The blog post explores the performance implications of Go's panic and recover mechanisms. It demonstrates through benchmarking that while the cost of a single panic/recover pair isn't exorbitant, frequent use, particularly nested recovery, can introduce significant overhead, especially when compared to error handling using if statements and explicit returns. The author highlights the observed costs in terms of both execution time and increased binary size, particularly when dealing with defer statements within the recovery block. Ultimately, the post cautions against overusing panic/recover for regular error handling, suggesting they are best suited for truly exceptional situations, advocating instead for more conventional Go error handling patterns.
The blog post "The cost of Go's panic and recover" by Roberto Clapis explores the performance implications of using Go's error handling mechanisms, specifically panic and recover, compared to traditional error return values. Clapis begins by acknowledging that while panic and recover are powerful tools for exceptional situations and halting execution upon encountering unrecoverable errors, their usage comes with a non-negligible performance overhead.
The author then details a series of benchmarks designed to quantify this overhead. These benchmarks compare the execution time of three distinct approaches to error handling: returning errors normally through the function's return value, using panic and recover to handle errors, and a hybrid approach that employs panic and recover but only within a specifically designated error handling function. The benchmarks cover various scenarios, including cases where errors are frequent and cases where they are rare.
The results of the benchmarks demonstrate that handling errors using the standard return mechanism is significantly faster than using panic and recover. This performance disparity is attributed to the additional work the runtime must perform when a panic occurs, such as unwinding the stack and executing deferred functions. The difference becomes more pronounced as the frequency of errors increases.
Interestingly, the benchmarks also reveal that using the hybrid approach, where panic and recover are confined within a dedicated error handling function, offers a compromise. This method, while still slower than standard error returns, performs considerably better than using panic and recover directly within the main execution flow. This suggests that strategically isolating panic and recover can mitigate some of their performance impact.
Clapis concludes by emphasizing that while panic and recover have their place, especially for truly unrecoverable errors, developers should be mindful of their performance implications. For routine error handling, the standard error return mechanism remains the more efficient choice. The hybrid approach can be a viable alternative when a degree of both control and error propagation is required, offering a balance between performance and the convenience of stack unwinding provided by panic and recover. The author reinforces the idea that understanding the cost associated with each error handling strategy allows developers to make informed decisions based on the specific needs of their application.
Summary of Comments ( 79 )
https://news.ycombinator.com/item?id=43217209
Hacker News users discuss the tradeoffs of Go's
panic/recovermechanism. Some argue it's overused for non-fatal errors, leading to difficult debugging and unpredictable behavior. They suggest alternatives like error handling with multiple return values or theerrorspackage for better control flow. Others defendpanic/recoveras a useful tool in specific situations, such as halting execution in truly unrecoverable states or within tightly controlled library functions where the expected behavior is clearly defined. The performance implications ofpanic/recoverare also debated, with some claiming it's costly, while others maintain it's negligible compared to other operations. Several commenters highlight the importance of thoughtful error handling strategies in Go, regardless of whetherpanic/recoveris employed.The Hacker News post "The cost of Go's panic and recover" (https://news.ycombinator.com/item?id=43217209) has generated a substantial discussion with several compelling comments exploring various facets of Go's error handling mechanisms.
Several commenters discuss the performance implications of
panicandrecover, agreeing that while there's a cost associated, it's often negligible in real-world applications. One commenter points out that the cost is minimal compared to the overhead of other operations like network calls or disk I/O. Another clarifies that the benchmark presented in the article likely exaggerates the cost in typical scenarios, as it involves panicking and recovering in a tight loop, which is uncommon. They suggest that for most use cases, the performance impact is insignificant and shouldn't discourage the appropriate use ofpanicandrecover.A recurring theme in the comments is the distinction between using
panicandrecoverfor exceptional situations versus routine error handling. Many agree thatpanicshould be reserved for truly unrecoverable errors, where the program is in an inconsistent state and continued execution is unsafe. They caution against usingpanicfor expected errors, advocating instead for Go's standard error handling pattern using multiple return values. One commenter emphasizes thatpanicis not a general-purpose error handling mechanism and should be used sparingly, whilerecovershould be restricted to carefully defined boundaries, such as the top level of a request handler. Usingpanicandrecoverfor flow control is generally discouraged.The discussion also touches upon the difficulties of reasoning about code that uses
panicandrecoverextensively. One commenter highlights the non-local nature ofpanicandrecover, making it harder to follow the control flow and understand the program's behavior. This complexity can lead to subtle bugs and make debugging more challenging. Another commenter suggests that usingpanicandrecovercan obscure the error handling logic, making it difficult to determine where errors are handled and what the intended behavior is.Finally, alternatives to
panicandrecoverare discussed, including the use of error return values and the possibility of introducing checked exceptions to Go. While some commenters express interest in exploring alternative error handling approaches, others argue that Go's existing mechanisms are sufficient and that checked exceptions would introduce unnecessary complexity. The overall sentiment seems to be that Go's current error handling approach, when used correctly, is effective and thatpanicandrecoverhave specific, limited roles to play in handling truly exceptional circumstances.