state

README

State Stores

State Stores provide a common way to interact with different data store implementations, and allow users to opt-in to advanced capabilities using defined metadata.

Currently supported state stores are:

• AWS DynamoDB
• Aerospike
• Azure Blob Storage
• Azure CosmosDB
• Azure Table Storage
• Cassandra
• Cloud Firestore (Datastore mode)
• CloudState
• Couchbase
• Etcd
• HashiCorp Consul
• Hazelcast
• Memcached
• MongoDB
• PostgreSQL
• Redis
• RethinkDB
• SQL Server
• Zookeeper

Implementing a new State Store

A compliant state store needs to implement one or more interfaces: Store and TransactionalStore.

The interface for Store:

type Store interface {
	Init(metadata Metadata) error
	Delete(req *DeleteRequest) error
	BulkDelete(req []DeleteRequest) error
	Get(req *GetRequest) (*GetResponse, error)
	Set(req *SetRequest) error
	BulkSet(req []SetRequest) error
}

The interface for TransactionalStore:

type TransactionalStore interface {
	Init(metadata Metadata) error
	Multi(reqs []TransactionalRequest) error
}

See the documentation site for examples.

Implementing State Query API

State Store has an optional API for querying the state.

Please refer to the documentation site for API description and definition.

// Querier is an interface to execute queries.
type Querier interface {
        Query(req *QueryRequest) (*QueryResponse, error)
}

Below are the definitions of structures (including nested) for QueryRequest and QueryResponse.

// QueryResponse is the request object for querying the state.
type QueryRequest struct {
        Query    query.Query       `json:"query"`
        Metadata map[string]string `json:"metadata,omitempty"`
}

type Query struct {
        Filters map[string]interface{} `json:"filter"`
        Sort    []Sorting              `json:"sort"`
        Page    Pagination             `json:"page"`

        // derived from Filters
        Filter Filter
}

type Sorting struct {
        Key   string `json:"key"`
        Order string `json:"order,omitempty"`
}

type Pagination struct {
        Limit int    `json:"limit"`
        Token string `json:"token,omitempty"`
}

// QueryResponse is the response object on querying state.
type QueryResponse struct {
        Results  []QueryItem       `json:"results"`
        Token    string            `json:"token,omitempty"`
        Metadata map[string]string `json:"metadata,omitempty"`
}

// QueryItem is an object representing a single entry in query results.
type QueryItem struct {
        Key   string  `json:"key"`
        Data  []byte  `json:"data"`
        ETag  *string `json:"etag,omitempty"`
        Error string  `json:"error,omitempty"`
}

Upon receiving the query request, Dapr validates it and transforms into object Query, which, in turn, is passed on to the state store component.

The Query object has a member Filter that implements parsing interface per component as described below.

type Filter interface {
	Parse(interface{}) error
}

type FilterEQ struct {
	Key string
	Val interface{}
}

type FilterIN struct {
	Key  string
	Vals []interface{}
}

type FilterAND struct {
	Filters []Filter
}

type FilterOR struct {
	Filters []Filter
}

To simplify the process of query translation, we leveraged visitor design pattern. A state store component developer would need to implement the visit method, and the runtime will use it to construct the native query statement.

type Visitor interface {
	// returns "equal" expression
	VisitEQ(*FilterEQ) (string, error)
	// returns "in" expression
	VisitIN(*FilterIN) (string, error)
	// returns "and" expression
	VisitAND(*FilterAND) (string, error)
	// returns "or" expression
	VisitOR(*FilterOR) (string, error)
	// receives concatenated filters and finalizes the native query
	Finalize(string, *MidQuery) error
}

The Dapr runtime implements QueryBuilder object that takes in Visitor interface and constructs the native query.

type QueryBuilder struct {
	visitor Visitor
}

func (h *QueryBuilder) BuildQuery(mq *MidQuery) error {...}

The last part is to implement Querier interface in the component:

type Querier interface {
	Query(req *QueryRequest) (*QueryResponse, error)
}

A sample implementation might look like that:

func (m *MyComponent) Query(req *state.QueryRequest) (*state.QueryResponse, error) {
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	query := &Query{} // Query implements Visitor interface
	qbuilder := state.NewQueryBuilder(query)
	if err := qbuilder.BuildQuery(&req.Query); err != nil {
		return &state.QueryResponse{}, err
	}
	data, token, err := query.execute(ctx)
	if err != nil {
		return &state.QueryResponse{}, err
	}
	return &state.QueryResponse{
		Results:  data,
		Token:    token,
	}, nil
}

Some of the examples of State Query API implementation are MongoDB and CosmosDB state store components.

