如何进行数据完整性和错误处理？

Question

Maybe this is a silly question, but after I asked some friends and googled for a while, and still cannot find a good explanation.

For example, I will do follow operations when one user posts:

1. MySQL.insert(user, postTitle, postBody, time)
2. Redis.incr user.totalPostCount
3. Redis.set last10Posts

So my question is, for example, if 1 success but 2 fails, what should I do?

Ignore the redis error and continue? then user.totalPostCount is incorrect.

Retry redis.incr ? What to do if retry fails?

Return error to end-user says post fail and let user post again?

Delete the post which previously inserted and return error to user?

mysql.insert({user: user, postTitle: postTitle, postBody: postBody}, function(err, mysqlId) {
  if(err) { return Error(500); }
  redis.incr({user: user, totalPostCount}, function(err, result) {
    if(err) { mysql.delete(mysqlId)}
    setLast10Post({newPost: {postTitle...}}, function(err, result) {
      if(err) {mysql.delete(mysqlId); redis.decr({user.totalPostcount})}
    })
  })

})

Answer 1

You probably want those 3 operations to be a single atomic operation. That is, if any step fails, you want to make sure the whole thing fails and nothing happens.

So for scenario 1 (1 success, 2 fail), you'd rollback the SQL query and report an error. You could forget anything happened or retry the whole process at that point.

As for actually creating this transaction, perhaps this link is helpful.