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Name

ngx_lua - Embed the power of Lua into nginx

Status

This module is still under active 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
           ';
    }
}

Description

This module embeds the Lua interpreter into the nginx core and integrates the powerful Lua threads (aka Lua coroutines) into the nginx event model by means of nginx subrequests.

Unlike Apache's mod_lua and Lighttpd's mod_magnet, Lua code written atop this module can be 100% non-blocking on network traffic as long as you use the ngx.location.capture interface to let the nginx core to do all your requests to mysql, postgresql, memcached, upstream http web services, and etc etc etc (see ngx_drizzle, ngx_postgres, ngx_memc, and ngx_proxy modules for details).

The Lua interpreter instance is shared across all the requests in a single nginx worker process.

Request contexts are isolated from each other by means of Lua (lightweight) threads (aka Lua coroutines). And Lua modules loaded are persistent on the nginx worker process level. So the memory footprint is quite small even when your nginx worker process is handling 10K requests at the same time.

We're already using this module very heavily in our production web applications here in Taobao.com, Alibaba Group.

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

Core constants

ngx.OK
ngx.DONE
ngx.AGAIN
ngx.ERROR

HTTP method constants

value = ngx.HTTP_GET
value = ngx.HTTP_HEAD
value = ngx.HTTP_PUT
value = ngx.HTTP_POST
value = ngx.HTTP_DELETE

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.NOTICE and prefix lua print: .

It's equivalent to

ngx.log(ngx.NOTICE, 'lua print: ', a, b, ...)

Nil arguments are accepted and result in literal "nil".

ngx.location.capture(uri, options?)

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

res = ngx.location.capture(uri)

Returns a Lua table with three slots (res.status, res.header, and res.body).

res.header holds all the response headers of the subrequest and it is a normal Lua table.

URI query strings can be concatenated to URI itself, for instance,

res = ngx.location.capture('/foo/bar?a=3&b=4')

Named locations like @foo are not allowed due to a limitation in the nginx core. Use normal locations combined with the internal directive to prepare internal-only locations.

An optional option table can be fed as the second argument, which support various options like method and body. Issuing a POST subrequest, for example, can be done as follows

res = ngx.location.capture(
    '/foo/bar',
    { method = ngx.HTTP_POST, body = 'hello, world' }
)

See HTTP method constants methods other than POST. The method option is ngx.HTTP_GET by default.

ngx.status

Read and write the response status. This should be called before sending out the response headers.

ngx.status = ngx.HTTP_CREATED
status = ngx.status

ngx.header.HEADER

Set/add/clear response headers. Underscores (_) in the header names will be replaced by dashes (-) and the header names will be matched case-insentively.

# equivalent to ngx.header["Content-Type"] = 'text/plain'
ngx.header.content_type = 'text/plain';

ngx.header["X-My-Header"] = 'blah blah';

Multi-value headers can be set this way:

ngx.header['Set-Cookie'] = {'a=32; path=/', 'b=4; path=/'}

will yield

Set-Cookie: a=32; path=/
Set-Cookie: b=4; path=/

in the response headers. Only array-like tables are accepted.

Note that, for those standard headers that only accepts a single value, like Content-Type, only the last element in the (array) table will take effect. So

ngx.header.content_type = {'a', 'b'}

is equivalent to

ngx.header.content_type = 'b'

Setting a slot to nil effectively removes it from the response headers:

ngx.header["X-My-Header"] = nil;

same does assigning an empty table:

ngx.header["X-My-Header"] = {};

ngx.header is not a normal Lua table so you cannot iterate through it.

Reading values from ngx.header.HEADER is not implemented yet.

ngx.exec(uri, args)

Does an internal redirect to uri with args.

ngx.exec('/some-location');
ngx.exec('/some-location', 'a=3&b=5&c=6');
ngx.exec('/some-location?a=3&b=5', 'c=6');

Named locations are also supported, but query strings are ignored. For example

location /foo {
    content_by_lua '
        ngx.exec("@bar");
    ';
}

location @bar {
    ...
}

This function never returns.

ngx.send_headers()

Explicitly send out the response headers.

Usually you don't have to send headers yourself. ngx_lua will automatically send out headers right before you output contents via ngx.say or ngx.print.

Headers will also be sent automatically when content_by_lua exits normally.

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

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

Nil arguments are not allowed.

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

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

Nil arguments are not allowed.

ngx.log(log_level, ...)

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

Nil arguments are accepted and result in literal "nil".

ngx.flush()

Force flushing the response outputs.

ngx.throw_error(status)

This function is deprecated; use ngx.exit(status) instead.

ngx.exit(status)

Interrupts the execution of the current Lua thread and returns status code to nginx.

The status argument can be ngx.OK, ngx.ERROR, 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.encode_base64(str)

Encode str to a base64 digest

newstr = ngx.encode_base64(str)

ngx.decode_base64(str)

Decode str as a base64 digest to the raw form

newstr = ngx.decode_base64(str)

ngx.today()

Returns today's date (in the format yyyy-mm-dd) from nginx cached time (no syscall involved unlike Lua's date library). .

ngx.now()

Returns the current timestamp (in the format yyyy-mm-dd hh:mm:ss) of the nginx cached time (no syscall involved unlike Lua's date library).

ngx.time()

Returns the current timestamp (in seconds) of the nginx cached time (no syscall involved unlike Lua's date library).

ngx.cookie_time(sec)

Returns a formated string can be used as the cookie expiration time. The parameter sec is the timestamp in seconds (like those returned from ngx.time).

ngx.say(ngx.cookie_time(1290079655))
    # yields "Thu, 18-Nov-10 11:27:35 GMT"

ndk.set_var.DIRECTIVE

This mechanism allows calling other nginx C modules' directives that are implemented by Nginx Devel Kit (NDK)'s set_var submodule's ndk_set_var_value.

For example, ngx_set_misc module's set_escape_uri, set_quote_sql_str, and etc.

For instance,

local res = ndk.set_var.set_escape_uri('a/b');
-- now res == 'a%2fb'

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 0.8.53 (see nginx compatibility), and then build the source with this module:

     $ wget 'http://sysoev.ru/nginx/nginx-0.8.53.tar.gz'
 $ tar -xzvf nginx-0.8.53.tar.gz
 $ cd nginx-0.8.53/

 # 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: 0.8.53)
  • 0.7.x >= 0.7.46 (last tested: 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.
  • Add ngx.location.capture_multi to allow multiple parallel subrequests.
  • Deal with TCP 3-second delay problem under great connection harness.
  • Add lua_code_cache on|off directive to allow .lua files updated on-the-fly during development.

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
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.