This module embeds Lua, via the standard interpreter or LuaJIT, into Nginx and by leveraging Nginx subrequests, allows the integration of the powerful Lua threads ( Lua coroutines) into the Nginx event model.
Unlike [Apache's mod_lua](http://httpd.apache.org/docs/2.3/mod/mod_lua.html) and [Lighttpd's mod_magnet](http://redmine.lighttpd.net/wiki/1/Docs:ModMagnet), Lua code executed using this module can be *100% non-blocking* on network traffic as long as either of the [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) or [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi) interfaces are used to handle
requests to upstream services such as mysql, postgresql, memcached, redis, or upstream http web services. (see [HttpDrizzleModule](http://wiki.nginx.org/HttpDrizzleModule), [ngx_postgres](http://github.com/FRiCKLE/ngx_postgres/), [HttpMemcModule](http://wiki.nginx.org/HttpMemcModule), [HttpRedis2Module](http://wiki.nginx.org/HttpRedis2Module) and [HttpProxyModule](http://wiki.nginx.org/HttpProxyModule) modules for details).
The Lua interpreter or LuaJIT instance is shared across all the requests in a single nginx worker process but request contexts are segregated using lightweight Lua coroutines.
Loaded Lua modules persist at the nginx worker process level resulting in a small memory footprint even when under heavy loads.
[content_by_lua_file](http://wiki.nginx.org/HttpLuaModule#content_by_lua_file), [rewrite_by_lua_file](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua_file), and
[access_by_lua_file](http://wiki.nginx.org/HttpLuaModule#access_by_lua_file), and also force Lua module reloading on a per-request basis.
Please note however, that Lua code inlined into nginx.conf
such as those specified by [set_by_lua](http://wiki.nginx.org/HttpLuaModule#set_by_lua), [content_by_lua](http://wiki.nginx.org/HttpLuaModule#content_by_lua),
[access_by_lua](http://wiki.nginx.org/HttpLuaModule#access_by_lua), and [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) will *always* be
The regular expressions used in [ngx.re.match](http://wiki.nginx.org/HttpLuaModule#ngx.re.match), [ngx.re.gmatch](http://wiki.nginx.org/HttpLuaModule#ngx.re.gmatch), [ngx.re.sub](http://wiki.nginx.org/HttpLuaModule#ngx.re.sub), and [ngx.re.gsub](http://wiki.nginx.org/HttpLuaModule#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:
Do not activate the `o` option for regexes (and/or `replace` string arguments for [ngx.re.sub](http://wiki.nginx.org/HttpLuaModule#ngx.re.sub) and [ngx.re.gsub](http://wiki.nginx.org/HttpLuaModule#ngx.re.gsub)) that are generated *on the fly* and give rise to infinite variations to avoid hitting the specified limit.
Executes code specified in `<lua-script-str>` with optional input arguments `$arg1 $arg2 ...`, and returns string output to `$res`.
The code in `<lua-script-str>` can make [API calls](http://wiki.nginx.org/HttpLuaModule#Nginx_API_for_Lua) and can retrieve input arguments from the `ngx.arg` table (index starts from `1` and increases sequentially).
This directive is designed to execute short, fast running code blocks as the Nginx event loop is blocked during code execution. Time consuming code sequences should therefore be avoided.
Note that I/O operations such as [ngx.say](http://wiki.nginx.org/HttpLuaModule#ngx.say), [ngx.exec](http://wiki.nginx.org/HttpLuaModule#ngx.exec), [echo](http://wiki.nginx.org/HttpEchoModule#echo) and similar are not permitted within the context of this directive.
In addition, note that this directive can only output a value to a single Nginx variable at
a time. However, a workaround is possible using the [ngx.var.VARIABLE](http://wiki.nginx.org/HttpLuaModule#ngx.var.VARIABLE) interface.
This directive can be freely mixed with all directives of the [HttpRewriteModule](http://wiki.nginx.org/HttpRewriteModule), [HttpSetMiscModule](http://wiki.nginx.org/HttpSetMiscModule), and [HttpArrayVarModule](http://wiki.nginx.org/HttpArrayVarModule) modules. All of these directives will run in the same order as they appear in the config file.
Equivalent to [set_by_lua](http://wiki.nginx.org/HttpLuaModule#set_by_lua), except that the file specified by `<path-to-lua-script-file>` contains the lua code to be executed.
The lua code may make [API calls](http://wiki.nginx.org/HttpLuaModule#Nginx_API_for_Lua) and is executed as a new spawned coroutine in an independent global environment (i.e. a sandbox).
Do not use this directive and other content handler directives in the same location. For example, this directive and the [proxy_pass](http://wiki.nginx.org/HttpProxyModule#proxy_pass) directive should not be used in the same location.
Equivalent to [content_by_lua](http://wiki.nginx.org/HttpLuaModule#content_by_lua), except that the file specified by `<path-to-lua-script-file>` contains the lua code to be executed.
Nginx variables can be used in the `<path-to-lua-script-file>` string to provide flexibility. This however carries some risks and is not ordinarily recommended.
Acts as a rewrite phase handler and executes lua code string specified in `<lua-script-str>` for every request.
The Lua code may make [API calls](http://wiki.nginx.org/HttpLuaModule#Nginx_API_for_Lua) and is executed as a new spawned coroutine in an independent global environment (i.e. a sandbox).
Note that this handler always runs *after* the standard [HttpRewriteModule](http://wiki.nginx.org/HttpRewriteModule). So the following will work as expected:
because `if` runs *before* [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) even if it is put after [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) in the config.
Note that the [ngx_eval](http://www.grid.net.ru/nginx/eval.en.html) module can be approximated using [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua). For example,
Note that when calling `ngx.exit(ngx.OK)` within a [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#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](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) handler, calling [ngx.exit](http://wiki.nginx.org/HttpLuaModule#ngx.exit) with status >= 200 (`ngx.HTTP_OK`) and status <300(`ngx.HTTP_SPECIAL_RESPONSE`)forsuccessfulquitsand`ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)`(oritsfriends)forfailures.
