[CLEANUP] backend: move LB algos to individual files
It was becoming painful to have all the LB algos in backend.c.
Let's move them to their own files. A few hashing functions still
need be broken in two parts, one for the contents and one for the
map position.
diff --git a/src/lb_fwrr.c b/src/lb_fwrr.c
new file mode 100644
index 0000000..84d179d
--- /dev/null
+++ b/src/lb_fwrr.c
@@ -0,0 +1,576 @@
+/*
+ * 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 <common/compat.h>
+#include <common/config.h>
+#include <common/debug.h>
+#include <common/eb32tree.h>
+
+#include <types/global.h>
+#include <types/server.h>
+
+#include <proto/backend.h>
+#include <proto/queue.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).
+ */
+static void fwrr_set_server_status_down(struct server *srv)
+{
+ struct proxy *p = srv->proxy;
+ struct fwrr_group *grp;
+
+ if (srv->state == srv->prev_state &&
+ srv->eweight == srv->prev_eweight)
+ return;
+
+ if (srv_is_usable(srv->state, srv->eweight))
+ goto out_update_state;
+
+ if (!srv_is_usable(srv->prev_state, srv->prev_eweight))
+ /* server was already down */
+ goto out_update_backend;
+
+ grp = (srv->state & SRV_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+ grp->next_weight -= srv->prev_eweight;
+
+ if (srv->state & SRV_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->state & SRV_BACKUP) &&
+ srv_is_usable(srv2->state, srv2->eweight)));
+ 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);
+ out_update_state:
+ srv->prev_state = srv->state;
+ srv->prev_eweight = srv->eweight;
+}
+
+/* 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.
+ */
+static void fwrr_set_server_status_up(struct server *srv)
+{
+ struct proxy *p = srv->proxy;
+ struct fwrr_group *grp;
+
+ if (srv->state == srv->prev_state &&
+ srv->eweight == srv->prev_eweight)
+ return;
+
+ if (!srv_is_usable(srv->state, srv->eweight))
+ goto out_update_state;
+
+ if (srv_is_usable(srv->prev_state, srv->prev_eweight))
+ /* server was already up */
+ goto out_update_backend;
+
+ grp = (srv->state & SRV_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+ grp->next_weight += srv->eweight;
+
+ if (srv->state & SRV_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->eweight;
+ fwrr_queue_srv(srv);
+
+out_update_backend:
+ /* check/update tot_used, tot_weight */
+ update_backend_weight(p);
+ out_update_state:
+ srv->prev_state = srv->state;
+ srv->prev_eweight = srv->eweight;
+}
+
+/* This function must be called after an update to server <srv>'s effective
+ * weight. It may be called after a state change too.
+ */
+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->state == srv->prev_state &&
+ srv->eweight == srv->prev_eweight)
+ 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_is_usable(srv->prev_state, srv->prev_eweight);
+ new_state = srv_is_usable(srv->state, srv->eweight);
+
+ if (!old_state && !new_state) {
+ srv->prev_state = srv->state;
+ srv->prev_eweight = srv->eweight;
+ 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;
+ }
+
+ grp = (srv->state & SRV_BACKUP) ? &p->lbprm.fwrr.bck : &p->lbprm.fwrr.act;
+ grp->next_weight = grp->next_weight - srv->prev_eweight + srv->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->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->eweight > 0) {
+ int prev_next = srv->npos;
+ int step = grp->next_weight / srv->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);
+ srv->prev_state = srv->state;
+ srv->prev_eweight = srv->eweight;
+}
+
+/* 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.
+ */
+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.
+ */
+static inline void fwrr_queue_by_weight(struct eb_root *root, struct server *s)
+{
+ s->lb_node.key = SRV_EWGHT_MAX - s->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->prev_eweight = srv->eweight = srv->uweight * BE_WEIGHT_SCALE;
+ srv->prev_state = srv->state;
+ }
+
+ 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_is_usable(srv->state, srv->eweight))
+ continue;
+ fwrr_queue_by_weight((srv->state & SRV_BACKUP) ?
