Definizioni

• cd candela: è l'intensità luminosa di una sorgente emettente una radiazione monocromatica della lunghezza d'onda pari a 555nm e di intensità radiante di 1/683 watt per steradiante
• lm lumen : 1lm = 1cd / 4π (dove 4π è il numero di steradianti di una sfera)

Confronto approssimativo con le lampadine ad incandescenza

Scegliere i lumen in base alla superficie da illuminare

lm = lux · m²

Valori indicativi per tipologia di luogo:

Range valori consigliabili:

Fonte: micronova.it, karmanitalia.it

Ingredienti:

• 400gr pici freschi
• 700gr pomodori freschi
• 3 spicchi di aglione
• 30ml vino bianco
• olio evo
• sale
• peperoncino

Procedimento:

1. Affettare l'aglione sottile e metterlo in una padella calda con l'olio

2. Coprire e cuocere a fiamma bassa fino al completo scioglimento dell'aglione

3. Sfumare col vino e lascialo evaporare a fiamma media

4. Aggiungere il pomodoro continuare la cottura per circa 20 minuti

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# download/upgrade
curl -L -o ~/bin/youtube-dl https://yt-dl.org/downloads/latest/youtube-dl

# build from source repo
git clone https://github.com/ytdl-org/youtube-dl.git
cd youtube-dl
make clean && make

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# to parse a playlist use "--yes-playlist url" or simply "playlist_id"

# downoload a playlist audio only
youtube-dl -i -o "%(title)s.%(ext)s" \
  -f bestaudio --extract-audio --audio-format mp3 --audio-quality 5 \
  --postprocessor-args "-ar 44100" \
  <playlist_id>

# extract audio tracks from an url list
cat list.txt | xargs youtube-dl -i -o "%(title)s.%(ext)s" \
  -f bestaudio --extract-audio --audio-format mp3 --audio-quality 5 \
  --postprocessor-args "-ar 44100"

# download a specific combination of audio and video in a single file
youtube-dl -F <url> # detect desired format codes
youtube-dl --merge-output-format mkv -f <code1>+<code2> <url>

Source: youtube-dl hp, stackoverflow.com, askubuntu.com

Table of contents:

1. Update raspbian linux to latest version
2. Change password, hostname, full xdm greeter
3. Configure a static IP address
4. Tune kernel settings
5. Tune video settings
6. Tune audio settings
7. Tune wifi settings
8. Remove tv black borders
9. Fix slow usb mouse
10. Reduce power consumption
11. Extend lifespan of mechanical HDD
12. Extend lifespan of sdcard
13. Extend your RAM by enabling ZRAM
14. Setup a NAS (via NFS)
15. Setup a remote desktop (via VNC)
16. Setup a shared printer
17. Setup the firewall
18. SSH access and tunnels
19. Dedicated posts:
    • Source a common bashrc for your users
    • Setup VeraCrypt volume manager
    • Setup Deluge torrent manager
    • Setup a DLNA media server
    • Setup Kodi media center
    • Setup a shared scanner
    • Setup an UPS monitor
    • Setup dnsmasq DNS server
    • Setup a freeDNS account
    • Setup a WebDav fileserver
    • Setup fail2ban to protect services
    • Setup a VPN to protect your privacy
    • Setup monitoring with Munin
    • Setup a good Screen config
    • Setup RetroPie
20. Tools
21. Backup
22. Miscellanea

Update raspbian linux to latest version:

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apt-get update
apt-get upgrade
apt-get dist-upgrade
apt-get clean
apt-get autoremove
rpi-update # update firmware & kernel

apt-get purge bash-completion     # speed up shell TAB-auto completion

# --- os version update, eg: from jessie (deb8) to stretch (deb9)
sed -i 's/jessie/stretch/g' /etc/apt/sources.list
sed -i 's/jessie/stretch/g' /etc/apt/sources.list.d/raspi.list
# repeat the commands above, then check the current version:
cat /etc/os-release

Debian 10 upgrade: see rpi blog post notes and comments.

