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Embed the Power of Lua into NginX

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README.markdown

Name

lua-nginx-module - Embed the power of Lua into nginx

Status

This module is at its early phase of development but is already production ready :)

Commit bit can be freely delivered at your request ;)

Example Config

# set search paths for pure Lua external libraries (';;' is the default path):
lua_package_path '/foo/bar/?.lua;/blah/?.lua;;';

# set search paths for Lua external libraries written in C (can also use ';;'):
lua_package_cpath '/bar/baz/?.so;/blah/blah/?.so;;';

server {
    location /inline_concat {
        # MIME type determined by default_type:
        default_type 'text/plain';

        set $a "hello";
        set $b "world";
        # inline lua script
        set_by_lua $res "return ngx.arg[1]..ngx.arg[2]" $a $b;
        echo $res;
    }

    location /rel_file_concat {
        set $a "foo";
        set $b "bar";
        # script path relative to nginx prefix
        # $ngx_prefix/conf/concat.lua contents:
        #
        #    return ngx.arg[1]..ngx.arg[2]
        #
        set_by_lua_file $res conf/concat.lua $a $b;
        echo $res;
    }

    location /abs_file_concat {
        set $a "fee";
        set $b "baz";
        # absolute script path not modified
        set_by_lua_file $res /usr/nginx/conf/concat.lua $a $b;
        echo $res;
    }

    location /lua_content {
        # MIME type determined by default_type:
        default_type 'text/plain';

        content_by_lua "ngx.say('Hello,world!')"
    }

    location /nginx_var {
        # MIME type determined by default_type:
        default_type 'text/plain';

        # try access /nginx_var?a=hello,world
        content_by_lua "ngx.print(ngx.var['arg_a'], '\\n')";
    }

    location /request_body {
        # force reading request body (default off)
        lua_need_request_body on;

        content_by_lua 'ngx.print(ngx.var.request_body)';
    }

    # transparent non-blocking I/O in Lua via subrequests
    location /lua {
        # MIME type determined by default_type:
        default_type 'text/plain';

        content_by_lua '
            local res = ngx.location.capture("/some_other_location")
            if res.status == 200 then
                ngx.print(res.body)
            end';
    }

    # GET /recur?num=5
    location /recur {
        # MIME type determined by default_type:
        default_type 'text/plain';

       content_by_lua '
           local num = tonumber(ngx.var.arg_num) or 0
           ngx.say("num is: ", num)

           if num > 0 then
               res = ngx.location.capture("/recur?num=" .. tostring(num - 1))
               ngx.print("status=", res.status, " ")
               ngx.print("body=", res.body)
           else
               ngx.say("end")
           end
           ';
    }
}

Directives

lua_package_path

  • Syntax: lua_package_path <lua-style-path-str>
  • Default: The content of LUA_PATH environ variable or Lua's compiled-in defaults.
  • Context: main

Set the Lua module searching path used by scripts specified by set_by_lua* and content_by_lua*. The path string is in standard Lua path form, and ;; can be used to stand for the original path.

lua_package_cpath

  • Syntax: lua_package_cpath <lua-style-cpath-str>
  • Default: The content of LUA_CPATH environ variable or Lua's compiled-in defaults.
  • Context: main

Set the Lua C-module searching path used by scripts specified by set_by_lua* and content_by_lua*. The cpath string is in standard Lua cpath form, and ;; can be used to stand for the original cpath.

set_by_lua

  • Syntax: set_by_lua $res <lua-script-str> [$arg1 $arg2 ...]
  • Context: main | server | location | sif | lif

Execute user code specified by <lua-script-str> with input arguments $arg1 $arg2 ..., and set the script's return value to $res in string form. In <lua-script-str> code the input arguments can be retrieved from ngx.arg table (index starts from 1 and increased sequentially).

set_by_lua* directives are designed to execute small and quick codes. NginX event loop is blocked during the code execution, so you'd better NOT call anything that may be blocked or time-costy.

set_by_lua_file

  • Syntax: set_by_lua_file $res <path-to-lua-script> [$arg1 $arg2 ...]
  • Context: main | server | location | sif | lif

Basically the same as set_by_lua, except the code to be executed is in the file specified by <path-lua-script>.

