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haproxy/include/proto/server.h
Willy Tarreau 4cae3bf631 BUG/MEDIUM: connection: don't keep more idle connections than ever needed 
When using "http-reuse safe", which is the default, a new incoming connection
does not automatically reuse an existing connection for the first request, as
we don't want to risk to lose the contents if we know the client will not be
able to replay the request. A side effect to this is that when dealing with
mostly http-close traffic, the reuse rate is extremely low and we keep
accumulating server-side connections that may even never be reused. At some
point we're limited to a ratio of file descriptors, but when the system is
configured with very high FD limits, we can still reach the limit of outgoing
source ports and make the system significantly slow down trying to find an
available port for outgoing connections. A simple test on my laptop with
ulimit 100000 and with the following config results in the load immediately
dropping after a few seconds :

   listen l1
        bind :4445
        mode http
        server s1 127.0.0.1:8000

As can be seen, the load falls from 38k cps to 400 cps during the first 200ms
(in fact when the source port table is full and connect() takes ages to find
a spare port for a new connection):

   $ injectl464 -p 4 -o 1 -u 10 -G 127.0.0.1:4445/ -F -c -w 100
   hits ^hits hits/s  ^h/s     bytes  kB/s  last  errs  tout htime  sdht ptime
   2439  2439  39338 39338    356094  5743  5743     0     0 0.4 0.5 0.4
   7637  5198  38185 37666   1115002  5575  5499     0     0 0.7 0.5 0.7
   7719    82  25730   820   1127002  3756   120     0     0 21.8 18.8 21.8
   7797    78  19492   780   1138446  2846   114     0     0 61.4 2.5 61.4
   7877    80  15754   800   1150182  2300   117     0     0 58.6 0.5 58.6
   7920    43  13200   430   1156488  1927    63     0     0 58.9 0.3 58.9

At this point, lots of connections are indeed in use, for only 10 connections
on the frontend side:

   $ ss -ant state established | wc -l
   39022

This patch makes sure we never keep more idle connections than we've ever
had outstanding requests on a server. This way the total number of idle
connections will never exceed the sum of maximum connections. Thus highly
loaded servers will be able to get many connections and slightly loaded
servers will keep less. Ideally we should apply similar limits per process
and the per backend, but in practice this already addresses the issues
pretty well:

   $ injectl464 -p 4 -o 1 -u 10 -G 127.0.0.1:4445/ -F -c -w 100
   hits ^hits hits/s  ^h/s     bytes  kB/s  last  errs  tout htime  sdht ptime
   4423  4423  40209 40209    645758  5870  5870     0     0 0.2 0.4 0.2
   8020  3597  40100 39966   1170920  5854  5835     0     0 0.2 0.4 0.2
  12037  4017  40123 40170   1757402  5858  5864     0     0 0.2 0.4 0.2
  16069  4032  40172 40320   2346074  5865  5886     0     0 0.2 0.4 0.2
  20047  3978  40013 39386   2926862  5842  5750     0     0 0.3 0.4 0.3
  24005  3958  40008 39979   3504730  5841  5837     0     0 0.2 0.4 0.2

   $ ss -ant state established | wc -l
   234

This patch must be backported to 2.0. It could be useful in 1.9 as well
eventhough pools and reuse are not enabled by default there.
2019-09-08 09:30:50 +02:00