Change password, hostname, full xdm greeter:

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sudo raspi-config # Change User Password; Hostname

# choose lightdm-gtk-greeter
sudo update-alternatives --config lightdm-greeter

Configure a static IP address (see also this and fallback method):

append the desired following blocks to /etc/dhcpcd.conf:

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interface eth0
fallback mylan

SSID my_wifi_ssid
fallback mylan

interface wlan0
fallback mylan

profile mylan
static ip_address=192.168.1.110/24
static routers=192.168.1.1
static domain_name_servers=84.200.69.80 37.235.1.174 84.200.70.40 37.235.1.177

Note: Do not use the directive inform 192.168.1.110 because it breaks the UPS monitor.

Optional do not wait for network at boot: run raspi-config and select Boot > Wait for Network at Boot > No.

Tune kernel settings

• Disable IPv6: append ipv6.disable=1 to kernel parameters in /boot/cmdline.txt or:

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# via sysctl:
echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.d/local.conf
# via modprobe:
echo "blacklist ipv6" >> /etc/modprobe.d/local.conf

• Set autoreboot on kernel panic: append panic=5 to kernel parameters in /boot/cmdline.txt or via sysctl:

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echo "kernel.panic = 5" >> /etc/sysctl.d/local.conf

• better/visible boot messages: append consoleblank=0 plymouth.enable=0 to kernel parameters in /boot/cmdline.txt

• Remove tv black borders: set disable_overscan=1 in the /boot/config.txt.

• Fix slow usb mouse: append usbhid.mousepoll=0 to kernel parameters in /boot/cmdline.txt.

Tune video settings

Run raspi-config and in the Advanced Options section, if using a raspberry pi 4 then enable both the GL driver and the Compositor otherwise turn them off.

• Note: to ensure the loading of Pi4's VC4/GL driver make sure to uninstall Xorg frame buffer drivers:

  1 2	apt install xserver-xorg-video-vesa apt purge xserver-xorg-video-fbdev xserver-xorg-video-fbturbo

• Fix HDMI no signal

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# /boot/config.txt
hdmi_force_hotplug=1
config_hdmi_boost=6

• Fix Pi4's DRM mem error:

  1	DRM_IOCTL_MODE_CREATE_DUMB failed: Cannot allocate memory

  If you see the above error then use these /boot/config.txt settings:

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  # force HD, and prevent 4K memory drain (optional) hdmi_group=1 hdmi_mode=16 [hdmi:0] hdmi_max_pixel_freq=200000000 [hdmi:1] hdmi_max_pixel_freq=200000000 [pi4] # Enable DRM VC4 V3D driver on top of the dispmanx display stack (default driver) dtoverlay=vc4-fkms-v3d # number of active displays 1-2 max_framebuffers=1 # disable any memory split #gpu_mem=256

  and append cma=384M to /boot/cmdline.txt.

Tune audio settings

• fix robotic/metallic audio

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# add tsched=0 in /etc/pulse/default.pa on this line:
load-module module-udev-detect tsched=0

• disable microphone auto adjust (src1, src2, src3):

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cd /usr/share/pulseaudio/alsa-mixer/paths
tar -czvf ../paths.tgz .  # backup
perl -pi -0 -e 's/(\[[A-Za-z ]*(Mic Boost|Capture)\][A-Za-z._=\s-]+volume *= *)merge/\1zero/g;' *mic*.conf
shutdown -r 0

Tune wifi settings

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# disable roaming
echo "options brcmfmac roamoff=1" >> /etc/modprobe.d/local.conf

# set correct regional domain
sed -i 's/REGDOMAIN=.*/REGDOMAIN=IT/' /etc/default/crda

# auto turn off power management
cd /etc/network/if-up.d/
echo -e '#!/bin/bash\n/sbin/iw dev wlan0 set power_save off' > local-wlan
chmod 755 local-wlan
# find an optimal MTU size via:
#   ping -c 2 -M do -s 1600 www.google.com
# then save it with:
echo "/sbin/ip link set dev wlan0 mtu 1400" >> local-wlan

Turn off bluetooth if unused, see this section.

