zookeeper watcher in ruby

I am using this gem: https://github.com/zk-ruby/zk for connecting to zookeeper, and get and set commands are working correctly.

I have tried adding a watcher client using the sample zookeeper client that comes along with the server build, and all works well there. I can add a watcher and when I update some znode from another client, the client is notified.

But I wish to integrate a watcher in ruby code, I am not getting any events when data on the node is changed.

This is a sample class:

class ZkConnect    attr_accessor :z, :sub, :k   include Singleton    @z = nil   @sub = nil   @watcher = nil   @callback = nil   @watcher = nil    def initialize     initialize_conns   end    def initialize_conns     @z = ZK.new("localhost:2181")     Rails.logger.info @z.inspect     # Rails.logger.info z.get_children(:path => "/system/production")     # Rails.logger.info z.get(:path => "/system/production")[:data]      # @sub = @z.register("/mypath") do |event, zookeeper_client|     #   Rails.logger.info "got an event"     #   Rails.logger.info "got an event on: #{event.inspect} #{zookeeper_client.inspect}"     # end     # Rails.logger.info @sub.inspect     w = watch     Rails.logger.info "dsmcldsm: #{w.inspect}"   end    # def watcher_callback   #   @callback ||= Proc.new do |event|   #     Rails.logger.info "dcbskcn : #{event.inspect}"   #     # Set new watcher   #     watch   #     # Rediscover   #     # discover   #   end   #   Rails.logger.info "nckdj cudsnciu sdcn: #{@callback.inspect}"   #   return @callback   # end    def watch     # return if @z.nil?     Rails.logger.info "synapse: setting watch at "      # @watcher = @z.register("/mypath", &watcher_callback)     @watcher = @z.register("/mypath") do |event|       Rails.logger.info "dcbskcn : #{event.inspect}"       puts "dcbskcn : #{event.inspect}"       watch     end     Rails.logger.info "cudsnciu: #{@watcher.inspect}"     return @watcher      # Verify that we actually set up the watcher.     # unless @zk.exists?(@discovery['path'], :watch => true)     #   log.error "synapse: zookeeper watcher path #{@discovery['path']} does not exist!"     #   zk_cleanup     # end     # log.debug "synapse: set watch at #{@discovery['path']}"   end end 

I took some code from here https://github.com/airbnb/synapse/blob/master/lib/synapse/service_watcher/zookeeper.rb for this, but didn't help.

I tried it on a rails project, tried running on thin and passenger, though I don't see how it would help.

I also don't see eventmachine as a dependency for this gem, so I don't really know how callbacks would be received.

1 Answers

Answers 1

I read changelog and decided to put a @z.stat("/mypath", :watch => true) after registering the watcher. And it started working. No idea why.

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