view src/http/ngx_http_upstream_round_robin.c @ 8018:5119c8150478

Fixed runtime handling of systems without EPOLLRDHUP support. In 7583:efd71d49bde0 (nginx 1.17.5) along with introduction of the ioctl(FIONREAD) support proper handling of systems without EPOLLRDHUP support in the kernel (but with EPOLLRDHUP in headers) was broken. Before the change, rev->available was never set to 0 unless ngx_use_epoll_rdhup was also set (that is, runtime test for EPOLLRDHUP introduced in 6536:f7849bfb6d21 succeeded). After the change, rev->available might reach 0 on systems without runtime EPOLLRDHUP support, stopping further reading in ngx_readv_chain() and ngx_unix_recv(). And, if EOF happened to be already reported along with the last event, it is not reported again by epoll_wait(), leading to connection hangs and timeouts on such systems. This affects Linux kernels before 2.6.17 if nginx was compiled with newer headers, and, more importantly, emulation layers, such as DigitalOcean's App Platform's / gVisor's epoll emulation layer. Fix is to explicitly check ngx_use_epoll_rdhup before the corresponding rev->pending_eof tests in ngx_readv_chain() and ngx_unix_recv().
author Marcus Ball <marcus.ball@live.com>
date Mon, 30 May 2022 02:38:07 +0300
parents 90cc7194e993
children
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


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


#define ngx_http_upstream_tries(p) ((p)->tries                                \
                                    + ((p)->next ? (p)->next->tries : 0))


static ngx_http_upstream_rr_peer_t *ngx_http_upstream_get_peer(
    ngx_http_upstream_rr_peer_data_t *rrp);

#if (NGX_HTTP_SSL)

static ngx_int_t ngx_http_upstream_empty_set_session(ngx_peer_connection_t *pc,
    void *data);
static void ngx_http_upstream_empty_save_session(ngx_peer_connection_t *pc,
    void *data);

#endif


ngx_int_t
ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
    ngx_http_upstream_srv_conf_t *us)
{
    ngx_url_t                      u;
    ngx_uint_t                     i, j, n, w, t;
    ngx_http_upstream_server_t    *server;
    ngx_http_upstream_rr_peer_t   *peer, **peerp;
    ngx_http_upstream_rr_peers_t  *peers, *backup;

    us->peer.init = ngx_http_upstream_init_round_robin_peer;

    if (us->servers) {
        server = us->servers->elts;

        n = 0;
        w = 0;
        t = 0;

        for (i = 0; i < us->servers->nelts; i++) {
            if (server[i].backup) {
                continue;
            }

            n += server[i].naddrs;
            w += server[i].naddrs * server[i].weight;

            if (!server[i].down) {
                t += server[i].naddrs;
            }
        }

        if (n == 0) {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "no servers in upstream \"%V\" in %s:%ui",
                          &us->host, us->file_name, us->line);
            return NGX_ERROR;
        }

        peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t));
        if (peers == NULL) {
            return NGX_ERROR;
        }

        peer = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peer_t) * n);
        if (peer == NULL) {
            return NGX_ERROR;
        }

        peers->single = (n == 1);
        peers->number = n;
        peers->weighted = (w != n);
        peers->total_weight = w;
        peers->tries = t;
        peers->name = &us->host;

        n = 0;
        peerp = &peers->peer;

        for (i = 0; i < us->servers->nelts; i++) {
            if (server[i].backup) {
                continue;
            }

            for (j = 0; j < server[i].naddrs; j++) {
                peer[n].sockaddr = server[i].addrs[j].sockaddr;
                peer[n].socklen = server[i].addrs[j].socklen;
                peer[n].name = server[i].addrs[j].name;
                peer[n].weight = server[i].weight;
                peer[n].effective_weight = server[i].weight;
                peer[n].current_weight = 0;
                peer[n].max_conns = server[i].max_conns;
                peer[n].max_fails = server[i].max_fails;
                peer[n].fail_timeout = server[i].fail_timeout;
                peer[n].down = server[i].down;
                peer[n].server = server[i].name;

                *peerp = &peer[n];
                peerp = &peer[n].next;
                n++;
            }
        }

        us->peer.data = peers;

