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view src/http/modules/ngx_http_upstream_ip_hash_module.c @ 7281:bd6563e81cea

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Limit req: improved handling of negative times. Negative times can appear since workers only update time on an event loop iteration start. If a worker was blocked for a long time during an event loop iteration, it is possible that another worker already updated the time stored in the node. As such, time since last update of the node (ms) will be negative. Previous code used ngx_abs(ms) in the calculations. That is, negative times were effectively treated as positive ones. As a result, it was not possible to maintain high request rates, where the same node can be updated multiple times from during an event loop iteration. In particular, this affected setups with many SSL handshakes, see http://mailman.nginx.org/pipermail/nginx/2018-May/056291.html. Fix is to only update the last update time stored in the node if the new time is larger than previously stored one. If a future time is stored in the node, we preserve this time as is. To prevent breaking things on platforms without monotonic time available if system time is updated backwards, a safety limit of 60 seconds is used. If the time stored in the node is more than 60 seconds in the future, we assume that the time was changed backwards and update lr->last to the current time.
author Maxim Dounin <mdounin@mdounin.ru>
date Wed, 30 May 2018 15:40:34 +0300
parents 29bf0dbc0a77
children ed599ea6c1f1
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef struct {
    /* the round robin data must be first */
    ngx_http_upstream_rr_peer_data_t   rrp;

    ngx_uint_t                         hash;

    u_char                             addrlen;
    u_char                            *addr;

    u_char                             tries;

    ngx_event_get_peer_pt              get_rr_peer;
} ngx_http_upstream_ip_hash_peer_data_t;


static ngx_int_t ngx_http_upstream_init_ip_hash_peer(ngx_http_request_t *r,
    ngx_http_upstream_srv_conf_t *us);
static ngx_int_t ngx_http_upstream_get_ip_hash_peer(ngx_peer_connection_t *pc,
    void *data);
static char *ngx_http_upstream_ip_hash(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);


static ngx_command_t  ngx_http_upstream_ip_hash_commands[] = {

    { ngx_string("ip_hash"),
      NGX_HTTP_UPS_CONF|NGX_CONF_NOARGS,
      ngx_http_upstream_ip_hash,
      0,
      0,
      NULL },

      ngx_null_command
};


static ngx_http_module_t  ngx_http_upstream_ip_hash_module_ctx = {
    NULL,                                  /* preconfiguration */
    NULL,                                  /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */

    NULL,                                  /* create location configuration */
    NULL                                   /* merge location configuration */
};


ngx_module_t  ngx_http_upstream_ip_hash_module = {
    NGX_MODULE_V1,
    &ngx_http_upstream_ip_hash_module_ctx, /* module context */
    ngx_http_upstream_ip_hash_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 u_char ngx_http_upstream_ip_hash_pseudo_addr[3];


static ngx_int_t
ngx_http_upstream_init_ip_hash(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
{
    if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
        return NGX_ERROR;
    }

    us->peer.init = ngx_http_upstream_init_ip_hash_peer;

    return NGX_OK;
}


static ngx_int_t
ngx_http_upstream_init_ip_hash_peer(ngx_http_request_t *r,
    ngx_http_upstream_srv_conf_t *us)
{
    struct sockaddr_in                     *sin;
#if (NGX_HAVE_INET6)
    struct sockaddr_in6                    *sin6;
#endif
    ngx_http_upstream_ip_hash_peer_data_t  *iphp;

    iphp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_ip_hash_peer_data_t));
    if (iphp == NULL) {
        return NGX_ERROR;
    }

    r->upstream->peer.data = &iphp->rrp;

    if (ngx_http_upstream_init_round_robin_peer(r, us) != NGX_OK) {
        return NGX_ERROR;
    }

    r->upstream->peer.get = ngx_http_upstream_get_ip_hash_peer;

    switch (r->connection->sockaddr->sa_family) {

    case AF_INET:
        sin = (struct sockaddr_in *) r->connection->sockaddr;
        iphp->addr = (u_char *) &sin->sin_addr.s_addr;
        iphp->addrlen = 3;
        break;

