I'm trying to display a count of impressions per day for the last 30 days in the specific users time zone. The trouble is that depending on the time zone, the counts are not always the same, and I'm having trouble reflecting that in a query.
For example, take two impressions that happen at 11:00pm in CDT (-5) on day one, and one impression that happens at 1:00am CDT. If you query using UTC (+0) you'll get all 3 impressions occurring on day two, instead of two the first day and one the second. Both CDT times land on the day two in UTC.
This is what I'm doing now, I know I must be missing something simple here:
start = 30.days.ago
finish = Time.now
# if the users time zone offset is less than 0 we need to make sure
# that we make it all the way to the newest data
if Time.now.in_time_zone(current_user.timezone) < 0
start += 1.day
finish += 1.day
end
(start.to_date...finish.to_date).map do |date|
# get the start of the day in the user's timezone in utc so we can properly
# query the database
day = date.to_time.in_time_zone(current_user.timezone).beginning_of_day.utc
[ (day.to_i * 1000), Impression.total_on(day) ]
end
Impressions model:
class Impression < ActiveRecord::Base
def self.total_on(day)
count(conditions: [ "created_at >= ? AND created_at < ?", day, day + 24.hours ])
end
end
I've been looking at other posts and it seems like I can let the database handle a lot of the heavy lifting for me, but I wasn't successful with using anything like AT TIME ZONE or INTERVAL.
What I have no seems really dirty, I know I must missing something obvious. Any help is appreciated.
Ok, with a little help from this awesome article I think I've figured it out. My problem stemmed from not knowing the difference between the system Ruby time methods and the time zone aware Rails methods. Once I set the correct time zone for the user using an around_filter like this I was able to use the built in Rails methods to simplify the code quite a bit:
# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
around_filter :set_time_zone
def set_time_zone
if logged_in?
Time.use_zone(current_user.time_zone) { yield }
else
yield
end
end
end
# app/controllers/charts_controller.rb
start = 30.days.ago
finish = Time.current
(start.to_date...finish.to_date).map do |date|
# Rails method that uses Time.zone set in application_controller.rb
# It's then converted to the proper time in utc
time = date.beginning_of_day.utc
[ (time.to_i * 1000), Impression.total_on(time) ]
end
# app/models/impression.rb
class Impression < ActiveRecord::Base
def self.total_on(time)
# time.tomorrow returns the time 24 hours after the instance time. so it stays UTC
count(conditions: [ "created_at >= ? AND created_at < ?", time, time.tomorrow ])
end
end
There might be some more that I can do, but I'm feeling much better about this now.
Presuming the around_filter correctly works and sets the Time.zone in the block, you should be able to refactor your query into this:
class Impression < ActiveRecord::Base
def self.days_ago(n, zone = Time.zone)
Impression.where("created_at >= ?", n.days.ago.in_time_zone(zone))
end
end
Related
currently I'm developing a system that manages work shifts.
The system contains an endpoint that returns the current shift based on server time. I created a query that works fine for regular shifts like 08:00 AM to 04:00 PM and so on but the challenge is when there is a dawn shift that starts at 10:00 PM until 06:00 AM from the other day.
My model contains the following fields:
name (String)
start_at (Time)
end_at (Time)
Ps.: I'm using Postgres as the database.
My code:
class Shift < ApplicationRecord
def self.current
current_time = Time.now()
current_time = current_time.change(year: 2000, month: 1, day: 1)
#current ||= Shift
.where('start_time <= ?', current_time)
.where('end_time >= ?', current_time)
.first()
end
end
Ps.: I guess, since I'm using the Time type in the database, I have to normalize the Time.now to use the 2000 - 01 - 01 date.
So, is there an easy/best way to do that?
Thanks for the help!
Interesting problem! So there's two cases: (1) a normal shift (where start_time <= end_time), and (2) a shift that overlaps midnight (where start_time > end_time).
You are already handling the first case by checking if the current time is between the start time and the end time.
I believe the second case can be handled by checking if the current time is either between the start time and midnight, or between midnight and the end time. Which translates to start_time <= ? OR end_time >= ?.
I haven't used Rails in a while, but I think you could do something like this:
#current ||= Shift
.where('start_time <= end_time')
.where('start_time <= ?', current_time)
.where('end_time >= ?', current_time)
.or(Shift
.where('start_time > end_time')
.or(Shift
.where('start_time <= ?', current_time)
.where('end_time >= ?', current_time)))
.first()
If you go with this, consider splitting the two cases into separate scopes, so you can write something more readable like this in this method:
#current ||= current_normal_shifts.or(current_dawn_shifts).first
You might be interested in the tod gem that provides a TimeOfDay class and a Shift class that takes two TimeOfDay objects to represent the start and end of the shift. It handles dawn shifts as expected.