The user code is loaded once at the first request and cached. Nginx config must be reloaded if you modified the file and expected to see updated behavior.

content_by_lua

  • Syntax: content_by_lua <lua-script-str>
  • Context: location | lif

Act as a content handler and execute user code specified by <lua-script-str> for every request. The user code may call predefined APIs to generate response content.

The use code is executed in a new spawned coroutine with independent globals environment (i.e. a sandbox). I/O operations in user code should only be done through predefined NginX APIs, otherwise NginX event loop may be blocked and performance may drop off dramatically.

As predefined NginX I/O APIs used coroutine yielding/resuming mechanism, the user code should not call any modules that used coroutine API to prevent obfuscating the predefined NginX APIs (actually coroutine module is masked off in content_by_lua* directives). This limitation is a little crucial, but don't worry! We're working on a alternative coroutine implementation that can be fit in the NginX event framework. When it is done, the user code will be able to use coroutine mechanism freely as in standard Lua again!

content_by_lua_file

  • Syntax: content_by_lua_file <path-to-lua-script>
  • Context: location | lif

Basically the same as content_by_lua, except the code to be executed is in the file specified by <path-lua-script>.

The user code is loaded once at the first request and cached. Nginx config must be reloaded if you modified the file and expected to see updated behavior.

lua_need_request_body

  • Syntax: lua_need_request_body <on | off>
  • Default: off
  • Context: main | server | location

Force reading request body data or not. The request data won't be read into $request_body NginX variable by default, so you have to explicitly force reading the body if you need its content.

Nginx APIs for set_by_lua*

Read and write arbitrary nginx variables by name:

value = ngx.var.some_nginx_variable_name
ngx.var.some_nginx_variable_name = value

Index the input arguments to the directive:

value = ngx.arg[n]

Nginx APIs for content_by_lua*

Read and write NginX variables

value = ngx.var.some_nginx_variable_name
ngx.var.some_nginx_variable_name = value

HTTP status constants

value = ngx.HTTP_OK
value = ngx.HTTP_CREATED
value = ngx.HTTP_MOVED_PERMANENTLY
value = ngx.HTTP_MOVED_TEMPORARILY
value = ngx.HTTP_NOT_MODIFIED
value = ngx.HTTP_BAD_REQUEST
value = ngx.HTTP_GONE
value = ngx.HTTP_NOT_FOUND
value = ngx.HTTP_NOT_ALLOWED
value = ngx.HTTP_FORBIDDEN
value = ngx.HTTP_INTERNAL_SERVER_ERROR
value = ngx.HTTP_SERVICE_UNAVAILABLE

NginX log level constants

log_level = ngx.STDERR
log_level = ngx.EMERG
log_level = ngx.ALERT
log_level = ngx.CRIT
log_level = ngx.ERR
log_level = ngx.WARN
log_level = ngx.NOTICE
log_level = ngx.INFO
log_level = ngx.DEBUG

print(a, b, ...)

Emit args concatenated to error.log, with log level ngx.ERR.

ngx.send_headers()

Explicitly send headers.

ngx.print(a, b, ...)

Emit args concatenated to the HTTP client (as response body).

ngx.log(log_level, ...)

Log args concatenated to error.log with the given logging level.

ngx.say(a, b, ...)

Just as ngx.print but also emit a trailing newline.

ngx.flush()

Force flushing the response outputs.

ngx.throw_error(status)

Throw out an error page and interrupts the execution of the current Lua thread, status can be ngx.HTTP_NOT_FOUND or other HTTP status numbers.

ngx.eof()

Explicitly specify the end of the response output stream.

ngx.escape_uri(str)

Escape str as a URI component.

newstr = ngx.escape_uri(str)

ngx.unescape_uri(str)

Unescape str as a escaped URI component.

newstr = ngx.unescape_uri(str)

ngx.location.capture(uri)

Issue a synchronous but still non-blocking subrequest using uri (e.g. /foo/bar).

res = ngx.location.capture(uri)

Returns a Lua table with two slots (res.status and res.body).