        /* backup servers */

        n = 0;
        w = 0;
        t = 0;

        for (i = 0; i < us->servers->nelts; i++) {
            if (!server[i].backup) {
                continue;
            }

            n += server[i].naddrs;
            w += server[i].naddrs * server[i].weight;

            if (!server[i].down) {
                t += server[i].naddrs;
            }
        }

        if (n == 0) {
            return NGX_OK;
        }

        backup = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t));
        if (backup == NULL) {
            return NGX_ERROR;
        }

        peer = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peer_t) * n);
        if (peer == NULL) {
            return NGX_ERROR;
        }

        peers->single = 0;
        backup->single = 0;
        backup->number = n;
        backup->weighted = (w != n);
        backup->total_weight = w;
        backup->tries = t;
        backup->name = &us->host;

        n = 0;
        peerp = &backup->peer;

        for (i = 0; i < us->servers->nelts; i++) {
            if (!server[i].backup) {
                continue;
            }

            for (j = 0; j < server[i].naddrs; j++) {
                peer[n].sockaddr = server[i].addrs[j].sockaddr;
                peer[n].socklen = server[i].addrs[j].socklen;
                peer[n].name = server[i].addrs[j].name;
                peer[n].weight = server[i].weight;
                peer[n].effective_weight = server[i].weight;
                peer[n].current_weight = 0;
                peer[n].max_conns = server[i].max_conns;
                peer[n].max_fails = server[i].max_fails;
                peer[n].fail_timeout = server[i].fail_timeout;
                peer[n].down = server[i].down;
                peer[n].server = server[i].name;

                *peerp = &peer[n];
                peerp = &peer[n].next;
                n++;
            }
        }

        peers->next = backup;

        return NGX_OK;
    }


    /* an upstream implicitly defined by proxy_pass, etc. */

    if (us->port == 0) {
        ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                      "no port in upstream \"%V\" in %s:%ui",
                      &us->host, us->file_name, us->line);
        return NGX_ERROR;
    }

    ngx_memzero(&u, sizeof(ngx_url_t));

    u.host = us->host;
    u.port = us->port;

    if (ngx_inet_resolve_host(cf->pool, &u) != NGX_OK) {
        if (u.err) {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "%s in upstream \"%V\" in %s:%ui",
                          u.err, &us->host, us->file_name, us->line);
        }

        return NGX_ERROR;
    }

    n = u.naddrs;

    peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t));
    if (peers == NULL) {
        return NGX_ERROR;
    }

    peer = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peer_t) * n);
    if (peer == NULL) {
        return NGX_ERROR;
    }

    peers->single = (n == 1);
    peers->number = n;
    peers->weighted = 0;
    peers->total_weight = n;
    peers->tries = n;
    peers->name = &us->host;

    peerp = &peers->peer;

    for (i = 0; i < u.naddrs; i++) {
        peer[i].sockaddr = u.addrs[i].sockaddr;
        peer[i].socklen = u.addrs[i].socklen;
        peer[i].name = u.addrs[i].name;
        peer[i].weight = 1;
        peer[i].effective_weight = 1;
        peer[i].current_weight = 0;
        peer[i].max_conns = 0;
        peer[i].max_fails = 1;
        peer[i].fail_timeout = 10;
        *peerp = &peer[i];
        peerp = &peer[i].next;
    }

    us->peer.data = peers;

    /* implicitly defined upstream has no backup servers */

    return NGX_OK;
}


ngx_int_t
ngx_http_upstream_init_round_robin_peer(ngx_http_request_t *r,
    ngx_http_upstream_srv_conf_t *us)
{
    ngx_uint_t                         n;
    ngx_http_upstream_rr_peer_data_t  *rrp;

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

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

        r->upstream->peer.data = rrp;
    }

    rrp->peers = us->peer.data;
    rrp->current = NULL;
    rrp->config = 0;

    n = rrp->peers->number;

    if (rrp->peers->next && rrp->peers->next->number > n) {
        n = rrp->peers->next->number;
    }

    if (n <= 8 * sizeof(uintptr_t)) {
        rrp->tried = &rrp->data;
        rrp->data = 0;

