How Do `time.Sleep`, Blocking Tickers, and `select` Differ in Go's Concurrency Model?

Behavior of Sleep and Select in Go

In Go, there are various ways to implement blocking/waiting operations, each with its own underlying behavior. This article explores the differences between time.Sleep, blocking tickers (<-t.C), and select on multiple channels, investigating how they affect system calls, CPU scheduling, and resource utilization.

time.Sleep

time.Sleep suspends the current goroutine for a specified duration. When called, it triggers a runtime.timer in the Go runtime. The runtime goroutine scheduler places the goroutine into a "parked" state, freeing up the thread for other goroutines. The timer callback function wakes up the goroutine when the time expires.

Blocking Ticker (-

A blocking ticker, created using time.NewTicker, employs a runtime.timer and a channel. The timer sends the current time to the channel periodically. When a blocking receive is performed on the channel, the goroutine is parked until the timer sends a value, similar to the behavior in time.Sleep.

Select Multiple Channels

A select statement allows for waiting on multiple channels concurrently. In your example, if otherChan remains empty, the behavior is identical to the blocking ticker, as the waiting goroutine is parked until either time.Ticker sends a value or the select statement closes the channel. When otherChan receives a value, it wakes up the goroutine, offering a more flexible waiting mechanism.

Resource Utilization

All three options involve parking the goroutine, so they do not directly allocate CPU resources. However, the channel-based operations (blocking ticker and select) introduce additional overhead due to channel management and the runtime goroutine that manages the timers. In the case where otherChan never receives values, time.Sleep may be slightly less resource-intensive due to its simpler implementation.

Conclusion

While all three options achieve the goal of waiting, their underlying implementations and overheads differ. time.Sleep offers a straightforward sleep mechanism, while blocking tickers and select statements provide more flexibility and control over waiting behavior. Careful consideration should be given to the specific requirements and performance trade-offs when selecting among these options.

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