aggregator

type Aggregator interface {
	// Aggregation returns an Aggregation interface to access the
	// current state of this Aggregator.  The caller is
	// responsible for synchronization and must not call any the
	// other methods in this interface concurrently while using
	// the Aggregation.
	Aggregation() aggregation.Aggregation

	// Update receives a new measured value and incorporates it
	// into the aggregation.  Update() calls may be called
	// concurrently.
	//
	// Descriptor.NumberKind() should be consulted to determine
	// whether the provided number is an int64 or float64.
	//
	// The Context argument comes from user-level code and could be
	// inspected for a `correlation.Map` or `trace.SpanContext`.
	Update(ctx context.Context, n number.Number, descriptor *sdkapi.Descriptor) error

	// SynchronizedMove is called during collection to finish one
	// period of aggregation by atomically saving the
	// currently-updating state into the argument Aggregator AND
	// resetting the current value to the zero state.
	//
	// SynchronizedMove() is called concurrently with Update().  These
	// two methods must be synchronized with respect to each
	// other, for correctness.
	//
	// After saving a synchronized copy, the Aggregator can be converted
	// into one or more of the interfaces in the `aggregation` sub-package,
	// according to kind of Aggregator that was selected.
	//
	// This method will return an InconsistentAggregatorError if
	// this Aggregator cannot be copied into the destination due
	// to an incompatible type.
	//
	// This call has no Context argument because it is expected to
	// perform only computation.
	//
	// When called with a nil `destination`, this Aggregator is reset
	// and the current value is discarded.
	SynchronizedMove(destination Aggregator, descriptor *sdkapi.Descriptor) error

	// Merge combines the checkpointed state from the argument
	// Aggregator into this Aggregator.  Merge is not synchronized
	// with respect to Update or SynchronizedMove.
	//
	// The owner of an Aggregator being merged is responsible for
	// synchronization of both Aggregator states.
	Merge(aggregator Aggregator, descriptor *sdkapi.Descriptor) error
}