Reduce power consumption:

put in /etc/rc.local:

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# turn off leds multiple times
(for i in 1 2 3 4 5; do
  for i in /sys/class/leds/led?; do
    echo none > $i/trigger
    echo 0    > $i/brightness
  done
  sleep 60
done) &

# disable HDMI output (and set boot to console via raspi-config)
/usr/bin/tvservice -o # -p to re-enable

set boot to console and reduce memory split:

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raspi-config # Boot Options > Desktop / CLI > Console
raspi-config # Advanced Options > Memory Split > 16

turn off unsued wlan/bluetooth (see /boot/overlays/README), put in /boot/config.txt:

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dtoverlay=pi3-disable-wifi
dtoverlay=pi3-disable-bt

and turn off the bluetooth services:

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systemctl disable hciuart
systemctl disable bluetooth

Extend lifespan of mechanical HDD:

put in /etc/hdparm.conf:

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/dev/sda {
  write_cache = on
  # -B -- disable Advanced Power Management
  apm = 254
  # -S -- 1h timeout
  spindown_time = 242
}

Extend lifespan of sdcard:

install my tmpfs-folders script and add a custom periodic cleaning of /var/log files in root crontab:

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#  m   h   dom   mon   dow   command
   0   0     *     *     3   /opt/systemd-units/clear_var_log.sh > /dev/null 2> /dev/null

Extend your RAM by enabling ZRAM (compressed RAM):

put in /etc/rc.local:

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if modprobe zram num_devices=1 ; then
  echo lz4  > /sys/block/zram0/comp_algorithm
  echo 384M > /sys/block/zram0/mem_limit
  echo 768M > /sys/block/zram0/disksize

  mkswap /dev/zram0
  swapon -p 10 /dev/zram0

  sysctl vm.swappiness=90
fi

and optionally disable dphys-swapfile swapfile service:

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systemctl disable dphys-swapfile

Setup a NAS (via NFS):

Server side commands:

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apt-get install nfs-kernel-server

systemctl enable rpcbind # it's disabled by default...
systemctl restart nfs-kernel-server

# add a share to /etc/exports
echo "/path 192.168.1.0/24(rw,sync,no_subtree_check,all_squash,anonuid=1001,anongid=1001)" >> /etc/exports

exportfs -ra # reload server

and append these lines to /ect/rc.local:

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# fix: nfs server doesn't start without rpcbind
systemctl start   rpcbind
systemctl restart nfs-kernel-server

Client side commands:

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echo "192.168.1.110:/path /mnt/path nfs defaults,user,exec 0 0" >> /etc/fstab
mount /mnt/path

Setup a remote desktop (via VNC):

You have three options:

1. Install the modern TigerVNC server, see the dedicated post
2. Use the lightdm TigerVNC service by enabling it in /etc/lightdm/lightdm.conf

3. Install the old TightVNC:

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   apt-get install tightvncserver # set a password and run a LQ server on display 1: vncpasswd vncserver -geometry 1024x768 -depth 8 :1 vncviewer server_ip:1 # connect from another host

Setup a shared printer:

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apt-get install cups
apt-get install hplip # HP printers drivers
hp-setup -i # install printer + dl drivers

elinks http://localhost:631
# Administration > Printers > Add printer
# Server settings > Share printers connected to this system

then turn the printer off and on again.

On Android you can install these apps: Let's print Droid, and Let's Print PDF.

