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This guide assumes that you recently run brew upgrade postgresql and discovered to your dismay that you accidentally bumped from one major version to another: say 9.3.x to 9.4.x. Yes, that is a major version bump in PG land.

First let's check something.

brew info postgresql

The top of what gets printed as a result is the most important:

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# could not connect to server: No such file or directory
#  Is the server running locally and accepting
# connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

Just run this command on the terminal

rm /usr/local/var/postgres/postmaster.pid

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# add scope (with one or more attributes) for has_many relationships

# This is great for polyphomism when you want different models to be able to have subscriptions; so that you don't just attach only one model to subscriptions

# Reference: http://edgeguides.rubyonrails.org/association_basics.html#scopes-for-has-many

class Question < ActiveRecord::Base
  has_many :subscriptions, -> { where "type = 'Question'" }, :foreign_key => "subscribed_item_id"
end

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Background jobs in rails applications make our development lives easier.

We rely on them for a lot of things - common use cases include sending emails, push notifications, processing 3rd party API interactions, transactions and long-running requests that tie up server resources.

In a typical production app, there's a possibility of processing hundreds of jobs per second under normal circumstances and thousands depending on the number of users and campaign going on.

I've been using Resque for a while but recently made a switch to Sidekiq on a few apps. I initially wanted to write about the switch but I soon realized that the knowledge of introducing Sidekiq to a new project is important and the post became really long so I decided to split it. In this post, I'm going to show you how to use Sidekiq for your background jobs on a new rails app. And in part 2, I'll write about switching from an existing app on Resque to Sidekiq.

Why S

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I had a challenge with pushing to another heroku account from my command line...

These are the steps I took to fix the error (redacted) below:

 !  Your account xxx@gmail.com does not have access to xx-heroku-app.
 !
 !  SSH Key Fingerprint: xx:xx:xx...

fatal: Could not read from remote repository.

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I have multiple verstions of rails and ruby gems on my machine and I ran into the error below when I tried to run any rails command such as rails -v, rails new new_app, etc.

.../ruby/2.3.0/rubygems/specification.rb:2274:in `check_version_conflict': can't activate activesupport-5.1.0, already activated activesupport-5.0.1 (Gem::LoadError)

Here's how I fixed it.

The version conflict points to ActiveSupport so I ran the command below to check the different versions of activesupport on my machine:

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This is useful for when debugging your tests.

Option 1:

puts page.body

Option 2:

save_and_open_page

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Today I learnt about jq - "a lightweight and flexible command-line JSON processor".

One of the use cases is pretty-printing JSON response on the terminal.

It essentially makes JSON data more readable on your terminal. If you work with a lot of JSON data on your terminal, you need to install jq.

Before jq:

$ curl localhost:3001/api/food?q=hash+browns

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To access the rails console in a docker container, run:

docker-compose run web rails console

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You attempted to start up a server, only to be confronted with the following error:

Address already in use - bind(2) for "0.0.0.0" port 3000 (Errno::EADDRINUSE)

What do you do?

1. Figure out what service is using that address port.