keyvalue

Documentation

Overview

Package keyvalue contains a base implementation of much of the common logic required for a scale-out tablestore implementation of an event store. Each store driver need only support four methods, which can be passed via the keyvalue.Options structure:

CheckSequence			// Check if a particular key/seq pair exists.
FetchEvents				// Fetch events forward from a particular sequence number
PutEvents				// Put a set of events into the store
Close					// Shut-down the driver

By abstracting store implementations down to this API, it's assumed it will be easier to add more providers later. Specific providers that suit this model include DynamoDB, Azure Tables, MongoDB, Cassandra - but the model will work for essentially any provider that has support for a dual-part unique key (Agg ID, Sequence) and supports range scans for these.

Index

• func NewStore(options Options) eventsourcing.EventStore
• type CloseCallback
• type Event
• type FetchCallback
• type KeyedEvent
• type Options
• type PutCallback
• type SequenceExistsCallback

Functions

func NewStore

func NewStore(options Options) eventsourcing.EventStore

NewStore creates a new key-value store that provides a simple baseline set of event storage capabilities

Types

type CloseCallback

type CloseCallback func() error

CloseCallback closes the KVS

type Event

type Event struct {
	EventType eventsourcing.EventType `json:"type"`
	EventData interface{}             `json:"data"`
}

Event is a raw event within a key-value store.

type FetchCallback

type FetchCallback func(key string, seq int64) ([]KeyedEvent, error)

FetchCallback is a function that describes the behaviour for fetching events from a key-value store. Typically this is a sequential crawl forward from the specified sequence for a partitioning key.

type KeyedEvent

type KeyedEvent struct {
	Key       string                  `json:"key"`
	Sequence  int64                   `json:"sequence"`
	EventType eventsourcing.EventType `json:"type"`
	EventData interface{}             `json:"data"`
}

KeyedEvent is an event with a key and sequence.

type Options

type Options struct {
	CheckSequence SequenceExistsCallback // Check function to see if seq exists
	FetchEvents   FetchCallback          // Fetch events function
	PutEvents     PutCallback            // Put events function
	Close         CloseCallback          // Close callback
}

Options is a structure containing the function callbacks required for a simple key-value store to be used as an event storage engine.

type PutCallback

type PutCallback func(events []KeyedEvent) error

PutCallback is a function that puts events into the store.

type SequenceExistsCallback

type SequenceExistsCallback func(key string, seq int64) (bool, error)

SequenceExistsCallback is a function that checks if given offset exists already within the store.