jjb

For years, people have been using jemalloc with ruby. There are various benchmarks and discussions. Legend had it that Jemalloc 5 doesn't work as well as Jemalloc 3.

Then, one day, hope appeared on the horizon. Someone offered a config for Jemalloc 5.

The recipe would be something like this (shown with official docker ruby image).

FROM ruby:3.1.2-bullseye

toshimaru

# Check server process is using jemalloc
# ref. [Japanese] https://tech.studyplus.co.jp/entry/2019/09/09/094140
class AppController < ActionController::Base
  def show
    r = `strings /proc/#{Process.pid}/maps | grep jemalloc`
    render plain: "<h1>#{ENV['LD_PRELOAD'].presence || 'empty'}</h1><pre>#{r}</pre>"
  end
end

barbietunnie

Useful Postgres Commands

1. Determine disk usage of a particular table/database

For a particular table,

SELECT pg_size_pretty( pg_total_relation_size('tablename') );

tbuehlmann

posts = Post.all
ActiveRecord::Associations::Preloader.new.preload(posts, :comments, Comment.where('id > 42'))

tbuehlmann

# config/initializers/draper.rb

Draper::CollectionDecorator.delegate :current_page, :total_pages, :limit_value, :total_count

raggi

# rack_sse.ru
#
# An example of basic real-time, single-room broadcast chat using Server Sent
# Events in plain old Rack. This example does NOT use hijack, or the async
# hacks, it just relies on a well implemented threaded Rack server (at time of
# writing this will therefore only work with puma!). Other servers should be
# fixed to support this, as it is pretty critical to how Rack *should* work on
# most servers. The only spec-acceptable failure in this case is not flushing
# the content stream on each yield (for which the rack spec has no workaround
# today).

ohcibi

class My::Channel < EM::Channel
  attr_accessor :watcher, :logger
  def self.create!
    channel = new
    channel.logger = Logger.new 'sinatra.log'
    channel.watcher
    channel
  end

  def watcher

tbuehlmann

Using an HTC Desire (Android 2.2 Froyo), I experienced two weird problems at some time.

1. When listening to music with the default player (didn't try others), I wasn't able to adjust the media volume. The media volume bar moved but the volume actually didn't change. This happened only when earphones/headphones were plugged in.

2. When having a phone call, the phone automagically switched to using the phone speakers. I had to manually switch the speakers off. Each time.

These problems appeared suddenly and were permanent.

I familiarized with the problems since I wasn't able to find a solution. I read about some solutions regarding resetting the phone completely and switching it "off and on again" (seriously…). Tried switching it off and on again, no changes. Didn't try resetting it.

tbuehlmann

$ sudo apt-get install build-essential zlib1g zlib1g-dev libruby1.9.1 libxml2 libxml2-dev libxslt1-dev
$ sudo apt-get build-dep ruby1.9.1

$ wget ftp://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.2-p0.tar.bz2
$ tar xvjf ruby-1.9.2-p0.tar.bz2

Open ruby-1.9.2-p0/ext/Setup and uncomment the zlib line

$ ./configure
$ make