    } else {
        n = (n + (8 * sizeof(uintptr_t) - 1)) / (8 * sizeof(uintptr_t));

        rrp->tried = ngx_pcalloc(r->pool, n * sizeof(uintptr_t));
        if (rrp->tried == NULL) {
            return NGX_ERROR;
        }
    }

    r->upstream->peer.get = ngx_http_upstream_get_round_robin_peer;
    r->upstream->peer.free = ngx_http_upstream_free_round_robin_peer;
    r->upstream->peer.tries = ngx_http_upstream_tries(rrp->peers);
#if (NGX_HTTP_SSL)
    r->upstream->peer.set_session =
                               ngx_http_upstream_set_round_robin_peer_session;
    r->upstream->peer.save_session =
                               ngx_http_upstream_save_round_robin_peer_session;
#endif

    return NGX_OK;
}


ngx_int_t
ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
    ngx_http_upstream_resolved_t *ur)
{
    u_char                            *p;
    size_t                             len;
    socklen_t                          socklen;
    ngx_uint_t                         i, n;
    struct sockaddr                   *sockaddr;
    ngx_http_upstream_rr_peer_t       *peer, **peerp;
    ngx_http_upstream_rr_peers_t      *peers;
    ngx_http_upstream_rr_peer_data_t  *rrp;

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

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

        r->upstream->peer.data = rrp;
    }

    peers = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peers_t));
    if (peers == NULL) {
        return NGX_ERROR;
    }

    peer = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peer_t)
                                * ur->naddrs);
    if (peer == NULL) {
        return NGX_ERROR;
    }

    peers->single = (ur->naddrs == 1);
    peers->number = ur->naddrs;
    peers->tries = ur->naddrs;
    peers->name = &ur->host;

    if (ur->sockaddr) {
        peer[0].sockaddr = ur->sockaddr;
        peer[0].socklen = ur->socklen;
        peer[0].name = ur->name.data ? ur->name : ur->host;
        peer[0].weight = 1;
        peer[0].effective_weight = 1;
        peer[0].current_weight = 0;
        peer[0].max_conns = 0;
        peer[0].max_fails = 1;
        peer[0].fail_timeout = 10;
        peers->peer = peer;

    } else {
        peerp = &peers->peer;

        for (i = 0; i < ur->naddrs; i++) {

            socklen = ur->addrs[i].socklen;

            sockaddr = ngx_palloc(r->pool, socklen);
            if (sockaddr == NULL) {
                return NGX_ERROR;
            }

            ngx_memcpy(sockaddr, ur->addrs[i].sockaddr, socklen);
            ngx_inet_set_port(sockaddr, ur->port);

            p = ngx_pnalloc(r->pool, NGX_SOCKADDR_STRLEN);
            if (p == NULL) {
                return NGX_ERROR;
            }

            len = ngx_sock_ntop(sockaddr, socklen, p, NGX_SOCKADDR_STRLEN, 1);

            peer[i].sockaddr = sockaddr;
            peer[i].socklen = socklen;
            peer[i].name.len = len;
            peer[i].name.data = p;
            peer[i].weight = 1;
            peer[i].effective_weight = 1;
            peer[i].current_weight = 0;
            peer[i].max_conns = 0;
            peer[i].max_fails = 1;
            peer[i].fail_timeout = 10;
            *peerp = &peer[i];
            peerp = &peer[i].next;
        }
    }

    rrp->peers = peers;
    rrp->current = NULL;
    rrp->config = 0;

    if (rrp->peers->number <= 8 * sizeof(uintptr_t)) {
        rrp->tried = &rrp->data;
        rrp->data = 0;

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

        rrp->tried = ngx_pcalloc(r->pool, n * sizeof(uintptr_t));
        if (rrp->tried == NULL) {
            return NGX_ERROR;
        }
    }

    r->upstream->peer.get = ngx_http_upstream_get_round_robin_peer;
    r->upstream->peer.free = ngx_http_upstream_free_round_robin_peer;
    r->upstream->peer.tries = ngx_http_upstream_tries(rrp->peers);
#if (NGX_HTTP_SSL)
    r->upstream->peer.set_session = ngx_http_upstream_empty_set_session;
    r->upstream->peer.save_session = ngx_http_upstream_empty_save_session;
#endif

    return NGX_OK;
}


ngx_int_t
ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
{
    ngx_http_upstream_rr_peer_data_t  *rrp = data;

    ngx_int_t                      rc;
    ngx_uint_t                     i, n;
    ngx_http_upstream_rr_peer_t   *peer;
    ngx_http_upstream_rr_peers_t  *peers;

