nginx patch for queue wait time

gistfile1.diff

--- src/http/modules/ngx_http_proxy_module.c.orig       2010-09-21 02:07:05.000000000 -0300
+++ src/http/modules/ngx_http_proxy_module.c    2010-09-21 02:09:05.000000000 -0300
@@ -74,6 +74,8 @@
 
     ngx_uint_t                     headers_hash_max_size;
     ngx_uint_t                     headers_hash_bucket_size;
+
+    ngx_flag_t                     queue_wait_hdrs;
 } ngx_http_proxy_loc_conf_t;
 
 
@@ -152,6 +154,7 @@
     ngx_http_proxy_loc_conf_t *plcf);
 #endif
 static void ngx_http_proxy_set_vars(ngx_url_t *u, ngx_http_proxy_vars_t *v);
+static ngx_str_t *queue_wait_headers(const ngx_http_request_t *r);
 
 
 static ngx_conf_post_t  ngx_http_proxy_lowat_post =
@@ -461,6 +464,13 @@
 
 #endif
 
+    { ngx_string("proxy_queue_wait_headers"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_proxy_loc_conf_t, queue_wait_hdrs),
+      NULL },
+
       ngx_null_command
 };
 
@@ -878,6 +888,7 @@
     ngx_http_script_engine_t      e, le;
     ngx_http_proxy_loc_conf_t    *plcf;
     ngx_http_script_len_code_pt   lcode;
+    ngx_str_t                    *qw_headers = NULL;
 
     u = r->upstream;
 
@@ -990,6 +1001,12 @@
         }
     }
 
+    if (plcf->queue_wait_hdrs == 1) {
+      if ( (qw_headers = queue_wait_headers(r)) == NULL) {
+       return NGX_ERROR;
+      }
+      len += qw_headers->len;
+    }
 
     b = ngx_create_temp_buf(r->pool, len);
     if (b == NULL) {
@@ -1118,6 +1135,14 @@
         }
     }

+    if (plcf->queue_wait_hdrs == 1) {
+      b->last = ngx_copy(b->last, qw_headers->data, qw_headers->len);
+      /* this is not necessary since the memory pool is destroyed when
+       * the request ends.
+       * ngx_pfree(r->pool, qw_headers->data);
+       * ngx_pfree(r->pool, qw_headers);
+       */
+    }
 
     /* add "\r\n" at the header end */
     *b->last++ = CR; *b->last++ = LF;
@@ -1951,6 +1976,8 @@
     conf->headers_hash_max_size = NGX_CONF_UNSET_UINT;
     conf->headers_hash_bucket_size = NGX_CONF_UNSET_UINT;
 
+    conf->queue_wait_hdrs = NGX_CONF_UNSET;
+
     return conf;
 }
 
@@ -2219,6 +2246,8 @@
         }
     }
 
+    ngx_conf_merge_value(conf->queue_wait_hdrs, prev->queue_wait_hdrs, 1);
+
     /* STUB */
     if (prev->proxy_lengths) {
         conf->proxy_lengths = prev->proxy_lengths;
@@ -3048,3 +3077,38 @@
 
     v->uri = u->uri;
 }
+
+
+static ngx_str_t *
+queue_wait_headers(const ngx_http_request_t *r)
+{
+  struct timeval tv;
+  uint64_t now_usec, req_start_usec, diff;
+  u_char *p;
+  size_t len;
+  ngx_str_t h1 = ngx_string("X-Request-Start: t=");
+  ngx_str_t h2 = ngx_string("X-Request-Read: t=");
+  ngx_str_t *res;
+
+  ngx_gettimeofday(&tv);
+  now_usec = (((uint64_t)tv.tv_sec * 1000 * 1000) + (uint64_t)tv.tv_usec);
+  req_start_usec = (((uint64_t)r->start_sec * 1000 * 1000) +
+                   ((uint64_t)r->start_msec * 1000));
+  diff = now_usec - req_start_usec;
+
+  len = h1.len + h2.len + (2*NGX_INT64_LEN) + (2*sizeof("\r\n"));
+  if ( (p = ngx_pnalloc(r->pool, len)) == NULL) {
+    return NULL;
+  }
+  ngx_memzero(p, len);
+  len = ngx_sprintf(p, "%V%L\r\n%V%L\r\n", &h1, now_usec, &h2, diff) - p;
+
+  if ( (res = (ngx_str_t *)ngx_pnalloc(r->pool, sizeof(ngx_str_t))) == NULL) {
+    return NULL;
+  }
+
+  ngx_memzero(res, sizeof(ngx_str_t));
+  res->len = len;
+  res->data = p;
+  return res;
+}