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https://github.com/pintsized/lua-resty-rack

A simple and extensible HTTP server framework for OpenResty.
https://github.com/pintsized/lua-resty-rack

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A simple and extensible HTTP server framework for OpenResty.

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# lua-resty-rack



A simple and extensible HTTP server framework for [OpenResty](http://openresty.org), providing a clean method for loading Lua HTTP applications ("resty" modules) into [Nginx](http://nginx.org).



Drawing inspiration from [Rack](http://rack.github.com/) and also [Connect](https://github.com/senchalabs/connect), **lua-resty-rack** allows you to load your application as a piece of middleware, alongside other middleware. Your application can either; ignore the current request, modify the request or response in some way and pass on to other middleware, or take responsibiliy for the request by generating a response. 



## Status



This library is considered experimental and the API may change without notice. Please feel free to offer suggestions or raise issues here on Github.



## Installation



Clone the repo and ensure the contents of `lib` are in your `lua_package_path` in `nginx.conf`.



## Using Middleware



To install middleware for a given `location`, you simply call `rack.use(middleware)` in the order you wish the modules to run, and then finally call `rack.run()`.



```nginx

server {

    location / {

        content_by_lua '

            local rack = require "resty.rack"



            rack.use(rack.middleware.method_override)

            rack.use(require "my.module")

            rack.run()

        ';

    }

}

```



### rack.use(...)



**Syntax:** `rack.use(route?, middleware, options?)`



If `route` is supplied, the middleware will only be run for requests where `route` is in the path (`ngx.var.uri`). If the middleware requires any options to be selected they can be provided, usually as a table, as the third parameter.



```lua

rack.use('/some/path', app, { foo = 'bar' })

```



For simple cases, the `middleware` parameter can also be a simple function rather than a Lua module. Your function should accept `req`, `res`, and `next` as parameters. See below for instructions on writing middleware.



```lua

rack.use(function(req, res, next)

    res.header["X-Homer"] = "Doh!"

    next()

end)

```



### rack.run()



**Syntax:** `rack.run()`



Runs each of the middleware in order, until one chooses to handle the response. Thus, the order in which you call `rack.use()` is important.



## Bundled Middleware



### method_override

```lua

rack.use(rack.middleware.method_override, { key = "METHOD" })

```



Override the HTTP method using a querystring value. The default argument name is "_method" but this can be overriden by setting the option "key".



### read_request_headers

```lua

rack.use(rack.middleware.read_request_headers, { max = 50 })

```



This is only needed if you wish to iterate over the HTTP request headers. They will be lazy loaded when accessed via `req.header`.



You may specify a limit to the number of request headers to be read, which defaults to `100`. The limit can be removed by specifying a max of `0`, but is [strongly discouraged](http://wiki.nginx.org/HttpLuaModule#ngx.req.get_headers).



### read_body

```lua

rack.use(rack.middleware.read_body)

```



Explicitly reads the request body (raw).



## Creating Middleware



Middleware applications are simply Lua modules which use the HTTP request and response as a minimal interface. They must implement the function `call(options)` which returns a function. The parameters `(req, res, next)` are defined below.



```lua

module("resty.rack.method_override", package.seeall)



_VERSION = '0.01'



function call(options)

    return function(req, res, next)

        local key = options['key'] or '_method'

        req.method = string.upper(req.args[key] or req.method)

        next()

    end

end

```



## API



### req.method



The HTTP method, e.g. `GET`, set from `ngx.var.request_method`.



### req.scheme



The protocol scheme `http|https`, set from `ngx.var.scheme`.



### req.uri



e.g. `/my/uri`, set from `ngx.var.uri`.



### req.host



The hostname, e.g. `example.com`, set from `ngx.var.host`.



### req.query



The querystring, e.g. `var1=1&var2=2`, set from `ngx.var.query_string`.

 

### req.args



The query args, as a `table`, set from `ngx.req.get_uri_args()`.



### req.header



A table containing the request headers. Keys are matched case insensitvely, and optionally with underscores instead of hyphens. e.g.



```lua

req.header["X-Foo"] = "bar"

res.body = req.header.x_foo

    --> "bar"

```



HTTP Request headers are read on demand and so cannot be iterated over unless the `read_request_headers` middleware is in use).



### req.body



An empty string until read with the `read_body` middleware.



### res.status



The HTTP status code to return. There are [constants defined](http://wiki.nginx.org/HttpLuaModule#HTTP_status_constants) for common statuses.



### res.header



A table of response headers, which can be matched case insensitively and optionally with underscores instead of hyphens (see `req.header` above).



### res.body



The response body.



### next



This parameter is a function provided to the middleware, which may be called to indicate rack should try the next middleware. If your application does not intend to send the response to the browser, it must call this function. If however your application is taking responsibility for the response, simply return without calling next.



*Example purely modifying the request.*

```lua

function call(options)

    return function(req, res, next)

        local key = options['key'] or '_method'

        req.method = string.upper(req.args[key] or req.method)

        next()

    end

end

```



*Example generating a response.*

```lua

function call(options)

    return function(req, res)

        res.status = 200

        res.header['Content-Type'] = "text/plain"

        res.body = "Hello World"

    end

end

```



### Enhancing req / res



Your application can add new fields or even functions to the req / res tables where appropriate, which could be used by other middleware so long as the dependencies are clear (and one calls `use()` in the correct order). 



## Author



James Hurst 



## Licence



This module is licensed under the 2-clause BSD license.



Copyright (c) 2012, James Hurst 



All rights reserved.



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



* Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.



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



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