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  1. MariaDB MaxScale
  2. MXS-1720

Priori causal read

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    • New Feature
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Fixed
    • None
    • 2.5.0
    • readwritesplit
    • None

    Description

      Using master_wait_gitd(MXS-199) to achieve causal read is not work so well when replication lag cannot ignore (such as > 100ms); We tested it with 5.7 and turn on logical clock, and set innodb_flush_log_at_trx_commit = 1000 on replica, read write ratio is 5:1, the performance is no better than route to single node; Maybe Mysql 8.0's Writeset-based replication will improve this, or Polardb's physical replication.

      Because replication lag has many influence factors,so we need another way to achieve causal read;

      Our proposal:
      1. Find a way to get latest gtid info of every replica;
      a. Regularly get it from monitor
      b. Update it when ok packet is received, if it is newer than recorded one, update it using CAS;
      2. Compare backend's gtid in proxy side;

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              markus makela markus makela
              dapeng dapeng huang
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                Resolved:

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