Golang sync Pool is used to create a self-managed object pool, with just New/Get/Set functions. The Pool implementation uses a mutex based locking for thread-safe operations from multiple Go routines.

Design Principles

• Golang sync. Pool use garbage collection to manage objects. The pool is essentially a list of user-defined blob objects that are GC’ed periodically.
• The application uses Get/Put for using an object from the Pool.
• The application defines a New method to create a new object.
• The application does not bother about object memory management.
• Unreferenced that is objects present in the Pool at a given time is GC’ed.
• There is no finalizer for objects deletion.
• Get randomly selected object from the list; if no object is available, creates a new object and returns it.
• Put places an object back to the Pool.
• The design wants to avoid hotspots and randomize object selections in Put and Get operations. So, Put and Get calls may not be co-related.
  • A Put op may randomly return without placing the object back to the Pool.
  • This intentional delay helps the Get to pick a new object.

What are Potential Problems with Pool

• If the object has allocated resources (socket, buffer), there is no way to free them!
• If the application has got an object and starts processing it with async operations, there is a risk of data corruption if the application returns the object to the Pool.

Best Use cases for Pool

• Plain buffer management
• Non-composite objects lifecycle management

Not to Use If

• Objects that dynamically allocate resources (buffer, sockets)
• Objects that are processed asynchronously.

References

• https://golang.org/src/sync/pool.go
• https://www.akshaydeo.com/blog/2017/12/23/How-did-I-improve-latency-by-700-percent-using-syncPool/