If the [HttpRewriteModule](http://wiki.nginx.org/HttpRewriteModule)'s [rewrite](http://wiki.nginx.org/HttpRewriteModule#rewrite) directive is used to change the URI and initiate location re-lookups (internal redirections), then any [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) or [rewrite_by_lua_file](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua_file) code sequences within the current location will not be executed. For example,
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.
Equivalent to [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua), except that the file specified by `<path-to-lua-script-file>` contains the Lua code to be executed.
Nginx variables can be used in the `<path-to-lua-script-file>` 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 the Lua source file is modified. The Lua code cache can be temporarily disabled during development by switching [lua_code_cache](http://wiki.nginx.org/HttpLuaModule#lua_code_cache) `off` in `nginx.conf` to avoid reloading Nginx.
Acts as an access phase handler and executes lua code string specified in `<lua-script-str>` for every request.
The Lua code may make [API calls](http://wiki.nginx.org/HttpLuaModule#Nginx_API_for_Lua) and is executed as a new spawned coroutine in an independent global environment (i.e. a sandbox).
Note that this handler always runs *after* the standard [HttpAccessModule](http://wiki.nginx.org/HttpAccessModule). So the following will work as expected:
That is, if a client IP address is in the blacklist, it will be denied before the MySQL query for more complex authentication is executed by [access_by_lua](http://wiki.nginx.org/HttpLuaModule#access_by_lua).
Note that the [ngx_auth_request](http://mdounin.ru/hg/ngx_http_auth_request_module/) module can be approximated using [access_by_lua](http://wiki.nginx.org/HttpLuaModule#access_by_lua):
Note that when calling `ngx.exit(ngx.OK)` within a [access_by_lua](http://wiki.nginx.org/HttpLuaModule#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](http://wiki.nginx.org/HttpLuaModule#access_by_lua) handler, calling [ngx.exit](http://wiki.nginx.org/HttpLuaModule#ngx.exit) with status >= 200 (`ngx.HTTP_OK`) and status <300(`ngx.HTTP_SPECIAL_RESPONSE`)forsuccessfulquitsand`ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)`(oritsfriends)forfailures.
Equivalent to [access_by_lua](http://wiki.nginx.org/HttpLuaModule#access_by_lua), except that the file specified by `<path-to-lua-script-file>` contains the Lua code to be executed.
Nginx variables can be used in the `<path-to-lua-script-file>` string to provide flexibility. This however carries some risks and is not ordinarily recommended.
and the Nginx config must be reloaded each time the Lua source file is modified.
The Lua code cache can be temporarily disabled during development by switching [lua_code_cache](http://wiki.nginx.org/HttpLuaModule#lua_code_cache) `off` in `nginx.conf` to avoid repeatedly reloading Nginx.
Uses Lua code specified in `<lua-script-str>` to define an output header filter. Note that the following API functions are currently disabled within this context:
* Output API functions (e.g., [ngx.say](http://wiki.nginx.org/HttpLuaModule#ngx.say) and [ngx.send_headers](http://wiki.nginx.org/HttpLuaModule#ngx.send_headers))
* Control API functions (e.g., [ngx.exit](http://wiki.nginx.org/HttpLuaModule#ngx.exit))
* Subrequest API functions (e.g., [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) and [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi))
Equivalent to [header_filter_by_lua](http://wiki.nginx.org/HttpLuaModule#header_filter_by_lua), except that the file specified by `<path-to-lua-script-file>` contains the lua code to be executed.
Determines whether to force the request body data to be read before running rewrite/access/access_by_lua* or not. The Nginx core does not read the client request body by default and if request body data is required, then this directive should be turned `on` or the [ngx.req.read_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.read_body) function should be called within the Lua code.
To read the request body data within the [$request_body](http://wiki.nginx.org/HttpCoreModule#.24request_body) variable,
[client_body_buffer_size](http://wiki.nginx.org/HttpCoreModule#client_body_buffer_size) must have the same value as [client_max_body_size](http://wiki.nginx.org/HttpCoreModule#client_max_body_size). Because when the content length exceeds [client_body_buffer_size](http://wiki.nginx.org/HttpCoreModule#client_body_buffer_size) but less than [client_max_body_size](http://wiki.nginx.org/HttpCoreModule#client_max_body_size), Nginx will automatically buffer the data into a temporary file on the disk, which will lead to empty value in the [$request_body](http://wiki.nginx.org/HttpCoreModule#.24request_body) variable.
If the current location includes [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) or [rewrite_by_lua_file](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua_file) directives,
then the request body will be read just before the [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) or [rewrite_by_lua_file](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua_file) code is run (and also at the
`rewrite` phase). Similarly, if only [content_by_lua](http://wiki.nginx.org/HttpLuaModule#content_by_lua) is specified,
It is recommended however, to use the [ngx.req.read_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.read_body) and [ngx.req.discard_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.discard_body) functions for finer control over the request body reading process instead.
This also applies to [access_by_lua](http://wiki.nginx.org/HttpLuaModule#access_by_lua) and [access_by_lua_file](http://wiki.nginx.org/HttpLuaModule#access_by_lua_file).
The various `*_by_lua` and `*_by_lua_file` configuration directives serve as gateways to the Lua API within the `nginx.conf` file. The Nginx Lua API described below can only be called within the user Lua code run in the context of these configuration directives.
The API is exposed to Lua in the form of two standard packages `ngx` and `ndk`. These packages are in the default global scope within `ngx_lua` and are always available within `ngx_lua` directives.
