Class: PerfectQueue::Backend::RDBCompatBackend

Inherits:
Object
  • Object
show all
Includes:
PerfectQueue::BackendHelper
Defined in:
lib/perfectqueue/backend/rdb_compat.rb

Defined Under Namespace

Classes: Token

Constant Summary collapse

DELETE_OFFSET =

timeout model

0 —- now-1Bs —- retention —|—– now – alive ——- FUTURE

~~~~~~~^  to be deleted ^      |~~~^~~~       ^ running or in-queue
 DELETE          13_0000_0000->|   to be acquired

NOTE: this architecture introduces Year 2042 problem.

10_0000_0000
EVENT_HORIZON =

2011-03-13 07:06:40 UTC

13_0000_0000
KEEPALIVE = 
10
MAX_RETRY = 
10
LOCK_WAIT_TIMEOUT = 
60
DEFAULT_DELETE_INTERVAL = 
20

Instance Attribute Summary collapse

Attributes included from PerfectQueue::BackendHelper

#client

Instance Method Summary collapse

Methods included from PerfectQueue::BackendHelper

#close

Constructor Details

#initialize(client, config) ⇒ RDBCompatBackend

Returns a new instance of RDBCompatBackend.



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 39

def initialize(client, config)
  super

  @pq_connect_timeout = config.fetch(:pq_connect_timeout, 20)
  url = config[:url]
  @table = config[:table]
  unless @table
    raise ConfigError, ":table option is required"
  end

  if /\Amysql2:/i =~ url
    options = {max_connections: 1, sslca: config[:sslca]}
    options[:connect_timeout] = config.fetch(:connect_timeout, 3)
    @db = Sequel.connect(url, options)
    if config.fetch(:use_connection_pooling, nil) != nil
      @use_connection_pooling = !!config[:use_connection_pooling]
    else
      @use_connection_pooling = !!config[:sslca]
    end
    @table_lock = lambda {
      locked = nil
      loop do
        @db.fetch("SELECT GET_LOCK('#{@table}', #{LOCK_WAIT_TIMEOUT}) locked") do |row|
          locked = true if row[:locked] == 1
        end
        break if locked
      end
    }
    @table_unlock = lambda {
      @db.run("DO RELEASE_LOCK('#{@table}')")
    }
  else
    raise ConfigError, "only 'mysql' is supported"
  end

  @last_time = Time.now.to_i
  @mutex = Mutex.new

  connect {
    # connection test
  }

  # MySQL's CONNECTION_ID() is a 64bit unsigned integer from the
  # server's internal thread ID counter. It is unique while the MySQL
  # server is running.
  # https://bugs.mysql.com/bug.php?id=19806
  #
  # An acquired task is marked with next_timeout and CONNECTION_ID().
  # Therefore while alive_time is not changed and we don't restart
  # the server in 1 second, they won't conflict.
  if config[:disable_resource_limit]
    @update_sql = "UPDATE `\#{@table}`\n  JOIN (\n  SELECT id\n    FROM `\#{@table}` FORCE INDEX (`index_\#{@table}_on_timeout`)\n   WHERE \#{EVENT_HORIZON} < timeout AND timeout <= :now\n   ORDER BY timeout ASC\nLIMIT :max_acquire) AS t1 USING(id)\n   SET timeout=:next_timeout, owner=CONNECTION_ID()\n"
    @sql = "SELECT id, timeout, data, created_at, resource\n  FROM `\#{@table}`\n WHERE timeout = ? AND owner = CONNECTION_ID()\n"
  else
    @update_sql = "UPDATE `\#{@table}`\n  JOIN (\n    SELECT id, IFNULL(max_running, 1) / (IFNULL(running, 0) + 1) AS weight\n    FROM `\#{@table}`\n    LEFT JOIN (\nSELECT resource, COUNT(1) AS running\nFROM `\#{@table}` AS t1\nWHERE timeout > :now AND resource IS NOT NULL\nGROUP BY resource\n    ) AS t2 USING(resource)\n    WHERE \#{EVENT_HORIZON} < timeout AND timeout <= :now AND IFNULL(max_running - running, 1) > 0\n    ORDER BY weight DESC, timeout ASC\n    LIMIT :max_acquire\n  ) AS t3 USING (id)\nSET timeout = :next_timeout, owner = CONNECTION_ID()\n"
