Create a "disk canary" feature that can be used as a background thread in MongoDB server applications, or as a standalone application that only functions as a disk canary. 

Requirements:

• Implemented as a standalone class or free functions & configuration structures with minimal dependencies. There should be very little existing MongoDB libraries required to implement this, C++ standard libraries such as filesystem should be sufficient.
• Must not use WiredTiger libraries - this should be an independent test of the storage device with operating system primitives, or the thin wrapper that std::filesystem provides.
• Must have configurable test conditions. Eg: checking for a size=0 write, with/without O_DIRECT, testing the creation, deletion, truncation, etc. of a file.
• Must have configurable location on the local filesystem, but default to a particular storage device or partition. 
• Must return an error code upon failure, so higher level wrappers can chose to ignore certain failures.
• Implement a background thread wrapper for easy integration in MongoDB applications eg: mongos or mongod.
• Implement a standalone executable wrapper that exits with a non-zero status when a check fails.

Possible Extensions:

• Configurable retry/level trigger logic. Eg: only fail the check if N failures within S seconds