staltz

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

---

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

---

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

andreicristianpetcu

An Ansible summary

Jon Warbrick, July 2014, V3.2 (for Ansible 1.7)

Configuration file

intro_configuration.html

First one found from of

josevalim

# You will need fswatch installed (available in homebrew and friends)
# The command below will run tests and wait until fswatch writes something.
# The --stale flag will only run stale entries, it requires Elixir v1.3.
fswatch lib/ test/ | mix test --stale --listen-on-stdin

kovetskiy

#!/bin/bash
###
### my-script — does one thing well
###
### Usage:
###   my-script <input> <output>
###
### Options:
###   <input>   Input file to read.
###   <output>  Output file to write. Use '-' for stdout.

pnc

Using OTP's observer (appmon replacement) remotely

$ ssh remote-host "epmd -names"
epmd: up and running on port 4369 with data:
name some_node at port 58769

Note the running on port for epmd itself and the port of the node you're interested in debugging. Reconnect to the remote host with these ports forwarded:

$ ssh -L 4369:localhost:4369 -L 58769:localhost:58769 remote-host

jadeallenx

When does terminate/2 get called in a gen_server?

This is what the [official documentation][1] says about the terminate/2 callback for a gen_server:

This function is called by a gen_server when it is about to terminate. It should be the opposite of Module:init/1 and do any necessary cleaning up. When it returns, the gen_server terminates with Reason. The return value is ignored.

Reason is a term denoting the stop reason and State is the internal state of the gen_server.

Reason depends on why the gen_server is terminating. If it is because another callback function has returned a stop tuple {stop,..}, Reason will have the value specified in that tuple. If it is due to a failure, Reason is the error reason.

aaronjensen

# ATTENTION: This is now supported in plug_cowboy as of 2.1.0:
# https://hexdocs.pm/plug_cowboy/Plug.Cowboy.Drainer.html

defmodule DrainStop do
  @moduledoc """
  DrainStop Attempts to gracefully shutdown an endpoint when a normal shutdown
  occurs. It first shuts down the acceptor, ensuring that no new requests can be
  made. It then waits for all pending requests to complete. If the timeout
  expires before this happens, it stops waiting, allowing the supervision tree
  to continue its shutdown order.

mmmries

Phoenix Nodes

First I created 3 droplets on digital ocean with 4-cores and 8GB of RAM. Login as root to each and run:

sysctl -w fs.file-max=12000500
sysctl -w fs.nr_open=20000500
ulimit -n 4000000
sysctl -w net.ipv4.tcp_mem='10000000 10000000 10000000'

bitwalker

defmodule Config do
  @moduledoc """
  This module handles fetching values from the config with some additional niceties
  """

  @doc """
  Fetches a value from the config, or from the environment if {:system, "VAR"}
  is provided.

  An optional default value can be provided if desired.