feature: expose the 'Last-Modified' response header as ngx.header["Last-Modified"]. (#1983)

Co-authored-by: Christian Becker <c.becker@mes-info.de>

Author: zhuizhuhaomeng

src/ngx_http_lua_headers.c

@@ -1068,6 +1068,7 @@ ngx_http_lua_ffi_get_resp_header(ngx_http_request_t *r,
 {
     int                  found;
     u_char               c, *p;
+    time_t               last_modified;
     ngx_uint_t           i;
     ngx_table_elt_t     *h;
     ngx_list_part_t     *part;
@@ -1134,6 +1135,28 @@ ngx_http_lua_ffi_get_resp_header(ngx_http_request_t *r,
 
         break;
 
+    case 13:
+        if (ngx_strncasecmp(key_buf, (u_char *) "Last-Modified", 13) == 0) {
+            last_modified = r->headers_out.last_modified_time;
+            if (last_modified >= 0) {
+                p = ngx_palloc(r->pool,
+                               sizeof("Mon, 28 Sep 1970 06:00:00 GMT"));
+                if (p == NULL) {
+                    *errmsg = "no memory";
+                    return NGX_ERROR;
+                }
+
+                values[0].data = p;
+                values[0].len = ngx_http_time(p, last_modified) - p;
+
+                return 1;
+            }
+
+            return 0;
+        }
+
+        break;
+
     default:
         break;
     }

t/016-resp-header.t

@@ -2141,3 +2141,88 @@ hi
 --- error_log
 my Content-Length: 8589934591
 upstream prematurely closed connection while sending to client
+
+
+
+=== TEST 95: Expose the 'Last-Modified' response header as ngx.header["Last-Modified"]
+--- config
+    location /a.txt {
+        header_filter_by_lua_block {
+            local last_modified = ngx.header["Last-Modified"]
+            if last_modified == nil then
+                ngx.log(ngx.ERR, "can not get lasted modified")
+                ngx.exit(500)
+                return
+            end
+
+            local last_mod = ngx.parse_http_time(last_modified)
+            local age = ngx.time() - last_mod
+            ngx.header["Age"] = age
+        }
+    }
+--- user_files
+>>> a.txt
+Foo
+--- request
+GET /a.txt
+--- raw_response_headers_like chomp
+Age: \d\r\n
+--- no_error_log
+[error]
+
+
+
+=== TEST 96: 'Last-Modified' from upstream
+--- config
+    location /test/ {
+        proxy_pass http://127.0.0.1:$server_port/;
+
+        header_filter_by_lua_block {
+            local last_modified = ngx.header["Last-Modified"]
+            if last_modified == nil then
+                ngx.log(ngx.ERR, "can not get lasted modified")
+                ngx.exit(500)
+                return
+            end
+
+            local last_mod = ngx.parse_http_time(last_modified)
+            local age = ngx.time() - last_mod
+            ngx.header["Age"] = age
+        }
+    }
+
+--- user_files
+>>> a.txt
+Foo
+--- request
+GET /test/a.txt
+--- raw_response_headers_like chomp
+Age: \d\r\n
+--- no_error_log
+[error]
+
+
+
+=== TEST 97: 'Last-Modified' does not exist
+--- config
+    location /test {
+        header_filter_by_lua_block {
+            local last_modified = ngx.header["Last-Modified"]
+            if last_modified == nil then
+                ngx.log(ngx.INFO, "Last-Modified is nil as expected")
+                return
+            end
+
+            ngx.log(ngx.ERR, "Last-Modified expected to be nil, but got ", last_modified)
+        }
+
+        content_by_lua_block {
+            ngx.say("Hello World")
+        }
+    }
+--- request
+GET /test
+--- response_body
+Hello World
+--- no_error_log
+[error]