Class: Herdis::Shepherd

Inherits:
Object
  • Object
show all
Defined in:
lib/herdis/shepherd.rb

Defined Under Namespace

Classes: Shard

Constant Summary collapse

CHECK_SLAVE_TIMER = 
(ENV["SHEPHERD_CHECK_SLAVE_TIMER"] || 10).to_f
CHECK_PREDECESSOR_TIMER = 
(ENV["SHEPHERD_CHECK_PREDECESSOR_TIMER"] || 1).to_f

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Shepherd

Returns a new instance of Shepherd.



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# File 'lib/herdis/shepherd.rb', line 137

def initialize(options = {})
  @dir = options.delete(:dir) || File.join(ENV["HOME"], ".herdis")
  @redis = options.delete(:redis) || "redis-server"
  @port = options.delete(:port) || 9000
  @logger = options.delete(:logger)
  @first_port = options.delete(:first_port) || 9080
  @inmemory = options.delete(:inmemory)
  @redundancy = options.delete(:redundancy) || 2
  @shepherd_id = options.delete(:shepherd_id) || rand(1 << 256).to_s(36)
  Dir.mkdir(dir) unless Dir.exists?(dir)

  @shepherds = {}
  @slaves = {}
  @masters = {}

  at_exit do
    shutdown
  end

  if connect_to = options.delete(:connect_to)
    join_cluster(connect_to)
  else
    Herdis::Common::SHARDS.times do |shard_id|
      create_master_shard(shard_id)
    end
    @shepherds[shepherd_id] = shepherd_status
  end
end

Instance Attribute Details

#dir ⇒ Object (readonly)

Returns the value of attribute dir.



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# File 'lib/herdis/shepherd.rb', line 124

def dir
  @dir
end

#first_port ⇒ Object (readonly)

Returns the value of attribute first_port.



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# File 'lib/herdis/shepherd.rb', line 126

def first_port
  @first_port
end

#inmemory ⇒ Object (readonly)

Returns the value of attribute inmemory.



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# File 'lib/herdis/shepherd.rb', line 127

def inmemory
  @inmemory
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.



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# File 'lib/herdis/shepherd.rb', line 131

def logger
  @logger
end

#masters ⇒ Object (readonly)

Returns the value of attribute masters.



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# File 'lib/herdis/shepherd.rb', line 133

def masters
  @masters
end

#port ⇒ Object (readonly)

Returns the value of attribute port.



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# File 'lib/herdis/shepherd.rb', line 130

def port
  @port
end

#redis ⇒ Object (readonly)

Returns the value of attribute redis.



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# File 'lib/herdis/shepherd.rb', line 125

def redis
  @redis
end

#redundancy ⇒ Object (readonly)

Returns the value of attribute redundancy.



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# File 'lib/herdis/shepherd.rb', line 129

def redundancy
  @redundancy
end

#shepherd_id ⇒ Object (readonly)

Returns the value of attribute shepherd_id.



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# File 'lib/herdis/shepherd.rb', line 128

def shepherd_id
  @shepherd_id
end

#shepherds ⇒ Object (readonly)

Returns the value of attribute shepherds.



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# File 'lib/herdis/shepherd.rb', line 135

def shepherds
  @shepherds
end

#slaves ⇒ Object (readonly)

Returns the value of attribute slaves.



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# File 'lib/herdis/shepherd.rb', line 134

def slaves
  @slaves
end

Instance Method Details

#add_shards(shepherd_id, shard_ids, check = true) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 222

def add_shards(shepherd_id, shard_ids, check = true)
  if shepherd_state = shepherds[shepherd_id]
    shard_id_set = Set.new(shard_ids)
    current_shard_id_set = Set.new(shepherd_state["masters"])
    unless current_shard_id_set.superset?(shard_id_set)
      shepherd_state["masters"] = (current_shard_id_set | shard_id_set).to_a
      to_each_sibling(:apost,
                      :path => "/#{shepherd_id}/shards",
                      :body => Yajl::Encoder.encode(:shard_ids => shard_ids.to_a)) do
        check_shards if check
      end
    end
  end
end

#add_shepherd(shepherd_status) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 201

def add_shepherd(shepherd_status)
  unless shepherd_status == shepherds[shepherd_status["id"]]
    shepherds[shepherd_status["id"]] = shepherd_status
    to_each_sibling(:aput,
                    :path => "/#{shepherd_status["id"]}",
                    :body => Yajl::Encoder.encode(shepherd_status)) do
      check_shards
    end
  end
end

