diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index ae56c12..fac45fe 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -96,6 +96,8 @@
     ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_http_upstream_response_time_variable(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
+static ngx_int_t ngx_http_upstream_response_length_variable(
+    ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data);
 
 static char *ngx_http_upstream(ngx_conf_t *cf, ngx_command_t *cmd, void *dummy);
 static char *ngx_http_upstream_server(ngx_conf_t *cf, ngx_command_t *cmd,
@@ -296,6 +298,10 @@
       ngx_http_upstream_response_time_variable, 0,
       NGX_HTTP_VAR_NOHASH|NGX_HTTP_VAR_NOCACHEABLE, 0 },
 
+    { ngx_string("upstream_response_length"), NULL,
+      ngx_http_upstream_response_length_variable, 0,
+      NGX_HTTP_VAR_NOHASH|NGX_HTTP_VAR_NOCACHEABLE, 0 },
+
     { ngx_null_string, NULL, NULL, 0, 0, 0 }
 };
 
@@ -1379,6 +1385,8 @@
     if (n) {
         u->buffer.last -= n;
 
+        u->state->response_length += n;
+
         if (u->input_filter(u->input_filter_ctx, n) == NGX_ERROR) {
             ngx_http_upstream_finalize_request(r, u, NGX_ERROR);
             return;
@@ -1581,6 +1589,8 @@
             return;
         }
 
+        u->state->response_length += n;
+
         if (u->input_filter(u->input_filter_ctx, n) == NGX_ERROR) {
             ngx_http_upstream_finalize_request(r, u, NGX_ERROR);
             return;
@@ -1609,7 +1619,7 @@
 ngx_http_upstream_send_response(ngx_http_request_t *r, ngx_http_upstream_t *u)
 {
     int                        tcp_nodelay;
-    ssize_t                    size;
+    ssize_t                    n;
     ngx_int_t                  rc;
     ngx_event_pipe_t          *p;
     ngx_connection_t          *c;
@@ -1681,12 +1691,14 @@
             c->tcp_nodelay = NGX_TCP_NODELAY_SET;
         }
 
-        size = u->buffer.last - u->buffer.pos;
+        n = u->buffer.last - u->buffer.pos;
 
-        if (size) {
+        if (n) {
             u->buffer.last = u->buffer.pos;
 
-            if (u->input_filter(u->input_filter_ctx, size) == NGX_ERROR) {
+            u->state->response_length += n;
+
+            if (u->input_filter(u->input_filter_ctx, n) == NGX_ERROR) {
                 ngx_http_upstream_finalize_request(r, u, 0);
                 return;
             }
@@ -1960,6 +1972,8 @@
             }
 
             if (n > 0) {
+                u->state->response_length += n;
+
                 if (u->input_filter(u->input_filter_ctx, n) == NGX_ERROR) {
                     ngx_http_upstream_finalize_request(r, u, 0);
                     return;
@@ -2480,6 +2494,10 @@
         tp = ngx_timeofday();
         u->state->response_sec = tp->sec - u->state->response_sec;
         u->state->response_msec = tp->msec - u->state->response_msec;
+
+        if (u->pipe) {
+            u->state->response_length = u->pipe->read_length;
+        }
     }
 
     u->finalize_request(r, rc);
@@ -3123,6 +3141,66 @@
 }
 
 
+static ngx_int_t
+ngx_http_upstream_response_length_variable(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    u_char                     *p;
+    size_t                      len;
+    ngx_uint_t                  i;
+    ngx_http_upstream_state_t  *state;
+
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+
+    if (r->upstream_states == NULL || r->upstream_states->nelts == 0) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    len = r->upstream_states->nelts * (NGX_OFF_T_LEN + 2);
+
+    p = ngx_pnalloc(r->pool, len);
+    if (p == NULL) {
+        return NGX_ERROR;
+    }
+
+    v->data = p;
+
+    i = 0;
+    state = r->upstream_states->elts;
+
+    for ( ;; ) {
+        p = ngx_sprintf(p, "%O", state[i].response_length);
+
+        if (++i == r->upstream_states->nelts) {
+            break;
+        }
+
+        if (state[i].peer) {
+            *p++ = ',';
+            *p++ = ' ';
+
+        } else {
+            *p++ = ' ';
+            *p++ = ':';
+            *p++ = ' ';
+
+            if (++i == r->upstream_states->nelts) {
+                break;
+            }
+
+            continue;
+        }
+    }
+
+    v->len = p - v->data;
+
+    return NGX_OK;
+}
+
+
 ngx_int_t
 ngx_http_upstream_header_variable(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data)
diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index d38d6c0..b6f2161 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -45,6 +45,7 @@
     ngx_uint_t                      status;
     time_t                          response_sec;
     ngx_uint_t                      response_msec;
+    off_t                           response_length;
 
     ngx_str_t                      *peer;
 } ngx_http_upstream_state_t;