view src/stream/ngx_stream_upstream_round_robin.c @ 8078:5244d3b165ff

SSL: single allocation in session cache on 32-bit platforms. Given the present typical SSL session sizes, on 32-bit platforms it is now beneficial to store all data in a single allocation, since rbtree node + session id + ASN1 representation of a session takes 256 bytes of shared memory (36 + 32 + 150 = about 218 bytes plus SNI server name). Storing all data in a single allocation is beneficial for SNI names up to about 40 characters long and makes it possible to store about 4000 sessions in one megabyte (instead of about 3000 sessions now). This also slightly simplifies the code.
author Maxim Dounin <mdounin@mdounin.ru>
date Wed, 12 Oct 2022 20:14:40 +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_stream.h>


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


static ngx_stream_upstream_rr_peer_t *ngx_stream_upstream_get_peer(
    ngx_stream_upstream_rr_peer_data_t *rrp);
static void ngx_stream_upstream_notify_round_robin_peer(
    ngx_peer_connection_t *pc, void *data, ngx_uint_t state);

#if (NGX_STREAM_SSL)

static ngx_int_t ngx_stream_upstream_set_round_robin_peer_session(
    ngx_peer_connection_t *pc, void *data);
static void ngx_stream_upstream_save_round_robin_peer_session(
    ngx_peer_connection_t *pc, void *data);
static ngx_int_t ngx_stream_upstream_empty_set_session(
    ngx_peer_connection_t *pc, void *data);
static void ngx_stream_upstream_empty_save_session(ngx_peer_connection_t *pc,
    void *data);

#endif


ngx_int_t
ngx_stream_upstream_init_round_robin(ngx_conf_t *cf,
    ngx_stream_upstream_srv_conf_t *us)
{
    ngx_url_t                        u;
    ngx_uint_t                       i, j, n, w, t;
    ngx_stream_upstream_server_t    *server;
    ngx_stream_upstream_rr_peer_t   *peer, **peerp;
    ngx_stream_upstream_rr_peers_t  *peers, *backup;

    us->peer.init = ngx_stream_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_stream_upstream_rr_peers_t));
        if (peers == NULL) {
            return NGX_ERROR;
        }

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

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

    peer = ngx_pcalloc(cf->pool, sizeof(ngx_stream_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_stream_upstream_init_round_robin_peer(ngx_stream_session_t *s,
    ngx_stream_upstream_srv_conf_t *us)
{
    ngx_uint_t                           n;
    ngx_stream_upstream_rr_peer_data_t  *rrp;

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

    if (rrp == NULL) {
        rrp = ngx_palloc(s->connection->pool,
                         sizeof(ngx_stream_upstream_rr_peer_data_t));
        if (rrp == NULL) {
            return NGX_ERROR;
        }

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

    s->upstream->peer.get = ngx_stream_upstream_get_round_robin_peer;
    s->upstream->peer.free = ngx_stream_upstream_free_round_robin_peer;
    s->upstream->peer.notify = ngx_stream_upstream_notify_round_robin_peer;
    s->upstream->peer.tries = ngx_stream_upstream_tries(rrp->peers);
#if (NGX_STREAM_SSL)
    s->upstream->peer.set_session =
                             ngx_stream_upstream_set_round_robin_peer_session;
    s->upstream->peer.save_session =
                             ngx_stream_upstream_save_round_robin_peer_session;
#endif

    return NGX_OK;
}


ngx_int_t
ngx_stream_upstream_create_round_robin_peer(ngx_stream_session_t *s,
    ngx_stream_upstream_resolved_t *ur)
{
    u_char                              *p;
    size_t                               len;
    socklen_t                            socklen;
    ngx_uint_t                           i, n;
    struct sockaddr                     *sockaddr;
    ngx_stream_upstream_rr_peer_t       *peer, **peerp;
    ngx_stream_upstream_rr_peers_t      *peers;
    ngx_stream_upstream_rr_peer_data_t  *rrp;

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

    if (rrp == NULL) {
        rrp = ngx_palloc(s->connection->pool,
                         sizeof(ngx_stream_upstream_rr_peer_data_t));
        if (rrp == NULL) {
            return NGX_ERROR;
        }

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

    peers = ngx_pcalloc(s->connection->pool,
                        sizeof(ngx_stream_upstream_rr_peers_t));
    if (peers == NULL) {
        return NGX_ERROR;
    }

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

    s->upstream->peer.get = ngx_stream_upstream_get_round_robin_peer;
    s->upstream->peer.free = ngx_stream_upstream_free_round_robin_peer;
    s->upstream->peer.tries = ngx_stream_upstream_tries(rrp->peers);
#if (NGX_STREAM_SSL)
    s->upstream->peer.set_session = ngx_stream_upstream_empty_set_session;
    s->upstream->peer.save_session = ngx_stream_upstream_empty_save_session;
#endif

    return NGX_OK;
}


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

    ngx_int_t                        rc;
    ngx_uint_t                       i, n;
    ngx_stream_upstream_rr_peer_t   *peer;
    ngx_stream_upstream_rr_peers_t  *peers;

