Embedding Mutex in Go: When is it the Right Approach?

In Go, mutexes play a crucial role in managing concurrent data access. When working with structs, developers face the dilemma of whether to embed a mutex within the struct itself or use a local or global mutex.

Benefits of Embedding Mutex in Struct

Embedding a mutex as a field of a struct offers several advantages:

• Data Protection: It ensures that the mutex is closely associated with the data it protects, making its purpose clear.
• Per-Value Protection: Each instance of the struct has its own dedicated mutex, protecting it from concurrent access individually.

When to Use Embedded Mutex

• When there is a single shared access point to a struct.
• When the struct fields need to be protected from concurrent modifications.
• When multiple instances of the struct need to be protected individually.

When to Use Local or Global Mutex

• Local Mutex: When the data access is limited to a specific function or scope.
• Global Mutex: When there is only one instance of the struct in the application, ensuring that data access is serialized.

True Embedding vs. Field Declaration

While the example in the question involves adding a named mutex field, true embedding in Go uses an embedded field declaration without specifying the field name. It allows direct access to mutex methods using the receiver syntax, as seen in the following code:

var hits struct {
    sync.Mutex
    n int
}

hits.Lock()
hits.n  
hits.Unlock()

Conclusion

The decision of whether to embed a mutex in a struct or use a local or global mutex depends on the specific requirements of the application. Embedding a mutex provides direct protection and per-value isolation, while local and global mutexes offer flexibility and scalability. Understanding these principles aids in designing efficient and scalable Go programs that handle concurrency effectively.