lita-timing

A small collection of utility classes that make it easier to work with time, recurring events and rate limits in lita.

Installation

Add this gem to your lita installation by including the following line in your Gemfile:

gem "lita-timing"

Usage

This gem is not a lita handler or plugin in its own right, but it is easily used by other lita plugins.

Rate Limits

lita comes with an "every" helper that executes a block of code at fixed intervals. However the interval is only stored in memory, which means long intervals will often be reset if the lita process restarts (like during a deploy).

For handlers that want to execute code at fixed intervals, the RateLimit class can be used in conjunction with the built in every() helper:

one_minute = 60
one_week = 60 + 60 + 24 + 7
every(one_minute) do
  RateLimit.new("interval-name", redis).once_every(one_week) do
    # weekly code in here
  end
end

Scheduled Timing

If you have code that should execute at a fixed time each day or week, Lita::Timing::Scheduled can be used in conjunction with the built-in every() helper.

For daily execution:

one_minute = 60
every(one_minute) do
  Lita::Timing::Scheduled.new("interval-name", redis).daily_at("11:00") do
    # daily code in here
  end
end

For daily execution on certain days:

one_minute = 60
every(one_minute) do
  Lita::Timing::Scheduled.new("interval-name", redis).daily_at("11:00", [:monday, :tuesday]) do
    # daily code in here
  end
end

For weekly execution:

one_minute = 60
every(one_minute) do
  Lita::Timing::Scheduled.new("interval-name", redis).weekly_at("11:00", :friday) do
    # weekly code in here
  end
end

All times should be specified in UTC.

Sliding Windows

Sometimes a handler wants to periodically execute a block of code with a start and end time, and ensure that every minute of the day is handled by one of the executions. The text-book use case is polling an external API for updates within a time range.

The SlidingWindow class can help. For best results, use it in conjunction with the built in every() helper.

Redis is used to persist the end of the last window that executed and ensure the block doesn't execute again until that window is passed.

window = SlidingWindow.new("my-sliding-window", redis)
every(one_minute) do
  window.advance(duration_minutes: 30) do |window_start, window_end|
    puts "#{window_start} -> #{window_end}"
  end
end

Call this as often as you like, and the block passed to advance() will only execute if it's been 30 minutes since the last time it executed.

TODO

• Add timezone support to Scheduled