Robust Timeout Handling in Rust

This challenge focuses on implementing robust timeout handling in Rust, a crucial aspect of building reliable and responsive applications. You'll create a function that executes a given closure with a specified timeout, gracefully handling cases where the closure takes too long to complete. This is essential for preventing indefinite blocking and ensuring system stability.

Problem Description

You are tasked with creating a function with_timeout that takes a closure (F) and a timeout duration (Duration). The closure F should accept a single argument of type T and return a result of type R. The with_timeout function should execute the closure F with the provided argument, but if the closure takes longer than the specified timeout duration to complete, it should return a Result::Err with a specific error message indicating the timeout. If the closure completes within the timeout, it should return Result::Ok containing the closure's result.

Key Requirements:

• Timeout Mechanism: The function must accurately enforce the specified timeout duration.
• Graceful Handling: The function should not panic or deadlock if the closure exceeds the timeout.
• Result Type: The function must return a Result<R, String> to indicate success or timeout.
• Closure Execution: The provided closure must be executed with the given argument.
• Error Message: The Err variant of the Result should contain a clear and informative error message indicating a timeout occurred.

Expected Behavior:

• If the closure completes within the timeout, Ok(closure_result) is returned.
• If the closure exceeds the timeout, Err("Timeout occurred") is returned.
• The function should handle potential panics within the closure gracefully (though not required to recover from them, simply return the Err in that case).

Edge Cases to Consider:

• Zero Timeout: What should happen if the timeout duration is zero? (Return Err immediately)
• Closure Panics: How should the function behave if the closure panics? (Return Err)
• Very Short Timeout: Test with timeouts shorter than the expected execution time of the closure.

Examples

Example 1:

Input: `with_timeout(|| Ok(5), Duration::from_secs(2))`
Output: `Ok(5)`
Explanation: The closure completes within the 2-second timeout, so the result (5) is returned wrapped in `Ok`.

Example 2:

Input: `with_timeout(|| std::thread::sleep(Duration::from_secs(3)); Ok(5), Duration::from_secs(2))`
Output: `Err("Timeout occurred")`
Explanation: The closure takes 3 seconds to complete, exceeding the 2-second timeout.  The function returns an `Err` with the timeout message.

Example 3: (Closure Panics)

Input: `with_timeout(|| panic!("Intentional panic"), Duration::from_secs(2))`
Output: `Err("Timeout occurred")`
Explanation: The closure panics. The function returns an `Err` with the timeout message.

Constraints

• Timeout Duration: The timeout duration will be a std::time::Duration.
• Closure Argument: The closure argument type T and return type R are generic.
• Performance: The solution should avoid unnecessary allocations or complex data structures that would significantly impact performance. While not a primary concern, avoid solutions that introduce excessive overhead.
• Error Message Length: The error message should be concise and informative (e.g., "Timeout occurred").

Notes

• Consider using std::time::Instant to measure elapsed time.
• You might find std::thread useful for simulating long-running operations.
• Think about how to interrupt the closure's execution if it exceeds the timeout. (Note: Interrupting arbitrary code is difficult and often unsafe. This challenge focuses on detecting the timeout, not forcibly stopping the closure.)
• The goal is to demonstrate a clear understanding of timeout handling concepts in Rust, not to create a production-ready, highly optimized timeout library.