#backup_ordinals ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 467

def backup_ordinals
  rval = Set.new
  ordered_keys = ordered_shepherd_keys
  my_index = ordered_keys.index(shepherd_id)
  [redundancy, ordered_keys.size - 1].min.times do |n|
    rval << (my_index - n - 1) % ordered_keys.size
  end
  rval
end

#backup_shards ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 477

def backup_shards
  rval = Set.new
  backup_ordinals.each do |ordinal|
    rval += shards_owned_by(ordinal)
  end
  rval
end

#check_predecessor ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 508

def check_predecessor
  pre = predecessor
  if pre && pre["id"] != shepherd_id
    Fiber.new do
      if EM::HttpRequest.new(pre["url"]).head.response_header.status != 204
        logger.warn("#{shepherd_id} *** dropping #{pre["id"]} due to failure to respond to ping")
        remove_shepherd(pre["id"])
      end
    end.resume
  end
end

#check_shards ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 372

def check_shards
  should_be_owned = owned_shards
  should_be_backed_up = backup_shards
  master_ids = Set.new(masters.keys)
  slave_ids = Set.new(slaves.keys)
  external_shards = create_external_shards(should_be_owned)
  externally_running = Set.new(external_shards.keys)

  needs_to_be_liberated = slave_ids - externally_running
  needs_to_be_enslaved = (master_ids & externally_running & should_be_backed_up) - should_be_owned
  needs_to_be_directed = slave_ids & externally_running & (should_be_backed_up | should_be_owned)
  slaves_needing_to_be_shut_down = (slave_ids & externally_running) - (should_be_backed_up | should_be_owned)
  masters_needing_to_be_shut_down = (master_ids & externally_running) - (should_be_backed_up | should_be_owned)
  new_slaves_needed = ((should_be_backed_up | should_be_owned) & externally_running) - (slave_ids | master_ids)

  handled = Set.new

  logger.debug "#{shepherd_id} *** liberating #{needs_to_be_liberated.inspect}" unless needs_to_be_liberated.empty?
  needs_to_be_liberated.each do |shard_id|
    handled.add(shard_id.to_s)
    slaves[shard_id.to_s].liberate!
  end
  add_shards(shepherd_id, needs_to_be_liberated, false)

  logger.debug "#{shepherd_id} *** enslaving #{needs_to_be_enslaved.inspect}" unless needs_to_be_enslaved.empty?
  needs_to_be_enslaved.each do |shard_id|
    raise "Already liberated #{shard_id}!" if handled.include?(shard_id.to_s)
    handled.add(shard_id.to_s)
    masters[shard_id.to_s].enslave!(external_shards[shard_id.to_s])
  end
  remove_shards(shepherd_id, needs_to_be_enslaved, false)

  logger.debug "#{shepherd_id} *** redirecting #{needs_to_be_directed.inspect}" unless needs_to_be_directed.empty?
  needs_to_be_directed.each do |shard_id|
    raise "Already liberated or enslaved #{shard_id}!" if handled.include?(shard_id.to_s)
    handled.add(shard_id.to_s)
    slaves[shard_id.to_s].enslave!(external_shards[shard_id.to_s])
  end

  logger.debug "#{shepherd_id} *** killing masters #{masters_needing_to_be_shut_down.inspect}" unless masters_needing_to_be_shut_down.empty?
  masters_needing_to_be_shut_down.each do |shard_id|
    raise "Already liberated, enslaved or directed #{shard_id}!" if handled.include?(shard_id.to_s)
    handled.add(shard_id.to_s)
    shutdown_shard(shard_id)
  end
  remove_shards(shepherd_id, masters_needing_to_be_shut_down, false)
  
  logger.debug "#{shepherd_id} *** killing slaves #{slaves_needing_to_be_shut_down.inspect}" unless slaves_needing_to_be_shut_down.empty?
  slaves_needing_to_be_shut_down.each do |shard_id|
    raise "Already liberated, enslaved, directed or shut down #{shard_id}!" if handled.include?(shard_id.to_s)
    handled.add(shard_id.to_s)
    shutdown_slave(shard_id)
  end

