ngx_lua - Embed the power of Lua into Nginx

This module is not distributed with the Nginx source. See the installation instructions.

This module is under active development and is production ready.

This document describes ngx_lua v0.3.1rc38 released on 2 December 2011.

# 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;
         client_max_body_size 50k;
         client_body_buffer_size 50k;

         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

           if num > 50 then
               ngx.say("num too big")
               return
           end

           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
           ';
    }

    location /foo {
        rewrite_by_lua '
            res = ngx.location.capture("/memc",
                { args = { cmd = 'incr', key = ngx.var.uri } }
            )
        ';

        proxy_pass http://blah.blah.com;
    }

    location /blah {
        access_by_lua '
            local res = ngx.location.capture("/auth")

            if res.status == ngx.HTTP_OK then
                return
            end

            if res.status == ngx.HTTP_FORBIDDEN then
                ngx.exit(res.status)
            end

            ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
        ';

        # proxy_pass/fastcgi_pass/postgres_pass/...
    }

    location /mixed {
        rewrite_by_lua_file /path/to/rewrite.lua;
        access_by_lua_file /path/to/access.lua;
        content_by_lua_file /path/to/content.lua;
    }

    # use nginx var in code path
    # WARN: contents in nginx var must be carefully filtered,
    # otherwise there'll be great security risk!
    location ~ ^/app/(.+) {
            content_by_lua_file /path/to/lua/app/root/$1.lua;
    }

    location / {
       lua_need_request_body on;

       client_max_body_size 100k;
       client_body_buffer_size 100k;

       access_by_lua '
           -- check the client IP addr is in our black list
           if ngx.var.remote_addr == "132.5.72.3" then
               ngx.exit(ngx.HTTP_FORBIDDEN)
           end

           -- check if the request body contains bad words
           if ngx.var.request_body and
                    string.match(ngx.var.request_body, "fsck")
           then
               return ngx.redirect("/terms_of_use.html")
           end

           -- tests passed
       ';

       # proxy_pass/fastcgi_pass/etc settings
    }
}

This module embeds the Lua interpreter or LuaJIT 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 or ngx.location.capture_multi interfaces to let the nginx core do all your requests to mysql, postgresql, memcached, redis, upstream http web services, and etc etc etc (see HttpDrizzleModule, ngx_postgres, HttpMemcModule, HttpRedis2Module and HttpProxyModule 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.

syntax: lua_code_cache on | off

default: lua_code_cache on

context: main, server, location, location if

Enable or disable the Lua code cache for set_by_lua_file, content_by_lua_file, rewrite_by_lua_file, and access_by_lua_file, and also force Lua module reloading on a per-request basis.

The Lua files referenced in set_by_lua_file, content_by_lua_file, access_by_lua_file, and rewrite_by_lua_file will not be cached at all, and Lua's package.loaded table will be cleared at the entry point of every request (such that Lua modules will not be cached either). With this in place, developers can follow the PHP way, i.e., edit-and-refresh.

Please note however, that Lua code inlined into nginx.conf such as those specified by set_by_lua, content_by_lua, access_by_lua, and rewrite_by_lua will always be cached because only the Nginx config file parser can correctly parse the nginx.conf file and the only ways to to reload the config file are to send a HUP signal or to restart Nginx.

The ngx_lua module currently does not support the "stat" mode like Apache's mod_lua does but this is planned for implementation in the future.

Disabling the Lua code cache is strongly discouraged for production use and should only be used during development as it has a significant impact on overall performance. In addition, race conditions when reloading Lua modules are common for concurrent requests when the code cache is disabled.

syntax: lua_regex_cache_max_entries <num>

default: lua_regex_cache_max_entries 1024

context: http

Specifies the maximum number of entries allowed in the worker process level compiled regex cache.

The regular expressions used in ngx.re.match, ngx.re.gmatch, ngx.re.sub, and ngx.re.gsub will be cached within this cache if the regex option o (i.e., compile-once flag) is specified.

The default number of entries allowed is 1024 and when this limit is reached, new regexes will not be cached (as if the o option was not specified) and there will be one, and only one, warning in the error.log file:

2011/08/27 23:18:26 [warn] 31997#0: *1 lua exceeding regex cache max entries (1024), ...

You should not activate the o option for regexes (and/or replace string arguments for ngx.re.sub and ngx.re.gsub) that are generated on the fly and give rise to infinite variations to avoid hitting the specified limit.

syntax: lua_package_path <lua-style-path-str>

default: The content of LUA_PATH environ variable or Lua's compiled-in defaults.

context: main

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

syntax: lua_package_cpath <lua-style-cpath-str>

default: The content of LUA_CPATH environ variable or Lua's compiled-in defaults.

context: main

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

syntax: set_by_lua $res <lua-script-str> [$arg1 $arg2 ...]

context: main, server, location, server if, location if

phase: rewrite

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 directive is designed to execute short, fast running code blocks. The Nginx event loop is blocked during code execution and time consuming code sequences should be avoided.

Note that set_by_lua can only output a value to a single Nginx variable at a time but a workaround is possible by using the ngx.var.VARIABLE interface. For example,

location /foo {
    set $diff ''; # we have to predefine the $diff variable here

    set_by_lua $sum '
        local a = 32
        local b = 56

        ngx.var.diff = a - b;  -- write to $diff directly
        return a + b;          -- return the $sum value normally
    ';

    echo "sum = $sum, diff = $diff";
}

This directive can be freely mixed with all the directives of HttpRewriteModule, HttpSetMiscModule, and HttpArrayVarModule. All of these directives will run in exactly the same order that they are written in the config file. For example,

set $foo 32;
set_by_lua $bar 'tonumber(ngx.var.foo) + 1';
set $baz "bar: $bar";  # $baz == "bar: 33"

This directive requires the ngx_devel_kit module.

syntax: set_by_lua_file $res <path-to-lua-script> [$arg1 $arg2 ...]

context: main, server, location, server if, location if

phase: rewrite

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

When the Lua code cache is on (default state), the user code is loaded once at the first request and cached and the Nginx config must be reloaded each time you modify the lua code file. You can temporarily disable the Lua code cache during development by switching lua_code_cache off in your nginx.conf to avoid reloading Nginx.

This directive requires the ngx_devel_kit module.

syntax: content_by_lua <lua-script-str>

context: location, location if

phase: content

Acts as a "content handler" and executes lua code string specified in <lua-script-str> for every request. The lua code may call predefined APIs to generate response content and is executed in a new spawned coroutine in an independent global environment (i.e. a sandbox).

