[nginx] Map: the "volatile" parameter.

[Eran Kornblau]

Ruslan, thank you very much !

Eran

-----Original Message-----
From: nginx-devel [mailto:nginx-devel-bounces at nginx.org] On Behalf Of Ruslan Ermilov
Sent: Thursday, December 8, 2016 8:47 PM
To: nginx-devel at nginx.org
Subject: [nginx] Map: the "volatile" parameter.

details:   http://hg.nginx.org/nginx/rev/ec10ce307dc0
branches:  
changeset: 6832:ec10ce307dc0
user:      Ruslan Ermilov <ru at nginx.com>
date:      Thu Dec 08 17:51:49 2016 +0300
description:
Map: the "volatile" parameter.

By default, "map" creates cacheable variables [1].  With this parameter it creates a non-cacheable variable.

An original idea was to deduce the cacheability of the "map"
variable by checking the cacheability of variables specified in source and resulting values, but it turned to be too hard.
For example, a cacheable variable can be overridden with the "set" directive or with the SSI "set" command.  Also, keeping "map" variables cacheable by default is good for performance reasons.  This required adding a new parameter.

[1] Before db699978a33f (1.11.0), the cacheability of the "map" variable could vary depending on the cacheability of variables specified in resulting values (ticket #1090).
This is believed to be a bug rather than a feature.

diffstat:

 src/http/modules/ngx_http_map_module.c |  15 ++++++++++++++-
 src/stream/ngx_stream_map_module.c     |  15 ++++++++++++++-
 2 files changed, 28 insertions(+), 2 deletions(-)

diffs (92 lines):

diff -r 014905eb7b3d -r ec10ce307dc0 src/http/modules/ngx_http_map_module.c
--- a/src/http/modules/ngx_http_map_module.c	Thu Dec 08 17:29:01 2016 +0300
+++ b/src/http/modules/ngx_http_map_module.c	Thu Dec 08 17:51:49 2016 +0300
@@ -26,7 +26,8 @@ typedef struct {
 
     ngx_http_variable_value_t  *default_value;
     ngx_conf_t                 *cf;
-    ngx_uint_t                  hostnames;      /* unsigned  hostnames:1 */
+    unsigned                    hostnames:1;
+    unsigned                    no_cacheable:1;
 } ngx_http_map_conf_ctx_t;
 
 
@@ -265,6 +266,7 @@ ngx_http_map_block(ngx_conf_t *cf, ngx_c
     ctx.default_value = NULL;
     ctx.cf = &save;
     ctx.hostnames = 0;
+    ctx.no_cacheable = 0;
 
     save = *cf;
     cf->pool = pool;
@@ -281,6 +283,10 @@ ngx_http_map_block(ngx_conf_t *cf, ngx_c
         return rv;
     }
 
+    if (ctx.no_cacheable) {
+        var->flags |= NGX_HTTP_VAR_NOCACHEABLE;
+    }
+
     map->default_value = ctx.default_value ? ctx.default_value:
                                              &ngx_http_variable_null_value;
 
@@ -395,6 +401,13 @@ ngx_http_map(ngx_conf_t *cf, ngx_command
         return NGX_CONF_OK;
     }
 
+    if (cf->args->nelts == 1
+        && ngx_strcmp(value[0].data, "volatile") == 0)
+    {
+        ctx->no_cacheable = 1;
+        return NGX_CONF_OK;
+    }
+
     if (cf->args->nelts != 2) {
         ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                            "invalid number of the map parameters"); diff -r 014905eb7b3d -r ec10ce307dc0 src/stream/ngx_stream_map_module.c
--- a/src/stream/ngx_stream_map_module.c	Thu Dec 08 17:29:01 2016 +0300
+++ b/src/stream/ngx_stream_map_module.c	Thu Dec 08 17:51:49 2016 +0300
@@ -26,7 +26,8 @@ typedef struct {
 
     ngx_stream_variable_value_t  *default_value;
     ngx_conf_t                   *cf;
-    ngx_uint_t                    hostnames;      /* unsigned  hostnames:1 */
+    unsigned                      hostnames:1;
+    unsigned                      no_cacheable:1;
 } ngx_stream_map_conf_ctx_t;
 
 
@@ -264,6 +265,7 @@ ngx_stream_map_block(ngx_conf_t *cf, ngx
     ctx.default_value = NULL;
     ctx.cf = &save;
     ctx.hostnames = 0;
+    ctx.no_cacheable = 0;
 
     save = *cf;
     cf->pool = pool;
@@ -280,6 +282,10 @@ ngx_stream_map_block(ngx_conf_t *cf, ngx
         return rv;
     }
 
+    if (ctx.no_cacheable) {
+        var->flags |= NGX_STREAM_VAR_NOCACHEABLE;
+    }
+
     map->default_value = ctx.default_value ? ctx.default_value:
                                              &ngx_stream_variable_null_value;
 
@@ -394,6 +400,13 @@ ngx_stream_map(ngx_conf_t *cf, ngx_comma
         return NGX_CONF_OK;
     }
 
+    if (cf->args->nelts == 1
+        && ngx_strcmp(value[0].data, "volatile") == 0)
+    {
+        ctx->no_cacheable = 1;
+        return NGX_CONF_OK;
+    }
+
     if (cf->args->nelts != 2) {
         ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                            "invalid number of the map parameters"); _______________________________________________
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