    @sql = "SELECT id, timeout, data, created_at, resource, max_running\n  FROM `\#{@table}`\n WHERE timeout = ? AND owner = CONNECTION_ID()\n"
  end

  @cleanup_interval = config[:cleanup_interval] || DEFAULT_DELETE_INTERVAL
  # If cleanup_interval > max_request_per_child / max_acquire,
  # some processes won't run DELETE query.
  # (it's not an issue when there are enough workers)
  @cleanup_interval_count = @cleanup_interval > 0 ? rand(@cleanup_interval) : 0
end

Instance Attribute Details

#db ⇒ Object (readonly)

Returns the value of attribute db.



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 137

def db
  @db
end

Instance Method Details

#acquire(alive_time, max_acquire, options) ⇒ Object

> [AcquiredTask]



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 240

def acquire(alive_time, max_acquire, options)
  now = (options[:now] || Time.now).to_i
  next_timeout = now + alive_time
  tasks = nil
  t0 = nil

  if @cleanup_interval_count <= 0
    connect {
      t0=Process.clock_gettime(Process::CLOCK_MONOTONIC)
      @db["DELETE FROM `#{@table}` WHERE timeout <= ?", now-DELETE_OFFSET].delete
      @cleanup_interval_count = @cleanup_interval
      STDERR.puts"PQ:delete from #{@table}:%6f sec" % [Process.clock_gettime(Process::CLOCK_MONOTONIC)-t0]
    }
  end

  connect_locked {
    t0=Process.clock_gettime(Process::CLOCK_MONOTONIC)
    n = @db[@update_sql, next_timeout: next_timeout, now: now, max_acquire: max_acquire].update
    if n <= 0
      return nil
    end
    @table_unlock.call

    tasks = []
    @db.fetch(@sql, next_timeout) {|row|
      attributes = create_attributes(nil, row)
      task_token = Token.new(row[:id])
      task = AcquiredTask.new(@client, row[:id], attributes, task_token)
      tasks.push task
    }
    @cleanup_interval_count -= 1

    return tasks
  }
ensure
  STDERR.puts "PQ:acquire from #{@table}:%6f sec (%d tasks)" % [Process.clock_gettime(Process::CLOCK_MONOTONIC)-t0,tasks.size] if tasks
end

#compress_data(data, compression) ⇒ Object 



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 198

def compress_data(data, compression)
  if compression == 'gzip'
    io = StringIO.new
    io.set_encoding(Encoding::ASCII_8BIT)
    gz = Zlib::GzipWriter.new(io)
    begin
      gz.write(data)
    ensure
      gz.close
    end
    data = io.string
    data = Sequel::SQL::Blob.new(data)
  end
  data
end

#finish(task_token, retention_time, options) ⇒ Object

> nil



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 283

def finish(task_token, retention_time, options)
  now = (options[:now] || Time.now).to_i
  delete_timeout = now - DELETE_OFFSET + retention_time
  key = task_token.key

  connect {
    n = @db["UPDATE `#{@table}` SET timeout=?, created_at=NULL, resource=NULL WHERE id=? AND created_at IS NOT NULL", delete_timeout, key].update
    if n <= 0
      raise IdempotentAlreadyFinishedError, "task key=#{key} does not exist or already finished."
    end
  }
  nil
end

#force_finish(key, retention_time, options) ⇒ Object 



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 278

def force_finish(key, retention_time, options)
  finish(Token.new(key), retention_time, options)
end

#get_task_metadata(key, options) ⇒ Object

> TaskStatus



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 167

def get_task_metadata(key, options)
  now = (options[:now] || Time.now).to_i

  connect {
    row = @db.fetch("SELECT timeout, data, created_at, resource, max_running FROM `#{@table}` WHERE id=? LIMIT 1", key).first
    unless row
      raise NotFoundError, "task key=#{key} does no exist"
    end
    attributes = create_attributes(now, row)