The packages can be introduced into external Lua modules by using the [package.seeall](http://www.lua.org/manual/5.1/manual.html#pdf-package.seeall) option:
Network I/O operations in user code should only be done through the Nginx Lua API calls as the Nginx event loop may be blocked and performance drop off dramatically otherwise. Disk operations with relatively small amount of data can be done using the standard Lua `io` library but huge file reading and writing should be avoided wherever possible as they may block the Nginx process significantly. Delegating all network and disk I/O operations to Nginx subrequests (via the [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.catpure) method and similar) is strongly recommended for maximum performance.
Index the input arguments to the [set_by_lua](http://wiki.nginx.org/HttpLuaModule#set_by_lua) and [set_by_lua_file](http://wiki.nginx.org/HttpLuaModule#set_by_lua_file) directives:
Note that only two of these constants are utilized by the [Nginx API for Lua](http://wiki.nginx.org/HttpLuaModule#Nginx_API_for_Lua) (i.e., [ngx.exit](http://wiki.nginx.org/HttpLuaModule#ngx.exit) accepts `NGX_OK` and `NGX_ERROR` as input).
These constants are usually used in [ngx.location.catpure](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) and [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi) method calls.
Here, modification of the `ngx.ctx.blah` entry in the subrequest does not affect the one in the parent request. This is because they have two separate versions of `ngx.ctx.blah`.
Arbitrary data values, including Lua closures and nested tables, can be inserted into this "matic" table. It also allows the registration of custom meta methods.
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](http://wiki.nginx.org/HttpLuaModule#ngx.redirect)) and internal redirection (via [ngx.exec](http://wiki.nginx.org/HttpLuaModule#ngx.exec)).
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](http://wiki.nginx.org/HttpLuaModule#ngx.ctx) table for the subrequest. It can be the current request's [ngx.ctx](http://wiki.nginx.org/HttpLuaModule#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.
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.
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.
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.
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](http://wiki.nginx.org/HttpLuaModule#ngx.encode_args) method.
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.
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.
The `ctx` option can be used to specify a custom Lua table to serve as the [ngx.ctx](http://wiki.nginx.org/HttpLuaModule#ngx.ctx) table for the subrequest.
It is also possible to use this `ctx` option to share the same [ngx.ctx](http://wiki.nginx.org/HttpLuaModule#ngx.ctx) table between the current (parent) request and the subrequest:
Please also refer to restrictions on [capturing locations that include Echo Module directives](http://wiki.nginx.org/HttpLuaModule#Locations_With_HttpEchoModule_Directives).
The [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) function is just a special form
of this function. Logically speaking, the [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) can be implemented like this
Please also refer to restrictions on [capturing locations that include Echo Module directives](http://wiki.nginx.org/HttpLuaModule#Locations_With_HttpEchoModule_Directives).
Set, add to, or clear the current request `HEADER` response header. Underscores (`_`) in the header names will be replaced by dashes (`-`) and the header names will be matched case-insensitively.
Only Lua tables are accepted (Only the last element in the table will take effect for standard headers such as `Content-Type` that only accept a single value).
Setting `ngx.header.HEADER` after sending out response headers (either explicitly with [ngx.send_headers](http://wiki.nginx.org/HttpLuaModule#ngx.send_headers) or implicitly with [ngx.print](http://wiki.nginx.org/HttpLuaModule#ngx.print) and similar) 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](http://wiki.nginx.org/HttpLuaModule#filter_header_by_lua) and [filter_header_by_lua_file](http://wiki.nginx.org/HttpLuaModule#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
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](http://wiki.nginx.org/HttpRewriteModule)'s [rewrite](http://wiki.nginx.org/HttpRewriteModule#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.
The `jump` can only be set to `true` in [rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) and [rewrite_by_lua_file](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua_file). Use of jump in other contexts is prohibited and will throw out a Lua exception.
Note that it is not possible to use this interface to rewrite URI arguments and that [ngx.req.set_uri_args](http://wiki.nginx.org/HttpLuaModule#ngx.req.set_uri_args) should be used for this instead. For instance, Nginx config
That is, they will take Lua boolean values `true`. However, they are different from arguments taking empty string values. `GET /test?foo=&bar=` will give something like
Note that a maximum of 100 request arguments are parsed by default (including those with the same name) and that additional request arguments are silently discarded to guard against potential denial of service attacks.
Returns a Lua table holding all the current request POST query arguments (of the MIME type `application/x-www-form-urlencoded`). Call [ngx.req.read_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.read_body) to read the request body first or turn on the [lua_need_request_body](http://wiki.nginx.org/HttpLuaModule#lua_need_request_body) directive to avoid Lua exception errors.
That is, they will take Lua boolean values `true`. However, they are different from arguments taking empty string values. `POST /test` with request body `foo=&bar=` will return something like
Note that a maximum of 100 request arguments are parsed by default (including those with the same name) and that additional request arguments are silently discarded to guard against potential denial of service attacks.
Note that the [ngx.var.HEADER](http://wiki.nginx.org/HttpLuaModule#ngx.var.VARIABLE) API call, which uses core [$http_HEADER](http://wiki.nginx.org/HttpCoreModule#.24http_HEADER) variables, may be more preferable for reading individual request headers.
For multiple instances of request headers such as:
Note that a maximum of 100 request headers are parsed by default (including those with the same name) and that additional request headers are silently discarded to guard against potential denial of service attacks.
If the request body is already read previously by turning on [lua_need_request_body](http://wiki.nginx.org/HttpLuaModule#lua_need_request_body) or by using other modules, then this function does not run and returns immediately.
If the request body has already been explicitly discarded, either by the [ngx.req.discard_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.discard_body) function or other modules, this function does not run and returns immediately.
In case of errors, such as connection errors while reading the data, this method will throw out a Lua exception *or* terminate the current request with a 500 status code immediately.