Do not use this directive and other content handler directives in a same location. For example, this directive and the proxy_pass directive should not be used in the same location.

syntax: content_by_lua_file <path-to-lua-script>

context: location, location if

phase: content

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

Nginx variables can be used in <path-to-lua-script> string to provide flexibility. This however carries some risks and is not ordinarily recommended.

When the Lua code cache is on (default state), the user code is loaded once at the first request and cached and the Nginx config must be reloaded each time you modify the lua code file. You can temporarily disable the Lua code cache during development by switching lua_code_cache off in your nginx.conf to avoid reloading Nginx.

syntax: rewrite_by_lua <lua-script-str>

context: http, server, location, location if

phase: post-rewrite

Acts as a rewrite phase handler and executes lua code string specified in <lua-script-str> for every request. The lua code may call predefined APIs to generate response content and is executed in a new spawned coroutine in an independent global environment (i.e. a sandbox).

This directive uses exactly the same mechamism as content_by_lua so all the nginx APIs defined there are also available here.

Note that this handler always runs after the standard HttpRewriteModule. So the following will work as expected:

   location /foo {
       set $a 12; # create and initialize $a
       set $b ""; # create and initialize $b
       rewrite_by_lua 'ngx.var.b = tonumber(ngx.var.a) + 1';
       echo "res = $b";
   }

because set $a 12 and set $b "" run before rewrite_by_lua.

On the other hand, the following will not work as expected:

?  location /foo {
?      set $a 12; # create and initialize $a
?      set $b ''; # create and initialize $b
?      rewrite_by_lua 'ngx.var.b = tonumber(ngx.var.a) + 1';
?      if ($b = '13') {
?         rewrite ^ /bar redirect;
?         break;
?      }
?
?      echo "res = $b";
?  }

because if runs before rewrite_by_lua even if it is put after rewrite_by_lua in the config.

The right way of doing this is as follows:

location /foo {
    set $a 12; # create and initialize $a
    set $b ''; # create and initialize $b
    rewrite_by_lua '
        ngx.var.b = tonumber(ngx.var.a) + 1
        if tonumber(ngx.var.b) == 13 then
            return ngx.redirect("/bar");
        end
    ';

    echo "res = $b";
}

It is worth mentioning that, the ngx_eval module can be approximately implemented by rewrite_by_lua. For example,

location / {
    eval $res {
        proxy_pass http://foo.com/check-spam;
    }

    if ($res = 'spam') {
        rewrite ^ /terms-of-use.html redirect;
    }

    fastcgi_pass ...;
}

can be implemented in terms of ngx_lua like this

location = /check-spam {
    internal;
    proxy_pass http://foo.com/check-spam;
}

location / {
    rewrite_by_lua '
        local res = ngx.location.capture("/check-spam")
        if res.body == "spam" then
            ngx.redirect("/terms-of-use.html")
        end
    ';

    fastcgi_pass ...;
}

Just as any other rewrite phase handlers, rewrite_by_lua also runs in subrequests.

Note that when calling ngx.exit(ngx.OK) within a rewrite_by_lua handler, the nginx request processing control flow will still continue to the content handler. To terminate the current request from within a rewrite_by_lua handler, calling ngx.exit with status >= 200 (ngx.HTTP_OK) and status < 300 (ngx.HTTP_SPECIAL_RESPONSE) for successful quits and ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR) (or its friends) for failures.

If the HttpRewriteModule's rewrite directive is used to change the URI and initiate location re-lookups (internal redirections), then any rewrite_by_lua or rewrite_by_lua_file code sequences within the current location will not be executed. For example,

location /foo {
    rewrite ^ /bar;
    rewrite_by_lua 'ngx.exit(503)';
}
location /bar {
    ...
}

Here the Lua code ngx.exit(503) will never run. This will be the case if rewrite ^ /bar last is used as this will similarly initiate an internal redirection. If the break modifier is used instead, there will be no internal rediction and the rewrite_by_lua code will be executed.

syntax: rewrite_by_lua_file <path-to-lua-script>

context: http, server, location, location if

phase: post-rewrite

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

Nginx variables can be used in <path-to-lua-script> string to provide flexibility. This however carries some risks and is not ordinarily recommended.

When the Lua code cache is on (default state), the user code is loaded once at the first request and cached and the Nginx config must be reloaded each time you modify the Lua source file. You can temporarily disable the Lua code cache during development by switching lua_code_cache off in your nginx.conf to avoid reloading Nginx.

syntax: access_by_lua <lua-script-str>

context: http, server, location, location if

phase: post-access

Acts as an access phase handler and executes lua code string specified in <lua-script-str> for every request. The user code may call predefined APIs to generate response content.

This directive uses exactly the same mechanism as content_by_lua so all the nginx APIs defined there are also available here.

Note that this handler always runs after the standard HttpAccessModule. So the following will work as expected:

location / {
    deny    192.168.1.1;
    allow   192.168.1.0/24;
    allow   10.1.1.0/16;
    deny    all;

    access_by_lua '
        local res = ngx.location.capture("/mysql", { ... })
        ...
    ';

    # proxy_pass/fastcgi_pass/...
}

That is, if a client address appears in the blacklist, then we do not have to bother sending a MySQL query to do more advanced authentication in access_by_lua.

It is worth mentioning that, the ngx_auth_request module can be approximately implemented by access_by_lua. For example,

location / {
    auth_request /auth;

    # proxy_pass/fastcgi_pass/postgres_pass/...
}

can be implemented in terms of ngx_lua like this

location / {
    access_by_lua '
        local res = ngx.location.capture("/auth")

        if res.status == ngx.HTTP_OK then
            return
        end

        if res.status == ngx.HTTP_FORBIDDEN then
            ngx.exit(res.status)
        end

        ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
    ';

    # proxy_pass/fastcgi_pass/postgres_pass/...
}

Just as any other access phase handlers, access_by_lua will not run in subrequests.

Note that when calling ngx.exit(ngx.OK) within a access_by_lua handler, the nginx request processing control flow will still continue to the content handler. To terminate the current request from within a access_by_lua handler, calling ngx.exit with status >= 200 (ngx.HTTP_OK) and status < 300 (ngx.HTTP_SPECIAL_RESPONSE) for successful quits and ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR) (or its friends) for failures.

syntax: access_by_lua_file <path-to-lua-script>

context: http, server, location, location if

phase: post-access

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

Nginx variables can be used in <path-to-lua-script> string to provide flexibility. This however carries some risks and is not ordinarily recommended.

