Class: Fluent::WebHDFSOutput

Inherits:
TimeSlicedOutput
  • Object
show all
Includes:
Mixin::ConfigPlaceholders, Mixin::PlainTextFormatter
Defined in:
lib/fluent/plugin/out_webhdfs.rb

Constant Summary collapse

CHUNK_ID_PLACE_HOLDER = 
'${chunk_id}'

Instance Method Summary collapse

Constructor Details

#initialize ⇒ WebHDFSOutput

Returns a new instance of WebHDFSOutput.



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 46

def initialize
  super
  require 'net/http'
  require 'time'
  require 'webhdfs'
end

Instance Method Details

#chunk_unique_id_to_str(unique_id) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 178

def chunk_unique_id_to_str(unique_id)
  unique_id.unpack('C*').map{|x| x.to_s(16).rjust(2,'0')}.join('')
end

#configure(conf) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 58

def configure(conf)
  if conf['path']
    if conf['path'].index('%S')
      conf['time_slice_format'] = '%Y%m%d%H%M%S'
    elsif conf['path'].index('%M')
      conf['time_slice_format'] = '%Y%m%d%H%M'
    elsif conf['path'].index('%H')
      conf['time_slice_format'] = '%Y%m%d%H'
    end
  end

  super

  if @host
    @namenode_host = @host
    @namenode_port = @port
  elsif @namenode
    unless /\A([a-zA-Z0-9][-a-zA-Z0-9.]*):(\d+)\Z/ =~ @namenode
      raise Fluent::ConfigError, "Invalid config value about namenode: '#{@namenode}', needs NAMENODE_HOST:PORT"
    end
    @namenode_host = $1
    @namenode_port = $2.to_i
  else
    raise Fluent::ConfigError, "WebHDFS host or namenode missing"
  end
  if @standby_namenode
    unless /\A([a-zA-Z0-9][-a-zA-Z0-9.]*):(\d+)\Z/ =~ @standby_namenode
      raise Fluent::ConfigError, "Invalid config value about standby namenode: '#{@standby_namenode}', needs STANDBY_NAMENODE_HOST:PORT"
    end
    if @httpfs
      raise Fluent::ConfigError, "Invalid configuration: specified to use both of standby_namenode and httpfs."
    end
    @standby_namenode_host = $1
    @standby_namenode_port = $2.to_i
  end
  unless @path.index('/') == 0
    raise Fluent::ConfigError, "Path on hdfs MUST starts with '/', but '#{@path}'"
  end

  @client = prepare_client(@namenode_host, @namenode_port, @username)
  if @standby_namenode_host
    @client_standby = prepare_client(@standby_namenode_host, @standby_namenode_port, @username)
  else
    @client_standby = nil
  end

  if not @append
    if @path.index(CHUNK_ID_PLACE_HOLDER).nil?
      raise Fluent::ConfigError, "path must contain ${chunk_id}, which is the placeholder for chunk_id, when append is set to false."
    end
  end
end

#is_standby_exception(e) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 167

def is_standby_exception(e)
  e.is_a?(WebHDFS::IOError) && e.message.match(/org\.apache\.hadoop\.ipc\.StandbyException/)
end

#namenode_available(client) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 127

def namenode_available(client)
  if client
    available = true
    begin
      client.list('/')
    rescue => e
      log.warn "webhdfs check request failed. (namenode: #{client.host}:#{client.port}, error: #{e.message})"
      available = false
    end
    available
  else
    false
  end
end

#namenode_failover ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 171

def namenode_failover
  if @standby_namenode
    @client, @client_standby = @client_standby, @client
    log.warn "Namenode failovered, now using #{@client.host}:#{@client.port}."
  end
end

#path_format(chunk_key) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 163

def path_format(chunk_key)
  Time.strptime(chunk_key, @time_slice_format).strftime(@path)
end

#prepare_client(host, port, username) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 111

def prepare_client(host, port, username)
  client = WebHDFS::Client.new(host, port, username)
  if @httpfs
    client.httpfs_mode = true
  end
  client.open_timeout = @open_timeout
  client.read_timeout = @read_timeout
  if @retry_known_errors
    client.retry_known_errors = true
    client.retry_interval = @retry_interval if @retry_interval
    client.retry_times = @retry_times if @retry_times
  end

  client
end

#send_data(path, data) ⇒ Object

TODO check conflictions



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 184

def send_data(path, data)
  if @append
    begin
      @client.append(path, data)
    rescue WebHDFS::FileNotFoundError
      @client.create(path, data)
    end
  else
    @client.create(path, data, {'overwrite' => 'true'})
  end
end

#shutdown ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 159

def shutdown
  super
end

#start ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 142

def start
  super

  if namenode_available(@client)
    log.info "webhdfs connection confirmed: #{@namenode_host}:#{@namenode_port}"
    return
  end
  if @client_standby && namenode_available(@client_standby)
    log.info "webhdfs connection confirmed: #{@standby_namenode_host}:#{@standby_namenode_port}"
    return
  end

  unless @ignore_start_check_error
    raise RuntimeError, "webhdfs is not available now."
  end
end

#write(chunk) ⇒ Object 



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# File 'lib/fluent/plugin/out_webhdfs.rb', line 196

def write(chunk)
  hdfs_path = if @append
                path_format(chunk.key)
              else
                path_format(chunk.key).gsub(CHUNK_ID_PLACE_HOLDER, chunk_unique_id_to_str(chunk.unique_id))
              end

  failovered = false
  begin
    send_data(hdfs_path, chunk.read)
  rescue => e
    log.warn "failed to communicate hdfs cluster, path: #{hdfs_path}"

    raise e if !@client_standby || failovered

    if is_standby_exception(e) && namenode_available(@client_standby)
      log.warn "Seems the connected host status is not active (maybe due to failovers). Gonna try another namenode immediately."
      namenode_failover
      failovered = true
      retry
    end
    if @num_errors && ((@num_errors + 1) >= @failures_before_use_standby) && namenode_available(@client_standby)
      log.warn "Too many failures. Try to use the standby namenode instead."
      namenode_failover
      failovered = true
      retry
    end
    raise e
  end
  hdfs_path
end