PROSAGA码农传奇-区块链扩展技术-高度分布式OLTP架构

0# 晴天？霹雳 | 2019-08-31 10-32

你看过Splice Machine了吗？它是一个完全符合ACID标准的RDBMS，它运行在hadoop堆栈（hbase，spark，hdfs，zookeeper）之上。它们具有双体系结构，使用hbase进行快速OLTP查询，并为OLAP查询提供内容，并且内置了不需要任何锁定的事务功能。

1# 晴天3 | 2019-08-31 10-32

基本上你需要的是一个分布式锁定机制。许多分布式服务器应用程序提供了这样的功能。

基本上，如果我们将您的问题转换为代码，它将看起来像这样


    
      // BANK WITHDRAWAL APPLICATION
// Fetch BankAccount object from NCache
BankAccount account = cache.Get(“Key”) as BankAccount; // balance = 30,000
Money withdrawAmount = 15000;
if (account != null && account.IsActive)
{
    // Withdraw money and reduce the balance
    account.Balance -= withdrawAmount;
// Update cache with new balance = 15,000
cache.Insert("Key", account);
}
</code>


  
  

   
    
      // BANK DEPOSIT APPLICATION
// Fetch BankAccount object from NCache
BankAccount account = cache.Get(“Key”) as BankAccount; // balance = 30,000
Money depositAmount = 5000;
if (account != null && account.IsActive)
{
    // Deposit money and increment the balance
    account.Balance += depositAmount;
// Update cache with new balance = 35,000
cache.Insert("Key", account); 
}
</code>
  

  
    这基本上是竞争条件的一个例子
  

  
    
      竞争条件是两个或更多用户同时尝试访问和更改相同的共享数据，但最终以错误的顺序执行此操作。
    

  

  
    分布式锁定中上述代码的答案是
  

   
    
      LockHandle lockHandle = new LockHandle();
// Specify time span of 10 sec for which the item remains locked
// NCache will auto release the lock after 10 seconds.
TimeSpan lockSpan = new TimeSpan(0, 0, 10); 
try
{
    // If item fetch is successful, lockHandle object will be populated
    // The lockHandle object will be used to unlock the cache item
    // acquireLock should be true if you want to acquire to the lock.
    // If item does not exists, account will be null
    BankAccount account = cache.Get(key, lockSpan,
    ref lockHandle, acquireLock) as BankAccount;
    // Lock acquired otherwise it will throw LockingException exception
if(account != null && account.IsActive)
{
    // Withdraw money or Deposit
    account.Balance += withdrawAmount;
    // account.Balance -= depositAmount;
    // Insert the data in the cache and release the lock simultaneously 
    // LockHandle initially used to lock the item must be provided
    // releaseLock should be true to release the lock, otherwise false
    cache.Insert("Key", account, lockHandle, releaseLock); 
}
else
{
    // Either does not exist or unable to cast
    // Explicitly release the lock in case of errors
    cache.Unlock("Key", lockHandle);
} 
}
catch(LockingException lockException)
{
    // Lock couldn’t be acquired
    // Wait and try again
}
</code>
  

  
    这个答案非常特定于NCache（分布式缓存）。我相信你会在关键字“分布式锁定”下找到更多解决方案
  

  
    
      资源

2# Jacob | 2019-08-31 10-32

ClustrixDB是另一种可能值得一试的解决方案。它使用Paxos进行分布式事务解析（内置于分布式，ACID，SQL兼容的RDBMS），并具有内置的容错功能。