📂 Add option for gzip_compression_level for Rack::Deflater.

[bayleedev]

This would be useful on a system with smaller memory to be set to a lower number, and a system with higher compression needs to compress up to level 9.

:gzip_compression_level :: An integer from 0 to 9 controlling the
level of compression; 1 is fastest and produces the least compression,
and 9 is slowest and produces the most compression. 0 is no compression.
The default is 6. This is only needed for the gzip type encoding.

[bayleedev]

cc @jeremyevans 572fe62 rack/rack/pull/1733 comment

[ioquatix]

This looks good to me.

Do you think gzip_compression_level is too specific, or maybe compression_level is sufficient?

[jeremyevans]

This also looks good to me. Currently, only gzip encoding is supported, but I could see br possibly being supported in the future, so gzip_compression_level may be fine as an option name. @ioquatix are you OK with the current option name?

[ioquatix]

I think if the compression algorithm could be different, which is possible and likely in the future, we should not embed the name of the compression algorithm in the option.

[bayleedev]

@ioquatix what were you thinking? gzip_options: { compression_level: 3 } ? Making it compression_level could make its use ambiguous with multiple compression algorithms.

EDIT:
gzip_options would require some refactoring as well - sync is a gzip specific option, hinting back at compression_level.

EDIT EDIT:
Personally, I think gzip_compression_level is the way to go. Happy to go either way on this though. Thank you!

[nateberkopec]

Just want to point out that brotli has a 10 compression level, zlib only goes up to 9 (insert spinal tap reference here)

[ioquatix]

I took a look at how this is implemented in other places.

In protocol-http (falcon) we use Zlib::Deflate which is non-algorithm-specific.

It would be nice to set options in a generic way.

I checked node.js and they expose gzip, deflate, brotli all through the same interface, but there is a way to set options. https://nodejs.org/api/zlib.html#zlib_brotli_constants

My suggestion would be something like:

deflater = Rack::Deflater.new(..., **options)
  # in initialize:
  @options = options

# In the deflater:
Zlib::Deflate.new(..., **options)

This is just pseudo code. This means we are not interpreting the value of the options which means we don't worry about naming or anything else.

[bayleedev]

I love the idea. I'm unsure how to implement that idea. Since ZLib::Deflate and Zlib::GzipWriter both take level as an unnamed positional argument, not options. Thoughts?

[bayleedev]

@ioquatix @nateberkopec any update on this? Happy to change the code. I'm mostly looking for the functionality to exist more than how I want the code to be structured. Let me know. [: