Write

• Setp 1 and 2 only create a record of new file on namenode, also namenode will check the permission and duplication before any things.
• The main component handles communication with datanode and namenode is DFSOutputStream. And it's warpped by FSDataOutputStream.
• FSDataOutputStream
  • Split data into packets
  • Queuing the packets into data queue.
  • Ack queue involve in the process of failover.
• DataStreamer
  • Consumes the data queue
  • Asking the namenode to allocate new blocks by picking a list of suitable datanodes to store replicas.
  • Streams the packets in the pipeline.(Step 4 and 5)