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

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

    peers = rrp->peers;
    ngx_http_upstream_rr_peers_wlock(peers);

    if (peers->single) {
        peer = peers->peer;

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

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

        rrp->current = peer;

    } else {

        /* there are several peers */

        peer = ngx_http_upstream_get_peer(rrp);

        if (peer == NULL) {
            goto failed;
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                       "get rr peer, current: %p %i",
                       peer, peer->current_weight);
    }

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

    peer->conns++;

    ngx_http_upstream_rr_peers_unlock(peers);

    return NGX_OK;

failed:

    if (peers->next) {

        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0, "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_http_upstream_rr_peers_unlock(peers);

        rc = ngx_http_upstream_get_round_robin_peer(pc, rrp);

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

        ngx_http_upstream_rr_peers_wlock(peers);
    }

    ngx_http_upstream_rr_peers_unlock(peers);

    pc->name = peers->name;

    return NGX_BUSY;
}


static ngx_http_upstream_rr_peer_t *
ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
{
    time_t                        now;
    uintptr_t                     m;
    ngx_int_t                     total;
    ngx_uint_t                    i, n, p;
    ngx_http_upstream_rr_peer_t  *peer, *best;

    now = ngx_time();

    best = NULL;
    total = 0;

#if (NGX_SUPPRESS_WARN)
    p = 0;
#endif

    for (peer = rrp->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;
        }

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

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

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

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

    if (best == NULL) {
        return NULL;
    }

    rrp->current = best;

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

    rrp->tried[n] |= m;

    best->current_weight -= total;

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

    return best;
}


void
ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
    ngx_uint_t state)
{
    ngx_http_upstream_rr_peer_data_t  *rrp = data;

    time_t                       now;
    ngx_http_upstream_rr_peer_t  *peer;

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                   "free rr peer %ui %ui", pc->tries, state);

    /* TODO: NGX_PEER_KEEPALIVE */

    peer = rrp->current;

    ngx_http_upstream_rr_peers_rlock(rrp->peers);
    ngx_http_upstream_rr_peer_lock(rrp->peers, peer);

    if (rrp->peers->single) {

        peer->conns--;

        ngx_http_upstream_rr_peer_unlock(rrp->peers, peer);
        ngx_http_upstream_rr_peers_unlock(rrp->peers);

        pc->tries = 0;
        return;
    }

    if (state & NGX_PEER_FAILED) {
        now = ngx_time();

        peer->fails++;
        peer->accessed = now;
        peer->checked = now;

        if (peer->max_fails) {
            peer->effective_weight -= peer->weight / peer->max_fails;

            if (peer->fails >= peer->max_fails) {
                ngx_log_error(NGX_LOG_WARN, pc->log, 0,
                              "upstream server temporarily disabled");
            }
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                       "free rr peer failed: %p %i",
                       peer, peer->effective_weight);

        if (peer->effective_weight < 0) {
            peer->effective_weight = 0;
        }

    } else {

        /* mark peer live if check passed */

        if (peer->accessed < peer->checked) {
            peer->fails = 0;
        }
    }

    peer->conns--;

    ngx_http_upstream_rr_peer_unlock(rrp->peers, peer);
    ngx_http_upstream_rr_peers_unlock(rrp->peers);

    if (pc->tries) {
        pc->tries--;
    }
}


#if (NGX_HTTP_SSL)

ngx_int_t
ngx_http_upstream_set_round_robin_peer_session(ngx_peer_connection_t *pc,
    void *data)
{
    ngx_http_upstream_rr_peer_data_t  *rrp = data;

    ngx_int_t                      rc;
    ngx_ssl_session_t             *ssl_session;
    ngx_http_upstream_rr_peer_t   *peer;
#if (NGX_HTTP_UPSTREAM_ZONE)
    int                            len;
    const u_char                  *p;
    ngx_http_upstream_rr_peers_t  *peers;
    u_char                         buf[NGX_SSL_MAX_SESSION_SIZE];
#endif

    peer = rrp->current;

