Every

Calculate even intervals for Process.send_after/3. Sometimes we need to have periodic tasks to be executed exactly at certain intervals, for example running a task every 15 minutes.

1. At the beginning of hour,
2. 15th minute,
3. 30th minute,
4. 45th minute.
5. etc.

So instead of doing it manually, it is better if it is automated.

Usage

Available functions:

• Every.minute/1
• Every.minutes/2
• Every.hour/1
• Every.hours/2
• Every.day/1

All functions accept an optional relative_to (DateTime or NaiveDateTime) parameter which can be used to fake the current moment in time. If it is not provided, the current time will be used.

Every.minute/1, Every.hour/1 and Every.day/1 only accept the optional relative_to parameter. They return the seconds left until the next minute/hour/day.

Every.minutes/2 and Every.hours/2 both accept an interval as first parameter and the optional relative_to as second parameter. They return the seconds until the the next interval.

Note: All functions return the difference in seconds!

How to use with periodic tasks

# Lets say we want to trigger our task every 5 minutes and current time is 12:02
# so next calls will be at 12:05, 12:10 ... 12:55 ...
Process.send_after(self(), :work, Every.minutes(5) * 1000)

# If we want to trigger every minute
Process.send_after(self(), :work, Every.minute() * 1000)

# If we want to trigger every hour
Process.send_after(self(), :work, Every.hour() * 1000)

# If we want to trigger every 2 hours
Process.send_after(self(), :work, Every.hours(2) * 1000)

# If we want to trigger every day
Process.send_after(self(), :work, Every.day() * 1000)

As you can see we multiply by 1000 because return value has only second resolution.

Installation

This library can be installed by adding every to the list of dependencies in your mix.exs:

def deps do
  [{:every, "~> 0.0.5"}]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/every.