  logger.debug "#{shepherd_id} *** creating slaves #{new_slaves_needed.inspect}" unless new_slaves_needed.empty?
  new_slaves_needed.each do |shard_id|
    raise "Already liberated, enslaved, directed or shut down #{shard_id}!" if handled.include?(shard_id.to_s)
    handled.add(shard_id.to_s)
    create_slave_shard(shard_id.to_s, external_shards[shard_id.to_s])
  end
  
  ensure_slave_check
  ensure_predecessor_check
end

#check_slaves ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 437

def check_slaves
  revolution = Set.new
  (owned_shards & slaves.keys).each do |shard_id|
    shard = slaves[shard_id.to_s]
    if shard.connection.info["master_sync_in_progress"] == "0"
      revolution << shard_id.to_s
    end
  end
  unless revolution.empty?
    logger.debug "#{shepherd_id} *** revolting #{revolution.inspect}"
    add_shards(shepherd_id, revolution.to_a)
  end
end

#cluster_info ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 270

def cluster_info
  {
    "shepherd_id" => shepherd_id,
    "ordinal" => ordinal,
    "slaves" => slaves.keys,
    "masters" => masters.keys,
    "redundancy" => redundancy,
    "siblings" => shepherds.keys.sort,
    "inmemory" => inmemory,
    "check_slave_timer" => CHECK_SLAVE_TIMER,
    "check_predecessor_timer" => CHECK_PREDECESSOR_TIMER,
    "sanity" => "#{url}/sanity",
    "cluster" => "#{url}/cluster"
  }
end

#cluster_status ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 331

def cluster_status
  shepherds.merge(shepherd_id => shepherd_status)
end

#create_external_shards(should_be_owned) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 358

def create_external_shards(should_be_owned)
  shepherds.values.inject({}) do |sum, shepherd_status|
    if shepherd_status["id"] == shepherd_id
      sum
    else
      shepherd_url = URI.parse(shepherd_status["url"])
      sum.merge(shepherd_status["masters"].inject({}) do |sum, shard_id|
                  shepherd_url = URI.parse(shepherd_status["url"])
                  sum.merge(shard_id.to_s => URI.parse("redis://#{shepherd_url.host}:#{shepherd_status["first_port"].to_i + shard_id.to_i}/"))
                end)
    end    
  end
end

#create_master_shard(shard_id) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 451

def create_master_shard(shard_id)
  masters[shard_id.to_s] = create_shard(shard_id)
end

#create_shard(shard_id, options = {}) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 524

def create_shard(shard_id, options = {})
  Shard.new(options.merge(:shepherd => self,
                          :id => shard_id))
end

#create_slave_shard(shard_id, external_uri) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 520

def create_slave_shard(shard_id, external_uri)
  slaves[shard_id.to_s] = create_shard(shard_id, :master => external_uri)
end

#ensure_predecessor_check ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 172

def ensure_predecessor_check
  @check_predecessor_timer ||= EM.add_periodic_timer(CHECK_PREDECESSOR_TIMER) do
    check_predecessor
  end
end

#ensure_slave_check ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 166

def ensure_slave_check
  @check_slave_timer ||= EM.add_periodic_timer(CHECK_SLAVE_TIMER) do
    check_slaves
  end
end

#host ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 252

def host
  @host = Fiber.current.host if Fiber.current.respond_to?(:host)
  @host || "localhost"
end

#join_cluster(url) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 194

def join_cluster(url)
  shutdown
  @shepherds = Yajl::Parser.parse(EM::HttpRequest.new(url).get(:path => "/cluster",
                                                               :head => {"Content-Type" => "application/json"}).response)
  add_shepherd(shepherd_status)
end

#ordered_shepherd_keys ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 459

def ordered_shepherd_keys
  shepherds.keys.sort
end

#ordinal ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 463

def ordinal
  shepherds.keys.sort.index(shepherd_id)
end

#owned_shards ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 494

def owned_shards
  shards_owned_by(ordinal)
end

#predecessor ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 498

def predecessor
  ordered_keys = ordered_shepherd_keys
  my_index = ordered_keys.index(shepherd_id)
  if my_index == 0
    shepherds[ordered_keys.last]
  else
    shepherds[ordered_keys[my_index - 1]]
  end
end

