Structured concurrency is a paradigm that is used to manage concurrency in Kotlin’s coroutines. It is based on the idea of treating concurrent code execution as a set of structured hierarchies. This approach helps in managing the concurrent code’s execution by providing a set of rules and guidelines that ensure the proper execution and management of concurrent code.
In structured concurrency, every coroutine execution is associated with a parent coroutine, which can be seen as a scope for child coroutines. The parent coroutine is responsible for defining the lifecycle of the associated child coroutines. The child coroutines must complete before the parent coroutine implementation completes, and if any child coroutine aborts or completes exceptionally, an unhandled exception will propagate to the parent coroutine, which will terminate all related coroutines.
Structured concurrency helps solve the problem of unstructured and unmanaged concurrency execution, which in a large, complex concurrent execution environment can lead to race conditions, deadlocks, and memory leakage. Structured concurrency employs the following principles to achieve its objectives.
Scoped concurrency: Every coroutine is tied to a specific scope, which is defined by its parent coroutine. This scope is responsible for controlling the lifecycle of its associated coroutines. A suspended or blocked coroutine should not outlive the parent’s scope.
Hierarchical structure: Every coroutine has a defined parent-child relationship that forms a hierarchical structure, defining the relationship between coroutines’ scopes in runtime. A parent coroutine can launch many child coroutines, which can also launch their child coroutines. This way, a single parent coroutine can manage an entire set of coroutines that are related to a specific task or objective.
Non-blocking execution: Structured concurrency is designed to achieve non-blocking execution with a structured approach. This way, a coroutine blocks neither the parent coroutine nor any of its siblings when it is waiting for the completion of a child coroutine. Non-blocking execution is achieved when a coroutine suspends itself, thus freeing up the runtime environment to execute other coroutines.
Exception handling: In structured concurrency, every coroutine is responsible for handling the exception it generates. The parent coroutine is informed when one of its child coroutines an exception from which it does not recover. This way, it throws the corresponding exception and terminates all its child coroutines.
In conclusion, structured concurrency in Kotlin’s coroutines provides a structured approach to handle and manage concurrent code execution. This way, it ensures the proper execution of concurrent code by providing a set of rules and guidelines for developing concurrent code without race conditions, memory leakage, and deadlocks. It also allows developers to represent complex flows of operations with a hierarchical structure that makes it easy to read, understand and ensures changes to the program’s flow without altering it fundamentally.