Setup the firewall:

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apt-get install ufw

ufw reset # reset to defaults

ufw default deny  incoming
ufw default allow outgoing

ufw allow from 192.168.1.0/24 # your intranet
ufw allow from x.x.x.x        # a trusted IP
ufw limit 22/tcp              # max 6 new connections every 30 seconds
ufw limit 2200:2230/udp       # mosh port range
ufw allow 1810:1820/tcp       # bittorent - data
ufw allow 1810:1820/udp
ufw allow 6881:6891/tcp       # bittorent - tracker
ufw allow 6881:6891/udp
ufw allow 6771/udp            # bittorent - local peer discovery

ufw enable

SSH access and tunnels:

Here is an example for creating some simple forward tunnels while connecting to a remote server:

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# deluge thin client & web ui, vnc, nginx
ssh \
  -L 58846:localhost:58846 \
  -L 8112:localhost:8112   \
  -L 5901:localhost:5901   \
  -L 1234:localhost:1234   \
  user@server_addr

There are some great SSH clients as PuTTY for windows/linux and juiceSSH on Android.

Use mosh (even with juiceSSH!) to reliably connect from unstable or high latency networks:

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apt-get install mosh               # run this both on client and server
mosh -p 2200:2230 user@server_addr # connect to opened UDP ports on server

Read the dedicated post for an advanced tunnel usage.

Read the dedicated post to setup a SOCKS proxy with SSH.

Note: if sshd is slow to start at boot (systemd-analyze blame) then install haveged to have more entropy.

Dedicated posts:

• Source a common bashrc for your users
• Setup VeraCrypt volume manager
• Setup Deluge torrent manager
• Setup a DLNA media server
• Setup Kodi media center
• Setup a shared scanner
• Setup an UPS monitor
• Setup dnsmasq DNS server
• Setup a freeDNS account
• Setup a WebDav fileserver
• Setup fail2ban to protect services
• Setup a VPN to protect your privacy
• Setup monitoring with Munin
• Setup a good Screen config
• Setup RetroPie

Tools:

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apt-get install rpi-chromium-mods # video acceleration on google chrome
apt-get install remmina           # very handy VNC/SSH GUI
apt-get install omxplayer         # accelerated cli media player

• Fast/light web browsers:

  • kweb - raspberry pi's custom webkit build with omxplayer support
  • vivaldi - opera like browser
  • midori

• OMXplayer GUIs:

  • gomx -- light Python+Tk via python-omxplayer-wrapper

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  sudo apt install libdbus-1-dev libglib2.0-dev pip install omxplayer-wrapper wget -O ~/bin/gomx https://github.com/vladcc/gomx/raw/master/gomx/gomx.py chmod 755 ~/bin/gomx sed -i 's/^PL_WIN_PAD = .*/PL_WIN_PAD = 0/' ~/bin/gomx # adjust padding

  • tboplayer -- via pyomxplayer + youtube-dl + lyrics

• raspi-keygen -- Patch for MPEG-2, VC-1 license (untested, use it at your own risk)

  1 2	cd /boot && cp start.elf start.elf_backup && \ perl -pne 's/\x47\xE9362H\x3C\x18/\x47\xE9362H\x3C\x1F/g' < start.elf_backup > start.elf

Backup:

You can do a full/raw sdcard backup, a live/tar one, or an incremental one.

As an alternative to 7za you can use xz just like the gz command (or use the -J option of tar).

Incremental backup commands

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# --- backup ----------------------------------------
cd /tmp && mkdir -p p1 p2
sudo mount -o ro /dev/sdc1 p1
sudo mount -o ro /dev/sdc2 p2

cd bkup-folder
sudo sfdisk -d /dev/sdc > ptable
mkdir -p p1 p2
sudo ribs -b --no-p p1 /tmp/p1
sudo ribs -b        p2 /tmp/p2

sudo umount /tmp/p?


# --- restore ---------------------------------------
cd bkup-folder

cd /tmp && mkdir -p p1 p2
sfdisk /dev/sdc < ptable
mkfs.vfat /dev/sdc1
mkfs.ext4 /dev/sdc2
sudo mount /dev/sdc1 p1
sudo mount /dev/sdc2 p2

sudo ribs -r p1 /tmp/p1
sudo ribs -r p2 /tmp/p2

cat ptable | grep label-id   # view old partition ID

# change to the new partition ID
sfdisk -d /dev/sdc | grep label-id
# update PARTUUID in p1/cmdline.txt 
# update PARTUUID in p2/etc/fstab

sudo umount /tmp/p?

