Introduced the "keepalive_time" directive.

Similar to lingering_time, it limits total connection lifetime before
keepalive is switched off.  The default is 1 hour, which is close to
the total maximum connection lifetime possible with default
keepalive_requests and keepalive_timeout.

src/core/ngx_connection.h

@@ -162,6 +162,7 @@ struct ngx_connection_s {
 
     ngx_atomic_uint_t   number;
 
+    ngx_msec_t          start_time;
     ngx_uint_t          requests;
 
     unsigned            buffered:8;

src/core/ngx_resolver.c

@@ -4459,6 +4459,8 @@ ngx_udp_connect(ngx_resolver_connection_t *rec)
 
     c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
 
+    c->start_time = ngx_current_msec;
+
     ngx_log_debug3(NGX_LOG_DEBUG_EVENT, &rec->log, 0,
                    "connect to %V, fd:%d #%uA", &rec->server, s, c->number);
 
@@ -4545,6 +4547,8 @@ ngx_tcp_connect(ngx_resolver_connection_t *rec)
 
     c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
 
+    c->start_time = ngx_current_msec;
+
     if (ngx_add_conn) {
         if (ngx_add_conn(c) == NGX_ERROR) {
             goto failed;

src/event/ngx_event_accept.c

@@ -256,6 +256,8 @@ ngx_event_accept(ngx_event_t *ev)
 
         c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
 
+        c->start_time = ngx_current_msec;
+
 #if (NGX_STAT_STUB)
         (void) ngx_atomic_fetch_add(ngx_stat_handled, 1);
 #endif

src/event/ngx_event_acceptex.c

@@ -80,6 +80,8 @@ ngx_event_acceptex(ngx_event_t *rev)
 
     c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
 
+    c->start_time = ngx_current_msec;
+
     ls->handler(c);
 
     return;

src/event/ngx_event_connect.c

@@ -193,6 +193,8 @@ ngx_event_connect_peer(ngx_peer_connection_t *pc)
 
     c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
 
+    c->start_time = ngx_current_msec;
+
     if (ngx_add_conn) {
         if (ngx_add_conn(c) == NGX_ERROR) {
             goto failed;

src/event/ngx_event_udp.c

@@ -363,6 +363,8 @@ ngx_event_recvmsg(ngx_event_t *ev)
 
         c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
 
+        c->start_time = ngx_current_msec;
+
 #if (NGX_STAT_STUB)
         (void) ngx_atomic_fetch_add(ngx_stat_handled, 1);
 #endif

src/http/modules/ngx_http_upstream_keepalive_module.c

@@ -13,6 +13,7 @@
 typedef struct {
     ngx_uint_t                         max_cached;
     ngx_uint_t                         requests;
+    ngx_msec_t                         time;
     ngx_msec_t                         timeout;
 
     ngx_queue_t                        cache;
@@ -86,6 +87,13 @@ static ngx_command_t  ngx_http_upstream_keepalive_commands[] = {
       0,
       NULL },
 
+    { ngx_string("keepalive_time"),
+      NGX_HTTP_UPS_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_msec_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_upstream_keepalive_srv_conf_t, time),
+      NULL },
+
     { ngx_string("keepalive_timeout"),
       NGX_HTTP_UPS_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_msec_slot,
@@ -149,6 +157,7 @@ ngx_http_upstream_init_keepalive(ngx_conf_t *cf,
     kcf = ngx_http_conf_upstream_srv_conf(us,
                                           ngx_http_upstream_keepalive_module);
 
+    ngx_conf_init_msec_value(kcf->time, 3600000);
     ngx_conf_init_msec_value(kcf->timeout, 60000);
     ngx_conf_init_uint_value(kcf->requests, 100);
 
@@ -326,6 +335,10 @@ ngx_http_upstream_free_keepalive_peer(ngx_peer_connection_t *pc, void *data,
         goto invalid;
     }
 
+    if (ngx_current_msec - c->start_time > kp->conf->time) {
+        goto invalid;
+    }
+
     if (!u->keepalive) {
         goto invalid;
     }
@@ -513,6 +526,7 @@ ngx_http_upstream_keepalive_create_conf(ngx_conf_t *cf)
      *     conf->max_cached = 0;
      */
 
+    conf->time = NGX_CONF_UNSET_MSEC;
     conf->timeout = NGX_CONF_UNSET_MSEC;
     conf->requests = NGX_CONF_UNSET_UINT;
 

src/http/ngx_http_core_module.c

@@ -495,6 +495,13 @@ static ngx_command_t  ngx_http_core_commands[] = {
       offsetof(ngx_http_core_loc_conf_t, limit_rate_after),
       NULL },
 
+    { ngx_string("keepalive_time"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_msec_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_core_loc_conf_t, keepalive_time),
+      NULL },
+
     { ngx_string("keepalive_timeout"),
       NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE12,
       ngx_http_core_keepalive,
@@ -1335,6 +1342,11 @@ ngx_http_update_location_config(ngx_http_request_t *r)
         } else if (r->connection->requests >= clcf->keepalive_requests) {
             r->keepalive = 0;
 
+        } else if (ngx_current_msec - r->connection->start_time
+                   > clcf->keepalive_time)
+        {
+            r->keepalive = 0;
+
         } else if (r->headers_in.msie6
                    && r->method == NGX_HTTP_POST
                    && (clcf->keepalive_disable
@@ -3500,6 +3512,7 @@ ngx_http_core_create_loc_conf(ngx_conf_t *cf)
     clcf->send_timeout = NGX_CONF_UNSET_MSEC;
     clcf->send_lowat = NGX_CONF_UNSET_SIZE;
     clcf->postpone_output = NGX_CONF_UNSET_SIZE;
+    clcf->keepalive_time = NGX_CONF_UNSET_MSEC;
     clcf->keepalive_timeout = NGX_CONF_UNSET_MSEC;
     clcf->keepalive_header = NGX_CONF_UNSET;
     clcf->keepalive_requests = NGX_CONF_UNSET_UINT;
@@ -3738,6 +3751,8 @@ ngx_http_core_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
         conf->limit_rate_after = prev->limit_rate_after;
     }
 
+    ngx_conf_merge_msec_value(conf->keepalive_time,
+                              prev->keepalive_time, 3600000);
     ngx_conf_merge_msec_value(conf->keepalive_timeout,
                               prev->keepalive_timeout, 75000);
     ngx_conf_merge_sec_value(conf->keepalive_header,

src/http/ngx_http_core_module.h

@@ -359,6 +359,7 @@ struct ngx_http_core_loc_conf_s {
 
     ngx_msec_t    client_body_timeout;     /* client_body_timeout */
     ngx_msec_t    send_timeout;            /* send_timeout */
+    ngx_msec_t    keepalive_time;          /* keepalive_time */
     ngx_msec_t    keepalive_timeout;       /* keepalive_timeout */
     ngx_msec_t    lingering_time;          /* lingering_time */
     ngx_msec_t    lingering_timeout;       /* lingering_timeout */

src/http/v2/ngx_http_v2.c

@@ -1369,7 +1369,9 @@ ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
                                         ngx_http_core_module);
 
     if (clcf->keepalive_timeout == 0
-        || h2c->connection->requests >= clcf->keepalive_requests)
+        || h2c->connection->requests >= clcf->keepalive_requests
+        || ngx_current_msec - h2c->connection->start_time
+           > clcf->keepalive_time)
     {
         h2c->goaway = 1;