The request body data read using this function can be retrieved later via [ngx.req.get_body_data](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_body_data) or, alternatively, the temporary file name for the body data cached to disk using [ngx.req.get_body_file](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_body_file). This depends on
1. whether the current request body is already larger than the [client_body_buffer_size](http://wiki.nginx.org/HttpCoreModule#client_body_buffer_size),
1. and whether [client_body_in_file_only](http://wiki.nginx.org/HttpCoreModule#client_body_in_file_only) has been switched on.
In cases where current request may have a request body and the request body data is not required, The [ngx.req.discard_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.discard_body) function must be used to explicitly discard the request body to avoid breaking things under HTTP 1.1 keepalive or HTTP 1.1 pipelining.
Explicitly discard the request body, i.e., read the data on the connection and throw it away immediately. Please note that ignoring request body is not the right way to discard it, and that this function must be called to avoid breaking things under HTTP 1.1 keepalive or HTTP 1.1 pipelining.
Retrieves in-memory request body data. It returns a Lua string rather than a Lua table holding all the parsed query arguments. Use the [ngx.req.get_post_args](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_post_args) function instead if a Lua table is required.
1. the request body has been read into disk temporary files,
1. or the request body has zero size.
If the request body has not been read yet, call [ngx.req.read_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.read_body) first (or turned on [lua_need_request_body](http://wiki.nginx.org/HttpLuaModule#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](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_body_file) function instead.
To force in-memory request bodies, try setting [client_body_buffer_size](http://wiki.nginx.org/HttpCoreModule#client_body_buffer_size) to the same size value in [client_max_body_size](http://wiki.nginx.org/HttpCoreModule#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](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_body_file).
The returned file is read only and is usually cleaned up automatically by Nginx's memory pool. It should not be manually modified, renamed, or removed in Lua code.
If the request body has not been read yet, call [ngx.req.read_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.read_body) first (or turned on [lua_need_request_body](http://wiki.nginx.org/HttpLuaModule#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](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_body_data) function instead.
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 1.0.11: [nginx-1.0.11-allow_request_body_updating.patch](https://github.com/agentzh/ngx_openresty/blob/master/patches/nginx-1.0.11-allow_request_body_updating.patch), and this patch should be applied cleanly to other releases of Nginx as well.
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](http://wiki.nginx.org/HttpLuaModule#ngx.req.set_body_data) are called in the same request. The `auto_clean` is default to `false`.
Please ensure that the file specified by the `file_name` argument exists and is readable by an Nginx worker process by setting its permission properly to avoid Lua exception errors.
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](https://github.com/agentzh/ngx_openresty/blob/master/patches/nginx-1.0.9-allow_request_body_updating.patch), and this patch should be applied cleanly to other releases of Nginx as well.
This patch has already been applied to [ngx_openresty](http://openresty.org/) 1.0.8.17 and above.
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](http://wiki.nginx.org/HttpLuaModule#ngx.encode_args) method.
This method is similar to the [echo_exec](http://wiki.nginx.org/HttpEchoModule#echo_exec) directive of the [HttpEchoModule](http://wiki.nginx.org/HttpEchoModule).
This method *must* be called before [ngx.send_headers](http://wiki.nginx.org/HttpLuaModule#ngx.send_headers) or explicit response body outputs by either [ngx.print](http://wiki.nginx.org/HttpLuaModule#ngx.print) or [ngx.say](http://wiki.nginx.org/HttpLuaModule#ngx.say).
Note that there is normally no need to manually send out response headers as `ngx_lua` will automatically send headers out
before content is output with [ngx.say](http://wiki.nginx.org/HttpLuaModule#ngx.say) or [ngx.print](http://wiki.nginx.org/HttpLuaModule#ngx.print) or when [content_by_lua](http://wiki.nginx.org/HttpLuaModule#content_by_lua) exits normally.
Emit arguments concatenated to the HTTP client (as response body). If response headers have not been sent, this function will send headers out first and then output body data.
This is an asynchronous call and will return immediately without waiting for all the data to be written into the system send buffer. To run in synchronous mode, call `ngx.flush(true)` after calling `ngx.print`. This can be particularly useful for streaming output. See [ngx.flush](http://wiki.nginx.org/HttpLuaModule#ngx.flush) for more details.
The `log_level` argument can take constants like `ngx.ERR` and `ngx.WARN`. Check out [Nginx log level constants](http://wiki.nginx.org/HttpLuaModule#Nginx_log_level_constants) for details.
`ngx.flush` accepts an optional boolean `wait` argument (Default: `false`) first introduced in the `v0.3.1rc34` release. When called with the default argument, it issues an asynchronous call (Returns immediately without waiting for output data to be written into the system send buffer). Calling the function with the `wait` argument set to `true` switches to synchronous mode.
In synchronous mode, the function will not return until all output data has been written into the system send buffer or until the [send_timeout](http://wiki.nginx.org/HttpCoreModule#send_timeout) setting has expired. Note that using the Lua coroutine mechanism means that this function does not block the Nginx event loop even in the synchronous mode.
When `ngx.flush(true)` is called immediately after `ngx.print` or `ngx.say`, it causes the latter functions to run in synchronous mode. This can be particularly useful for streaming output.
Note that `ngx.flush` is non functional when in the HTTP 1.0 output buffering mode. See [HTTP 1.0 support](http://wiki.nginx.org/HttpLuaModule#HTTP_1.0_support).
When `status == 0` (i.e., `ngx.OK`), it will only quit the current phase handler (or the content handler if the [content_by_lua](http://wiki.nginx.org/HttpLuaModule#content_by_lua) directive is used) and continue to run later phases (if any) for the current request.
Note that while this method accepts all [HTTP status constants](http://wiki.nginx.org/HttpLuaModule#HTTP_status_constants) as input, it only accepts `NGX_OK` and `NGX_ERROR` of the [core constants](http://wiki.nginx.org/HttpLuaModule#core_constants).
