walimpls

type OpenOption struct {
	Channel types.PChannelInfo // Channel to open.
}

type OpenerBuilderImpls interface {
	// Name of the wal builder, should be a lowercase string.
	Name() string

	// Build build a opener impls instance.
	Build() (OpenerImpls, error)
}

type OpenerImpls interface {
	// Open open a WALImpls instance.
	Open(ctx context.Context, opt *OpenOption) (WALImpls, error)

	// Close release the resources.
	Close()
}

type ReadOption struct {
	// The name of the reader.
	Name string
	// ReadAheadBufferSize sets the size of scanner read ahead queue size.
	// Control how many messages can be read ahead by the scanner.
	// Higher value could potentially increase the scanner throughput but bigger memory utilization.
	// 0 is the default value determined by the underlying wal implementation.
	ReadAheadBufferSize int
	// DeliverPolicy sets the deliver policy of the reader.
	DeliverPolicy options.DeliverPolicy
}

type ScannerImpls interface {
	// Name returns the name of scanner.
	Name() string

	// Chan returns the channel of message.
	Chan() <-chan message.ImmutableMessage

	// Error returns the error of scanner failed.
	// Will block until scanner is closed or Chan is dry out.
	Error() error

	// Done returns a channel which will be closed when scanner is finished or closed.
	Done() <-chan struct{}

	// Close the scanner, release the underlying resources.
	// Return the error same with `Error`
	Close() error
}

type WALImpls interface {
	// WALName returns the name of the wal.
	WALName() string

	// Channel returns the channel assignment info of the wal.
	// Should be read-only.
	Channel() types.PChannelInfo

	// Append writes a record to the log.
	Append(ctx context.Context, msg message.MutableMessage) (message.MessageID, error)

	// Read returns a scanner for reading records from the wal.
	Read(ctx context.Context, opts ReadOption) (ScannerImpls, error)

	// Close closes the wal instance.
	Close()
}