wal

Documentation

Index

• Variables
• type AppendResult
• type HandleParam
• type HandleResult
• type MessageFilter
• type MessageHandler
• type OpenOption
• type Opener
• type OpenerBuilder
• type ReadOption
• type Scanner
• type WAL

Variables

var ErrUpstreamClosed = errors.New("upstream closed")

Types

type AppendResult

type AppendResult = types.AppendResult

type HandleParam

type HandleParam struct {
	Ctx          context.Context
	Upstream     <-chan message.ImmutableMessage
	Message      message.ImmutableMessage
	TimeTickChan <-chan struct{}
}

type HandleResult

type HandleResult struct {
	Incoming        message.ImmutableMessage // Not nil if upstream return new message.
	MessageHandled  bool                     // True if Message is handled successfully.
	TimeTickUpdated bool                     // True if TimeTickChan is triggered.
	Error           error                    // Error is context is canceled.
}

type MessageFilter

type MessageFilter = func(message.ImmutableMessage) bool

type MessageHandler

type MessageHandler interface {
	// Handle is the callback for handling message.
	Handle(param HandleParam) HandleResult

	// Close is called after all messages are handled or handling is interrupted.
	Close()
}

MessageHandler is used to handle message read from log. TODO: should be removed in future after msgstream is removed.

type OpenOption

type OpenOption struct {
	Channel types.PChannelInfo
}

OpenOption is the option for allocating wal instance.

type Opener

type Opener interface {
	// Open open a wal instance.
	Open(ctx context.Context, opt *OpenOption) (WAL, error)

	// Close closes the opener resources.
	Close()
}

Opener is the interface for build wal instance.

type OpenerBuilder

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

	Build() (Opener, error)
}

OpenerBuilder is the interface for build wal opener.

type ReadOption

type ReadOption struct {
	VChannel       string // vchannel name
	DeliverPolicy  options.DeliverPolicy
	MessageFilter  []options.DeliverFilter
	MesasgeHandler MessageHandler // message handler for message processing.

}

ReadOption is the option for reading records from the wal.

type Scanner

type Scanner interface {
	// Chan returns the channel of message if Option.MessageHandler is nil.
	Chan() <-chan message.ImmutableMessage

	// Channel returns the channel assignment info of the wal.
	Channel() types.PChannelInfo

	// 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
}

Scanner is the interface for reading records from the wal.

type WAL

type WAL interface {
	WALName() string

	// Channel returns the channel assignment info of the wal.
	Channel() types.PChannelInfo

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

	// Append a record to the log asynchronously.
	AppendAsync(ctx context.Context, msg message.MutableMessage, cb func(*AppendResult, error))

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

	// Available return a channel that will be closed when the wal is available.
	Available() <-chan struct{}

	// IsAvailable returns if the wal is available.
	IsAvailable() bool

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

WAL is the WAL framework interface. !!! Don't implement it directly, implement walimpls.WAL instead.