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/*
* include/proto/server.h
* This file defines everything related to servers.
*
* Copyright (C) 2000-2009 Willy Tarreau - w@1wt.eu
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, version 2.1
* exclusively.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _PROTO_SERVER_H
#define _PROTO_SERVER_H
#include <unistd.h>
#include <common/config.h>
#include <common/time.h>
#include <types/applet.h>
#include <types/dns.h>
#include <types/proxy.h>
#include <types/queue.h>
#include <types/server.h>
#include <proto/queue.h>
#include <proto/log.h>
#include <proto/freq_ctr.h>
__decl_hathreads(extern HA_SPINLOCK_T idle_conn_srv_lock);
extern struct eb_root idle_conn_srv;
extern struct task *idle_conn_task;
extern struct task *idle_conn_cleanup[MAX_THREADS];
extern struct list toremove_connections[MAX_THREADS];
int srv_downtime(const struct server *s);
int srv_lastsession(const struct server *s);
int srv_getinter(const struct check *check);
int parse_server(const char *file, int linenum, char **args, struct proxy *curproxy, struct proxy *defproxy, int parse_addr);
int update_server_addr(struct server *s, void *ip, int ip_sin_family, const char *updater);
const char *update_server_addr_port(struct server *s, const char *addr, const char *port, char *updater);
struct server *server_find_by_id(struct proxy *bk, int id);
struct server *server_find_by_name(struct proxy *bk, const char *name);
struct server *server_find_best_match(struct proxy *bk, char *name, int id, int *diff);
void apply_server_state(void);
void srv_compute_all_admin_states(struct proxy *px);
int srv_set_addr_via_libc(struct server *srv, int *err_code);
int srv_init_addr(void);
struct server *cli_find_server(struct appctx *appctx, char *arg);
struct server *new_server(struct proxy *proxy);
/* functions related to server name resolution */
int snr_update_srv_status(struct server *s, int has_no_ip);
const char *update_server_fqdn(struct server *server, const char *fqdn, const char *updater, int dns_locked);
int snr_resolution_cb(struct dns_requester *requester, struct dns_nameserver *nameserver);
int snr_resolution_error_cb(struct dns_requester *requester, int error_code);
struct server *snr_check_ip_callback(struct server *srv, void *ip, unsigned char *ip_family);
struct task *srv_cleanup_idle_connections(struct task *task, void *ctx, unsigned short state);
struct task *srv_cleanup_toremove_connections(struct task *task, void *context, unsigned short state);
/* increase the number of cumulated connections on the designated server */
static inline void srv_inc_sess_ctr(struct server *s)
{
_HA_ATOMIC_ADD(&s->counters.cum_sess, 1);
HA_ATOMIC_UPDATE_MAX(&s->counters.sps_max,
update_freq_ctr(&s->sess_per_sec, 1));
}
/* set the time of last session on the designated server */
static inline void srv_set_sess_last(struct server *s)
{
s->counters.last_sess = now.tv_sec;
}
/*
* Registers the server keyword list <kwl> as a list of valid keywords for next
* parsing sessions.
*/
void srv_register_keywords(struct srv_kw_list *kwl);
/* Return a pointer to the server keyword <kw>, or NULL if not found. */
struct srv_kw *srv_find_kw(const char *kw);
/* Dumps all registered "server" keywords to the <out> string pointer. */
void srv_dump_kws(char **out);
/* Recomputes the server's eweight based on its state, uweight, the current time,
* and the proxy's algorihtm. To be used after updating sv->uweight. The warmup
* state is automatically disabled if the time is elapsed.
*/
void server_recalc_eweight(struct server *sv, int must_update);
/* returns the current server throttle rate between 0 and 100% */
static inline unsigned int server_throttle_rate(struct server *sv)
{
struct proxy *px = sv->proxy;
/* when uweight is 0, we're in soft-stop so that cannot be a slowstart,
* thus the throttle is 100%.
*/
if (!sv->uweight)
return 100;
return (100U * px->lbprm.wmult * sv->cur_eweight + px->lbprm.wdiv - 1) / (px->lbprm.wdiv * sv->uweight);
}
/*
* Parses weight_str and configures sv accordingly.
* Returns NULL on success, error message string otherwise.
*/
const char *server_parse_weight_change_request(struct server *sv,
const char *weight_str);
/*
* Parses addr_str and configures sv accordingly. updater precise
* the source of the change in the associated message log.
* Returns NULL on success, error message string otherwise.
*/
const char *server_parse_addr_change_request(struct server *sv,
const char *addr_str, const char *updater);
/*
* Parses maxconn_str and configures sv accordingly.
* Returns NULL on success, error message string otherwise.
*/
const char *server_parse_maxconn_change_request(struct server *sv,
const char *maxconn_str);
/*
* Return true if the server has a zero user-weight, meaning it's in draining
* mode (ie: not taking new non-persistent connections).
*/
static inline int server_is_draining(const struct server *s)
{
