folly::observer::AtomicObserver

An AtomicObserver provides read‐optimized caching for an Observer using std::atomic. Reading only requires atomic loads unless the cached value is stale. If the cache needs to be refreshed, a mutex is used to synchronize the update. This avoids creating a shared_ptr for every read.

Synopsis

Declared in <folly/observer/Observer.h>

template<typename T>
class AtomicObserver;

Description

AtomicObserver models CopyConstructible and MoveConstructible. Copying or moving simply invalidates the cache.

AtomicObserver is ideal when there are lots of reads on a trivially‐copyable type. if std::atomic<T> is not possible but you still want to optimize reads, consider a TLObserver.

Observer<int> observer = ...; AtomicObserver<int> atomicObserver(observer); auto value = *atomicObserver;