+ p->lbprm.fwrr.bck.init :
+ p->lbprm.fwrr.act.init,
+ srv);
+ }
+}
+
+/* simply removes a server from a weight tree */
+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.
+ */
+static void fwrr_queue_srv(struct server *s)
+{
+ struct proxy *p = s->proxy;
+ struct fwrr_group *grp;
+
+ grp = (s->state & SRV_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 theorical new window.
+ */
+ if (!srv_is_usable(s->state, s->eweight)) {
+ fwrr_remove_from_tree(s);
+ }
+ else if (s->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 eb3é_insert().
+ */
+ s->lb_node.key = SRV_UWGHT_RANGE * s->npos +
+ (unsigned)(SRV_EWGHT_MAX + s->rweight - s->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 */
+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 */
+static inline void fwrr_get_srv_next(struct server *s)
+{
+ struct fwrr_group *grp = (s->state & SRV_BACKUP) ?
+ &s->proxy->lbprm.fwrr.bck :
+ &s->proxy->lbprm.fwrr.act;
+
+ s->npos += grp->curr_weight;
+}
+
+/* prepares a server when it was marked down */
+static inline void fwrr_get_srv_down(struct server *s)
+{
+ struct fwrr_group *grp = (s->state & SRV_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 */
+static void fwrr_get_srv(struct server *s)
+{
+ struct proxy *p = s->proxy;
+ struct fwrr_group *grp = (s->state & SRV_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.
+ */
+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.
+ */
+static struct server *fwrr_get_server_from_group(struct fwrr_group *grp)
+{
+ struct eb32_node *node;
+ struct server *s;
+
+ node = eb32_first(&grp->curr);
+ s = eb32_entry(node, struct server, lb_node);
+
+ if (!node || s->npos > grp->curr_pos) {
+ /* either we have no server left, or we have a hole */
+ struct eb32_node *node2;
+ node2 = eb32_first(grp->init);
+ if (node2) {
+ node = node2;
+ s = eb32_entry(node, struct server, lb_node);
+ fwrr_get_srv_init(s);
+ if (s->eweight == 0) /* FIXME: is it possible at all ? */
+ node = NULL;
+ }
+ }
+ if (node)
+ return s;
+ else
+ return NULL;
+}
+
+/* Computes next position of server <s> in the group. It is mandatory for <s>
+ * to have a non-zero, positive eweight.
+*/
+static inline void fwrr_update_position(struct fwrr_group *grp, struct server *s)
+{
+ if (!s->npos) {
+ /* first time ever for this server */
+ s->lpos = grp->curr_pos;
+ s->npos = grp->curr_pos + grp->next_weight / s->eweight;
+ s->rweight += grp->next_weight % s->eweight;
+
+ if (s->rweight >= s->eweight) {
+ s->rweight -= s->eweight;
+ s->npos++;
+ }
+ } else {
+ s->lpos = s->npos;
+ s->npos += grp->next_weight / s->eweight;
+ s->rweight += grp->next_weight % s->eweight;
+
+ if (s->rweight >= s->eweight) {
+ s->rweight -= s->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.
+ */
+struct server *fwrr_get_next_server(struct proxy *p, struct server *srvtoavoid)
+{
+ struct server *srv, *full, *avoided;
+ struct fwrr_group *grp;
+ int switched;
+
+ if (p->srv_act)
+ grp = &p->lbprm.fwrr.act;
+ else if (p->lbprm.fbck)
+ return p->lbprm.fbck;
+ else if (p->srv_bck)
+ grp = &p->lbprm.fwrr.bck;
+ else
+ return NULL;
+
+ 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;
+ break;
+ }
+ 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->nbpend && 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;
+ }
+
+ /* 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 (unsucessfully) and chained, omit it now.
+ */
+ 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);
+ }
+ }
+ return srv;
+}
+
+/*
+ * Local variables:
+ * c-indent-level: 8
+ * c-basic-offset: 8
+ * End:
+ */