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ctxdump: Stash and apply the old ngx.ctx for avoiding being destoried after NGINX internal redirect happens

Installation

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CentOS/RHEL 6, 7, 8 or Amazon Linux 2

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install lua-resty-ctxdump

To use this Lua library with NGINX, ensure that nginx-module-lua is installed.

This document describes lua-resty-ctxdump v0.1 released on Jan 07 2021.


lua-resty-ctxdump - stash and apply the ngx.ctx, avoiding being destoried after Nginx internal redirect happens.

Build Status

Status

Probably production ready in most cases, though not yet proven in the wild. Please check the issues list and let me know if you have any problems / questions.

Synopsis

location /t1 {
    set $ctx_ref = "";
    content_by_lua_block {
         local ctxdump = require "resty.ctxdump"
         ngx.ctx = {
             Date = "Wed May  3 15:18:04 CST 2017",
             Site = "unknown"
        }
        ngx.var.ctx_ref = ctxdump.stash_ngx_ctx()
        ngx.exec("/t2")
    }
}

location /t2 {
    internal;
    content_by_lua_block {
         local ctxdump = require "resty.ctxdump"
         ngx.ctx = {
             Date = "Wed May  3 15:18:04 CST 2017",
             Site = "unknown"
        }
        ngx.ctx = ctxdump.apply_ngx_ctx(ngx.var.ctx_ref)
        ngx.say("Date: " .. ngx.ctx["Date"] .. " Site: " .. ngx.ctx["Site"])
    }
}

Methods

stash_ngx_ctx

syntax: ref = stash_ngx_ctx()
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*

Reference the ngx.ctx, returns an anchor(a new reference maintained by lua-resty-ctxdump).

Note: stash_ngx_ctx and apply_ngx_ctx must be called in pairs, otherwise memory leak will happen! See apply_ngx_ctx.

apply_ngx_ctx

syntax: old_ngx_ctx = apply_ngx_ctx(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*

fetch the old ngx.ctx with the anchor returns from stash_ngx_ctx. After that, the anchor will be out of work.

Note: stash_ngx_ctx and apply_ngx_ctx must be called in pairs, otherwise memory leak will happen! See stash_ngx_ctx.

Author

Alex Zhang(张超) tokers@apache.org, @api7.ai.

The bundle itself is licensed under the 2-clause BSD license.

Copyright (c) 2017-2021, Alex Zhang.

This module is licensed under the terms of the BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

See Also

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-ctxdump.

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