#if (NGX_HTTP_UPSTREAM_ZONE)
    peers = rrp->peers;

    if (peers->shpool) {
        ngx_http_upstream_rr_peers_rlock(peers);
        ngx_http_upstream_rr_peer_lock(peers, peer);

        if (peer->ssl_session == NULL) {
            ngx_http_upstream_rr_peer_unlock(peers, peer);
            ngx_http_upstream_rr_peers_unlock(peers);
            return NGX_OK;
        }

        len = peer->ssl_session_len;

        ngx_memcpy(buf, peer->ssl_session, len);

        ngx_http_upstream_rr_peer_unlock(peers, peer);
        ngx_http_upstream_rr_peers_unlock(peers);

        p = buf;
        ssl_session = d2i_SSL_SESSION(NULL, &p, len);

        rc = ngx_ssl_set_session(pc->connection, ssl_session);

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                       "set session: %p", ssl_session);

        ngx_ssl_free_session(ssl_session);

        return rc;
    }
#endif

    ssl_session = peer->ssl_session;

    rc = ngx_ssl_set_session(pc->connection, ssl_session);

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                   "set session: %p", ssl_session);

    return rc;
}


void
ngx_http_upstream_save_round_robin_peer_session(ngx_peer_connection_t *pc,
    void *data)
{
    ngx_http_upstream_rr_peer_data_t  *rrp = data;

    ngx_ssl_session_t             *old_ssl_session, *ssl_session;
    ngx_http_upstream_rr_peer_t   *peer;
#if (NGX_HTTP_UPSTREAM_ZONE)
    int                            len;
    u_char                        *p;
    ngx_http_upstream_rr_peers_t  *peers;
    u_char                         buf[NGX_SSL_MAX_SESSION_SIZE];
#endif

#if (NGX_HTTP_UPSTREAM_ZONE)
    peers = rrp->peers;

    if (peers->shpool) {

        ssl_session = ngx_ssl_get0_session(pc->connection);

        if (ssl_session == NULL) {
            return;
        }

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                       "save session: %p", ssl_session);

        len = i2d_SSL_SESSION(ssl_session, NULL);

        /* do not cache too big session */

        if (len > NGX_SSL_MAX_SESSION_SIZE) {
            return;
        }

        p = buf;
        (void) i2d_SSL_SESSION(ssl_session, &p);

        peer = rrp->current;

        ngx_http_upstream_rr_peers_rlock(peers);
        ngx_http_upstream_rr_peer_lock(peers, peer);

        if (len > peer->ssl_session_len) {
            ngx_shmtx_lock(&peers->shpool->mutex);

            if (peer->ssl_session) {
                ngx_slab_free_locked(peers->shpool, peer->ssl_session);
            }

            peer->ssl_session = ngx_slab_alloc_locked(peers->shpool, len);

            ngx_shmtx_unlock(&peers->shpool->mutex);

            if (peer->ssl_session == NULL) {
                peer->ssl_session_len = 0;

                ngx_http_upstream_rr_peer_unlock(peers, peer);
                ngx_http_upstream_rr_peers_unlock(peers);
                return;
            }

            peer->ssl_session_len = len;
        }

        ngx_memcpy(peer->ssl_session, buf, len);

        ngx_http_upstream_rr_peer_unlock(peers, peer);
        ngx_http_upstream_rr_peers_unlock(peers);

        return;
    }
#endif

    ssl_session = ngx_ssl_get_session(pc->connection);

    if (ssl_session == NULL) {
        return;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                   "save session: %p", ssl_session);

    peer = rrp->current;

    old_ssl_session = peer->ssl_session;
    peer->ssl_session = ssl_session;

    if (old_ssl_session) {

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                       "old session: %p", old_ssl_session);

        /* TODO: may block */

        ngx_ssl_free_session(old_ssl_session);
    }
}


static ngx_int_t
ngx_http_upstream_empty_set_session(ngx_peer_connection_t *pc, void *data)
{
    return NGX_OK;
}


static void
ngx_http_upstream_empty_save_session(ngx_peer_connection_t *pc, void *data)
{
    return;
}

#endif