#if (NGX_HAVE_INET6)
    case AF_INET6:
        sin6 = (struct sockaddr_in6 *) r->connection->sockaddr;
        iphp->addr = (u_char *) &sin6->sin6_addr.s6_addr;
        iphp->addrlen = 16;
        break;
#endif

    default:
        iphp->addr = ngx_http_upstream_ip_hash_pseudo_addr;
        iphp->addrlen = 3;
    }

    iphp->hash = 89;
    iphp->tries = 0;
    iphp->get_rr_peer = ngx_http_upstream_get_round_robin_peer;

    return NGX_OK;
}


static ngx_int_t
ngx_http_upstream_get_ip_hash_peer(ngx_peer_connection_t *pc, void *data)
{
    ngx_http_upstream_ip_hash_peer_data_t  *iphp = data;

    time_t                        now;
    ngx_int_t                     w;
    uintptr_t                     m;
    ngx_uint_t                    i, n, p, hash;
    ngx_http_upstream_rr_peer_t  *peer;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                   "get ip hash peer, try: %ui", pc->tries);

    /* TODO: cached */

    ngx_http_upstream_rr_peers_wlock(iphp->rrp.peers);

    if (iphp->tries > 20 || iphp->rrp.peers->single) {
        ngx_http_upstream_rr_peers_unlock(iphp->rrp.peers);
        return iphp->get_rr_peer(pc, &iphp->rrp);
    }

    now = ngx_time();

    pc->cached = 0;
    pc->connection = NULL;

    hash = iphp->hash;

    for ( ;; ) {

        for (i = 0; i < (ngx_uint_t) iphp->addrlen; i++) {
            hash = (hash * 113 + iphp->addr[i]) % 6271;
        }

        w = hash % iphp->rrp.peers->total_weight;
        peer = iphp->rrp.peers->peer;
        p = 0;

        while (w >= peer->weight) {
            w -= peer->weight;
            peer = peer->next;
            p++;
        }

        n = p / (8 * sizeof(uintptr_t));
        m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));

        if (iphp->rrp.tried[n] & m) {
            goto next;
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                       "get ip hash peer, hash: %ui %04XL", p, (uint64_t) m);

        if (peer->down) {
            goto next;
        }

        if (peer->max_fails
            && peer->fails >= peer->max_fails
            && now - peer->checked <= peer->fail_timeout)
        {
            goto next;
        }

        if (peer->max_conns && peer->conns >= peer->max_conns) {
            goto next;
        }

        break;

    next:

        if (++iphp->tries > 20) {
            ngx_http_upstream_rr_peers_unlock(iphp->rrp.peers);
            return iphp->get_rr_peer(pc, &iphp->rrp);
        }
    }

    iphp->rrp.current = peer;

    pc->sockaddr = peer->sockaddr;
    pc->socklen = peer->socklen;
    pc->name = &peer->name;

    peer->conns++;

    if (now - peer->checked > peer->fail_timeout) {
        peer->checked = now;
    }

    ngx_http_upstream_rr_peers_unlock(iphp->rrp.peers);

    iphp->rrp.tried[n] |= m;
    iphp->hash = hash;

    return NGX_OK;
}


static char *
ngx_http_upstream_ip_hash(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_upstream_srv_conf_t  *uscf;

    uscf = ngx_http_conf_get_module_srv_conf(cf, ngx_http_upstream_module);

    if (uscf->peer.init_upstream) {
        ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                           "load balancing method redefined");
    }

    uscf->peer.init_upstream = ngx_http_upstream_init_ip_hash;

    uscf->flags = NGX_HTTP_UPSTREAM_CREATE
                  |NGX_HTTP_UPSTREAM_WEIGHT
                  |NGX_HTTP_UPSTREAM_MAX_CONNS
                  |NGX_HTTP_UPSTREAM_MAX_FAILS
                  |NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
                  |NGX_HTTP_UPSTREAM_DOWN;

    return NGX_CONF_OK;
}