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RocksDB from 2 processes: IO error: While lock file: sample.db/LOCK: Resource temporarily unavailable – Debian

I am using RocksDB and i love the performance of it. I am using it in my high requests/second server for the GET operation.

The problem is that i need to update my RocksDB from time to time.

So, i have Process_A that keeps rocksdb opened and keeps on performing get operations on it.

Now, i want Process_B to run in a crontab every X amount of time (let’s say 30 minutes) that will come and add a couple of entries in the RocksDB.

The problem is that the file is in use, and i get the LOCK error, naturally.
I am running this on debian buster.
What puzzles me though, is that it kind of works randomly.

Did anybody try this scenario? Or maybe knows a better way of doing this?

The other way would be to stop Process_A, perform the updates with Process_B, then restart Process_A, but this would cause me to lose requests…

Thank you.

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  1. Chosen as BEST ANSWER
    0

    For whoever meets this scenario, just found out. It's totally possible, you just have to open the RocksDB from Process_A with readonly mode.

    Not sure what's the method for the native rocksdb library, i'm using RocsDB-Sharp for C# and it has a method called RocksDB.OpenReadonly() (instead of just Open()).

    Next, i'll test if the changes actually applies when i insert data while opened in the other process, or if i have to close the DB from Process_A and reopen it each time i insert something.

    I'll keep you posted.


  2. 0

    You cannot open the same DB with 2 processes, if both have write permission.

    If you have one process for write, another one for read, the data will not be synced until it’s flushed. For concurrently read/write, typically the user creates multiple threads in one process.

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