How to Maintain a Constant Number of Concurrent Goroutines in Go?

How to Ensure a Constant Number of Goroutines

Concurrent programming in Go involves creating multiple goroutines (lightweight threads) to perform tasks concurrently. While it's common to manage the completion of goroutines, a different challenge arises when you need to guarantee a specific number of goroutines running simultaneously.

Consider a scenario where you have a significant number of tasks to process and want to limit the number of active goroutines at any given time. For instance, you could have a process that handles incoming requests and wants to restrict the number of concurrent requests to maintain system stability.

To achieve this, we can employ the technique of "bounded parallelism," as described in the Go Concurrency Patterns article. The key idea is to use a channel of empty structs as a limiting guard to control the number of worker goroutines.

In the provided code snippet, the guard channel is initialized with a capacity equal to the maximum number of goroutines we want to run concurrently (in this case, 10). To ensure this limit, any new goroutine creation first tries to receive an empty struct from the guard channel. If the channel is full (indicating that the goroutine limit is reached), the creation is blocked until a slot becomes available.

As each goroutine completes its work, it returns the empty struct to the guard channel, making it available for another goroutine to start. Through this mechanism, we ensure that the number of active goroutines remains within the specified bounds.

In the example:

• The maxGoroutines variable defines the maximum number of concurrent goroutines.
• The guard channel is initialized with a capacity of 10, which limits the maximum number of goroutines that can be created.
• The worker function represents the individual task that each goroutine executes.
• The main function creates 30 goroutines, but only 10 of them can execute simultaneously due to the guard channel's limit.

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