An implementation might look like this:
require 'tod'
class Shift < ApplicationRecord
def self.current
find(&:current?)
end
def current?
schedule.include?(Tod::TimeOfDay(Time.now))
end
def schedule
Tod::Shift.new(Tod::TimeOfDay(start_time), Tod::TimeOfDay(end_time))
end
end
I am trying to find results from today onwards but also want to include the yesterdays plans if the time is between 12:00am-5:00am
Right now i have the following
def self.current
where(
"plan_date >= :today",
today: Date.current,
)
end
Is there a way i can know the time of the day based on the users timezone which am setting as bellow in the app controller and make sure that if its before 6:am the next day i want to include the previous days results as well.
def set_time_zone(&block)
if current_user
Time.use_zone(current_user.time_zone_name, &block)
else
yield
end
end
Try this:
def self.current
where(
"plan_date >= :today",
today: (Time.zone.now.in_time_zone(get_user_time_zone) - 6.hours).beginning_of_day,
)
end
...where get_user_time_zone returns the time zone for the user (E.G.: America/New_York). I'm using - 6.hours because you wanted it to be "before 6am" local time.
I have many User objects with created_at attribute e.g.
I get objects with #users = User.all
I want get the count of User objects with various ages from creation with
#users.size
for these date ranges:
yesterday
last week
last month
last year.
How can I do it?
I use mongoid.
You can write scopes for this:
class User
include Mongoid::Document
...
## Scopes for calculating relative users
scope :created_yesterday, lambda { where(:created_at.gte => (Time.now - 1.day)) }
scope :created_last_week, lambda { where(:created_at.gte => (Time.now - 1.week)) }
scope :created_last_month, lambda { where(:created_at.gte => (Time.now - 1.month)) }
scope :created_last_year, lambda { where(:created_at.gte => (Time.now - 1.year)) }
...
end
The reason we need to use a lambda here is that it delays the evaluation of the Time.now argument to when the scope is actually invoked. Without the lambda the time that would be used in the query logic would be the time that the class was first evaluated, not the scope itself.
Now we can get the counts, by simply calling:
User.created_yesterday.count
User.created_last_week.count
...
If you want the objects:
#users_created_yesterday = User.created_yesterday
You can use #users_created_yesterday in the views.
Update
Well with yesterday, if you mean time between, yesterday beginning of day 0:00 and yesterday end of day 23:59, you will have to take Time zones into consideration.
Fo example, in your application.rb, if you have written:
# Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
# Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
config.time_zone = 'Central Time (US & Canada)'
If you have use this, all the times fetched by activerecord queries will be converted to this time zone, Central Time (US & Canada). In the database, all the times will be stored in UTC and will be converted to the time zone on fetching from the database. If you have commented out this line, default will be UTC. You can get all the time zones using the rake task rake time:zones:all or only the US timezones using rake time:zones:us.
If you want the time zone specified in the application.rb, you need to use Time.zone.now, in the following code. If you use Time.now in the following code, you will get the time zone according to the time zone of your server machine.
class User
include Mongoid::Document
...
scope :created_between, lambda { |start_time, end_time| where(:created_at => (start_time...end_time)) }
class << self
## Class methods for calculating relative users
def created_yesterday
yesterday = Time.zone.now - 1.day
created_between(yesterday.beginning_of_day, yesterday.end_of_day)
end
def created_last_week
start_time = (Time.zone.now - 1.week).beginning_of_day
end_time = Time.zone.now
created_between(start_time, end_time)
end
def created_last_month
start_time = (Time.zone.now - 1.month).beginning_of_day
end_time = Time.zone.now
created_between(start_time, end_time)
end
def created_last_year
start_time = (Time.zone.now - 1.year).beginning_of_day
end_time = Time.zone.now
created_between(start_time, end_time)
end
end
..
..
end
So, you can write class methods and calculate start time and end time, supply it to the scope created_between, and you will be able to call them like User.created_yesterday, like we called before.
