Mercurial > hg > nginx
view src/http/modules/ngx_http_degradation_module.c @ 4207:4fc91bae6f83
Better recheck of dead upstream servers.
Previously nginx used to mark backend again as live as soon as fail_timeout
passes (10s by default) since last failure. On the other hand, detecting
dead backend takes up to 60s (proxy_connect_timeout) in typical situation
"backend is down and doesn't respond to any packets". This resulted in
suboptimal behaviour in the above situation (up to 23% of requests were
directed to dead backend with default settings).
More detailed description of the problem may be found here (in Russian):
http://mailman.nginx.org/pipermail/nginx-ru/2011-August/042172.html
Fix is to only allow one request after fail_timeout passes, and
mark backend as "live" only if this request succeeds.
Note that with new code backend will not be marked "live" unless "check"
request is completed, and this may take a while in some specific workloads
(e.g. streaming). This is believed to be acceptable.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Wed, 12 Oct 2011 14:22:48 +0000 |
parents | 147d8a86dd02 |
children | d620f497c50f |
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/* * Copyright (C) Igor Sysoev */ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_http.h> typedef struct { size_t sbrk_size; } ngx_http_degradation_main_conf_t; typedef struct { ngx_uint_t degrade; } ngx_http_degradation_loc_conf_t; static ngx_conf_enum_t ngx_http_degrade[] = { { ngx_string("204"), 204 }, { ngx_string("444"), 444 }, { ngx_null_string, 0 } }; static void *ngx_http_degradation_create_main_conf(ngx_conf_t *cf); static void *ngx_http_degradation_create_loc_conf(ngx_conf_t *cf); static char *ngx_http_degradation_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child); static char *ngx_http_degradation(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static ngx_int_t ngx_http_degradation_init(ngx_conf_t *cf); static ngx_command_t ngx_http_degradation_commands[] = { { ngx_string("degradation"), NGX_HTTP_MAIN_CONF|NGX_CONF_TAKE1, ngx_http_degradation, NGX_HTTP_MAIN_CONF_OFFSET, 0, NULL }, { ngx_string("degrade"), NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1, ngx_conf_set_enum_slot, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_degradation_loc_conf_t, degrade), &ngx_http_degrade }, ngx_null_command }; static ngx_http_module_t ngx_http_degradation_module_ctx = { NULL, /* preconfiguration */ ngx_http_degradation_init, /* postconfiguration */ ngx_http_degradation_create_main_conf, /* create main configuration */ NULL, /* init main configuration */ NULL, /* create server configuration */ NULL, /* merge server configuration */ ngx_http_degradation_create_loc_conf, /* create location configuration */ ngx_http_degradation_merge_loc_conf /* merge location configuration */ }; ngx_module_t ngx_http_degradation_module = { NGX_MODULE_V1, &ngx_http_degradation_module_ctx, /* module context */ ngx_http_degradation_commands, /* module directives */ NGX_HTTP_MODULE, /* module type */ NULL, /* init master */ NULL, /* init module */ NULL, /* init process */ NULL, /* init thread */ NULL, /* exit thread */ NULL, /* exit process */ NULL, /* exit master */ NGX_MODULE_V1_PADDING }; static ngx_int_t ngx_http_degradation_handler(ngx_http_request_t *r) { ngx_http_degradation_loc_conf_t *dlcf; dlcf = ngx_http_get_module_loc_conf(r, ngx_http_degradation_module); if (dlcf->degrade && ngx_http_degraded(r)) { return dlcf->degrade; } return NGX_DECLINED; } ngx_uint_t ngx_http_degraded(ngx_http_request_t *r) { time_t now; ngx_uint_t log; static size_t sbrk_size; static time_t sbrk_time; ngx_http_degradation_main_conf_t *dmcf; dmcf = ngx_http_get_module_main_conf(r, ngx_http_degradation_module); if (dmcf->sbrk_size) { log = 0; now = ngx_time(); /* lock mutex */ if (now != sbrk_time) { /* * ELF/i386 is loaded at 0x08000000, 128M * ELF/amd64 is loaded at 0x00400000, 4M * * use a function address to substract the loading address */ sbrk_size = (size_t) sbrk(0) - ((uintptr_t) ngx_palloc & ~0x3FFFFF); sbrk_time = now; log = 1; } /* unlock mutex */ if (sbrk_size >= dmcf->sbrk_size) { if (log) { ngx_log_error(NGX_LOG_NOTICE, r->connection->log, 0, "degradation sbrk:%uzM", sbrk_size / (1024 * 1024)); } return 1; } } return 0; } static void * ngx_http_degradation_create_main_conf(ngx_conf_t *cf) { ngx_http_degradation_main_conf_t *dmcf; dmcf = ngx_pcalloc(cf->pool, sizeof(ngx_http_degradation_main_conf_t)); if (dmcf == NULL) { return NULL; } return dmcf; } static void * ngx_http_degradation_create_loc_conf(ngx_conf_t *cf) { ngx_http_degradation_loc_conf_t *conf; conf = ngx_palloc(cf->pool, sizeof(ngx_http_degradation_loc_conf_t)); if (conf == NULL) { return NULL; } conf->degrade = NGX_CONF_UNSET_UINT; return conf; } static char * ngx_http_degradation_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child) { ngx_http_degradation_loc_conf_t *prev = parent; ngx_http_degradation_loc_conf_t *conf = child; ngx_conf_merge_uint_value(conf->degrade, prev->degrade, 0); return NGX_CONF_OK; } static char * ngx_http_degradation(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_http_degradation_main_conf_t *dmcf = conf; ngx_str_t *value, s; value = cf->args->elts; if (ngx_strncmp(value[1].data, "sbrk=", 5) == 0) { s.len = value[1].len - 5; s.data = value[1].data + 5; dmcf->sbrk_size = ngx_parse_size(&s); if (dmcf->sbrk_size == (size_t) NGX_ERROR) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid sbrk size \"%V\"", &value[1]); return NGX_CONF_ERROR; } return NGX_CONF_OK; } ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid parameter \"%V\"", &value[1]); return NGX_CONF_ERROR; } static ngx_int_t ngx_http_degradation_init(ngx_conf_t *cf) { ngx_http_handler_pt *h; ngx_http_core_main_conf_t *cmcf; cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module); h = ngx_array_push(&cmcf->phases[NGX_HTTP_PREACCESS_PHASE].handlers); if (h == NULL) { return NGX_ERROR; } *h = ngx_http_degradation_handler; return NGX_OK; }