When the Lua code cache is on (default state), the user code is loaded once at the first request and cached and the Nginx config must be reloaded each time you modify the lua code file. You can temporarily disable the Lua code cache during development by switching lua_code_cache off in your nginx.conf to avoid reloading Nginx.

syntax: header_filter_by_lua <lua-script-str>

context: http, server, location, location if

phase: output-header-filter

Uses Lua code specified in <lua-script-str> to define an output header filter. Note that the following Nginx Lua APIs are currently disabled within this context:

• Output API (e.g., ngx.say and ngx.send_headers)
• Control APIs (e.g., ngx.exit)
• Subrequest APIs (e.g., ngx.location.capture and ngx.location.capture_multi)

Here is an example of overriding a response header (or adding one if absent) in our Lua header filter:

location / {
    proxy_pass http://mybackend;
    header_filter_by_lua 'ngx.header.Foo = "blah"';
}

This directive was first introduced in the v0.2.1rc20 release.

syntax: header_filter_by_lua_file <path-to-lua-script-file>

context: http, server, location, location if

phase: output-header-filter

Use Lua code defined in a separate file specified by <path-to-lua-script-file> to define an output header filter.

This is very much like header_filter_by_lua except that it loads Lua code from an external Lua source file.

This directive was first introduced in the v0.2.1rc20 release.

syntax: lua_need_request_body <on | off>

default: off

context: main | server | location

phase: depends on usage

Determines whether to force reading of the request body data before running rewrite/access/access_by_lua* or not. The Nginx core does not read the client request body by default and if you need the request body then you must turn this directive on or call the ngx.req.read_body function from within your Lua code.

To read the request body data within the $request_body variable, client_body_buffer_size must have the same value as client_max_body_size. Because when the content length exceeds client_body_buffer_size but less than client_max_body_size, Nginx will automatically buffer the data into a temporary file on the disk, which will lead to empty value in the $request_body variable.

If the current location includes rewrite_by_lua or rewrite_by_lua_file directives, then the request body will be read just before the rewrite_by_lua or rewrite_by_lua_file code is run (and also at the rewrite phase). Similarly, if only content_by_lua is specified, the request body will not be read until the content handler's Lua code is about to run (i.e., the request body will be read during the content phase).

It is recommended however, to use the ngx.req.read_body and ngx.req.discard_body functions for finer control over the request body reading process instead.

This also applies to access_by_lua and access_by_lua_file.

syntax: lua_shared_dict <name> <size>

default: no

context: main

phase: depends on usage

Declares a shared memory zone, <name>, to serve as storage for the shm-based Lua dictionary ngx.shared.<name>.

The <size> argument accepts size units such as k and m:

http {
    lua_shared_dict dogs 10m;
    ...
}

See ngx.shared.DICT for details.

This directive was first introduced in the v0.3.1rc22 release.

The Nginx API exposed to the Lua land is provided in the form of two standard packages ngx and ndk. These packages are in the default global scope within ngx_lua and can also be introduced to external Lua modules by using the package.seeall option:

module("my_module", package.seeall)

function say(a) ngx.say(a) end

Alternatively, they can be imported external Lua modules by using file scoped local Lua variables:

local ngx = ngx
module("my_module")

function say(a) ngx.say(a) end

It is also possible to directly require the packages:

local ngx = require "ngx"
local ndk = require "ndk"

The ability to require these packages was introduced in the v0.2.1rc19 release.

Network I/O operations in user code should only be done through Nginx API calls as the Nginx event loop may be blocked and performance may drop off dramatically otherwise. Minor disk file operations may be done via Lua's standard io and file libraries but these should be avoided wherever possible as these also block the Nginx process. Delegating all network and disk I/O operations to Nginx subrequests (via the ngx.location.capture method and its friends) is strongly recommended for maximum performance.

syntax: val = ngx.arg[index]

context: set_by_lua*

Index the input arguments to the set_by_lua and set_by_lua_file directives:

value = ngx.arg[n]

Here is an example

location /foo {
    set $a 32;
    set $b 56;

    set_by_lua $res
        'return tonumber(ngx.arg[1]) + tonumber(ngx.arg[2])'
        $a $b;

    echo $sum;
}

that outputs 88, the sum of 32 and 56.

syntax: ngx.var.VAR_NAME

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

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

Note that you can only write to nginx variables that are already defined. For example:

location /foo {
    set $my_var ''; # this line is required to create $my_var at config time
    content_by_lua '
        ngx.var.my_var = 123;
        ...
    ';
}

That is, nginx variables cannot be created on-the-fly.

Some special nginx variables like $args and $limit_rate can be assigned a value, some are not, like $arg_PARAMETER.

Nginx regex group capturing variables $1, $2, $3, and etc, can be read by this interface as well, by writing ngx.var[1], ngx.var[2], ngx.var[3], and etc.

Setting nil values to ngx.var.Foo will effectively make Nginx variable $Foo undefined. For instance,

ngx.var.args = nil

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

  ngx.OK (0)
  ngx.ERROR (-1)
  ngx.AGAIN (-2)
  ngx.DONE (-4)

They take the same values of NGX_OK, NGX_AGAIN, NGX_DONE, NGX_ERROR, and etc. But now only ngx.exit only take two of these values, i.e., NGX_OK and NGX_ERROR.

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

  ngx.HTTP_GET
  ngx.HTTP_HEAD
  ngx.HTTP_PUT
  ngx.HTTP_POST
  ngx.HTTP_DELETE

These constants are usually used in ngx.location.catpure and ngx.location.capture_multi method calls.

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

  value = ngx.HTTP_OK (200)
  value = ngx.HTTP_CREATED (201)
  value = ngx.HTTP_SPECIAL_RESPONSE (300)
  value = ngx.HTTP_MOVED_PERMANENTLY (301)
  value = ngx.HTTP_MOVED_TEMPORARILY (302)
  value = ngx.HTTP_SEE_OTHER (303)
  value = ngx.HTTP_NOT_MODIFIED (304)
  value = ngx.HTTP_BAD_REQUEST (400)
  value = ngx.HTTP_UNAUTHORIZED (401)
  value = ngx.HTTP_FORBIDDEN (403)
  value = ngx.HTTP_NOT_FOUND (404)
  value = ngx.HTTP_NOT_ALLOWED (405)
  value = ngx.HTTP_GONE (410)
  value = ngx.HTTP_INTERNAL_SERVER_ERROR (500)
  value = ngx.HTTP_METHOD_NOT_IMPLEMENTED (501)
  value = ngx.HTTP_SERVICE_UNAVAILABLE (503)
  value = ngx.HTTP_GATEWAY_TIMEOUT (504) (first added in the v0.3.1rc38 release)

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

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

These constants are usually used by the ngx.log method.

syntax: print(...)

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Emit args concatenated to nginx's error.log file, with log level ngx.NOTICE and prefix lua print: .

