Name

lua-resty-upload - Streaming reader and parser for HTTP file uploading based on ngx_lua cosocket

Status

This library is considered experimental and still under active development.

The API is still in flux and may change without notice.

Description

This Lua library is a streaming file uploading API for the ngx_lua nginx module:

http://wiki.nginx.org/HttpLuaModule

The multipart/form-data MIME type is supported.

The API of this library just returns tokens one by one. The user just needs to call the read method repeatedly until a nil token type is returned. For each token returned from the read method, just check the first return value for the current token type. The token type can be header, body, and part end. Each multipart/form-data form field parsed consists of several header tokens holding each field header, several body tokens holding each body data chunk, and a part end flag indicating the field end.

This is how streaming reading works. Even for giga bytes of file data input, the memory used in the lua land can be small and constant, as long as the user does not accumulate the input data chunks herself.

This Lua library takes advantage of ngx_lua's cosocket API, which ensures 100% nonblocking behavior.

Note that at least ngx_lua 0.5.0rc5 or ngx_openresty 1.0.11.7 is required.

Synopsis

lua_package_path "/path/to/lua-resty-redis/lib/?.lua;;";

server {
    location /test {
        content_by_lua '
            local upload = require "resty.upload"
            local cjson = require "cjson"

            local chunk_size = 5 -- should be set to 4096 or 8192
                                 -- for real-world settings

            local form = upload:new(chunk_size)

            form:set_timeout(1000) -- 1 sec

            while true do
                local typ, res, err = form:read()
                if not typ then
                    ngx.say("failed to read: ", err)
                    return
                end

                ngx.say("read: ", cjson.encode({typ, res}))

                if typ == "eof" then
                    break
                end
            end

            local typ, res, err = form:read()
            ngx.say("read: ", cjson.encode({typ, res}))
        ';
    }
}

A typical output of the /test location defined above is:

read: ["header",["Content-Disposition","form-data; name=\"file1\"; filename=\"a.txt\""]]
read: ["header",["Content-Type","text\/plain"]]
read: ["body","Hello"]
read: ["body",", wor"]
read: ["body","ld"]
read: ["part_end"]
read: ["header",["Content-Disposition","form-data; name=\"test\""]]
read: ["body","value"]
read: ["body","\r\n"]
read: ["part_end"]
read: ["eof"]
read: ["eof"]

You can use the lua-resty-string library to compute SHA-1 and MD5 digest of the file data incrementally. Here is such an example:

local resty_sha1 = require "resty.sha1"
local upload = require "resty.upload"

local chunk_size = 4096
local form = upload:new(chunk_size)
local sha1 = resty_sha1:new()
local file
while true do
    local typ, res, err = form:read()

    if not typ then
         ngx.say("failed to read: ", err)
         return
    end

    if typ == "header" then
        local file_name = my_get_file_name(res)
        if file_name then
            file = io.open(file_name, "w+")
            if not file then
                ngx.say("failed to open file ", file_name)
                return
            end
        end

     elseif typ == "body" then
        if file then
            file:write(res)
            sha1:update(res)
        end

    elseif typ == "part_end" then
        file:close()
        file = nil
        local sha1_sum = sha1:final()
        sha1:reset()
        my_save_sha1_sum(sha1_sum)

    elseif typ == "eof" then
        break

    else
        -- do nothing
    end
end

If you want to copmute MD5 sums for the uploaded files, just use the resty.md5 module shipped by the lua-resty-string library. It has a similar API as resty.sha1.

For big file uploading, it is important not to buffer all the data in memory. That is, you should never accumulate data chunks either in a huge Lua string or in a huge Lua table. You must write the data chunk into files as soon as possible and throw away the data chunk immediately (to let the Lua GC free it up).

Instead of writing the data chunk into files (as shown in the example above), you can also write the data chunks to upstream cosocket connections if you do not want to save the data on local file systems.

Author

Zhang "agentzh" Yichun (章亦春) agentzh@gmail.com

Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2012, by Zhang "agentzh" Yichun (章亦春) agentzh@gmail.com.

All rights reserved.

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

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

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

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.

See Also

• the ngx_lua module
• the lua-resty-string library
• the lua-resty-memcached library
• the lua-resty-redis library
• the lua-resty-mysql library