Miscellanea:

• Fix TV/monitor not detected unless powered on first:

  1	sudo tvservice -d /boot/edid.dat

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  # /boot/config.txt hdmi_edid_file=1 hdmi_force_hotplug=1

• Test if we are on a raspberry (/sys, /proc/cpuinfo):

  1 2	cat /sys/firmware/devicetree/base/model # Raspberry Pi 3 Model B Rev 1.2 grep Hardware /proc/cpuinfo # Hardware : BCM2708

• To save space on new installs of ruby gems, put in ~/.gemrc:

  1 2	install: --no-rdoc --no-ri -​-no-document update: --no-rdoc --no-ri -​-no-document

  and to install a gem in the user $HOME use this command:

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  gem install --user-install bundler # remember to update your PATH adding this line to ~/.bashrc export PATH=$HOME/.gem/ruby/2.1.0/bin:$PATH

• If you have a logitech wireless keyboard (eg: K400+) then you can use solaar to query and configure it:

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  git clone https://github.com/pwr/Solaar.git cd Solaar/bin solaar show all solaar show 1 | grep Battery solaar config 1 fn-swap off # toggle function keys

• If you have a keyboard without the F# keys (like the kano keybord) you can emulate them with xdotool and then run it via xbindkeys:

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  sudo apt-get install xdotool xbindkeys xbindkeys-config xdotool key ctrl+alt+F1 # emulate these key press xbindkeys-config # create and save your bindings xbindkeys # run daemon

  or you can use xmodmap to remap existing keys:

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  xmodmap -pke | tee ~/.Xmodmap > ~/.Xmodmap-orig nano ~/.Xmodmap # edit keys xmodmap ~/.Xmodmap # load changes (run this on X startup)

  see Xorg keyboard references on the bottom.

• Autostart programs when loggin in LXDE: put your commands prefixed by @ in ~/.config/lxsession/LXDE-pi/autostart

• Change video mode/resolution without rebooting -- see rpi forum post

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# query available video modes
tvservice -m CEA
#Group CEA has 16 modes:
#           mode  4: 1280x720  @ 60Hz 16:9, clock:74MHz progressive 
#           mode 19: 1280x720  @ 50Hz 16:9, clock:74MHz progressive 
#  (prefer) mode 16: 1920x1080 @ 60Hz 16:9, clock:148MHz progressive 

# set custom video mode
tvservice -e "CEA 4 HDMI"
#fbset -depth 8 ; fbset -depth 16
fbset -g 1280 720 1280 720 16
xrefresh

# set default video mode
tvservice -p

• Android/LineageOS: images by Konsta, forum

• Zoom: arm port request, forum

Notes:

• Raspberry Pi 3 provides 1.2A USB current by default (no need to set max_usb_current=1 in /boot/config.txt). Of course a 2.5A PSU is mandatory.

Tips:

• SenseHAT: blog post
• hplayer (mplayer)
• SSHfs
• read-only sdcard: adafruits post from raspi post

Sources:

• power consumption: pidramble, jeffgeerling
• ZRAM: kernel, raspberry pi 3 gist, with-raspberrypi blog, stoned.io
• NFS server in Raspbian: can't connect
• Reduce SDcard wearing: stackexchange post e ramlog pkg
• Xorg keyboard: keysym list, xmodmap tutorials by xahlee and archlinux wiki
• upgrade raspbian8 to 9
• Fix wifi poor performance + turn power management off + optimize