Calculates the CRC-32 (Cyclic Redundancy Code) digest for the `str` argument.
This method performs better on relatively short `str` inputs (i.e., less than 30 ~ 60 bytes), as compared to [ngx.crc32_long](http://wiki.nginx.org/HttpLuaModule#ngx.crc32_long). The result is exactly the same as [ngx.crc32_long](http://wiki.nginx.org/HttpLuaModule#ngx.crc32_long).
Behind the scene, it is just a thin wrapper around the `ngx_crc32_short` function defined in the Nginx core.
This API was first introduced in the `v0.3.1rc8` release.
Calculates the CRC-32 (Cyclic Redundancy Code) digest for the `str` argument.
This method performs better on relatively long `str` inputs (i.e., longer than 30 ~ 60 bytes), as compared to [ngx.crc32_short](http://wiki.nginx.org/HttpLuaModule#ngx.crc32_short). The result is exactly the same as [ngx.crc32_short](http://wiki.nginx.org/HttpLuaModule#ngx.crc32_short).
Behind the scene, it is just a thin wrapper around the `ngx_crc32_long` function defined in the Nginx core.
This API was first introduced in the `v0.3.1rc8` release.
Computes the [HMAC-SHA1](http://en.wikipedia.org/wiki/HMAC) digest of the argument `str` and turns the result using the secret key `<secret_key>`.
The raw binary form of the `HMAC-SHA1` digest will be generated, use [ngx.encode_base64](http://wiki.nginx.org/HttpLuaModule#ngx.encode_base64), for example, to encode the result to a textual representation if desired.
Returns a floating-point number for the elapsed time in seconds (including microseconds as the decimal part) from the epoch for the current timestamp from the nginx cached time (no syscall involved unlike Lua's date library).
Use the Nginx core [timer_resolution](http://wiki.nginx.org/CoreModule#timer_resolution) directive to adjust the accuracy or forcibly update the Nginx time cache by calling [ngx.update_time](http://wiki.nginx.org/HttpLuaModule#ngx.update_time) first.
Returns the current timestamp (in the format `yyyy-mm-dd hh:mm:ss`) of the nginx cached time (no syscall involved unlike Lua's [os.date](http://www.lua.org/manual/5.1/manual.html#pdf-os.date) function).
Returns the current timestamp (in the format `yyyy-mm-dd hh:mm:ss`) of the nginx cached time (no syscall involved unlike Lua's [os.date](http://www.lua.org/manual/5.1/manual.html#pdf-os.date) function).
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](http://wiki.nginx.org/HttpLuaModule#ngx.time)).
Returns a formated string can be used as the http header time (for example, being used in `Last-Modified` header). The parameter `sec` is the timestamp in seconds (like those returned from [ngx.time](http://wiki.nginx.org/HttpLuaModule#ngx.time)).
Parse the http time string (as returned by [ngx.http_time](http://wiki.nginx.org/HttpLuaModule#ngx.http_time)) into seconds. Returns the seconds or `nil` if the input string is in bad forms.
Only the first occurrence of the match is returned, or `nil` if no match is found. In case of fatal errors, like seeing bad `UTF-8` sequences in `UTF-8` mode, a Lua exception will be raised.
When a match is found, a Lua table `captures` is returned, where `captures[0]` holds the whole substring being matched, and `captures[1]` holds the first parenthesized subpattern's capturing, `captures[2]` the second, and so on.
The `o` option is useful for performance tuning, because the regex pattern in question will only be compiled once, cached in the worker-process level, and shared among all requests in the current Nginx worker process. The upper limit of the regex cache can be tuned via the [lua_regex_cache_max_entries](http://wiki.nginx.org/HttpLuaModule#lua_regex_cache_max_entries) directive.
The optional fourth argument, `ctx`, can be a Lua table holding an optional `pos` field. When the `pos` field in the `ctx` table argument is specified, `ngx.re.match` will start matching from that offset. Regardless of the presence of the `pos` field in the `ctx` table, `ngx.re.match` will always set this `pos` field to the position *after* the substring matched by the whole pattern in case of a successful match. When match fails, the `ctx` table will be left intact.
Note that, the `options` argument is not optional when the `ctx` argument is specified and that the empty Lua string (`""`) must be used as placeholder for `options` if no meaningful regex options are required.
This method requires the PCRE library enabled in Nginx. ([Known Issue With Special PCRE Sequences](http://wiki.nginx.org/HttpLuaModule#Special_PCRE_Sequences)).
Similar to [ngx.re.match](http://wiki.nginx.org/HttpLuaModule#ngx.re.match), but returns a Lua iterator instead, so as to let the user programmer iterate all the matches over the `<subject>` string argument with the PCRE `regex`.
The current implementation requires that the iterator returned should only be used in a single request. That is, one should *not* assign it to a variable belonging to persistent namespace like a Lua package.
This method requires the PCRE library enabled in Nginx. ([Known Issue With Special PCRE Sequences](http://wiki.nginx.org/HttpLuaModule#Special_PCRE_Sequences)).
Substitutes the first match of the Perl-compatible regular expression `regex` on the `subject` argument string with the string or function argument `replace`. The optional `options` argument has exactly the same meaning as in [ngx.re.match](http://wiki.nginx.org/HttpLuaModule#ngx.re.match).
This method returns the resulting new string as well as the number of successful substitutions, or throw out a Lua exception when an error occurred (syntax errors in the `<replace>` string argument, for example).
When the `replace` is a string, then it is treated as a special template for string replacement. For example,
local newstr, n = ngx.re.sub("hello, 1234", "([0-9])[0-9]", "[$0][$1]")
-- newstr == "hello, [12][1]34"
-- n == 1
where `$0` referring to the whole substring matched by the pattern and `$1` referring to the first parenthesized capturing substring.
