Zk leader election (sequence)

example/nerve.conf.json

@@ -8,6 +8,7 @@
       "zk_hosts": ["localhost:2181"],
       "zk_path": "/nerve/services/your_http_service/services",
       "check_interval": 2,
+      "sequential": false,
       "checks": [
         {
           "type": "http",

lib/nerve/reporter.rb

@@ -10,10 +10,18 @@ def initialize(opts)
         raise ArgumentError, "you need to specify required argument #{required}" unless opts[required]
       end
 
+      defaults = {
+        :sequential => false,
+      }
+      opts = defaults.merge(opts)
+
       @path = opts['hosts'].shuffle.join(',') + opts['path']
       @data = parse_data(opts['data'] || '')
       @key = opts['key']
       @key.insert(0,'/') unless @key[0] == '/'
+      @sequential = opts['sequential']
+      @key.insert('-') if @sequential
+      @full_key = @key
     end
 
     def start()
@@ -23,7 +31,7 @@ def start()
       log.info "nerve: successfully created zk connection to #{@path}"
     end
 
-    def report_up()
+    def report_up
       zk_save
     end
 
@@ -43,15 +51,17 @@ def ping?
     private
 
     def zk_delete
-      @zk.delete(@key, :ignore => :no_node)
+      @zk.delete(@full_key, :ignore => :no_node)
     end
 
     def zk_save
-      log.debug "nerve: writing data #{@data.class} to zk at #{@key} with #{@data.inspect}"
+      log.debug "nerve: writing data #{@data.class} to zk at #{@key} with #{@data.inspect} and sequential 
+      flag is #{@sequential}"
       begin
-        @zk.set(@key,@data)
+        @zk.set(@full_key, @data)
       rescue ZK::Exceptions::NoNode => e
-        @zk.create(@key,:data => @data, :mode => :ephemeral)
+        @full_key = @zk.create(@key,:data => @data, :ephemeral => true, 
+          :sequential => @sequential)
       end
     end
 

lib/nerve/service_watcher.rb

@@ -23,6 +23,7 @@ def initialize(service={})
           'path' => service['zk_path'],
           'key' => "#{service['instance_id']}_#{@name}",
           'data' => {'host' => service['host'], 'port' => service['port']},
+          'sequential' => service['sequential'] | false
         })
 
       # instantiate the checks for this service