It is equivalent to

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

Lua nil arguments are accepted and result in literal "nil", and Lua booleans result in "true" or "false".

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

This table can be used to store per-request context data for Lua programmers.

This table has a liftime identical to the current request (just like Nginx variables). Consider the following example,

location /test {
    rewrite_by_lua '
        ngx.say("foo = ", ngx.ctx.foo)
        ngx.ctx.foo = 76
    ';
    access_by_lua '
        ngx.ctx.foo = ngx.ctx.foo + 3
    ';
    content_by_lua '
        ngx.say(ngx.ctx.foo)
    ';
}

Then GET /test will yield the output

foo = nil
79

That is, the ngx.ctx.foo entry persists across the rewrite, access, and content phases of a request.

Also, every request has its own copy, include subrequests, for example:

location /sub {
    content_by_lua '
        ngx.say("sub pre: ", ngx.ctx.blah)
        ngx.ctx.blah = 32
        ngx.say("sub post: ", ngx.ctx.blah)
    ';
}

location /main {
    content_by_lua '
        ngx.ctx.blah = 73
        ngx.say("main pre: ", ngx.ctx.blah)
        local res = ngx.location.capture("/sub")
        ngx.print(res.body)
        ngx.say("main post: ", ngx.ctx.blah)
    ';
}

Then GET /main will give the output

main pre: 73
sub pre: nil
sub post: 32
main post: 73

We can see that modification of the ngx.ctx.blah entry in the subrequest does not affect the one in its parent request. They do have two separate versions of ngx.ctx.blah per se.

Internal redirection will destroy the original request's ngx.ctx data (if any) and the new request will have an emptied ngx.ctx table. For instance,

location /new {
    content_by_lua '
        ngx.say(ngx.ctx.foo)
    ';
}

location /orig {
    content_by_lua '
        ngx.ctx.foo = "hello"
        ngx.exec("/new")
    ';
}

Then GET /orig will give you

nil

rather than the original "hello" value.

Arbitrary data values can be inserted into this "matic" table, including Lua closures and nested tables. You can also register your own meta methods with it.

Overriding ngx.ctx with a new Lua table is also supported, for example,

ngx.ctx = { foo = 32, bar = 54 }

syntax: res = ngx.location.capture(uri, options?)

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Issue a synchronous but still non-blocking Nginx Subrequest using uri.

Nginx subrequests provide a powerful way to make non-blocking internal requests to other locations configured with disk file directory or any other nginx C modules like ngx_proxy, ngx_fastcgi, ngx_memc, ngx_postgres, ngx_drizzle, and even ngx_lua itself and etc etc etc.

Also note that subrequests just mimic the HTTP interface but there is no extra HTTP/TCP traffic nor IPC involved. Everything works internally, efficiently, on the C level.

Subrequests are completely different from HTTP 301/302 redirection (via ngx.redirect) and internal redirection (via ngx.exec).

Here is a basic example:

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. For multi-value response headers, the value is a Lua (array) table that holds all the values in the order that they appear. For instance, if the subrequest response headers contains the following lines:

Set-Cookie: a=3
Set-Cookie: foo=bar
Set-Cookie: baz=blah

Then res.header["Set-Cookie"] will be evaluted to the table value {"a=3", "foo=bar", "baz=blah"}.

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 the options:

• method specify the subrequest's request method, which only accepts constants like ngx.HTTP_POST.
• body specify the subrequest's request body (string value only).
• args specify the subrequest's URI query arguments (both string value and Lua tables are accepted)
• ctx specify a Lua table to be the ngx.ctx table for the subrequest. It can be the current request's ngx.ctx table, which effectively make the parent and its subrequest to share exactly the same context table. This option was first introduced in the v0.3.1rc25 release.
• vars take a Lua table which holds the values to set the specified Nginx variables in the subrequest as this option's value. This option was first introduced in the v0.3.1rc31 release.
• copy_all_vars specify whether to copy over all the Nginx variable values of the current request to the subrequest in question. modifications of the nginx variables in the subrequest will not affect the current (parent) request. This option was first introduced in the v0.3.1rc31 release.
• share_all_vars specify whether to share all the Nginx variables of the subrequest with the current (parent) request. modifications of the Nginx variables in the subrequest will affect the current (parent) request.

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.

The args option can specify extra URI arguments, for instance,

ngx.location.capture('/foo?a=1',
    { args = { b = 3, c = ':' } }
)

is equivalent to

ngx.location.capture('/foo?a=1&b=3&c=%3a')

that is, this method will automatically escape argument keys and values according to URI rules and concatenating them together into a complete query string. The format for the Lua table passed as the args argument is identical to the format used in the ngx.encode_args method.

The args option can also take plain query strings:

ngx.location.capture('/foo?a=1',
    { args = 'b=3&c=%3a' } }
)

This is functionally identical to the previous examples.

The share_all_vars option controls whether to share nginx variables among the current request and new subrequests. If this option is set to true, then the current request and associated subrequests will share the same Nginx variable scope. Hence, changes to Nginx variables made by a subrequest will affect the current request.

Care should be taken in using this option as variable scope sharing can have unexpected side effects. The args, vars, or copy_all_vars options are generally preferable instead.

This option is set to false by default

location /other {
    set $dog "$dog world";                  
    echo "$uri dog: $dog";                    
}                                     

location /lua {
    set $dog 'hello';
    content_by_lua '
        res = ngx.location.capture("/other",
            { share_all_vars = true });
            
        ngx.print(res.body)
        ngx.say(ngx.var.uri, ": ", ngx.var.dog)
    ';  
}           

Accessing location /lua gives

/other dog: hello world
/lua: hello world

The copy_all_vars option provides a copy of the parent request's Nginx variables to subrequests when such subrequests are issued. Changes made to these variables by such subrequests will not affect the parent request or any other subrequests sharing the parent request's variables.

location /other {
    set $dog "$dog world";
    echo "$uri dog: $dog";
}

location /lua {
    set $dog 'hello';
    content_by_lua '
        res = ngx.location.capture("/other",
            { copy_all_vars = true });

        ngx.print(res.body)
        ngx.say(ngx.var.uri, ": ", ngx.var.dog)
    ';
}

Request GET /lua will give the output

/other dog: hello world
/lua: hello

Note that if both share_all_vars and copy_all_vars are set to true, then the variable scope will be shared.