When the `replace` argument is of type "function", then it will be invoked with the "match table" as the argument to generate the replace string literal for substitution. The "match table" fed into the `replace` function is exactly the same as the return value of [ngx.re.match](http://wiki.nginx.org/HttpLuaModule#ngx.re.match). Here is an example:
This method requires the PCRE library enabled in Nginx. ([Known Issue With Special PCRE Sequences](http://wiki.nginx.org/HttpLuaModule#Special_PCRE_Sequences)).
This method requires the PCRE library enabled in Nginx. ([Known Issue With Special PCRE Sequences](http://wiki.nginx.org/HttpLuaModule#Special_PCRE_Sequences)).
Fetching the shm-based Lua dictionary object for the shared memory zone named `DICT` defined by the [lua_shared_dict](http://wiki.nginx.org/HttpLuaModule#lua_shared_dict) directive.
The resulting object `dict` has the following methods:
The number `8` will be consistently output when accessing `/get` regardless of how many Nginx workers there are because the `dogs` dictionary resides in the shared memory and visible to *all* of the worker processes.
The shared dictionary will retain its contents through a server config reload (either by sending the `HUP` signal to the Nginx process or by using the `-s reload` command-line option).
Retrieving the value in the dictionary [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT) for the key `key`. If the key does not exist or has been expired, then `nil` will be returned.
The value returned will have the original data type when they were inserted into the dictionary, for example, Lua booleans, numbers, or strings.
The first argument to this method must be the dictionary object itself, for example,
Unconditionally sets a key-value pair into the shm-based dictionary [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT). Returns three values:
*`success`: boolean value to indicate whether the key-value pair is stored or not.
*`err`: textual error message, can be `"no memory"`.
*`forcible`: a boolean value to indicate whether other valid items have been removed forcibly when out of storage in the shared memory zone.
The `value` argument inserted can be Lua booleans, numbers, strings, or `nil`. Their value type will also be stored into the dictionary and the same data type can be retrieved later via the [get](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT.get) method.
The optional `exptime` argument specifies expiration time (in seconds) for the inserted key-value pair. The time resolution is `0.001` seconds. If the `exptime` takes the value `0` (which is the default), then the item will never be expired.
When it fails to allocate memory for the current key-value item, then `set` will try removing existing items in the storage according to the Least-Recently Used (LRU) algorithm. Note that, LRU takes priority over expiration time here. If up to tens of existing items have been removed and the storage left is still insufficient (either due to the total capacity limit specified by [lua_shared_dict](http://wiki.nginx.org/HttpLuaModule#lua_shared_dict) or memory segmentation), then the `err` return value will be `no memory` and `success` will be `false`.
If this method succeeds in storing the current item by forcibly removing other not-yet-expired items in the dictionary via LRU, the `forcible` return value will be `true`. If it stores the item without forcibly removing other valid items, then the return value `forcible` will be `false`.
Just like the [set](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT.set) method, but only stores the key-value pair into the dictionary [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT) if the key does *not* exist.
If the `key` argument already exists in the dictionary (and not expired for sure), the `success` return value will be `false` and the `err` return value will be `"exists"`.
This feature was first introduced in the `v0.3.1rc22` release.
See also [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT).
Just like the [set](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT.set) method, but only stores the key-value pair into the dictionary [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT) if the key *does* exist.
If the `key` argument does *not* exist in the dictionary (or expired already), the `success` return value will be `false` and the `err` return value will be `"not found"`.
This feature was first introduced in the `v0.3.1rc22` release.
See also [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT).
Increments the (numerical) value for `key` in the shm-based dictionary [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT) by the step value `value`. Returns the new resulting number if the operation is successfully completed or `nil` and an error message otherwise.
The key must already exist in the dictionary, otherwise it will return `nil` and `"not found"`.
If the original value is not a valid Lua number in the dictionary, it will return `nil` and `"not a number"`.
The `value` argument can be any valid Lua numbers, like negative numbers or floating-point numbers.
This feature was first introduced in the `v0.3.1rc22` release.
This mechanism allows calling other nginx C modules' directives that are implemented by [Nginx Devel Kit](https://github.com/simpl/ngx_devel_kit) (NDK)'s set_var submodule's `ndk_set_var_value`.
Similarly, the following directives provided by [HttpEncryptedSessionModule](http://wiki.nginx.org/HttpEncryptedSessionModule) can be invoked from within Lua too:
**NOTE: This mechanism behaves differently when code cache is turned off and should be considered a DIRTY TRICK. Note that backward compatibility is NOT guaranteed and that there may be other undesirable consequences. A new data sharing mechanism will be designed later.**
To globally share data among all the requests handled by the same nginx worker process, encapsulate the shared data into a Lua module, use the Lua `require` builtin to import the module, and then manipulate the shared data in Lua. This works because required Lua modules are loaded only once and all coroutines will share the same copy of the module. Note however that Lua global variables WILL NOT persist between requests because of the one-coroutine-per-request isolation design.
Note that this data sharing is on a *per-worker* basis and not on a ''per-server' basis'. That is, when there are multiple nginx worker processes under an Nginx master, data sharing cannot cross the process boundary between these workers.
1. Use the [ngx.shared.DICT](http://wiki.nginx.org/HttpLuaModule#ngx.shared.DICT) API provied by this module.
1. Use only a single nginx worker and a single server. This is however not recommended when there is a multi core CPU or multiple CPUs in a single machine.
