feature: ctxdump.lua: added support for stash and restore ngx.ctx. (#50)

Author: zhuizhuhaomeng

README.markdown

@@ -20,6 +20,7 @@ Table of Contents
     * [resty.core.shdict](#restycoreshdict)
     * [resty.core.var](#restycorevar)
     * [resty.core.ctx](#restycorectx)
+    * [resty.core.ctxdump](#restycorectxdump)
     * [get_ctx_table](#get_ctx_table)
     * [resty.core.request](#restycorerequest)
     * [resty.core.response](#restycoreresponse)
@@ -189,6 +190,60 @@ API Implemented
 
 * [ngx.ctx](https://github.com/openresty/lua-nginx-module#ngxctx)
 
+[Back to TOC](#table-of-contents)
+
+## resty.core.ctxdump
+
+nginx core clears all modules' ctx data upon internal redirects. If we want to
+share ngx.ctx between main request and subrequests, we need to stash ngx.ctx in
+main request and then restore ngx.ctx in the subrequest.
+
+Synopsis
+========
+
+```lua
+
+location /t1 {
+    set $ctx_ref "";
+    content_by_lua_block {
+        local ctxdump = require "resty.core.ctxdump"
+        ngx.ctx = {
+            Date = "Wed May  3 15:18:04 CST 2017",
+            Site = "unknown"
+        }
+        ctxdump.stash_ref()
+        ngx.exec("/t2")
+    }
+}
+
+location /t2 {
+    internal;
+    content_by_lua_block {
+        local ctxdump = require "resty.core.ctxdump"
+        ctxdump.apply_ref()
+        ngx.say("Date: " .. ngx.ctx["Date"] .. " Site: " .. ngx.ctx["Site"])
+    }
+}
+
+```
+
+**syntax:** *ctx = resty.core.ctx.stash_ref()*
+
+**phase:** *init_worker_by_lua\*, set_by_lua\*, rewrite_by_lua\*, access_by_lua\*,
+    content_by_lua\*, header_filter_by_lua\*, body_filter_by_lua\*, log_by_lua\*,
+    ngx.timer.\*, balancer_by_lua\*
+
+stash ngx.ctx reference index in ngx.var.ctx_ref.
+
+**syntax:** *ctx = resty.core.ctx.apply_ref()*
+
+**phase:** *init_worker_by_lua\*, set_by_lua\*, rewrite_by_lua\*, access_by_lua\*,
+    content_by_lua\*, header_filter_by_lua\*, body_filter_by_lua\*, log_by_lua\*,
+    ngx.timer.\*, balancer_by_lua\*
+
+restore ngx.ctx by reference index saved in the ngx.var.ctx_ref.
+
+
 [Back to TOC](#table-of-contents)
 
 ## get_ctx_table

lib/resty/core.lua

@@ -25,6 +25,7 @@ end
 
 require "resty.core.misc"
 require "resty.core.ctx"
+require "resty.core.ctxdump"
 
 
 local base = require "resty.core.base"

lib/resty/core/ctxdump.lua

@@ -0,0 +1,102 @@
+-- A module for sharing ngx.ctx between subrequests.
+-- Original work by Alex Zhang (openresty/lua-nginx-module/issues/1057)
+-- updated by 3scale/apicast.
+--
+-- Copyright (c) 2016 3scale Inc.
+-- Licensed under the Apache License, Version 2.0.
+-- License text: See LICENSE
+--
+-- Modifications by Kong Inc.
+--   * updated module functions signatures
+--   * made module function idempotent
+--   * replaced thrown errors with warn logs
+--   * allow passing of context
+--   * updated to work with new 1.19.x apis
+
+local ffi = require "ffi"
+local base = require "resty.core.base"
+
+
+local C = ffi.C
+local ngx = ngx
+local debug = require "debug"
+local tonumber = tonumber
+local registry = debug.getregistry()
+local subsystem = ngx.config.subsystem
+
+
+local ngx_lua_ffi_get_ctx_ref
+if subsystem == "http" then
+    ngx_lua_ffi_get_ctx_ref = C.ngx_http_lua_ffi_get_ctx_ref
+elseif subsystem == "stream" then
+    ngx_lua_ffi_get_ctx_ref = C.ngx_stream_lua_ffi_get_ctx_ref
+end
+
+
+local in_ssl_phase = ffi.new("int[1]")
+local ssl_ctx_ref = ffi.new("int[1]")
+
+
+local FFI_NO_REQ_CTX = base.FFI_NO_REQ_CTX
+
+
+local _M = {
+    _VERSION = base.version
+}
+
+function _M.stash_ref(ctx)
+    local r = base.get_request()
+    if not r then
+        ngx.log(ngx.WARN, "could not stash ngx.ctx ref: no request found")
+        return
+    end
+
+    do
+        local ctx_ref = ngx.var.ctx_ref
+        if not ctx_ref or ctx_ref ~= "" then
+            return
+        end
+
+        if not ctx then
+            local _ = ngx.ctx -- load context if not previously loaded
+        end
+    end
+    local ctx_ref = ngx_lua_ffi_get_ctx_ref(r, in_ssl_phase, ssl_ctx_ref)
+    if ctx_ref == FFI_NO_REQ_CTX then
+        ngx.log(ngx.WARN, "could not stash ngx.ctx ref: no ctx found")
+        return
+    end
+
+    ngx.var.ctx_ref = ctx_ref
+end
+
+
+function _M.apply_ref()
+    local r = base.get_request()
+    if not r then
+        ngx.log(ngx.WARN, "could not apply ngx.ctx: no request found")
+        return
+    end
+
+    local ctx_ref = ngx.var.ctx_ref
+    if not ctx_ref or ctx_ref == "" then
+        return
+    end
+
+    ctx_ref = tonumber(ctx_ref)
+    if not ctx_ref then
+        return
+    end
+
+    local orig_ctx = registry.ngx_lua_ctx_tables[ctx_ref]
+    if not orig_ctx then
+        ngx.log(ngx.WARN, "could not apply ngx.ctx: no ctx found")
+        return
+    end
+
+    ngx.ctx = orig_ctx
+    ngx.var.ctx_ref = ""
+end
+
+
+return _M

t/ctx.t

@@ -10,7 +10,7 @@ log_level('debug');
 #repeat_each(120);
 repeat_each(2);
 
-plan tests => repeat_each() * (blocks() * 4 - 1);
+plan tests => repeat_each() * (blocks() * 4 - 2);
 
 #no_diff();
 #no_long_string();
@@ -1015,3 +1015,34 @@ reused
 reused again
 --- no_error_log
 [error]
+
+
+
+=== TEST 14: stash_ctx
+--- config
+    location = /t {
+        set $ctx_ref "";
+        content_by_lua_block {
+            ngx.ctx.num = 999
+
+            local ctxdump = require "resty.core.ctxdump"
+            ctxdump.stash_ref() 
+            ngx.exec("/t2")
+        }
+    }
+
+    location /t2 {
+        internal;
+        content_by_lua_block {
+            local ctxdump = require "resty.core.ctxdump"
+            ctxdump.apply_ref() 
+
+            ngx.say("num: ", ngx.ctx.num)
+        }
+    }
+--- request
+GET /t
+--- response_body
+num: 999
+--- no_error_log
+[error]