In addition to the two settings above, it is possible to specify values for variables in the subrequest using the vars option. These variables are set after the sharing or copying of variables has been evaluated, and provides a more efficient method of passing specific values to a subrequest over encoding them as URL arguments and unescaping them in the Nginx config file.

location /other {
    content_by_lua '
        ngx.say("dog = ", ngx.var.dog)
        ngx.say("cat = ", ngx.var.cat)
    ';
}

location /lua {
    set $dog '';
    set $cat '';
    content_by_lua '
        res = ngx.location.capture("/other",
            { vars = { dog = "hello", cat = 32 }});

        ngx.print(res.body)
    ';
}

Accessing /lua will yield the output

dog = hello
cat = 32

The ctx option can be used to specify a custom Lua table to serve as the ngx.ctx table for the subrequest.

location /sub {
    content_by_lua '                          
        ngx.ctx.foo = "bar";                  
    ';
}   
location /lua {
    content_by_lua '
        local ctx = {}                        
        res = ngx.location.capture("/sub", { ctx = ctx })
        
        ngx.say(ctx.foo);
        ngx.say(ngx.ctx.foo);                 
    ';                                        
}

Then request GET /lua gives

bar                                               
nil

It is also possible to use this ctx option to share the same ngx.ctx table between the current (parent) request and the subrequest:

location /sub {
    content_by_lua '
        ngx.ctx.foo = "bar";
    ';
}
location /lua {
    content_by_lua '
        res = ngx.location.capture("/sub", { ctx = ngx.ctx })
        ngx.say(ngx.ctx.foo);
    ';
}

Request GET /lua yields the output

bar

Note that, by default, subrequests issued by ngx.location.capture inherit all the request headers of the current request. This may have unexpected side effects on the subrequest responses. For example, when you are using the standard ngx_proxy module to serve your subrequests, then an "Accept-Encoding: gzip" header in your main request may result in gzipped responses that your Lua code will not able to handle properly. So always set proxy_pass_request_headers off in your subrequest location to ignore the original request headers.

Please also refer to restrictions on capturing locations that include Echo Module directives.

syntax: res1, res2, ... = ngx.location.capture_multi({ {uri, options?}, {uri, options?}, ... })

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Just like ngx.location.capture, but supports multiple subrequests running in parallel.

This function issue several parallel subrequests specified by the input table, and returns their results in the same order. For example,

res1, res2, res3 = ngx.location.capture_multi{
    { "/foo", { args = "a=3&b=4" } },
    { "/bar" },
    { "/baz", { method = ngx.HTTP_POST, body = "hello" } },
}

if res1.status == ngx.HTTP_OK then
    ...
end

if res2.body == "BLAH" then
    ...
end

This function will not return until all the subrequests terminate. The total latency is the longest latency of the subrequests, instead of their sum.

When you do not know how many subrequests you want to issue in advance, you can use Lua tables for both requests and responses. For instance,

-- construct the requests table
local reqs = {}
table.insert(reqs, { "/mysql" })
table.insert(reqs, { "/postgres" })
table.insert(reqs, { "/redis" })
table.insert(reqs, { "/memcached" })

-- issue all the requests at once and wait until they all return
local resps = { ngx.location.capture_multi(reqs) }

-- loop over the responses table
for i, resp in ipairs(resps) do
    -- process the response table "resp"
end

The ngx.location.capture function is just a special form of this function. Logically speaking, the ngx.location.capture can be implemented like this

ngx.location.capture =
    function (uri, args)
        return ngx.location.capture_multi({ {uri, args} })
    end

Please also refer to restrictions on capturing locations that include Echo Module directives.

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Read and write the current request's response status. This should be called before sending out the response headers.

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

syntax: ngx.header.HEADER = VALUE

syntax: value = ngx.header.HEADER

context: rewrite_by_lua, access_by_lua*, content_by_lua*, header_filter_by_lua**

When assigning to ngx.header.HEADER will set, add, or clear the current request's response header named HEADER. Underscores (_) in the header names will be replaced by dashes (-) and the header names will be matched case-insensitively.

-- 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"] = {};

Setting ngx.header.HEADER after sending out response headers (either explicitly with ngx.send_headers or implicitly with ngx.print and its friends) will throw out a Lua exception.

Reading ngx.header.HEADER will return the value of the response header named HEADER. Underscores (_) in the header names will also be replaced by dashes (-) and the header names will be matched case-insensitively. If the response header is not present at all, nil will be returned.

This is particularly useful in the context of filter_header_by_lua and filter_header_by_lua_file, for example,

location /test {
    set $footer '';

    proxy_pass http://some-backend;

    header_filter_by_lua '
        if ngx.header["X-My-Header"] == "blah" then
            ngx.var.footer = "some value"
        end
    ';

    echo_after_body $footer;
}

For multi-value headers, all of the values of header will be collected in order and returned as a Lua table. For example, response headers

Foo: bar
Foo: baz

will result in

{"bar", "baz"}

to be returned when reading ngx.header.Foo.

Note that ngx.header is not a normal Lua table so you cannot iterate through it using Lua's ipairs function.

For reading request headers, use the ngx.req.get_headers function instead.

syntax: ngx.req.set_uri(uri, jump?)

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Rewrite the current request's (parsed) URI by the uri argument. The uri argument must be a Lua string and cannot be of zero length, or a Lua exception will be thrown.

The optional boolean jump argument can trigger location rematch (or location jump) as HttpRewriteModule's rewrite directive, that is, when jump is true (default to false), this function will never return and it will tell Nginx to try re-searching locations with the new URI value at the later post-rewrite phase and jumping to the new location. Location jump will not be triggered otherwise, and only the current request's URI will be modified, which is also the default behavior. This function will return but with no returned values when the jump argument is false or absent altogether.

For example, the following nginx config snippet

rewrite ^ /foo last;

can be coded in Lua like this:

ngx.req.set_uri("/foo", true)

Similarly, Nginx config

rewrite ^ /foo break;

can be coded in Lua as

ngx.req.set_uri("/foo", false)

or equivalently,

ngx.req.set_uri("/foo")

The jump can only be set to true in rewrite_by_lua and rewrite_by_lua_file. Use of jump in other contexts is prohibited and will throw out a Lua exception.

A more sophisticated example involving regex substitutions is as follows

location /test {
    rewrite_by_lua '
        local uri = ngx.re.sub(ngx.var.uri, "^/test/(.*)", "$1", "o")
        ngx.req.set_uri(uri)
    ';
    proxy_pass http://my_backend;
}

which is functionally equivalent to

location /test {
    rewrite ^/test/(.*) /$1 break;
    proxy_pass http://my_backend;
}

Note that you cannot use this interface to rewrite URI arguments, and you need to use ngx.req.set_uri_args for that. For instance, Nginx config

rewrite ^ /foo?a=3? last;

can be coded as

ngx.req.set_uri_args("a=3")
ngx.req.set_uri("/foo", true)

or

ngx.req.set_uri_args({a = 3})
ngx.req.set_uri("/foo", true)

This interface was first introduced in the v0.3.1rc14 release.

syntax: ngx.req.set_uri_args(args)

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Rewrite the current request's URI query arguments by the args argument. The args argument can be either a Lua string, as in

ngx.req.set_uri_args("a=3&b=hello%20world")

or a Lua table holding the query arguments' key-value pairs, as in

ngx.req.set_uri_args({ a = 3, b = "hello world" })

where in the latter case, this method will automatically escape argument keys and values according to the URI escaping rule.

