	 * and select the closest server.
+	 */
+	dp = hash - prev->key;
+	dn = next->key - hash;
+
+	if (dp <= dn) {
+		next = prev;
+		nsrv = psrv;
+	}
+
+	loop = 0;
+	while (nsrv == avoid || (p->lbprm.hash_balance_factor && !chash_server_is_eligible(nsrv))) {
+		next = eb32_next(next);
+		if (!next) {
+			next = eb32_first(root);
+			if (++loop > 1) // protection against accidental loop
+				break;
+		}
+		nsrv = eb32_entry(next, struct tree_occ, node)->server;
+	}
+
+ out:
+	HA_RWLOCK_RDUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+	return nsrv;
+}
+
+/* Return next server from the CHASH tree in backend <p>. If the tree is empty,
+ * return NULL. Saturated servers are skipped.
+ *
+ * The lbprm's lock will be used in R/W mode. The server's lock is not used.
+ */
+struct server *chash_get_next_server(struct proxy *p, struct server *srvtoavoid)
+{
+	struct server *srv, *avoided;
+	struct eb32_node *node, *stop, *avoided_node;
+	struct eb_root *root;
+
+	srv = avoided = NULL;
+	avoided_node = NULL;
+
+	HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock);
+	if (p->srv_act)
+		root = &p->lbprm.chash.act;
+	else if (p->lbprm.fbck) {
+		srv = p->lbprm.fbck;
+		goto out;
+	}
+	else if (p->srv_bck)
+		root = &p->lbprm.chash.bck;
+	else {
+		srv = NULL;
+		goto out;
+	}
+
+	stop = node = p->lbprm.chash.last;
+	do {
+		struct server *s;
+
+		if (node)
+			node = eb32_next(node);
+		if (!node)
+			node = eb32_first(root);
+
+		p->lbprm.chash.last = node;
+		if (!node) {
+			/* no node is available */
+			srv = NULL;
+			goto out;
+		}
+
+		/* Note: if we came here after a down/up cycle with no last
+		 * pointer, and after a redispatch (srvtoavoid is set), we
+		 * must set stop to non-null otherwise we can loop forever.
+		 */
+		if (!stop)
+			stop = node;
+
+		/* OK, we have a server. However, it may be saturated, in which
+		 * case we don't want to reconsider it for now, so we'll simply
+		 * skip it. Same if it's the server we try to avoid, in which
+		 * case we simply remember it for later use if needed.
+		 */
+		s = eb32_entry(node, struct tree_occ, node)->server;
+		if (!s->maxconn || (!s->queue.length && s->served < srv_dynamic_maxconn(s))) {
+			if (s != srvtoavoid) {
+				srv = s;
+				break;
+			}
+			avoided = s;
+			avoided_node = node;
+		}
+	} while (node != stop);
+
+	if (!srv) {
+		srv = avoided;
+		p->lbprm.chash.last = avoided_node;
+	}
+
+ out:
+	HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock);
+	return srv;
+}
+
+/* This function is responsible for building the active and backup trees for
+ * constistent hashing. The servers receive an array of initialized nodes
+ * with their assigned keys. It also sets p->lbprm.wdiv to the eweight to
+ * uweight ratio.
+ * Return 0 in case of success, -1 in case of allocation failure.
+ */
+int chash_init_server_tree(struct proxy *p)
+{
+	struct server *srv;
+	struct eb_root init_head = EB_ROOT;
+	int node;
+
+	p->lbprm.set_server_status_up   = chash_set_server_status_up;
+	p->lbprm.set_server_status_down = chash_set_server_status_down;
+	p->lbprm.update_server_eweight  = chash_update_server_weight;
+	p->lbprm.server_take_conn = NULL;
+	p->lbprm.server_drop_conn = NULL;
+
+	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);
+
+	p->lbprm.chash.act = init_head;
+	p->lbprm.chash.bck = init_head;
+	p->lbprm.chash.last = NULL;
+
+	/* queue active and backup servers in two distinct groups */
+	for (srv = p->srv; srv; srv = srv->next) {
+		srv->lb_tree = (srv->flags & SRV_F_BACKUP) ? &p->lbprm.chash.bck : &p->lbprm.chash.act;
+		srv->lb_nodes_tot = srv->uweight * BE_WEIGHT_SCALE;
+		srv->lb_nodes_now = 0;
+		srv->lb_nodes = calloc(srv->lb_nodes_tot,
+				       sizeof(*srv->lb_nodes));
+		if (!srv->lb_nodes) {
+			ha_alert("failed to allocate lb_nodes for server %s.\n", srv->id);
+			return -1;
+		}
+		for (node = 0; node < srv->lb_nodes_tot; node++) {
+			srv->lb_nodes[node].server = srv;
+			srv->lb_nodes[node].node.key = full_hash(srv->puid * SRV_EWGHT_RANGE + node);
+		}
+
+		if (srv_currently_usable(srv))
+			chash_queue_dequeue_srv(srv);
+	}
+	return 0;
+}