node-pre-gyp ERR! build error | yarn install | Rails | Mac – Mojave

I encountered a series of errors when I tried to run my existing Rails5 app in my freshly installed macOS Mojave.

$ bundle exec rails s

this generated some errors like, node not found, then I installed node using brew.

$ brew install node


$ npm install yarn
$ yarn install 
gyp ERR! build error
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack     at ChildProcess.onExit (/Users/john/projects/sifaris/node_modules/node-gyp/lib/build.js:262:23)
gyp ERR! stack     at ChildProcess.emit (events.js:196:13)
gyp ERR! stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:256:12)
gyp ERR! System Darwin 18.5.0
gyp ERR! command "/usr/local/Cellar/node/12.1.0/bin/node" "/Users/john/projects/sifaris/node_modules/node-gyp/bin/node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsass_library="
gyp ERR! cwd /Users/john/projects/sifaris/node_modules/node-sass
gyp ERR! node -v v12.1.0
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok
$ bundle exec rails s
=> Booting Puma
=> Rails 5.2.3 application starting in development
=> Run `rails server -h` for more startup options
error Lockfile does not contain pattern: "yarn@^1.15.2"
error Couldn't find an integrity file
error Found 2 errors.

  Your Yarn packages are out of date!
  Please run `yarn install --check-files` to update.


$ rm yarn.lock
$ yarn cache clean
$ yarn install
$ yarn install v1.15.2

now it installs all the dependencies properly

bundle exec rails s
=> Booting Puma
=> Rails 5.2.3 application starting in development
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 3.12.1 (ruby 2.6.0-p0), codename: Llamas in Pajamas
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://localhost:3000
Use Ctrl-C to stop
yarn install v1.15.2

Rails : PaperTrail gem : Custom events to track fields changed

In my project, I was asked to keep track of changes in records. I found PaperTrails gem, and its found to be pretty useful.

But it lacks a straightforward feature to know the fields changed in that particular version. Then I thought to write custom event name so that I could grep the field_name I wish to check.

# == Schema Information
# Table name: tasks
#  id                :integer          not null, primary key
#  worker_id         :integer
#  customer_id       :integer
#  kind              :integer          default(0)
#  status            :integer          default(0)
#  note              :text
#  start_on          :datetime
#  complete_on       :datetime
#  started_on        :datetime
#  completed_on      :datetime
#  created_at        :datetime         not null
#  updated_at        :datetime         not null
#  driver_acceptance :integer          default(0)
#  refuel_id         :integer
#  shift_id          :integer

class Task < ActiveRecord::Base
  include Timeable
  # Update event-name on update
  before_save :paper_trail_events, on: :update

  enum status: { scheduled: 0, started: 1, skipped: 2, completed: 3, paused: 4, rescheduled: 5 }
  enum kind: { inter_location: 0, refuel: 1, break: 2 }
  enum driver_acceptance: { pending: 0, accepted: 1, rejected: 2, sent: 3 }


    def paper_trail_events
      changed_fields         = self.changes.keys - ['created_at', 'updated_at']
      self.paper_trail_event = "Updated #{changed_fields.join(',')}"

In Rails Console

> Task.find(1768) &:event
=> ["Updated start_on,complete_on,status", "Updated worker_id"]


Rails | Avoiding race conditions while updating particular field in DB

It’s okay to make mistakes when you are up to building simple applications. But for mission critical applications like Banking/Payment Processors, you gotta be very careful and keep listening to seniors and experts in critical matters.

Lets say you are working on a feature to update the total amount deposited in a particular account. Simple code will do like

# just after amount is debited from payee's account
def credit_receiver_account(debited_amount)
  update_attribute :total_amount, total + debited_amount

What’s wrong with the code above?

Continue reading