view src/stream/ngx_stream_upstream_least_conn_module.c @ 6694:ea9dfe2f62e7

Stream: preread phase. In this phase, head of a stream is read and analysed before proceeding to the content phase. Amount of data read is controlled by the module implementing the phase, but not more than defined by the "preread_buffer_size" directive. The time spent on processing preread is controlled by the "preread_timeout" directive. The typical preread phase module will parse the beginning of a stream and set variable that may be used by the content phase, for example to make routing decision.
author Vladimir Homutov <vl@nginx.com>
date Thu, 15 Sep 2016 14:56:02 +0300
parents 8ed51b02f655
children 914d8a63dbad
line wrap: on
line source


/*
 * Copyright (C) Maxim Dounin
 * Copyright (C) Nginx, Inc.
 */


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


static ngx_int_t ngx_stream_upstream_init_least_conn_peer(
    ngx_stream_session_t *s, ngx_stream_upstream_srv_conf_t *us);
static ngx_int_t ngx_stream_upstream_get_least_conn_peer(
    ngx_peer_connection_t *pc, void *data);
static char *ngx_stream_upstream_least_conn(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);


static ngx_command_t  ngx_stream_upstream_least_conn_commands[] = {

    { ngx_string("least_conn"),
      NGX_STREAM_UPS_CONF|NGX_CONF_NOARGS,
      ngx_stream_upstream_least_conn,
      0,
      0,
      NULL },

      ngx_null_command
};


static ngx_stream_module_t  ngx_stream_upstream_least_conn_module_ctx = {
    NULL,                                    /* preconfiguration */
    NULL,                                    /* postconfiguration */

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

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


ngx_module_t  ngx_stream_upstream_least_conn_module = {
    NGX_MODULE_V1,
    &ngx_stream_upstream_least_conn_module_ctx, /* module context */
    ngx_stream_upstream_least_conn_commands, /* module directives */
    NGX_STREAM_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_stream_upstream_init_least_conn(ngx_conf_t *cf,
    ngx_stream_upstream_srv_conf_t *us)
{
    ngx_log_debug0(NGX_LOG_DEBUG_STREAM, cf->log, 0,
                   "init least conn");

    if (ngx_stream_upstream_init_round_robin(cf, us) != NGX_OK) {
        return NGX_ERROR;
    }

    us->peer.init = ngx_stream_upstream_init_least_conn_peer;

    return NGX_OK;
}


static ngx_int_t
ngx_stream_upstream_init_least_conn_peer(ngx_stream_session_t *s,
    ngx_stream_upstream_srv_conf_t *us)
{
    ngx_log_debug0(NGX_LOG_DEBUG_STREAM, s->connection->log, 0,
                   "init least conn peer");

    if (ngx_stream_upstream_init_round_robin_peer(s, us) != NGX_OK) {
        return NGX_ERROR;
    }

    s->upstream->peer.get = ngx_stream_upstream_get_least_conn_peer;

    return NGX_OK;
}


static ngx_int_t
ngx_stream_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
{
    ngx_stream_upstream_rr_peer_data_t *rrp = data;

    time_t                           now;
    uintptr_t                        m;
    ngx_int_t                        rc, total;
    ngx_uint_t                       i, n, p, many;
    ngx_stream_upstream_rr_peer_t   *peer, *best;
    ngx_stream_upstream_rr_peers_t  *peers;

    ngx_log_debug1(NGX_LOG_DEBUG_STREAM, pc->log, 0,
                   "get least conn peer, try: %ui", pc->tries);

    if (rrp->peers->single) {
        return ngx_stream_upstream_get_round_robin_peer(pc, rrp);
    }

    pc->connection = NULL;

    now = ngx_time();

    peers = rrp->peers;

    ngx_stream_upstream_rr_peers_wlock(peers);

    best = NULL;
    total = 0;

#if (NGX_SUPPRESS_WARN)
    many = 0;
    p = 0;
#endif

    for (peer = peers->peer, i = 0;
         peer;
         peer = peer->next, i++)
    {

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

        if (rrp->tried[n] & m) {
            continue;
        }

        if (peer->down) {
            continue;
        }

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

        /*
         * select peer with least number of connections; if there are
         * multiple peers with the same number of connections, select
         * based on round-robin
         */

        if (best == NULL
            || peer->conns * best->weight < best->conns * peer->weight)
        {
            best = peer;
            many = 0;
            p = i;

        } else if (peer->conns * best->weight == best->conns * peer->weight) {
            many = 1;
        }
    }

    if (best == NULL) {
        ngx_log_debug0(NGX_LOG_DEBUG_STREAM, pc->log, 0,
                       "get least conn peer, no peer found");

        goto failed;
    }

    if (many) {
        ngx_log_debug0(NGX_LOG_DEBUG_STREAM, pc->log, 0,
                       "get least conn peer, many");

        for (peer = best, i = p;
             peer;
             peer = peer->next, i++)
        {
            n = i / (8 * sizeof(uintptr_t));
            m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));

            if (rrp->tried[n] & m) {
                continue;
            }

            if (peer->down) {
                continue;
            }

            if (peer->conns * best->weight != best->conns * peer->weight) {
                continue;
            }

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

            peer->current_weight += peer->effective_weight;
            total += peer->effective_weight;

            if (peer->effective_weight < peer->weight) {
                peer->effective_weight++;
            }

            if (peer->current_weight > best->current_weight) {
                best = peer;
                p = i;
            }
        }
    }

    best->current_weight -= total;

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

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

    best->conns++;

    rrp->current = best;

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

    rrp->tried[n] |= m;

    ngx_stream_upstream_rr_peers_unlock(peers);

    return NGX_OK;

failed:

    if (peers->next) {
        ngx_log_debug0(NGX_LOG_DEBUG_STREAM, pc->log, 0,
                       "get least conn peer, backup servers");

        rrp->peers = peers->next;

        n = (rrp->peers->number + (8 * sizeof(uintptr_t) - 1))
                / (8 * sizeof(uintptr_t));

        for (i = 0; i < n; i++) {
            rrp->tried[i] = 0;
        }

        ngx_stream_upstream_rr_peers_unlock(peers);

        rc = ngx_stream_upstream_get_least_conn_peer(pc, rrp);

        if (rc != NGX_BUSY) {
            return rc;
        }

        ngx_stream_upstream_rr_peers_wlock(peers);
    }

    /* all peers failed, mark them as live for quick recovery */

    for (peer = peers->peer; peer; peer = peer->next) {
        peer->fails = 0;
    }

    ngx_stream_upstream_rr_peers_unlock(peers);

    pc->name = peers->name;

    return NGX_BUSY;
}


static char *
ngx_stream_upstream_least_conn(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_stream_upstream_srv_conf_t  *uscf;

    uscf = ngx_stream_conf_get_module_srv_conf(cf, ngx_stream_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_stream_upstream_init_least_conn;

    uscf->flags = NGX_STREAM_UPSTREAM_CREATE
                  |NGX_STREAM_UPSTREAM_WEIGHT
                  |NGX_STREAM_UPSTREAM_MAX_FAILS
                  |NGX_STREAM_UPSTREAM_FAIL_TIMEOUT
                  |NGX_STREAM_UPSTREAM_DOWN
                  |NGX_STREAM_UPSTREAM_BACKUP;

    return NGX_CONF_OK;
}