1. Use data storage mechanisms such as `memcached`, `redis`, `MySQL` or `PostgreSQL`. [The ngx_openresty bundle](http://openresty.org) associated with this module comes with a set of companion Nginx modules that provide interfaces with these data storage mechanisms. See the [HttpMemcModule](http://wiki.nginx.org/HttpMemcModule), [HttpRedis2Module](http://wiki.nginx.org/HttpRedis2Module), [HttpDrizzleModule](http://wiki.nginx.org/HttpDrizzleModule) and [HttpPostgresModule](http://github.com/FRiCKLE/ngx_postgres/) modules for details
* As the module's predefined Nginx I/O API uses the coroutine yielding/resuming mechanism, user code should not call any Lua modules that use the Lua coroutine mechanism in order to prevent conflicts with the module's predefined Nginx API methods such as [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) (Actually, coroutine modules have been masked off in [content_by_lua](http://wiki.nginx.org/HttpLuaModule#content_by_lua) directives and others). This limitation is significant and work is ongoing on an alternative coroutine implementation that can fit into the Nginx event model to address this. When this is done, it will be possible to use the Lua coroutine mechanism freely as it is in standard Lua implementations.
* Lua's `dofile` builtin is implemented as a C function in both Lua 5.1 and LuaJIT 2.0 and when [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) is called, [ngx.exec](http://wiki.nginx.org/HttpLuaModule#ngx.exec), [ngx.exit](http://wiki.nginx.org/HttpLuaModule#ngx.exit) or [ngx.req.read_body](http://wiki.nginx.org/HttpLuaModule#ngx.req.read_body) or similar in the file to be loaded by `dofile`, a coroutine yield across the C function boundary will be initiated. This however is not allowed within ngx_lua and will usually result in error messages like `lua handler aborted: runtime error: attempt to yield across C-call boundary`. To avoid this, define a real Lua module and use the Lua `require` builtin instead.
* Because the standard Lua 5.1 interpreter's VM is not fully resumable, the methods [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture), [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi), [ngx.redirect](http://wiki.nginx.org/HttpLuaModule#ngx.redirect), [ngx.exec](http://wiki.nginx.org/HttpLuaModule#ngx.exec), and [ngx.exit](http://wiki.nginx.org/HttpLuaModule#ngx.exit) cannot be used within the context of a Lua [pcall()](http://www.lua.org/manual/5.1/manual.html#pdf-pcall) or [xpcall()](http://www.lua.org/manual/5.1/manual.html#pdf-xpcall) when the standard Lua 5.1 interpreter is used and the `attempt to yield across metamethod/C-call boundary` error will be produced. Please use LuaJIT 2.0, which supports a fully resumable VM, to avoid this.
It is recommended to always place the following piece of code at the end of Lua modules that use the [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) or [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi) directives to prevent casual use of module-level global variables that are shared among *all* requests:
getmetatable(foo.bar).__newindex = function (table, key, val)
error('Attempt to write to undeclared variable "' .. key .. '": '
Assuming the current Lua module is named `foo.bar`, this will guarantee that local variables in module `foo.bar` functions have been declared as "local". It prevents undesirable race conditions while accessing such variables. See [Data Sharing within an Nginx Worker](http://wiki.nginx.org/HttpLuaModule#Data_Sharing_within_an_Nginx_Worker) for the reasons behind this.
Locations With [HttpEchoModule](http://wiki.nginx.org/HttpEchoModule) Directives
--------------------------------------------
The [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) and [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi) directives cannot capture locations that include the [echo_location](http://wiki.nginx.org/HttpEchoModule#echo_location), [echo_location_async](http://wiki.nginx.org/HttpEchoModule#echo_location_async), [echo_subrequest](http://wiki.nginx.org/HttpEchoModule#echo_subrequest), or [echo_subrequest_async](http://wiki.nginx.org/HttpEchoModule#echo_subrequest_async) directives.
PCRE sequences such as `\d`, `\s`, or `\w`, require special attention because in string literals, the backslash character, `\`, is stripped out by both the Lua language parser and by the Nginx config file parser before processing. So the following snippet will not work as expected:
Here, `\\\\d+` is stripped down to `\\d+` by the Nginx config file parser and this is further stripped down to `\d+` by the Lua language parser before running.
Alternatively, the regex pattern can be presented as a long-bracketed lua string literal by encasing it in "long brackets", `[[...]]`, in which case backslashes have to only be escaped once for the Nginx config file parser.
Note that a longer from of the long bracket, `[=[...]=]`, may be required if the regex pattern contains `[...]` sequences.
The `[=[...]=]` form may be used as the default form if desired and it may help with readability if a space is inserted between the long brackets and the regex patterns.
An alternative approach to escaping PCRE sequences is to ensure that Lua code is placed in external script files and executed using the various `*_by_lua_file` directives.
* Mashup'ing and processing outputs of various nginx upstream outputs (proxy, drizzle, postgres, redis, memcached, and etc) in Lua,
* doing arbitrarily complex access control and security checks in Lua before requests actually reach the upstream backends,
* manipulating response headers in an arbitrary way (by Lua)
* fetching backend information from external storage backends (like redis, memcached, mysql, postgresql) and use that information to choose which upstream backend to access on-the-fly,
* coding up arbitrarily complex web applications in a content handler using synchronous but still non-blocking access to the database backends and other storage,
* doing very complex URL dispatch in Lua at rewrite phase,
* using Lua to implement advanced caching mechanism for nginx subrequests and arbitrary locations.
The possibilities are unlimited as the module allows bringing together various elements within Nginx as well as exposing the power of the Lua language to the user. The module provides the full flexibility of scripting while offering performance levels comparable with native C language programs both in terms of CPU time as well as memory footprint. This is particularly the case when LuaJIT 2.0 is enabled.
The Lua state (Lua VM instance) is shared across all the requests handled by a single nginx worker process to miminize memory use.
On a ThinkPad T400 2.80 GHz laptop, the HelloWorld example readily achieves 28k req/sec using `http_load -p 10`. By contrast, Nginx + php-fpm 5.2.8 + Unix Domain Socket yields 6k req/sec and [Node.js](http://nodejs.org/) v0.6.1 yields 10.2k req/sec for their HelloWorld equivalents.
