ActiveSwitch

ActiveSwitch stores last reported at timestamps in Redis so you can detect if cron style jobs are running at an expected interval.

Add this line to your application's Gemfile:

gem 'active_switch'

And then execute:

$ bundle

Or install it yourself as:

$ gem install active_switch

First, configure ActiveSwitch, for instance in a Rails initializer:

# config/initializers/active_switch.rb

# configure the Redis client
ActiveSwitch.redis = Redis.new

# expect the big batch job to run within past day
ActiveSwitch.register(:big_batch_job, 1.day)

# expect the weekly mailer to run within the past week
ActiveSwitch.register(:weekly_mailer, 1.week)

Attempting to register the same name more than once will raise an ActiveSwitch::AlreadyRegistered exception.

Alternatively, you can register in one call with a hash:

ActiveSwitch.register({
  big_batch_job: 1.day,
  weekly_mailer: 1.week
})

After your scheduled task or background job completes, you can report it complete:

ActiveSwitch.report(:weekly_mailer) # => true

Attempting to report on an unregistered name will raise an ActiveSwitch::UnknownName exception. This prevents dead code paths or typos of names.

Alternatively, you can provide .report a block to yield:

ActiveSwitch.report(:weekly_mailer) { 2 + 2 } # => 4

Statuses can be retrieved with .all, .active, or .inactive:

ActiveSwitch.report(:weekly_mailer)

# Returns hash of statuses with keys "big_batch_job" and "weekly_mailer"
#
#   {
#     "big_batch_job"=>#<ActiveSwitch::Status:0x007fbb9309e880 @name="big_batch_job", @last_reported_at=nil, @threshold_seconds=86400>},
#     "weekly_mailer"=>#<ActiveSwitch::Status:0x007fbb9309f990 @name="weekly_mailer", @last_reported_at=2017-12-03 23:02:42 -0800, @threshold_seconds=604800>}
#   }
ActiveSwitch.all

# Returns hash of statuses with key "weekly_mailer"
#
#   {
#     "weekly_mailer"=>#<ActiveSwitch::Status:0x007fbb9309f990 @name="weekly_mailer", @last_reported_at=2017-12-03 23:02:42 -0800, @threshold_seconds=604800>}
#   }
ActiveSwitch.active

# Returns hash of statuses with key "big_batch_job"
#
#   {
#     "big_batch_job"=>#<ActiveSwitch::Status:0x007fbb9309e880 @name="big_batch_job", @last_reported_at=nil, @threshold_seconds=86400>}
#   }
ActiveSwitch.inactive

Individual status may also be retrieved with .status

ActiveSwitch.status(:weekly_mailer)
# => <ActiveSwitch::Status:0x007fbb9309f990 @name="weekly_mailer", @last_reported_at=2017-12-03 23:02:42 -0800, @threshold_seconds=604800>

A status instance can be asked for its values:

status = ActiveSwitch.status(:weekly_mailer)
status.name #=> "weekly_mailer"
status.last_reported_at #=> 2017-12-03 23:02:42 -0800
status.threshold_seconds #=> 604800

It can also be checked if active or inactive:

status.active? #=> true
status.inactive? #=> false
status.state #=> "ACTIVE"

A status is considered active if it was last reported within its registered threshold seconds.

All data is stored in a single Redis hash to avoid n+1 roundtrip lookups to Redis when gathering all statuses. Care should be taken to avoid tracking too many switches to avoid overloading the hash. A maximum of about 1000 would be sane, and likely beyond typical use.

The hash is stored under the key active_switch_last_reported_ats and reflects the following format:

# Values are epoch seconds
{
  "weekly_mailer" => "1512371591",
  "big_batch_job" => "1512285202"
}

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/bemurphy/active_switch.

The gem is available as open source under the terms of the MIT License.