HTTP Error 412: Precondition Failed

[KhanKrum]

What is that:
Challenge cracker for correct results
Remote request exception: HTTP Error 412: Precondition Failed
Sleeping...
.....

[RealEnder]

This is part of Proof-of-Work, we've implemented recently. There are some rogue clients that just pull uncracked hashes without actually trying to crack them. In this case we send known crackable hashes and expect the client to return at least them to confirm this work unit was tried.
This has several negative consequences:

• If you run help_crack.py, then stop it and run it again, it will have to wait for the timeout (currently 1h) to pass.
• If you run more than one help_crack.py client behind one public IP, one of the clients will also hit PoW barrier.

[KhanKrum]

Oh, I see! But why did I get stuck in this trap? Actually, I try to process as many hashes as possible, and I'm even surprised how I always manage to crack something in every session...