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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 09:35:11 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 09:35:11 +0000 |
commit | da76459dc21b5af2449af2d36eb95226cb186ce2 (patch) | |
tree | 542ebb3c1e796fac2742495b8437331727bbbfa0 /src/lb_fas.c | |
parent | Initial commit. (diff) | |
download | haproxy-da76459dc21b5af2449af2d36eb95226cb186ce2.tar.xz haproxy-da76459dc21b5af2449af2d36eb95226cb186ce2.zip |
Adding upstream version 2.6.12.upstream/2.6.12upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/lb_fas.c | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/src/lb_fas.c b/src/lb_fas.c new file mode 100644 index 0000000..d90388b --- /dev/null +++ b/src/lb_fas.c @@ -0,0 +1,348 @@ +/* + * First Available Server load balancing algorithm. + * + * This file implements an algorithm which emerged during a discussion with + * Steen Larsen, initially inspired from Anshul Gandhi et.al.'s work now + * described as "packing" in section 3.5: + * + * http://reports-archive.adm.cs.cmu.edu/anon/2012/CMU-CS-12-109.pdf + * + * Copyright 2000-2012 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> + + +/* 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 server's lock and the lbprm's lock must be held. + */ +static inline void fas_remove_from_tree(struct server *s) +{ + s->lb_tree = NULL; +} + +/* simply removes a server from a tree. + * + * The lbprm's lock must be held. + */ +static inline void fas_dequeue_srv(struct server *s) +{ + eb32_delete(&s->lb_node); +} + +/* Queue a server in its associated tree, assuming the weight is >0. + * Servers are sorted by unique ID so that we send all connections to the first + * available server in declaration order (or ID order) until its maxconn is + * reached. It is important to understand that the server weight is not used + * here. + * + * The lbprm's lock must be held. + */ +static inline void fas_queue_srv(struct server *s) +{ + s->lb_node.key = s->puid; + eb32_insert(s->lb_tree, &s->lb_node); +} + +/* Re-position the server in the FS tree after it has been assigned one + * connection or after it has released one. Note that it is possible that + * the server has been moved out of the tree due to failed health-checks. + * The lbprm's lock will be used. + */ +static void fas_srv_reposition(struct server *s) +{ + HA_RWLOCK_WRLOCK(LBPRM_LOCK, &s->proxy->lbprm.lock); + if (s->lb_tree) { + fas_dequeue_srv(s); + fas_queue_srv(s); + } + HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &s->proxy->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 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 fas_set_server_status_down(struct server *srv) +{ + struct proxy *p = srv->proxy; + + 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; + + 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--; + } + + fas_dequeue_srv(srv); + fas_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 fas_set_server_status_up(struct server *srv) +{ + struct proxy *p = srv->proxy; + + 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; + + if (srv->flags & SRV_F_BACKUP) { + srv->lb_tree = &p->lbprm.fas.bck; + 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 { + srv->lb_tree = &p->lbprm.fas.act; + p->lbprm.tot_wact += srv->next_eweight; + p->srv_act++; + } + + /* note that eweight cannot be 0 here */ + fas_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 fas_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) { + fas_set_server_status_up(srv); + return; + } + else if (old_state && !new_state) { + fas_set_server_status_down(srv); + return; + } + + HA_RWLOCK_WRLOCK(LBPRM_LOCK, &p->lbprm.lock); + + if (srv->lb_tree) + fas_dequeue_srv(srv); + + if (srv->flags & SRV_F_BACKUP) { + p->lbprm.tot_wbck += srv->next_eweight - srv->cur_eweight; + srv->lb_tree = &p->lbprm.fas.bck; + } else { + p->lbprm.tot_wact += srv->next_eweight - srv->cur_eweight; + srv->lb_tree = &p->lbprm.fas.act; + } + + fas_queue_srv(srv); + + update_backend_weight(p); + HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &p->lbprm.lock); + + srv_lb_commit_status(srv); +} + +/* This function is responsible for building the trees in case of fast + * weighted least-conns. It also sets p->lbprm.wdiv to the eweight to + * uweight ratio. Both active and backup groups are initialized. + */ +void fas_init_server_tree(struct proxy *p) +{ + struct server *srv; + struct eb_root init_head = EB_ROOT; + + p->lbprm.set_server_status_up = fas_set_server_status_up; + p->lbprm.set_server_status_down = fas_set_server_status_down; + p->lbprm.update_server_eweight = fas_update_server_weight; + p->lbprm.server_take_conn = fas_srv_reposition; + p->lbprm.server_drop_conn = fas_srv_reposition; + + 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.fas.act = init_head; + p->lbprm.fas.bck = init_head; + + /* queue active and backup servers in two distinct groups */ + for (srv = p->srv; srv; srv = srv->next) { + if (!srv_currently_usable(srv)) + continue; + srv->lb_tree = (srv->flags & SRV_F_BACKUP) ? &p->lbprm.fas.bck : &p->lbprm.fas.act; + fas_queue_srv(srv); + } +} + +/* Return next server from the FS tree in backend <p>. If the tree is empty, + * return NULL. Saturated servers are skipped. + * + * The lbprm's lock will be used. The server's lock is not used. + */ +struct server *fas_get_next_server(struct proxy *p, struct server *srvtoavoid) +{ + struct server *srv, *avoided; + struct eb32_node *node; + + srv = avoided = NULL; + + HA_RWLOCK_RDLOCK(LBPRM_LOCK, &p->lbprm.lock); + if (p->srv_act) + node = eb32_first(&p->lbprm.fas.act); + else if (p->lbprm.fbck) { + srv = p->lbprm.fbck; + goto out; + } + else if (p->srv_bck) + node = eb32_first(&p->lbprm.fas.bck); + else { + srv = NULL; + goto out; + } + + while (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. + */ + struct server *s; + + s = eb32_entry(node, struct server, lb_node); + if (!s->maxconn || (!s->queue.length && s->served < srv_dynamic_maxconn(s))) { + if (s != srvtoavoid) { + srv = s; + break; + } + avoided = s; + } + node = eb32_next(node); + } + + if (!srv) + srv = avoided; + out: + HA_RWLOCK_RDUNLOCK(LBPRM_LOCK, &p->lbprm.lock); + return srv; +} + + +/* + * Local variables: + * c-indent-level: 8 + * c-basic-offset: 8 + * End: + */ |