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

    pc->connection = NULL;

    peers = rrp->peers;
    ngx_stream_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_stream_upstream_get_peer(rrp);

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

        ngx_log_debug2(NGX_LOG_DEBUG_STREAM, 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_stream_upstream_rr_peers_unlock(peers);

    return NGX_OK;

failed:

    if (peers->next) {

        ngx_log_debug0(NGX_LOG_DEBUG_STREAM, 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_stream_upstream_rr_peers_unlock(peers);

        rc = ngx_stream_upstream_get_round_robin_peer(pc, rrp);

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

        ngx_stream_upstream_rr_peers_wlock(peers);
    }

    ngx_stream_upstream_rr_peers_unlock(peers);

    pc->name = peers->name;

    return NGX_BUSY;
}


static ngx_stream_upstream_rr_peer_t *
ngx_stream_upstream_get_peer(ngx_stream_upstream_rr_peer_data_t *rrp)
{
    time_t                          now;
    uintptr_t                       m;
    ngx_int_t                       total;
    ngx_uint_t                      i, n, p;
    ngx_stream_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_stream_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
    ngx_uint_t state)
{
    ngx_stream_upstream_rr_peer_data_t  *rrp = data;

    time_t                          now;
    ngx_stream_upstream_rr_peer_t  *peer;

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

    peer = rrp->current;

    ngx_stream_upstream_rr_peers_rlock(rrp->peers);
    ngx_stream_upstream_rr_peer_lock(rrp->peers, peer);

    if (rrp->peers->single) {
        peer->conns--;

        ngx_stream_upstream_rr_peer_unlock(rrp->peers, peer);
        ngx_stream_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_STREAM, 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_stream_upstream_rr_peer_unlock(rrp->peers, peer);
    ngx_stream_upstream_rr_peers_unlock(rrp->peers);

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


static void
ngx_stream_upstream_notify_round_robin_peer(ngx_peer_connection_t *pc,
    void *data, ngx_uint_t type)
{
    ngx_stream_upstream_rr_peer_data_t  *rrp = data;

    ngx_stream_upstream_rr_peer_t  *peer;

    peer = rrp->current;

    if (type == NGX_STREAM_UPSTREAM_NOTIFY_CONNECT
        && pc->connection->type == SOCK_STREAM)
    {
        ngx_stream_upstream_rr_peers_rlock(rrp->peers);
        ngx_stream_upstream_rr_peer_lock(rrp->peers, peer);

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

        ngx_stream_upstream_rr_peer_unlock(rrp->peers, peer);
        ngx_stream_upstream_rr_peers_unlock(rrp->peers);
    }
}


#if (NGX_STREAM_SSL)

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

    ngx_int_t                        rc;
    ngx_ssl_session_t               *ssl_session;
    ngx_stream_upstream_rr_peer_t   *peer;
#if (NGX_STREAM_UPSTREAM_ZONE)
    int                              len;
    const u_char                    *p;
    ngx_stream_upstream_rr_peers_t  *peers;
    u_char                           buf[NGX_SSL_MAX_SESSION_SIZE];
#endif

    peer = rrp->current;

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

    if (peers->shpool) {
        ngx_stream_upstream_rr_peers_rlock(peers);
        ngx_stream_upstream_rr_peer_lock(peers, peer);

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

        len = peer->ssl_session_len;

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

        ngx_stream_upstream_rr_peer_unlock(peers, peer);
        ngx_stream_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_STREAM, 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_STREAM, pc->log, 0,
                   "set session: %p", ssl_session);

    return rc;
}


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

    ngx_ssl_session_t               *old_ssl_session, *ssl_session;
    ngx_stream_upstream_rr_peer_t   *peer;
#if (NGX_STREAM_UPSTREAM_ZONE)
    int                              len;
    u_char                          *p;
    ngx_stream_upstream_rr_peers_t  *peers;
    u_char                           buf[NGX_SSL_MAX_SESSION_SIZE];
#endif

#if (NGX_STREAM_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_STREAM, 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_stream_upstream_rr_peers_rlock(peers);
        ngx_stream_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_stream_upstream_rr_peer_unlock(peers, peer);
                ngx_stream_upstream_rr_peers_unlock(peers);
                return;
            }

            peer->ssl_session_len = len;
        }

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

        ngx_stream_upstream_rr_peer_unlock(peers, peer);
        ngx_stream_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_STREAM, 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_STREAM, pc->log, 0,
                       "old session: %p", old_ssl_session);

        /* TODO: may block */

        ngx_ssl_free_session(old_ssl_session);
    }
}


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


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

#endif