This interface was first introduced in the v0.3.1rc13 release.

See also ngx.req.set_uri.

syntax: args = ngx.req.get_uri_args()

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Returns a Lua table holds all of the current request's request URL query arguments.

Here is an example,

location = /test {
    content_by_lua '
        local args = ngx.req.get_uri_args()
        for key, val in pairs(args) do
            if type(val) == "table" then
                ngx.say(key, ": ", table.concat(val, ", "))
            else
                ngx.say(key, ": ", val)
            end
        end
    ';
}

Then GET /test?foo=bar&bar=baz&bar=blah will yield the response body

foo: bar
bar: baz, blah

Multiple occurrences of an argument key will result in a table value holding all of the values for that key in order.

Keys and values will be automatically unescaped according to URI escaping rules. For example, in the above settings, GET /test?a%20b=1%61+2 will yield the output

a b: 1a 2

Arguments without the =<value> parts are treated as boolean arguments. For example, GET /test?foo&bar will yield the outputs

foo: true
bar: true

That is, they will take Lua boolean values true. However, they're different from arguments taking empty string values. For example, GET /test?foo=&bar= will give something like

foo: 
bar: 

Empty key arguments are discarded, for instance, GET /test?=hello&=world will yield empty outputs.

Updating query arguments via the nginx variable $args (or ngx.var.args in Lua) at runtime are also supported:

ngx.var.args = "a=3&b=42"
local args = ngx.req.get_uri_args()

Here the args table will always look like

{a = 3, b = 42}

regardless of the actual request query string.

syntax: ngx.req.get_post_args()

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Returns a Lua table holds all of the current request's POST query arguments (of the MIME type application/x-www-form-urlencoded). It is required to read the request body first by calling ngx.req.read_body or to turn on the lua_need_request_body directive, or a Lua exception will be thrown.

Here is an example,

location = /test {
    content_by_lua '
        ngx.req.read_body()
        local args = ngx.req.get_post_args()
        for key, val in pairs(args) do
            if type(val) == "table" then
                ngx.say(key, ": ", table.concat(val, ", "))
            else
                ngx.say(key, ": ", val)
            end
        end
    ';
}

Then

# Post request with the body 'foo=bar&bar=baz&bar=blah'
$ curl --data 'foo=bar&bar=baz&bar=blah' localhost/test

will yield the response body like

foo: bar
bar: baz, blah

Multiple occurrences of an argument key will result in a table value holding all of the values for that key in order.

Keys and values will be automatically unescaped according to URI escaping rules. For example, in the above settings,

# POST request with body 'a%20b=1%61+2'
$ curl -d 'a%20b=1%61+2' localhost/test

will yield the output

a b: 1a 2

Arguments without the =<value> parts are treated as boolean arguments. For example, GET /test?foo&bar will yield the outputs

foo: true
bar: true

That is, they will take Lua boolean values true. However, they're different from arguments taking empty string values. For example, POST /test with request body foo=&bar= will give something like

foo: 
bar: 

Empty key arguments are discarded, for instance, POST /test with body =hello&=world will yield empty outputs.

syntax: headers = ngx.req.get_headers()

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Returns a Lua table holds all of the current request's request headers.

Here is an example,

local h = ngx.req.get_headers()
for k, v in pairs(h) do
    ...
end

To read an individual header:

ngx.say("Host: ", ngx.req.get_headers()["Host"])

For multiple instances of request headers like

Foo: foo
Foo: bar
Foo: baz

the value of ngx.req.get_headers()["Foo"] will be a Lua (array) table like this:

{"foo", "bar", "baz"}

Another way to read individual request headers is to use ngx.var.http_HEADER, that is, nginx's standard $http_HEADER variables.

syntax: ngx.req.set_header(header_name, header_value)

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Set the current request's request header named header_name to value header_value, overriding any existing ones. None of the current request's subrequests will be affected.

Here is an example of setting the Content-Length header:

ngx.req.set_header("Content-Type", "text/css")

The header_value can take an array list of values, for example,

ngx.req.set_header("Foo", {"a", "abc"})

will produce two new request headers:

Foo: a
Foo: abc

and old Foo headers will be overridden if there is any.

When the header_value argument is nil, the request header will be removed. So

ngx.req.set_header("X-Foo", nil)

is equivalent to

ngx.req.clear_header("X-Foo")

syntax: ngx.req.read_body()

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Read the client request body synchronously but still non-blockingly.

If the request body is already read previously by turning on lua_need_request_body or by using other modules, then this function is a no-op and returns immediately.

If the request body has already been explicitly discarded, either by this module's ngx.req.discard_body or other modules, this function is a no-op and returns immediately.

In case of errors, like connection errors while reading the data, this method will throw out a Lua exception or terminate the current request with the 500 status code immediately.

You can later either retrieve the request body data via ngx.req.get_body_data or retrieve the temporary file name for the body data cached to disk via ngx.req.get_body_file, depending on

1. whether the current request body is already exceeding your client_body_buffer_size,
2. and whether you have turned on client_body_in_file_only.

In case that you do not want to read the request body and the current request may have a request body, then it is crucial to use the ngx.req.discard_body function to explicitly discard the request body, or you'll break HTTP 1.1 keepalive and HTTP 1.1 pipelining.

Here is a small example:

ngx.req.read_body()
local args = ngx.req.get_post_args()

This function was first introduced in the v0.3.1rc17 release.

syntax: ngx.req.discard_body()

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Explicitly discard the request body, i.e., read the data on the connection and throw it away immediately. Please note that, simply ignoring request body is not the right way to discard it, you need to call this function, or you'll break things under HTTP 1.1 keepalive or HTTP 1.1 pipelining.

This function is an asynchronous call and returns immediately.

If the request body has already been read, this function does nothing and returns immediately.

This function was first introduced in the v0.3.1rc17 release.

See also ngx.req.read_body.

syntax: data = ngx.req.get_body_data()

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Retrieves the in-memory request body data. It returns a Lua string rather than a Lua table holding all the parsed query arguments. If you want the latter, use ngx.req.get_post_args instead.

