go-patterns — вопросы и ответы

Question 1

Что это такое?

Accepted Answer

Это подборка идиоматичных паттернов проектирования и прикладных паттернов для языка Go (Golang): классические порождающие, структурные и поведенческие паттерны, а также специфичные для Go категории: синхронизация, конкурентность, обмен сообщениями, стабильность и антипаттерны.

Question 2

Это просто список названий паттернов или здесь есть готовый к запуску код на Go?

Accepted Answer

Это справочный список в виде таблиц Markdown. В каждой записи есть колонка «Status»: паттерны, отмеченные галочкой, имеют реальную реализацию на Go в репозитории, а отмеченные символом x только описаны и пока не написаны в коде.

Question 3

Какие паттерны конкурентности реализованы в виде рабочих примеров?

Accepted Answer

Bounded Parallelism, Generators, Parallelism, Fan-In и Fan-Out отмечены как реализованные, а N-Barrier, Broadcast, Coroutines, Reactor и Producer-Consumer пока числятся как todo.

Question 4

Можно ли скопировать реализацию паттерна прямо в свой проект?

Accepted Answer

Каждый реализованный паттерн лежит в репозитории отдельным Go-файлом в папке своей категории (например, creational или concurrency), так что нужный файл можно открыть и использовать напрямую.

Question 5

Зачем в списке паттернов проектирования есть паттерны стабильности, например Circuit-Breaker?

Accepted Answer

Автор дополняет классический каталог паттернами, которые часто встречаются в реальных сервисах на Go, например Circuit-Breaker для остановки запросов, которые, скорее всего, завершатся ошибкой, и Deadline для отказа от слишком медленных ответов.

Pattern	Description	Status
Abstract Factory	Provides an interface for creating families of releated objects	✘
Builder	Builds a complex object using simple objects	✔
Factory Method	Defers instantiation of an object to a specialized function for creating instances	✔
Object Pool	Instantiates and maintains a group of objects instances of the same type	✔
Singleton	Restricts instantiation of a type to one object	✔

Pattern	Description	Status
Bridge	Decouples an interface from its implementation so that the two can vary independently	✘
Composite	Encapsulates and provides access to a number of different objects	✘
Decorator	Adds behavior to an object, statically or dynamically	✔
Facade	Uses one type as an API to a number of others	✘
Flyweight	Reuses existing instances of objects with similar/identical state to minimize resource usage	✘
Proxy	Provides a surrogate for an object to control it's actions	✔

Pattern	Description	Status
Chain of Responsibility	Avoids coupling a sender to receiver by giving more than object a chance to handle the request	✘
Command	Bundles a command and arguments to call later	✘
Mediator	Connects objects and acts as a proxy	✘
Memento	Generate an opaque token that can be used to go back to a previous state	✘
Observer	Provide a callback for notification of events/changes to data	✔
Registry	Keep track of all subclasses of a given class	✘
State	Encapsulates varying behavior for the same object based on its internal state	✘
Strategy	Enables an algorithm's behavior to be selected at runtime	✔
Template	Defines a skeleton class which defers some methods to subclasses	✘
Visitor	Separates an algorithm from an object on which it operates	✘

Pattern	Description	Status
Condition Variable	Provides a mechanism for threads to temporarily give up access in order to wait for some condition	✘
Lock/Mutex	Enforces mutual exclusion limit on a resource to gain exclusive access	✘
Monitor	Combination of mutex and condition variable patterns	✘
Read-Write Lock	Allows parallel read access, but only exclusive access on write operations to a resource	✘
Semaphore	Allows controlling access to a common resource	✔

Pattern	Description	Status
N-Barrier	Prevents a process from proceeding until all N processes reach to the barrier	✘
Bounded Parallelism	Completes large number of independent tasks with resource limits	✔
Broadcast	Transfers a message to all recipients simultaneously	✘
Coroutines	Subroutines that allow suspending and resuming execution at certain locations	✘
Generators	Yields a sequence of values one at a time	✔
Reactor	Demultiplexes service requests delivered concurrently to a service handler and dispatches them syncronously to the associated request handlers	✘
Parallelism	Completes large number of independent tasks	✔
Producer Consumer	Separates tasks from task executions	✘

go-patterns README

Go Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Synchronization Patterns

Concurrency Patterns

Messaging Patterns

Stability Patterns

Profiling Patterns

Idioms

Anti-Patterns

Pattern	Description	Status
Fan-In	Funnels tasks to a work sink (e.g. server)	✔
Fan-Out	Distributes tasks among workers (e.g. producer)	✔
Futures & Promises	Acts as a place-holder of a result that is initially unknown for synchronization purposes	✘
Publish/Subscribe	Passes information to a collection of recipients who subscribed to a topic	✔
Push & Pull	Distributes messages to multiple workers, arranged in a pipeline	✘

Pattern	Description	Status
Bulkheads	Enforces a principle of failure containment (i.e. prevents cascading failures)	✘
Circuit-Breaker	Stops the flow of the requests when requests are likely to fail	✔
Deadline	Allows clients to stop waiting for a response once the probability of response becomes low (e.g. after waiting 10 seconds for a page refresh)	✘
Fail-Fast	Checks the availability of required resources at the start of a request and fails if the requirements are not satisfied	✘
Handshaking	Asks a component if it can take any more load, if it can't, the request is declined	✘
Steady-State	For every service that accumulates a resource, some other service must recycle that resource	✘