TODO

• https://www.toptal.com/ruby-on-rails/rails-6-features
• https://bogdanvlviv.com/posts/ruby/rails/what-is-new-in-rails-6_0.html
• https://medium.com/rubyinside/whats-coming-to-rails-6-0-8ec79eea66da
• https://prograils.com/posts/new-features-rails-6-multiple-databases-parallel-tests-action-mailbox-etc
• https://matthewhoelter.com/2018/09/18/deploying-ruby-on-rails-for-ubuntu-1804.html
• https://github.com/wg/wrk
• -----
• cleanup fish/fisher
• install: rvm + function, nvm + function, node, yarn
• rails new rails6test
• -----
• testing howto
• news in JS?
• multi threading notes

• News { ActiveRecord | ActionView | ActiveJob | ActionCable | Frontend | Email | ActiveStorage | Security | Core | Devel | Tools&Gems | Testing | Info }

• Altro { Upgrade Exp. | References | Tools | Bench. | Books }

New in rails (till 2019-07-06)

⇑ ActiveRecord

• ActiveRecord::Relation#pick => .limit(1).pluck(*column_names).first
• Model errors as objects @ Rails >= 6.1
• ActiveRecord store wrapper around serialize to easily manage a hash value with attribute/keys methods accessors -- api, PR for dirty methods
• Model.optimizer_hints PR and Model.annotate PR
• leaverage DB unique constraints:
  • ActiveRecord's insert_all and upsert_all bulk insert/update methods leaveraging DB unique constraints -- PR, post
  • ActiveRecord#create_or_find_by -- relies on unique constrains, PR
• ActiveRecord's reselect, rewhere, reorder
• ActiveRecord enum attribute (int value by name) -- api
• Item.where(price: 10..) -- endless ranges in where conditions
• ActiveRecord::Base.verbose_query_logs = true: show the query source code line number
• multi-db support: suggestions, rake tasks per db, replica option/ro db
  • migrations path: PR1, PR2 -- define migrations_paths in database.yml
  • eileen slides
  • connects_to, connected_to switch DB connection PR; connected_to? check role and connection
  • rails db:schema:cache:dump, rails db:schema:cache:clear -- PR
  • fix query cache for multiple connections PR
  • Model.while_blocking_writes{} blocks/deny DB writes
• Change SQLite 3 boolean serialization from t/f to use 1/0 => migrate old data in DB
• Model#delegate_missing_to -- PR
• belongs_to new :default option -- es: belongs_to :person, default: -> {​ Person.current }
• ActiveRecord changes in callbacks: PR and reference table
• find_each{|r| ... } shortcut to find_in_batches{|b| b.each{|r| ... } }
  • also supports limit: Post.limit(10_000).find_each{​|p| ... }​
• DB comments
• db:migrate creates development and test databases
• migrations: sql expr as default value, es: t.datetime :published_at, default: -> { 'NOW()' }
• models derive from ApplicationRecord instead of ActiveRecord::Base
• ActiveRecord OR support, es: Post.where('id = 1').or(Post.where('id = 2'))
• after commit shortcuts:
  • ActiveRecord new callback after_save_commit = after_commit :hook, on: [ :create, :update ] -- PR
  • after_commit .. on: xxx shortcuts: after_xxx_commit -- xxx=create/update/destroy
• ActiveRecord Model.left_outer_joins support
• foreign keys now supported in create_table DSL
• Active Record ignored_columns -- no accessor methods and no show in queries
• multi context validations -- es: record.valid?(:ctx_name)
• People.in_batches(of: 100){|rel| rel.where... } -- vedi ActiveRecord::Relation#in_batches
• ActiveRecord.suppress -- silently disable record save in block (es: Model.suppress{...})
• Attributes API: define attr with a Proc, see commit (no more serialize misuse)
• DB connection pool explained here -- sqlite has no pool
  • Set database poolsize via RAILS_MAX_THREADS env
  • ActiveRecord::Base.connection_pool.stat -- status info hash
• find_in_batches got an end_at option
• active_record.warn_on_records_fetched_greater_than -- info