This function returns nil if

1. the request body has not been read,
2. the request body has been read into disk temporary files,
3. or the request body has zero size.

If the request body has not been read yet, call ngx.req.read_body first (or turned on lua_need_request_body to force this module to read the request body automatically, but this is not recommended).

If the request body has been read into disk files, try calling the ngx.req.get_body_file function instead.

In case that you want to enforce in-memory request bodies, try setting client_body_buffer_size to the same size value in client_max_body_size.

Note that calling this function instead of using ngx.var.request_body or ngx.var.echo_request-body is more efficient because it can save one dynamic memory allocation and one data copy.

This function was first introduced in the v0.3.1rc17 release.

See also ngx.req.get_body_file.

syntax: file_name = ngx.req.get_body_file()

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Retrieves the file name for the in-file request body data. Returns nil if the request body has not been read or has been read into memory.

The returned file is read only and is usually cleaned up automatically by Nginx's memory pool. It should not be modified, renamed, or removed by your own Lua code.

If the request body has not been read yet, call ngx.req.read_body first (or turned on lua_need_request_body to force this module to read the request body automatically, but this is not recommended).

If the request body has been read into memory, try calling the ngx.req.get_body_data function instead.

In case that you want to enforce in-file request bodies, try turning on client_body_in_file_only.

This function was first introduced in the v0.3.1rc17 release.

See also ngx.req.get_body_data.

syntax: ngx.req.set_body_data(data)

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Set the current request's request body using the in-memory data specified by the data argument.

If the current request's request body has not been read, then it will be properly discarded. When the current request's request body has been read into memory or buffered into a disk file, then the old request body's memory will be freed or the disk file will be cleaned up immediately, respectively.

This function requires patching the Nginx core to function properly because the Nginx core does not allow modifying request bodies by the current design. Here is a patch for Nginx 1.0.9: nginx-1.0.9-allow_request_body_updating.patch, and this patch should be applied cleanly to other releases of Nginx as well.

If you're using ngx_openresty 1.0.8.17+, then you've already had this patch applied.

This function was first introduced in the v0.3.1rc18 release.

See also ngx.req.set_body_file.

syntax: ngx.req.set_body_file(file_name, auto_clean?)

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Set the current request's request body using the in-file data specified by the file_name argument.

If the optional auto_clean argument is given a true value, then this file will be automatically removed at request completion or the next time this function or ngx.req.set_body_data are called in the same request. The auto_clean is default to false.

You must ensure that the file specified by the file_name argument exists and is readable by an Nginx worker process by setting its permission properly. Otherwise a Lua exception will be thrown.

If the current request's request body has not been read, then it will be properly discarded. When the current request's request body has been read into memory or buffered into a disk file, then the old request body's memory will be freed or the disk file will be cleaned up immediately, respectively.

This function requires patching the Nginx core to function properly because the Nginx core does not allow modifying request bodies by the current design. Here is a patch for Nginx 1.0.9: nginx-1.0.9-allow_request_body_updating.patch, and this patch should be applied cleanly to other releases of Nginx as well.

If you're using ngx_openresty 1.0.8.17+, then you've already had this patch applied.

This function was first introduced in the v0.3.1rc18 release.

See also ngx.req.set_body_data.

syntax: ngx.req.clear_header(header_name)

context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua**

Clear the current request's request header named header_name. None of the current request's subrequests will be affected.

syntax: ngx.exec(uri, args?)

context: rewrite_by_lua, access_by_lua*, content_by_lua**

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 {
    ...
}

The optional second args can be used to specify extra URI query arguments, for example:

ngx.exec("/foo", "a=3&b=hello%20world")

Alternatively, you can pass a Lua table for the args argument and let ngx_lua do URI escaping and string concatenation automatically for you, for instance,

ngx.exec("/foo", { a = 3, b = "hello world" })

The result is exactly the same as the previous example. The format for the Lua table passed as the args argument is identical to the format used in the ngx.encode_args method.

Note that this is very different from ngx.redirect in that it is just an internal redirect and no new HTTP traffic is involved.

This method never returns.

This method must be called before ngx.send_headers or explicit response body outputs by either ngx.print or ngx.say.

This method is very much like the echo_exec directive in HttpEchoModule.

syntax: ngx.redirect(uri, status?)

context: rewrite_by_lua, access_by_lua*, content_by_lua**

Issue an HTTP 301 or 302 redirection to <code>uri.

return ngx.redirect("/foo")

return ngx.redirect("http://localhost:1984/foo", ngx.HTTP_MOVED_TEMPORARILY)

return ngx.redirect("/foo", 301)

rewrite ^ /foo? redirect;  # nginx config

return ngx.redirect('/foo');  -- lua code

rewrite ^ /foo? permanent;  # nginx config

return ngx.redirect('/foo', ngx.HTTP_MOVED_PERMANENTLY)  -- Lua code

return ngx.redirect('/foo?a=3&b=4')

local table = {
    "hello, ",
    {"world: ", true, " or ", false,
        {": ", nil}}
}
ngx.print(table)

hello, world: true or false: nil

ngx.status = ngx.HTTP_GONE
ngx.say("This is our own content")
-- to cause quit the whole request rather than the current phase handler
ngx.exit(ngx.HTTP_OK)

$ curl -i http://localhost/test
HTTP/1.1 410 Gone
Server: nginx/1.0.6
Date: Thu, 15 Sep 2011 00:51:48 GMT
Content-Type: text/plain
Transfer-Encoding: chunked
Connection: keep-alive

This is our own content

ngx.exit(501)

ngx.say(ngx.unescape_uri("b%20r56+7"))

b r56 7

ngx.encode_args({foo = 3, ["b r"] = "hello world"})

foo=3&b%20r=hello%20world

ngx.encode_args({baz = {32, "hello"}})

baz=32&baz=hello

ngx.encode_args({a = true, b = 1})

a&b=1

local key = "thisisverysecretstuff"
local src = "some string we want to sign"
local digest = ngx.hmac_sha1(key, src)
ngx.say(ngx.encode_base64(digest))

R/pvxzHC4NLtj7S+kXFg/NePTmk=

location = /md5 {
    content_by_lua 'ngx.say(ngx.md5("hello"))';
}

5d41402abc4b2a76b9719d911017c592

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

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

local time = ngx.parse_http_time("Thu, 18 Nov 10 11:27:35 GMT")
if time == nil then
    ...
end

local m = ngx.re.match("hello, 1234", "[0-9]+")
-- m[0] == "1234"



local m = ngx.re.match("hello, 1234", "([0-9])[0-9]+")
-- m[0] == "1234"
-- m[1] == "1"

local m = ngx.re.match("hello, world", "(world)|(hello)")
-- m[0] == "hello"
-- m[1] == nil
-- m[2] == "hello"

a             anchored mode (only match from the beginning)

d             enable the DFA mode (or the longest token match semantics).
              this requires PCRE 6.0+ or else a Lua exception will be thrown.
              first introduced in ngx_lua v0.3.1rc30.