    return TaskMetadata.new(@client, key, attributes)
  }
end

#heartbeat(task_token, alive_time, options) ⇒ Object

> nil



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 298

def heartbeat(task_token, alive_time, options)
  now = (options[:now] || Time.now).to_i
  next_timeout = now + alive_time
  key = task_token.key
  data = options[:data]

  sql = "UPDATE `#{@table}` SET timeout=?"
  params = [sql, next_timeout]
  if data
    sql << ", data=?"
    params << compress_data(data.to_json, options[:compression])
  end
  sql << " WHERE id=? AND created_at IS NOT NULL"
  params << key

  connect {
    n = @db[*params].update
    if n <= 0
      row = @db.fetch("SELECT id, timeout, created_at FROM `#{@table}` WHERE id=? LIMIT 1", key).first
      if row == nil
        raise PreemptedError, "task key=#{key} does not exist or preempted."
      elsif row[:created_at] == nil
        raise PreemptedError, "task key=#{key} preempted."
      else # row[:timeout] == next_timeout
        # ok
      end
    end
  }
  nil
end

#init_database(options) ⇒ Object 



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 144

def init_database(options)
  sql = []
  sql << "DROP TABLE IF EXISTS `#{@table}`" if options[:force]
  sql << "    CREATE TABLE IF NOT EXISTS `\#{@table}` (\n      id VARCHAR(255) NOT NULL,\n      timeout INT NOT NULL,\n      data LONGBLOB NOT NULL,\n      created_at INT,\n      resource VARCHAR(255),\n      max_running INT,\n      /* CONNECTION_ID() can be 64bit: https://bugs.mysql.com/bug.php?id=19806 */\n      owner BIGINT(21) UNSIGNED NOT NULL DEFAULT 0,\n      PRIMARY KEY (id)\n    )\n    SQL\n  sql << \"CREATE INDEX `index_\#{@table}_on_timeout` ON `\#{@table}` (`timeout`)\"\n  connect {\n    sql.each(&@db.method(:run))\n  }\nend\n"

#list(options, &block) ⇒ Object

yield [TaskWithMetadata]



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 186

def list(options, &block)
  now = (options[:now] || Time.now).to_i

  connect {
    @db.fetch("SELECT id, timeout, data, created_at, resource, max_running FROM `#{@table}` ORDER BY timeout ASC") {|row|
      attributes = create_attributes(now, row)
      task = TaskWithMetadata.new(@client, row[:id], attributes)
      yield task
    }
  }
end

#preempt(key, alive_time, options) ⇒ Object

> AcquiredTask

Raises:



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 181

def preempt(key, alive_time, options)
  raise NotSupportedError.new("preempt is not supported by rdb_compat backend")
end

#release(task_token, alive_time, options) ⇒ Object 



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 329

def release(task_token, alive_time, options)
  heartbeat(task_token, alive_time, options)
end

#submit(key, type, data, options) ⇒ Object

> Task



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# File 'lib/perfectqueue/backend/rdb_compat.rb', line 215

def submit(key, type, data, options)
  now = (options[:now] || Time.now).to_i
  now = 1 if now < 1  # 0 means cancel requested
  run_at = (options[:run_at] || now).to_i
  user = options[:user]
  user = user.to_s if user
  max_running = options[:max_running]
  data = data ? data.dup : {}
  data['type'] = type
  d = compress_data(data.to_json, options[:compression])

  connect {
    begin
      @db[
        "INSERT INTO `#{@table}` (id, timeout, data, created_at, resource, max_running) VALUES (?, ?, ?, ?, ?, ?)",
        key, run_at, d, now, user, max_running
      ].insert
      return Task.new(@client, key)
    rescue Sequel::UniqueConstraintViolation
      raise IdempotentAlreadyExistsError, "task key=#{key} already exists"
    end
  }
end