harssh

Optimizing Rust container builds

I'm a Rust newbie, and one of the things that I've found frustrating is that the default docker build experience is extremely slow. As it downloads crates, then dependencies, then finally my app - I often get distracted, start doing something else, then come back several minutes later and forget what I was doing

Recently, I had the idea to make it a little better by combining multistage builds with some of the amazing features from BuildKit. Specifically, cache mounts, which let a build container cache directories for compilers & package managers. Here's a quick annotated before & after from a real app I encountered.

Before

This is a standard enough multistage Dockerfile. Nothing seemingly terrible or great here - just a normal build stage, and a smaller runtime stage.

harssh

require 'benchmark'
require 'etc'

Ractor.new { :warmup } if defined?(Ractor)

def fibonacci(n)
  return n if (0..1).include? n

  fibonacci(n - 1) + fibonacci(n - 2)
end

harssh

require 'fog'

username = 'testuser'
bucket = 'uniquebucketname1234'

aws_credentials = { 
  :aws_access_key_id => 'YOUR-ACCESS-KEY-ID',   
  :aws_secret_access_key => 'YOUR-SECRET-ACCESS-KEY'
}

harssh

#resides in app/models/connectors/
class Connectors::Aws
	attr_reader :aws_access_key_id, :aws_secret_access_key, :aws_security_token, :expires_at

	def initialize
		if ENV.has_key?('AWS_SECURITY_TOKEN') #localhost
			@aws_access_key_id = ENV['AWS_ACCESS_KEY_ID']
			@aws_secret_access_key = ENV['AWS_SECRET_ACCESS_KEY']
			@aws_security_token = ENV['AWS_SECURITY_TOKEN']
			@expires_at = Time.now + 10.hours

harssh

Note: As of Ruby 3.0.0, Hash#except is now [part][1] of the language. However, Ruby does not implement Hash#except!.

Sometimes I want to remove a specific key-value pair from a Ruby hash and get the resulting hash back. If you're using Rails or ActiveSupport you can accomplish this using Hash#except:

hash = { a: 1, b: 2, c: 3 }
hash.except(:a)     # => { b: 2, c: 3 }

# note, the original hash is not modified
hash # => { a: 1, b: 2, c: 3 }

harssh

require 'parallel'
require 'rtesseract'
require 'mini_magick'

source = "/MyDirectory/my.pdf"
doc = {}
pdf = MiniMagick::Image.open(source)
Parallel.map(pdf.pages.each_with_index, in_threads: 8) do |page, idx|
  tmpfile = Tempfile.new(['', '.tif'])
  MiniMagick::Tool::Convert.new do |convert|

harssh

class UserObserver < Mongoid::Observer

  def after_save(record)
    expire_cache(record)
  end

  private
  def expire_cache(record)
    Rails.cache.delete("user:#{record.id}")
  end

harssh

namespace :clean_code do
  # rubcop only available in dev
  if Rails.env.development?
    require 'rubocop/rake_task'
    def diff_files
      cmd = %q( git diff --name-only --diff-filter=ACMRTUXB \
      $(git merge-base HEAD origin/master) \
      | egrep '\.rake$|\.rb$' )
      diff = `#{cmd}`
      diff.split("\n")

harssh

git --no-pager diff --name-only develop | tr '\n' ',' | sed 's/\(.*\),/\1 /'

harssh

Model
  .where(
    "EXTRACT(dow FROM log_in) IN (1,2,3,4,5)"
  )
  .where(
    "log_in::time BETWEEN '9:00' AND '18:00'"
  )
  .where(
    "log_in BETWEEN now()::timestamp - (interval '1 week' AND now()::timestamp)"
  )