This module performs best when built with [LuaJIT 2.0](http://luajit.org/luajit.html).
Nginx Compatibility
===================
The module is compatible with the following versions of Nginx:
The [ngx_openresty bundle](http://openresty.org) can be used to install Nginx, `ngx_lua`, either one of the standard Lua 5.1 interpreter or LuaJIT 2.0, as well as a package of powerful companion Nginx modules. The basic installation step is a simple `./configure --with-luajit && make && make install`.
1. Install LuaJIT 2.0 (Recommended) or Lua 5.1. Lua can be obtained free from the [the LuaJIT download page](http://luajit.org/download.html) or [the standard Lua homepage](http://www.lua.org/). Some distribution package managers also distribute Lua and LuaJIT.
* add `ignore_resp_headers`, `ignore_resp_body`, and `ignore_resp` options to [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) and ngx.location.capture_multi` methods, to allow micro performance tuning on the user side.
* add directives to run lua codes when nginx stops/reloads.
* deal with TCP 3-second delay problem under great connection harness.
* add options to [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) and [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi) in order to share and copy a particular set of nginx variables with subrequests, specified by the user.
* add an option to [ngx.location.capture](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture) and [ngx.location.capture_multi](http://wiki.nginx.org/HttpLuaModule#ngx.location.capture_multi) so as to specify the [ngx.ctx](http://wiki.nginx.org/HttpLuaModule#ngx.ctx) table for subrequests.
* add support for multi-value arguments to [[#ngx.req.set_uri_args]] if its `args` argument is a Lua table.
* add the "cosocket" mechamism to emulate a common Lua socket API set that will provide transparent nonblocking capability out of the box and that avoids Nginx subrequest overheads.
* added the [header_filter_by_lua](http://wiki.nginx.org/HttpLuaModule#header_filter_by_lua) and [header_filter_by_lua_file](http://wiki.nginx.org/HttpLuaModule#header_filter_by_lua_file) directives. thanks Liseen Wan (万珣新).
* implemented the PCRE regex API for Lua: [ngx.re.match](http://wiki.nginx.org/HttpLuaModule#ngx.re.match), [ngx.re.gmatch](http://wiki.nginx.org/HttpLuaModule#ngx.re.gmatch), [ngx.re.sub](http://wiki.nginx.org/HttpLuaModule#ngx.re.sub), and [ngx.re.gsub](http://wiki.nginx.org/HttpLuaModule#ngx.re.gsub).
* now we add the `ngx` and `ndk` table into `package.loaded` such that the user can write `local ngx = require 'ngx'` and `local ndk = require 'ndk'`. thanks @Lance.
* added new directive [lua_regex_cache_max_entries](http://wiki.nginx.org/HttpLuaModule#lua_regex_cache_max_entries) to control the upper limit of the worker-process-level compiled-regex cache enabled by the `o` regex option.
* implemented the special [ngx.ctx](http://wiki.nginx.org/HttpLuaModule#ngx.ctx) Lua table for user programmers to store per-request Lua context data for their applications. thanks 欧远宁 for suggesting this feature.
* now [ngx.print](http://wiki.nginx.org/HttpLuaModule#ngx.print) and [ngx.say](http://wiki.nginx.org/HttpLuaModule#ngx.say) allow (nested) array-like table arguments. the array elements in them will be sent piece by piece. this will avoid string concatenation for templating engines like [ltp](http://www.savarese.com/software/ltp/).
* implemented the [ngx.req.get_post_args](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_post_args) method for fetching url-encoded POST query arguments from within Lua.
* implemented the [ngx.req.get_uri_args](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_uri_args) method to fetch parsed URL query arguments from within Lua. thanks Bertrand Mansion (golgote).
* added new function [ngx.parse_http_time](http://wiki.nginx.org/HttpLuaModule#ngx.parse_http_time), thanks James Hurst.
* now we allow Lua boolean and `nil` values in arguments to [ngx.say](http://wiki.nginx.org/HttpLuaModule#ngx.say), [ngx.print](http://wiki.nginx.org/HttpLuaModule#ngx.print), [ngx.log](http://wiki.nginx.org/HttpLuaModule#ngx.log) and [print](http://wiki.nginx.org/HttpLuaModule#print).
* added support for user C macros `LUA_DEFAULT_PATH` and `LUA_DEFAULT_CPATH`. for now we can only define them in `ngx_lua`'s `config` file because nginx `configure`'s `--with-cc-opt` option hates values with double-quotes in them. sigh. This feature is used by [The ngx_openresty bundle](http://openresty.org) to bundle third party Lua libraries.
* worked-around the "stack overflow" issue while using `luarocks.loader` and disabling [lua_code_cache](http://wiki.nginx.org/HttpLuaModule#lua_code_cache), as described as github issue #27. thanks Patrick Crosby.
* fixed the `zero size buf in output` alert while combining [lua_need_request_body](http://wiki.nginx.org/HttpLuaModule#lua_need_request_body) on + [access_by_lua](http://wiki.nginx.org/HttpLuaModule#access_by_lua)/[rewrite_by_lua](http://wiki.nginx.org/HttpLuaModule#rewrite_by_lua) + [proxy_pass](http://wiki.nginx.org/HttpProxyModule#proxy_pass)/[fastcgi_pass](http://wiki.nginx.org/HttpFcgiModule#fastcgi_pass). thanks Liseen Wan (万珣新).
* fixed issues with HTTP 1.0 HEAD requests.
* made setting `ngx.header.HEADER` after sending out response headers throw out a Lua exception to help debugging issues like github issue #49. thanks Bill Donahue (ikhoyo).
* fixed an issue regarding defining global variables in C header files: we should have defined the global `ngx_http_lua_exception` in a single compilation unit. thanks @姜大炮.
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