Expeditor provides asynchronous execution and fault tolerance for Microservices
Expeditor is a Ruby library that provides asynchronous execution and fault tolerance for microservices.
It is inspired by Netflix/Hystrix.
Expeditor currently supports Ruby 2.1 and higher.
Add this line to your application's Gemfile:
gem 'expeditor'
And then execute:
$ bundle
Or install it yourself as:
$ gem install expeditor
command1 = Expeditor::Command.new do ... endcommand2 = Expeditor::Command.new do ... end
command1.start # non blocking command2.start # non blocking
command1.get # wait until command1 execution is finished and get the result command2.get # wait until command2 execution is finished and get the result
command1 = Expeditor::Command.new do ... endcommand2 = Expeditor::Command.new do ... end
command3 = Expeditor::Command.new(dependencies: [command1, command2]) do |val1, val2| ... end
command3.start # command1 and command2 are started concurrently, execution of command3 is wait until command1 and command2 are finished.
command = Expeditor::Command.new do # something that may be failed enduse fallback value if command is failed
command_with_fallback = command.set_fallback do |e| log(e) default_value end
command.start.get #=> error may be raised command_with_fallback.start.get #=> default_value if command is failed
If you set
falseto
Expeditor::Service#fallback_enabled, fallbacks do not occur. It is useful in test codes.
command = Expeditor::Command.new(timeout: 1) do ... endcommand.start command.get #=> Timeout::Error is raised if execution is timed out
command = Expeditor::Command.new do ... endthe option is completely same as retryable gem
command.start_with_retry( tries: 3, sleep: 1, on: [StandardError], )
Expeditor use concurrent-ruby's executors as thread pool.
require 'concurrent'service = Expeditor::Service.new( executor: Concurrent::ThreadPoolExecutor.new( min_threads: 0, max_threads: 5, max_queue: 100, ) )
command = Expeditor::Command.new(service: service) do ... end
service.status
=> #<:status:0x007fdeeeb18468>
service.reset_status! # reset status in the service </:status:0x007fdeeeb18468>
The circuit breaker needs a service metrics (success, failure, timeout, ...) to decide open the circuit or not. Expeditor's circuit breaker has a few configuration for how it collects service metrics and how it opens the circuit.
For service metrics, Expeditor collects them with the given time window. The metrics is gradually collected by breaking given time window into some peice of short time windows and resetting previous metrics when passing each short time window.
service = Expeditor::Service.new( threshold: 0.5, # If the failure rate is more than or equal to threshold, the circuit will be opened. sleep: 1, # If once the circuit is opened, the circuit is still open until sleep time seconds is passed even though failure rate is less than threshold. non_break_count: 20, # If the total count of metrics is not more than non_break_count, the circuit is not opened even though failure rate is more than threshold. period: 10, # Time window of collecting metrics (in seconds). )command = Expeditor::Command.new(service: service) do ... end
non_break_countis used to ignore requests to the service which is not frequentlly requested. Configure this value considering your estimated "requests per period to the service". For example, when
period = 10and
non_break_count = 20and the requests do not occur more than 20 per 10 seconds, the circuit never opens because Expeditor ignores that "small number of requests". If you don't ignore the failures in that case, set
non_break_countto smaller value than
20.
The default values are:
Use
current_threadoption of
#start, command executes synchronous on current thread.
command1 = Expeditor::Command.new do ... endcommand2 = Expeditor::Command.new do ... end
command1.start(current_thread: true) # blocking command2.start(current_thread: true) # blocking
command1.get command2.get
After checking out the repo, run
bin/setupto install dependencies. Then, run
bin/consolefor 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 releaseto create a git tag for the version, push git commits and tags, and push the
.gemfile to rubygems.org.
git checkout -b my-new-feature)
git commit -am 'Add some feature')
git push origin my-new-feature)