i             caseless mode (similar to Perl's /i modifier)

j             enable PCRE JIT compilation, this requires PCRE 8.20+ and
              PCRE must be built with the --enable-jit option, or it is
              a no-op. this should always be used along with the <code>o</code> 
              option to gain the full performance benefit.
              first introduced in ngx_lua v0.3.1rc30.

m             multi-line mode (similar to Perl's /m modifier)

o             compile-once mode (similar to Perl's /o modifer),
              to enable the worker-process-level compiled-regex cache

s             single-line mode (similar to Perl's /s modifier)

u             UTF-8 mode. this requires PCRE to be built with
              the --enable-utf8 option or else a Lua exception will be thrown.

x             extended mode (similar to Perl's /x modifier)

local m = ngx.re.match("hello, world", "HEL LO", "ix")
-- m[0] == "hello"



local m = ngx.re.match("hello, 美好生活", "HELLO, (.{2})", "iu")
-- m[0] == "hello, 美好"
-- m[1] == "美好"

local ctx = {}
local m = ngx.re.match("1234, hello", "[0-9]+", "", ctx)
     -- m[0] = "1234"
     -- ctx.pos == 4



local ctx = { pos = 2 }
local m = ngx.re.match("1234, hello", "[0-9]+", "", ctx)
     -- m[0] = "34"
     -- ctx.pos == 4

local iterator = ngx.re.gmatch("hello, world!", "([a-z]+)", "i")
local m
m = iterator()    -- m[0] == m[1] == "hello"
m = iterator()    -- m[0] == m[1] == "world"
m = iterator()    -- m == nil

for m in ngx.re.gmatch("hello, world!", "([a-z]+)", "i")
    ngx.say(m[0])
    ngx.say(m[1])
end

local newstr, n = ngx.re.sub("hello, 1234", "([0-9])[0-9]", "[$0][$1]")
    -- newstr == "hello, [12][1]34"
    -- n == 1

local newstr, n = ngx.re.sub("hello, 1234", "[0-9]", "${0}00")
    -- newstr == "hello, 10034"
    -- n == 1

local newstr, n = ngx.re.sub("hello, 1234", "[0-9]", "$$")
    -- newstr == "hello, $234"
    -- n == 1

local func = function (m)
    return "[" .. m[0] .. "][" .. m[1] .. "]"
end
local newstr, n = ngx.re.sub("hello, 1234", "( [0-9] ) [0-9]", func, "x")
    -- newstr == "hello, [12][1]34"
    -- n == 1

local newstr, n = ngx.re.gsub("hello, world", "([a-z])[a-z]+", "[$0,$1]", "i")
    -- newstr == "[hello,h], [world,w]"
    -- n == 2



local func = function (m)
    return "[" .. m[0] .. "," .. m[1] .. "]"
end
local newstr, n = ngx.re.gsub("hello, world", "([a-z])[a-z]+", func, "i")
    -- newstr == "[hello,h], [world,w]"
    -- n == 2

http {
    lua_shared_dict dogs 10m;
    server {
        location /set {
            content_by_lua '
                local dogs = ngx.shared.dogs
                dogs:set("Jim", 8)
                ngx.say("STORED")
            ';
        }
        location /get {
            content_by_lua '
                local dogs = ngx.shared.dogs
                ngx.say(dogs:get("Jim"))
            ';
        }
    }
}

$ curl localhost/set
STORED

$ curl localhost/get
8

$ curl localhost/get
8

local cats = ngx.shared.cats
local value = cats.get(cats, "Marry")

local cats = ngx.shared.cats
local value = cats:get("Marry")

local cats = ngx.shared.cats
local succ, err, forcible = cats.set(cats, "Marry", "it is a nice cat!")

local cats = ngx.shared.cats
local succ, err, forcible = cats:set("Marry", "it is a nice cat!")

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

-- mydata.lua
module("mydata", package.seeall)

local data = {
    dog = 3,
    cat = 4,
    pig = 5,
}

function get_age(name)
    return data[name]
end

location /lua {
    content_lua_by_lua '
        local mydata = require("mydata")
        ngx.say(mydata.get_age("dog"))
    ';
}

    local xxx = require('xxx')


instead of the old deprecated form:


    require('xxx')


If you have to use the old form, force reload the module for every request by using the `package.loaded.<module>` command:


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

getmetatable(foo.bar).__newindex = function (table, key, val)
    error('Attempt to write to undeclared variable "' .. key .. '": '
            .. debug.traceback())
end

location /foo {
    content_by_lua '
        res = ngx.location.capature("/bar")
    ';
}
location /bar {
    echo_location /blah;
}
location /blah {
    echo "Success!";
}



$ curl -i http://example.com/foo

# nginx.conf
? location /test {
?     content_by_lua '
?         local regex = "\d+"  -- THIS IS WRONG!!
?         local m = ngx.re.match("hello, 1234", regex)
?         if m then ngx.say(m[0]) else ngx.say("not matched!") end
?     ';
? }
# evaluates to "not matched!"

# nginx.conf
location /test {
    content_by_lua '
        local regex = "\\\\d+"
        local m = ngx.re.match("hello, 1234", regex)
        if m then ngx.say(m[0]) else ngx.say("not matched!") end
    ';
}
# evaluates to "1234"

# nginx.conf
location /test {
    content_by_lua '
        local regex = [[\\d+]]
        local m = ngx.re.match("hello, 1234", regex)
        if m then ngx.say(m[0]) else ngx.say("not matched!") end
    ';
}
# evaluates to "1234"

# nginx.conf
location /test {
    content_by_lua '
        local regex = [=[ [0-9]+ ]=]
        local m = ngx.re.match("hello, 1234", regex)
        if m then ngx.say(m[0]) else ngx.say("not matched!") end
    ';
}
# evaluates to "1234"

-- test.lua
local regex = "\\d+"
local m = ngx.re.match("hello, 1234", regex)
if m then ngx.say(m[0]) else ngx.say("not matched!") end
-- evaluates to "1234"

-- test.lua
local regex = [[\d+]]
local m = ngx.re.match("hello, 1234", regex)
if m then ngx.say(m[0]) else ngx.say("not matched!") end
-- evaluates to "1234"