1 zookeeper

  • What are they

    • Maintains state machines for each system in a distributed environment
    • Service registration, service discovery
    • A distributed lock
    • Distributed storage of a small amount of critical data

  • Zk system model

/ ├ ─ ─ / API │ ├ ─ ─ member - API │ ├ ─ ─ the order - API │ └ ─ ─ the product - API ├ ─ ─ / db │ ├ ─ ─ mysql │ └ ─ ─ redis └ ─ ─ / services ├ ─ ─ ├─ order-srv ├─ product-srvCopy the code

  • Zk Node type

    • Persistent node
    • Temporary node
    • Persist sequential nodes
    • Temporary sequence node

  • Zk distributed lock

    • ZAB consistency protocol – Ensures the synchronization of node status
    • Temporary sequential nodes – Ensure that each thread that requests a lock can create a node with an increasing node number
    • When a thread disconnects from zK, the temporary node created by the thread can be automatically deleted, and subsequent threads can create a node with a minimum number to acquire the lock
    • The amount of concurrent lock acquisition is limited by the amount of node creation concurrency zK can handle

2 Distributed lock – ETCD

  • What can ETCD do

    • Distributed kv
    • Service discovery/registration
    • A distributed lock
    • Release subscription

  • Principle of distributed locking

    • Create a globally unique prefix_lock_key to lock
    • The client creates the lease
    • LeaseId + prefix_lock_key constitutes a globally unique session
    • OpGet gets all revisions

3 Distributed lock – redis

  • Distributed implementation
  • red lock
  • unlock
if redis.call('get',KEYS[1]) == ARGV[1] then 
   return redis.call('del',KEYS[1]) 
else
   return 0 
end
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4 Distributed lock – mysql