⇑ ActionView

• ActionText: rich text editor integrated with ActiveRecord and ActiveStorage (images/attachments)!! -- guide, intro
• ActionView helper current_page?
• form_with = form_for + form_tag: article, PR1, PR2
• new tag helpers -- es: tag.div(...)
• better controller's helpers proxy to use user defined helpers
• ActionController::Parameters#dig come per Hash#dig
• ActionDispatch Rails.application.reloader.wrap{} callback
• Per-form CSRF tokens -- config.per_form_csrf_tokens_enabled = false/true
• protect_from_forgery doen't run first anymore, it is simply queued as the other callbacks, use option prepend: true to set it as the first callback
  • NB: request_forgery_protection initializer removed from Rails --api because usually not needed
• controller/model's strong parameters
• controller actions default to head :ok if no template exists
• helpers div_for and content_tag_for will be gone in Rails 5 => recordtaghelper gem
• introduced the #{partial_name}_iteration local variable in partials rendered with a collection
• live streaming for persistent connections
• caching/faster rendering:
  • template dependencies with wildcard support
  • strong ETag -- Response#strong_etag=, weak_etag=, fresh_when, stale?
  • views cache control -- es: fresh_when
  • declarative etags

⇑ ActiveJob / background jobs

• ActiveJob -- interface for existing queuing systems
• vedi anche: ActionMailer#deliver_later, GlobalID
• retry_job, retry_on and discard_on catch multiple exceptions
• ActiveJob priority support
• config.active_job.queue_adapter = :async -- run jobs in threads a la sucker_punch
• queue_name_prefix -- PR

⇑ ActionCable / websockets

• ActionCable channel_prefix in your cable.yml
• ActionCable -- websockets: live features, chat, notifications | via redis or postgres
  • see ActionController::Renderer to render views, and use puma as a separate process in production

⇑ Frontend

• webpack integration: PR1, PR2 (make default), hp
• yarn javascript package manager used by default -- PR1, PR2, folders
• removed jQuery; vanilla UJS -- guide, jquery-rails, jquery-ujs
• turbolinks:
  • turbolinks 5 and 📺 railsconf video
  • moved to a separate repo
  • data-turbolinks-track="true" moved to data-turbolinks-track="reload"
• Sprockets gzip files
• Sprockets 4 upgrade -- source maps, manifest.js, ES6 support

⇑ Email

• ActionMailbox to process incoming emails -- guide
• Action Mailer Preprocessing -- eg: InvitationMailer.with(invitee: person).account_invitation.deliver_later, see also
• email previews
• ActionMailer rescue_from come nel controller

⇑ ActiveStorage / upload to cloud -- guide

• ActiveStorage/ActiveJob Mirror direct uploads
• include blob via Model.with_attached_columnname -- avoids N+1 query
• video/pdf preview
• custom previewers
• config.active_storage.routes_prefix = '/files' custom route prefix

⇑ Security & Paranoia

• MessageEncryptor -- enc/dec strings
• logger/inspect's per model attributes filter -- es: Model.filter_attributes = [:iban, :cf]
• config.action_dispatch.use_cookies_with_metadata = true -- Add Purpose/Name Metadata to Cookies to enhance security
• ActiveRecord.has_secure_password: you can specify the attribute name
• app-wide config.force_ssl deprecates ActionController#force_ssl
• new default headers X-Download-Options: noopen and X-Permitted-Cross-Domain-Policies: none
• Content-Security-Policy header DSL, moz ref -- disabled by default in 5.2
• credentials storage PR, guide -- rails credentials:edit
  • multi env support: config/credentials/production.yml.enc takes precedence over config/credentials.yml.enc, use rails credentials:edit --environment staging to edit specific file
  • secrets PR, guide -- eg: rails secrets:edit, rails secrets:show
• secure cookies server side enforced expire time -- es: cookies.signed[:user_name] = { value: "bob", expires: 2.hours }
• SSL exclude option: config.ssl_options = { redirect: { exclude: -> request { request.path !~ /healthcheck/ } } }
• Active Support's way to write to a file atomically (thread safe) with File.atomic_write