Credits: EdgeRails. Since it is Mongoid, I had to look up at Mongoid docs
I'm spec'ing a scope in a Rails 3.0 app as follows:
class DrawingList < ActiveRecord::Base
scope :active_drawings, where('start_date <= ? AND end_date >= ?', Date.today, Date.today)
end
In my spec, I want to do:
before do
#list = DrawingList.create #things that include begin and end dates
end
it "doesn't find an active drawing if they are out of range" do
pending "really need to figure out how to work timecop in the presence of scopes"
Timecop.travel(2.days)
puts Date.today.to_s
DrawingList.active_drawings.first.should be_nil
end
As you might imagine, the puts really shows that Date.today is two days hence. However, the scope is evaluated in a different context, so it uses the old "today". How does one get today evaluated in a context that Timecop can affect.
Thanks!
This is a really common mistake. As you've written in the date used by the scope is the date as it was when the code was loaded. Were you to run this in production where code is only reloaded if you restart the app (unlike development where it is reloaded on each request), you'd get the right results on the day you restarted the app, but the next day the results would be out by one day, the day after by 2 days etc.
The correct way of defining a scope like that is
scope :active_drawings, lambda { where('start_date <= ? AND end_date >= ?', Date.today, Date.today)}
The lambda ensures that those dates are evaluated each time the scope is used.
I have a noisy problems with UTC on my Rails project.
class ApplicationController < ActionController::Base
before_filter :set_timezone
def set_timezone
Time.zone = current_user.time_zone if current_user
end
Cool. I overrided the time zone.
And now, server' time zone is +3. User's time zone is +5. I hope that any requests to Time should get the User's time zone, but this code returns not expected values:
render :text => Time.zone.to_s + "<br/>" +
Time.now.to_s + "<br/>" +
Time.now.in_time_zone.to_s
RESULT:
(GMT+05:00) Tashkent
Thu Oct 20 19:41:11 +0300 2011
2011-10-20 21:41:11 +0500
Where does from +0300 offset comes??
To get the current time in the currently set timezone you can use
Time.zone.now
Your server' time zone is +3 and
Time.now.to_s is returning this
saha! Sorry, but I have not a 15 points of reputation to give you the level-up)).
Anyway thanks for your help.
I wrote a TimeUtil helper, an uses it for time correction. This is my current pseudo-code:
class RacesController < ApplicationController
def create
#race = Race.new(params[:race])
#race.correct_time_before_save #can be before_save
#race.save
end
class Race < ActiveRecord::Base
def correct_time_before_save
date = self.attributes["race_date"]
time = self.attributes["race_time"]
datetime = Time.local(date.year, date.month, date.day, time.hour, time.min, time.sec)
datetime_corrected = TimeUtil::override_offset(datetime)
self.race_date = datetime_corrected.to_date
self.race_time = datetime_corrected.to_time
end
# TimeUtil is uses for time correction. It should be very clear, please read description before using.
# It's for time correction, when server's and user's time zones are different.
# Example: User lives in Madrid where UTC +1 hour, Server had deployed in New York, UTC -5 hours.
# When user say: I want this race to be started in 10:00.
# Server received this request, and say: Okay man, I can do it!
# User expects to race that should be started in 10:00 (UTC +1hour) = 09:00 UTC+0
# Server will start the race in 10:00 (UTC -5 hour) = 15:00 UTC+0
#
# This module brings the workaround. All that you need is to make a preprocess for all incoming Time data from users.
# Check the methods descriptions for specific info.
#
# The Time formula is:
# UTC + offset = local_time
# or
# UTC = local_time - offset
#
module TimeUtil
# It returns the UTC+0 DateTime object, that computed from incoming parameter "datetime_arg".
# The offset data in "datetime_arg" is ignored - it replaces with Time.zone offset.
# Time.zone offset initialized in ApplicationController::set_timezone before-filter method.
#
def self.override_offset datetime_arg
Time.zone.parse(datetime_arg.strftime("%D %T")).utc
end
ActiveRecord getters adapted to user's time zones too. Time is stored in database (mysql) in "utc+0" format, and we want to get this time in current user's timezone format:
class Race < ActiveRecord::Base
def race_date
date = self.attributes["race_date"]
time = self.attributes["race_time"]
datetime = Time.utc(date.year, date.month, date.day, time.hour, time.min, time.sec).in_time_zone
datetime.to_date
end
def race_time
date = self.attributes["race_date"]
time = self.attributes["race_time"]
datetime = Time.utc(date.year, date.month, date.day, time.hour, time.min, time.sec).in_time_zone
datetime.to_time
end