return !s->uweight || (s->cur_admin & SRV_ADMF_DRAIN);
}
/* Shutdown all connections of a server. The caller must pass a termination
* code in <why>, which must be one of SF_ERR_* indicating the reason for the
* shutdown.
*/
void srv_shutdown_streams(struct server *srv, int why);
/* Shutdown all connections of all backup servers of a proxy. The caller must
* pass a termination code in <why>, which must be one of SF_ERR_* indicating
* the reason for the shutdown.
*/
void srv_shutdown_backup_streams(struct proxy *px, int why);
void srv_append_status(struct buffer *msg, struct server *s, struct check *,
int xferred, int forced);
void srv_set_stopped(struct server *s, const char *reason, struct check *check);
void srv_set_running(struct server *s, const char *reason, struct check *check);
void srv_set_stopping(struct server *s, const char *reason, struct check *check);
/* Enables admin flag <mode> (among SRV_ADMF_*) on server <s>. This is used to
* enforce either maint mode or drain mode. It is not allowed to set more than
* one flag at once. The equivalent "inherited" flag is propagated to all
* tracking servers. Maintenance mode disables health checks (but not agent
* checks). When either the flag is already set or no flag is passed, nothing
* is done. If <cause> is non-null, it will be displayed at the end of the log
* lines to justify the state change.
*/
void srv_set_admin_flag(struct server *s, enum srv_admin mode, const char *cause);
/* Disables admin flag <mode> (among SRV_ADMF_*) on server <s>. This is used to
* stop enforcing either maint mode or drain mode. It is not allowed to set more
* than one flag at once. The equivalent "inherited" flag is propagated to all
* tracking servers. Leaving maintenance mode re-enables health checks. When
* either the flag is already cleared or no flag is passed, nothing is done.
*/
void srv_clr_admin_flag(struct server *s, enum srv_admin mode);
/* Calculates the dynamic persitent cookie for a server, if a secret key has
* been provided.
*/
void srv_set_dyncookie(struct server *s);
/* Puts server <s> into maintenance mode, and propagate that status down to all
* tracking servers.
*/
static inline void srv_adm_set_maint(struct server *s)
{
srv_set_admin_flag(s, SRV_ADMF_FMAINT, NULL);
srv_clr_admin_flag(s, SRV_ADMF_FDRAIN);
}
/* Puts server <s> into drain mode, and propagate that status down to all
* tracking servers.
*/
static inline void srv_adm_set_drain(struct server *s)
{
srv_set_admin_flag(s, SRV_ADMF_FDRAIN, NULL);
srv_clr_admin_flag(s, SRV_ADMF_FMAINT);
}
/* Puts server <s> into ready mode, and propagate that status down to all
* tracking servers.
*/
static inline void srv_adm_set_ready(struct server *s)
{
srv_clr_admin_flag(s, SRV_ADMF_FDRAIN);
srv_clr_admin_flag(s, SRV_ADMF_FMAINT);
}
/* appends an initaddr method to the existing list. Returns 0 on failure. */
static inline int srv_append_initaddr(unsigned int *list, enum srv_initaddr addr)
{
int shift = 0;
while (shift + 3 < 32 && (*list >> shift))
shift += 3;
if (shift + 3 > 32)
return 0;
*list |= addr << shift;
return 1;
}
/* returns the next initaddr method and removes it from <list> by shifting
* it right (implying that it MUST NOT be the server's. Returns SRV_IADDR_END
* at the end.
*/
static inline enum srv_initaddr srv_get_next_initaddr(unsigned int *list)
{
enum srv_initaddr ret;
ret = *list & 7;
*list >>= 3;
return ret;
}
/* This adds an idle connection to the server's list if the connection is
* reusable, not held by any owner anymore, but still has available streams.
*/
static inline int srv_add_to_idle_list(struct server *srv, struct connection *conn)
{
if (srv && srv->pool_purge_delay > 0 &&
(srv->max_idle_conns == -1 || srv->max_idle_conns > srv->curr_idle_conns) &&
(srv->cur_sess + srv->curr_idle_conns <= srv->counters.cur_sess_max) &&
!(conn->flags & CO_FL_PRIVATE) &&
((srv->proxy->options & PR_O_REUSE_MASK) != PR_O_REUSE_NEVR) &&
!conn->mux->used_streams(conn) && conn->mux->avail_streams(conn) &&
ha_used_fds < global.tune.pool_low_count) {
int retadd;
retadd = _HA_ATOMIC_ADD(&srv->curr_idle_conns, 1);
if (retadd > srv->max_idle_conns) {
_HA_ATOMIC_SUB(&srv->curr_idle_conns, 1);
return 0;
}
LIST_DEL(&conn->list);
LIST_ADDQ_LOCKED(&srv->idle_orphan_conns[tid], &conn->list);
srv->curr_idle_thr[tid]++;
conn->idle_time = now_ms;
__ha_barrier_full();
if ((volatile void *)srv->idle_node.node.leaf_p == NULL) {
HA_SPIN_LOCK(OTHER_LOCK, &idle_conn_srv_lock);
if ((volatile void *)srv->idle_node.node.leaf_p == NULL) {
srv->idle_node.key = tick_add(srv->pool_purge_delay,
now_ms);
eb32_insert(&idle_conn_srv, &srv->idle_node);
if (!task_in_wq(idle_conn_task) && !
task_in_rq(idle_conn_task)) {
task_schedule(idle_conn_task,
srv->idle_node.key);
}
}
HA_SPIN_UNLOCK(OTHER_LOCK, &idle_conn_srv_lock);
}
return 1;
}
return 0;
}
#endif /* _PROTO_SERVER_H */
/*
* Local variables:
* c-indent-level: 8
* c-basic-offset: 8
* End:
*/
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