Performance

The Lua state (aka the Lua vm instance) is shared across all the requests handled by a single nginx worker process to miminize memory use.

On a ThinkPad T400 2.96 GHz laptop, it's easy to achieve 25k req/sec using ab w/o keepalive and 37k+ req/sec with keepalive.

You can get better performance when building this module with LuaJIT 2.0.

Installation

  1. Install lua into your system. At least Lua 5.1 is required. Lua can be obtained freely from its project homepage.

  2. Download the latest version of the release tarball of this module from lua-nginx-module file list.

  3. Grab the nginx source code from nginx.net, for example, the version 0.8.41 (see nginx compatibility), and then build the source with this module:

    $ wget 'http://sysoev.ru/nginx/nginx-0.8.41.tar.gz'
    $ tar -xzvf nginx-0.8.41.tar.gz
    $ cd nginx-0.8.41/
    
    # tell nginx's build system where to find lua:
    export LUA_LIB=/path/to/lua/lib
    export LUA_INC=/path/to/lua/include
    
    # or tell where to find LuaJIT when you want to use JIT instead
    # export LUAJIT_LIB=/path/to/luajit/lib
    # export LUAJIT_INC=/path/to/luajit/include/luajit-2.0
    
    # Here we assume you would install you nginx under /opt/nginx/.
    $ ./configure --prefix=/opt/nginx \
        --add-module=/path/to/ndk_devel_kit \
        --add-module=/path/to/lua-nginx-module
    
    $ make -j2
    $ make install
    

Compatibility

The following versions of Nginx should work with this module:

  • 0.8.x (last tested version is 0.8.47)
  • 0.7.x >= 0.7.46 (last tested version is 0.7.67)

Earlier versions of Nginx like 0.6.x and 0.5.x will not work.

If you find that any particular version of Nginx above 0.7.44 does not work with this module, please consider reporting a bug.

Test Suite

To run the test suite, you also need the following perl and nginx modules:

These module's adding order is IMPORTANT! For filter modules's position in filtering chain affects a lot. The correct configure adding order is:

  1. ngx_devel_kit
  2. set-misc-nginx-module
  3. ngx_http_auth_request_module
  4. echo-nginx-module
  5. memc-nginx-module
  6. lua-nginx-module (i.e. this module)
  7. srcache-nginx-module
  8. drizzle-nginx-module
  9. rds-json-nginx-module

Todo

  • Add directives to run lua codes when nginx stops/reloads
  • Implement ngx.exec() functionality
  • Deal with TCP 3-second delay problem under great connection harness

Future Plan

  • Add 'lua_require' directive to load module into main thread's globals
  • Add Lua VM passive yield and resume (using debug hook)
  • Make set_by_lua using the same mechanism as content_by_lua

Known Issues

  • WATCH OUT: Globals WON'T persist between requests, due to the one-coroutine-per-request designing. Especially watch yourself when using require() to import modules, use this form:

    local xxx = require('xxx')
    

    instead of the old deprecated form:

    require('xxx')
    

    The old form will cause module unusable in requests for the reason told previously. If you have to stick with the old form, you can always force loading module for every request by clean package.loaded.<module>, like this:

    package.loaded.xxx = nil
    require('xxx')
    

See Also

Authors

  • chaoslawful (王晓哲)
  • agentzh (章亦春)

Copyright & License

This module is licenced under the BSD license.

Copyright (C) 2009, Taobao Inc., Alibaba Group ( http://www.taobao.com ).

Copyright (C) 2009 by Xiaozhe Wang (chaoslawful) <chaoslawful@gmail.com>.

Copyright (C) 2009 by Yichun Zhang (agentzh) <agentzh@gmail.com>.

All rights reserved.

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.

    * Neither the name of the Taobao Inc. nor the names of its
    contributors may be used to endorse or promote products derived from
    this software without specific prior written permission.

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
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