#remove_shards(shepherd_id, shard_ids, check = true) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 237

def remove_shards(shepherd_id, shard_ids, check = true)
  if shepherd_state = shepherds[shepherd_id]
    shard_id_set = Set.new(shard_ids)
    current_shard_id_set = Set.new(shepherd_state["masters"])
    unless (shard_id_set & current_shard_id_set).empty?
      shepherd_state["masters"] = (current_shard_id_set - shard_id_set).to_a
      to_each_sibling(:adelete,
                      :path => "/#{shepherd_id}/shards",
                      :body => Yajl::Encoder.encode(:shard_ids => shard_ids.to_a)) do
        check_shards if check
      end
    end
  end
end

#remove_shepherd(shepherd_id) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 212

def remove_shepherd(shepherd_id)
  if shepherds.include?(shepherd_id)
    shepherds.delete(shepherd_id)
    to_each_sibling(:adelete,
                    :path => "/#{shepherd_id}") do
      check_shards
    end
  end
end

#sanity ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 286

def sanity
  creators = Set.new
  min_created_at = nil
  max_created_at = nil
  masters = 0
  slaves = 0
  consistent = true
  urls = []
  shard_status.each do |shard_url|
    urls << shard_url
    url = URI.parse(shard_url)
    shard_connection = Redis.new(:host => url.host, :port => url.port)
    info = shard_connection.info
    masters += 1 if info["role"] == "master"
    slaves += 1 if info["role"] == "slave"
    created_at = shard_connection.get("#{Herdis::Shepherd::Shard.name}.created_at").to_i
    min_created_at = created_at if min_created_at.nil? || created_at < min_created_at
    max_created_at = created_at if max_created_at.nil? || created_at > max_created_at
    creators << shard_connection.get("#{Herdis::Shepherd::Shard.name}.created_by")
  end
  {
    :creators => creators.to_a,
    :consistent => creators.size == 1 && masters == Herdis::Common::SHARDS && slaves == 0,
    :min_created_at => Time.at(min_created_at).to_s,
    :max_created_at => Time.at(max_created_at).to_s,
    :masters => masters,
    :slaves => slaves,
    :shards => urls
  }
end

#shard_status ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 317

def shard_status
  rval = []
  cluster_status.each do |shepherd_id, shepherd_status|
    shepherd_status["masters"].each do |shard_id|
      if rval[shard_id.to_i].nil?
        rval[shard_id.to_i] = "redis://#{host}:#{shard_id.to_i + shepherd_status["first_port"].to_i}/"
      else
        raise Goliath::Validation::InternalServerError.new("Duplicate masters: #{shard_id}")
      end
    end
  end
  rval
end

#shards_owned_by(ordinal) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 485

def shards_owned_by(ordinal)
  rval = Set.new
  while ordinal < Herdis::Common::SHARDS
    rval << ordinal.to_s
    ordinal += shepherds.size
  end
  rval
end

#shepherd_status ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 261

def shepherd_status
  {
    "url" => url,
    "id" => shepherd_id,
    "first_port" => first_port,
    "masters" => masters.keys
  }
end

#shutdown ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 349

def shutdown
  masters.keys.each do |shard_id|
    shutdown_shard(shard_id)
  end
  slaves.keys.each do |shard_id|
    shutdown_slave(shard_id)
  end
end

#shutdown_shard(shard_id) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 335

def shutdown_shard(shard_id)
  if shard = masters[shard_id.to_s]
    shard.connection.shutdown
    masters.delete(shard_id.to_s)
  end
end

#shutdown_slave(shard_id) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 342

def shutdown_slave(shard_id)
  if shard = slaves[shard_id.to_s]
    shard.connection.shutdown
    slaves.delete(shard_id.to_s)
  end
end

#status ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 455

def status
  204
end

#to_each_sibling(method, options, &block) ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 178

def to_each_sibling(method, options, &block)
  default_options = {:head => {"Content-Type" => "application/json"}}
  multi = EM::Synchrony::Multi.new
  shepherds.each do |shepherd_id, shepherd|
    unless shepherd_id == self.shepherd_id
      multi.add(shepherd_id, 
                EM::HttpRequest.new(shepherd["url"]).send(method, 
                                                          default_options.rmerge(options)))
    end
  end
  yield
  Fiber.new do
    multi.perform while !multi.finished?
  end.resume
end

#url ⇒ Object 



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# File 'lib/herdis/shepherd.rb', line 257

def url
  "http://#{host}:#{port}"
end