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Status

Current stateDone

Released: 4.5.0

Problem

  • the interface, wire protocol and storage all support 64 bits ledger id.

  • however, the ledger id generation on zookeeper only generate 32 bits ledger id.
  • the zookeeper-based ledger metadata store uses 2-4-4 split to store 32 bits ledger id.
  • we need to find a solution to support 64 bits in zookeeper-based ledger metadata store.

Proposal

  • there are 3 major concerns for this problem
    • how to store metadata for 64-bits-id ledgers in zookeeper?
    • how to generate 64-bits ledger id using zookeeper?
    • how to achieve backward compatibility?
  • how to store?
    • Salesforce built a Long Hierarchical Ledger Manager
    • Ledger ID is split in 3-4-4-4-4 components.
    • No backward compatible on initial built
    • backward compatibility?
      • for ledger id whose higher 32 bits are zero, use split 2-4-4
      • for ledger id whose higher 32 bits are higher than zero, use split 3-4-4-4-4
      • since the first component has different characters (2 vs 3), it is easy to achieve backward compatibility
    • negative ledger id discussion
  • how to generate?

    • use zookeeper sequence znode to create lower 32 bits

    • use another znode to create sequential buckets, the buckets are used for higher 32 bits.
    • when to create bucket?
      • when lower 32-bits generation is approaching 31 bits, create a new bucket.
      • creating a new bucket and the id generation will happen under one zookeeper 'multi' transaction call to guarantee there is only one bucket is created.

Action

 

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