ZkRecipes

Installation

Add this line to your application's Gemfile:

gem "zk_recipes"

And then execute:

$ bundle

Or install it yourself as:

$ gem install zk_recipes

Usage

A cache that creates its own ZK client:

logger = Logger.new(STDERR)
cache = ZkRecipes::Cache.new(host: "my-host:1234", logger: logger, timeout: 10, zk_opts: { timeout: 5 }) do |z|
  z.register("/test/boom", "goat")
  z.register("/test/foo", 1) { |raw_value| raw_value.to_i * 2 }
end

puts cache["/test/boom"]
cache.close!

A cache that uses an existing ZK client:

logger = Logger.new(STDERR)
zk = ZK.new("my-host:1234", connect: false)
cache = ZkRecipes::Cache.new(logger: logger)
cache.register("/test/boom", "goat") { |string| "Hello, #{string}" }
cache.setup_callbacks(zk) # no more paths can be registered after this

puts cache["/test/boom"] # => "Hello, goat"

zk.connect
cache.wait_for_warm_cache(10) # wait up to 10s for the cache to warm

zk.create("/test/boom")
zk.set("/test/boom", "cat")

sleep 1

puts cache["/test/boom"] # => "Hello, cat"
cache.close!
zk.close!

Handling forks with a cache that creates it's own ZK client:

zk = ZK.new("my-host:1234") # zk client for writing only

logger = Logger.new(STDERR)
cache = ZkRecipes::Cache.new(host: "my-host:1234", logger: logger, timeout: 10) do |z|
  z.register("/test/boom", "goat")
end


puts cache["/test/boom"] # => "goat"

if fork
  # parent
  zk.set("/test/boom", "mouse")
  cache.close!
  zk.close!
else
  # child
  cache.reopen # wait up to 10s for ZK to reconnect and the cache to warm
  puts cache["/test/boom"] # => "mouse"
  cache.close!
  zk.close!
end

Handling forks with an existing ZK client:

logger = Logger.new(STDERR)
zk = ZK.new("my-host:1234", connect: false)
cache = ZkRecipes::Cache.new(logger: logger)
cache.register("/test/boom", "goat")
cache.setup_callbacks(zk) # no more paths can be registered after this

puts cache["/test/boom"] # => "goat"

zk.connect
cache.wait_for_warm_cache(10) # wait up to 10s for the cache to warm

zk.create("/test/boom")
zk.set("/test/boom", "cat")

sleep 1

puts cache["/test/boom"] # => "cat"

if fork
  # parent
  zk.set("/test/boom", "mouse")
  cache.close!
  zk.close!
else
  # child
  cache.reopen
  zk.reopen
  cache.wait_for_warm_cache(10) # wait up to 10s for the cache to warm again
  puts cache["/test/boom"] # => "mouse"
  cache.close!
  zk.close!
end

ActiveSupport::Notifications

ZkRecipes use ActiveSupport::Notifications for callbacks.

WARNING: exceptions raised in ActiveSupport::Notifications.subscribe will bubble up to the line where the notification is instrumented. MAKE SURE YOU CATCH EXCEPTIONS IN YOUR SUBSCRIBE BLOCKS!

Example:

ActiveSupport::Notifications.subscribe("cache.zk_recipes") do |_name, _start, _finish, _id, payload|
  if payload[:error]
    puts "There was a ZkRecipes::Cache error #{payload[:error]}"
    puts "The error occurred trying to deserialize a value from ZK "\
      "path=#{payload[:path] raw_zk_value=#{payload[:raw_value]}"
  else
    puts "Received and update for path=#{payload[:path}."
    puts "The update in ZK happened #{payload[:latency_seconds]} seconds ago."
    puts "The path's data is #{payload[:data_length]} bytes."
    puts "The path's version is #{payload[:version]}."
  end
end

Development

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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/nerdrew/ruby-zk_recipes. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

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

zk_recipes

Runtime