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Implementation of Read Operations

TODO: File a subtask under HDDS-9862 and complete this page or section.

Reading Metadata​

Reading Data​

Trace every part of a read request from beginning to end. This includes:

  • Client getting encryption keys
  • Client calling OM to create key
  • OM validating client's Kerberos principal
  • OM checking permissions (Ranger or Native ACLs)
  • OM generating block tokens from the shared secret previously retrieved from SCM
  • OM getting block locations from SCM or from its cache.
  • OM returning container, blocks, pipeline, block tokens
  • Client sending block tokens and Datanode validating based on the shared secret from SCM
  • Client sending read chunk requests to Datanode to fetch the data.
    • For replication:
      • Include topology choices of which Datanodes to use
      • Include failover handling
    • For EC, link to the EC feature page.
  • Client validating checksums