⇑ Core/config changes

• new Zeitwerk library loader: blog post, HP
• HTTP early hints/preloading
  • preload_link_tag helper: preload + http2 early hints
  • HTTP2 early hints, PR
• bootsnap installed by default -- TODO: crontab for periodic clean of tmp/cache
• routes: Custom url helpers and polymorphic mapping
• monkey patching is the past:
  • use ruby refinements instead of monkey patching
  • Deprecate alias_method_chain in favor of Module#prepend -- howto
• rails API mode: hp
• rake xxx:yyy tasks proxied by rails xxx:yyy
• config serve_static_files moved to public_file_server.enabled

⇑ Development

• rails console --sandbox don't write changes to DB -- PR+cfg
• byebug > 8.2.1 is faster
• faster dev reload: set in Gemfile group :development{gem 'listen', '~> 3.0.4'}

⇑ Tools / External gems

• Router Visualizer: PR, sample -- install graphviz dot command, run Rails.application.routes.router.visualizer and save the string to an html file
• ActiveRecord XML serialization moved in a gem
• Rails-observers -- separa le callbacks dai models/controllers
• ActiveResource -- consume json via rest

⇑ Testing

• Capybara Integration with Rails (AKA System Tests) -- with selenium and chrome, guide, parallel tests

⇑ Info / Minor changes / Good to know

• Array#extract! -- removes and returns the elements for which the block returns a true value (come select ma modifica la variabile)
• execjs: mini_racer replaces therubyracer
• rails notes custom tags -- PR
• rails notes task -- shows search code for FIXME/OPTIMIZE/TODO
• 📺 Rails 5 video tour by DHH on youtube
• rails new adds a default config/puma.rb
• String#parameterize per creare id ai titoli dei blog posts
• Array#inquiry.any?(:xxx) -- finds symbols and strings matching xxx
• locale yaml files auto-reloaded in development
• date and time:
  • DateTime.now.prev_occurring(:monday) -- PR
  • Date/Time #on_weekend? and #on_weekday? :D
  • Time vs DateTime -- commit
• Enumerable#pluck

⇑ Upgrade experiences -- google search

• kickstarter
• github
• ombulabs

⇑ References

• what's new: https://medium.com/rubyinside/whats-coming-to-rails-6-0-8ec79eea66da
• https://bogdanvlviv.com/posts/ruby/rails/what-is-new-in-rails-6_0.html
• -------------
• https://weblog.rubyonrails.org
• https://guides.rubyonrails.org/upgrading_ruby_on_rails.html
• https://edgeguides.rubyonrails.org/6_0_release_notes.html
• https://guides.rubyonrails.org/5_2_release_notes.html
• https://guides.rubyonrails.org/5_1_release_notes.html
• https://guides.rubyonrails.org/5_0_release_notes.html
• https://guides.rubyonrails.org/4_2_release_notes.html
• https://guides.rubyonrails.org

⇑ Tools

• scaling ruby apps
• 📺 DHH youtube videos on writing sw well
• MiniMagick
• ruby's set: a collection of unordered values with no duplicates
• obj.method(:method_name).source_location => mostra dov'e' definito il metodo
• <<~TAG ... TAG al poso di <<-TAG...TAG rimuove gli spazi di indentazione!
• thor -- build powerful command-line interfaces

⇑ Benchmark howto

docs, ips extension, article

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require 'benchmark'

a = [:a, :b]
b = :b
n = 10000000
Benchmark.bm do |x|
  x.report { n.times do !(Array(a) & Array(b)).empty? end }
  x.report { n.times do Array(a).include?(b) end }
end

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require 'benchmark/ips' # instructions per second
require 'uri'

uri = 'http://example.com/foos_json?foo=heyo'

Benchmark.ips do |x|
  x.report('URI.parse') { URI.parse(uri) }
end

vedi esempi di barnchmark in Hash#deep_merge PR

• StackProf hp, article

⇑ Books

• rails6 (beta)
• rails5 test