删除Solr服务器上的updateLog(Remove updateLog on Solr server)

 对于在同一个表上运行50到100个并发进程的系统，我对此进行了大量的研究和实验。 除了基本的死锁之外，还有许多事务失败。 我的案例包括read committed和serializable事务。 在应用程序级别处理此问题并不会导致任何问题。 幸运的是Postgres会立即失败，所以唯一的性能打击是应用程序，对数据库没有任何重要意义。 
 
 关键组件是捕获每种类型的错误 ，知道哪些情况需要回滚，并具有重试的指数退避 。 我发现立即重试或静态睡眠时间会导致进程重复地相互死锁并引起一些多米诺骨牌效应，这是有道理的。 
 
 这是我的系统处理每个并发问题（伪代码）所需的完整逻辑： 
 
begin transaction (either read committed or serializable)
while not successful and count < 5
    try 
        execute sql
        commit
    except
        if error code is '40P01' or '55P03'
            # Deadlock or lock not available
            sleep a random time (200 ms to 1 sec) * number of retries
        else if error code is '40001' or '25P02'
            # "In failed sql transaction" or serialized transaction failure
            rollback
            sleep a random time (200 ms to 1 sec) * number of retries
            begin transaction
        else if error message is 'There is no active transaction'
            sleep a random time (200 ms to 1 sec) * number of retries
            begin transaction
    increment count

I did a lot of research and experimentation into this for a system that's running 50 to 100 concurrent processes on the same tables. There are a number of transaction failures that can happen besides basic deadlocks. My case includes both read committed and serializable transactions. There's no situation where handling this at the application level caused any issues. Fortunately Postgres will fail immediately, so the only performance hit is to the application, nothing significant to the database.
 
The key components are catching every type of error, knowing which cases require a rollback, and having an exponential backoff for retries. I found that immediate retries or static sleep times cause processes to simply deadlock each other repeatedly and cause a bit of a domino effect, which makes sense.
 
This is the complete logic my system requires to handle every concurrency issue (pseudocode):
 
begin transaction (either read committed or serializable)
while not successful and count < 5
    try 
        execute sql
        commit
    except
        if error code is '40P01' or '55P03'
            # Deadlock or lock not available
            sleep a random time (200 ms to 1 sec) * number of retries
        else if error code is '40001' or '25P02'
            # "In failed sql transaction" or serialized transaction failure
            rollback
            sleep a random time (200 ms to 1 sec) * number of retries
            begin transaction
        else if error message is 'There is no active transaction'
            sleep a random time (200 ms to 1 sec) * number of retries
            begin transaction
    increment count