How to protect your database from corruption

[appy-one]

While testing and debugging new AceBase functionality today, I ran into a situation where I managed to corrupt my test database file because I broke the locking mechanism in an important part of the code. This caused the recursive loading of data paths because a child key pointed back to a parent record address, causing an endless loop. I've seen this happening before, but I never felt the need to do anything about it because, well, these things can happen during development.

Today was different though. I wanted the code to discover this endless loop, stop execution and throw an error. While building this, I started documenting the code to tell other developers that might run into this issue to understand what might be causing this. And then I realized there were multiple scenarios that could cause a database file to become corrupted.

I thought I'd share that info here!

I'm adding the following comments to storage-acebase.js:

If you don't want to corrupt your database, here's how:

• DO NOT use multiple AceBase instances on a single database in your app.
  Instead: use a shared AceBase instance throughout your app: new AceBase("mydb"); only ONCE per db in your code!
• DO NOT let multiple apps access the same database at the same time
  Instead: setup an AceBaseServer and use an AceBaseClient to connect to it.
• DO NOT let multiple instances of your app (in isolated processes) access the same database at the same time
  Instead: Use NodeJS or pm2 clustering functionality to fork the process (IPC is available)
• Do NOT run multiple AceBaseServer instances on the same database files without an IPC server.
  Instead: Setup an AceBaseServer IPC Server

I hope you are reading this because you just stumbled upon it, and not because you have a corrupted database. But if you do, you probably now know why (above reasons) and how to prevent it from happening again. I will be also providing ways to fix your db soon. Keep an eye on this discussion or post a comment here if you need help!

UPDATE 2022/08/22: To fix broken nodes, see PR #142

Please refer to the AceBaseServer IPC Server documentation if you are running / want to run AceBase in multi-process / auto-scaling environments.