This is a module that is distributed with tengine which is a distribution of Nginx that is used by the e-commerce/auction site Taobao.com. This distribution contains some modules that are new on the Nginx scene. The ngx_http_slice_module module is one of them.

This module can be thought out as a reverse byte-range request header. It's main utility is to allow Nginx to slice a big file in small pieces (byte-ranges) while permitting to use on-the-fly gzip compression.

A typical example is for allowing someone to download a large video file while keeping the bandwith usage minimal. This might also be used as device for selling a video file by pieces where each link points to different zones of the file splitted by file ranges.

Other use would be to use a generic CSS file and use only part of it for each section of a site. Granted that byte-range slicing isn't the most intuitive for such.

Note also that using arguments is more useful than byte-ranges in the sense that they can be set in a normal link, while byte ranges require a special HTTP header.

location ^~ /video-dump/ {
    slice; # enable slicing
    slice_start_arg s;
    slice_end_arg e;    
}

So we would request the first 1k of the file like this:

http://example.com/video-dump/large_vid.mp4?s=0&e=1024

Notice s=0, start at 0 and e=1024, stop at 1024 bytes (1k).

slice

context: location

It enables the content slicing in a given location.

slice_arg_begin string

default: begin

context: http, server, location

Defines the argument that defines the request range of bytes start.

slice_arg_end string

default: end

context: http, server, location

Defines the argument that defines the request range of bytes end.

slice_header string

context: http, server, location

Defines the string to be used as the header of each slice being served by Nginx.

slice_footer string

context: http, server, location

Defines the string to be used as the footer of each slice being served by Nginx.

slice_header_first on | off

default: on

context: http, server, location

If set to off and when requesting the first byte of the file do not serve the header.

This directive is particularly useful to differentiate the first slice from the remaining slices. The first slice is the one which has no header.

slice_footer_last on | off

default: on

context: http, server, location

If set to off and when requesting the last byte of the file do not serve the header.

This directive is particularly useful to differentiate the last slice from the remaining slices. The last slice is the one which has no footer.

Here's some examples that explore all the options.

location ^~ /dbdumps/ {
    slice; # enable slicing
    slice_start_arg first;
    slice_end_arg last;
    slice_header '-- **db-slice-start**';
    slice_header_first off;
}

Then a request like this:

http://example.com/dbdumps/somedb.sql?first=0&last=1048576

Send the first 1M and skip the -- **db-slice-start** header.

location ^~ /dbdumps/ {
    slice; # enable slicing
    slice_start_arg first;
    slice_end_arg last;
    slice_header '-- **db-slice-start**';
    slice_header_first off;
    slice_footer '-- **db-slice-end**';
}

This differs from the previous in the sense that it sends a footer.

location ^~ /dbdumps/ {
    slice; # enable slicing
    slice_start_arg first;
    slice_end_arg last;
    slice_header '-- **db-slice-start**';
    slice_header_first off;
    slice_footer '-- **db-slice-end**';
    slice_footer_last off; 
}

Then a request like this:

http://example.com/dbdumps/somedb.sql?first=0&last=1048576

Send the first 1M and skip the -- **db-slice-start** header.

If the file is 200MB, we get the last slice with:

http://example.com/dbdumps/somedb.sql?first=208666624&last=209715200

this last slice has no footer.

1. Clone the git repo.

   git clone git://github.com/alibaba/nginx-http-slice.git
   

2. Add the module to the build configuration by adding --add-module=/path/to/nginx-http-slice.

3. Build the nginx binary.

4. Install the nginx binary.

5. Configure contexts where concat is enabled.

6. Build your links such that the above format, i.e., all URIs that correspond to specific ranges. As example here's how to link to the first 4k of a file.

   <a href="http://example.com/datadumps/dump0.sql?start=0&end=4096" />db dump</a>
   

7. Done.

I'm tagging each release in synch with the Tengine releases.

• http concat: allows to concatenate a given set of files and ship a single response from the server. It's particularly useful for aggregating CSS and Javascript files.

• footer filter: allows to add some extra data (markup or not) at the end of a request body. It's pratical for things like adding time stamps or other miscellaneous stuff without having to tweak your application.

1. As referred at the outset this module is part of the tengine Nginx distribution. So you might want to save yourself some work and just build it from scratch using tengine in lieu if the official Nginx source.

2. If you fancy a bleeding edge Nginx package (from the dev releases) for Debian made to measure then you might be interested in my debian Nginx package. Instructions for using the repository and making the package live happily inside a stable distribution installation are provided.

Thanks to Joshua Zhu and the Taobao platform engineering team for releasing tengine. Also for being kind enough to clarify things regarding this module on the Tengine mailing list.

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