Documentation

Index

• Constants
• func CheckRequestOptions(options interface{}) error
• func DeleteWithOptions(method func(req *DeleteRequest) error, req *DeleteRequest) error
• func SetWithOptions(method func(req *SetRequest) error, req *SetRequest) error
• type BulkGetResponse
• type BulkStore
• type DefaultBulkStore
  • func NewDefaultBulkStore(store Store) DefaultBulkStore
  • func (b *DefaultBulkStore) BulkDelete(req []DeleteRequest) error
  • func (b *DefaultBulkStore) BulkGet(req []GetRequest) (bool, []BulkGetResponse, error)
  • func (b *DefaultBulkStore) BulkSet(req []SetRequest) error
  • func (b *DefaultBulkStore) Features() []Feature
• type DeleteRequest
  • func (r DeleteRequest) GetKey() string
  • func (r DeleteRequest) GetMetadata() map[string]string
• type DeleteStateOption
• type ETagError
  • func NewETagError(kind ETagErrorKind, err error) *ETagError
  • func (e *ETagError) Error() string
  • func (e *ETagError) Kind() ETagErrorKind
• type ETagErrorKind
• type Feature
  • func (f Feature) IsPresent(features []Feature) bool
• type GetRequest
• type GetResponse
• type GetStateOption
• type KeyInt
• type Metadata
• type OperationType
• type Querier
• type QueryItem
• type QueryRequest
• type QueryResponse
• type SetRequest
  • func (r SetRequest) GetKey() string
  • func (r SetRequest) GetMetadata() map[string]string
• type SetStateOption
• type Store
• type TransactionalStateOperation
• type TransactionalStateRequest
• type TransactionalStore

Constants

const (
	FirstWrite = "first-write"
	LastWrite  = "last-write"
	Strong     = "strong"
	Eventual   = "eventual"
)

Functions

func CheckRequestOptions

func CheckRequestOptions(options interface{}) error

CheckRequestOptions checks if request options use supported keywords.

func DeleteWithOptions

func DeleteWithOptions(method func(req *DeleteRequest) error, req *DeleteRequest) error

DeleteWithOptions handles DeleteRequest with options.

func SetWithOptions

func SetWithOptions(method func(req *SetRequest) error, req *SetRequest) error

SetWithOptions handles SetRequest with request options.

Types

type BulkGetResponse

type BulkGetResponse struct {
	Key      string            `json:"key"`
	Data     []byte            `json:"data"`
	ETag     *string           `json:"etag,omitempty"`
	Metadata map[string]string `json:"metadata"`
	Error    string            `json:"error,omitempty"`
}

BulkGetResponse is the response object for bulk get response.

type BulkStore

type BulkStore interface {
	BulkDelete(req []DeleteRequest) error
	BulkGet(req []GetRequest) (bool, []BulkGetResponse, error)
	BulkSet(req []SetRequest) error
}

BulkStore is an interface to perform bulk operations on store.

type DefaultBulkStore

type DefaultBulkStore struct {
	// contains filtered or unexported fields
}

DefaultBulkStore is a default implementation of BulkStore.

func NewDefaultBulkStore

func NewDefaultBulkStore(store Store) DefaultBulkStore

NewDefaultBulkStore build a default bulk store.

func (*DefaultBulkStore) BulkDelete

func (b *DefaultBulkStore) BulkDelete(req []DeleteRequest) error

BulkDelete performs a bulk delete operation.

func (*DefaultBulkStore) BulkGet

func (b *DefaultBulkStore) BulkGet(req []GetRequest) (bool, []BulkGetResponse, error)

BulkGet performs a bulks get operations.

func (*DefaultBulkStore) BulkSet

func (b *DefaultBulkStore) BulkSet(req []SetRequest) error

BulkSet performs a bulks save operation.

func (*DefaultBulkStore) Features

func (b *DefaultBulkStore) Features() []Feature

Features returns the features of the encapsulated store.

type DeleteRequest

type DeleteRequest struct {
	Key      string            `json:"key"`
	ETag     *string           `json:"etag,omitempty"`
	Metadata map[string]string `json:"metadata"`
	Options  DeleteStateOption `json:"options,omitempty"`
}

DeleteRequest is the object describing a delete state request.

func (DeleteRequest) GetKey

func (r DeleteRequest) GetKey() string

Key gets the Key on a DeleteRequest.

func (DeleteRequest) GetMetadata

func (r DeleteRequest) GetMetadata() map[string]string

Metadata gets the Metadata on a DeleteRequest.

type DeleteStateOption

type DeleteStateOption struct {
	Concurrency string `json:"concurrency,omitempty"` // "concurrency"
	Consistency string `json:"consistency"`           // "eventual, strong"
}

DeleteStateOption controls how a state store reacts to a delete request.

type ETagError

type ETagError struct {
	// contains filtered or unexported fields
}

ETagError is a custom error type for etag exceptions.

func NewETagError

func NewETagError(kind ETagErrorKind, err error) *ETagError

NewETagError returns an ETagError wrapping an existing context error.

func (*ETagError) Error

func (e *ETagError) Error() string

func (*ETagError) Kind

func (e *ETagError) Kind() ETagErrorKind

type ETagErrorKind

type ETagErrorKind string

const (
	ETagInvalid  ETagErrorKind = "invalid"
	ETagMismatch ETagErrorKind = "mismatch"
)

type Feature

type Feature string

Feature names a feature that can be implemented by PubSub components.

const (
	// FeatureETag is the feature to etag metadata in state store.
	FeatureETag Feature = "ETAG"
	// FeatureTransactional is the feature that performs transactional operations.
	FeatureTransactional Feature = "TRANSACTIONAL"
)

func (Feature) IsPresent

func (f Feature) IsPresent(features []Feature) bool

IsPresent checks if a given feature is present in the list.

type GetRequest

type GetRequest struct {
	Key      string            `json:"key"`
	Metadata map[string]string `json:"metadata"`
	Options  GetStateOption    `json:"options,omitempty"`
}

GetRequest is the object describing a state fetch request.

type GetResponse

type GetResponse struct {
	Data     []byte            `json:"data"`
	ETag     *string           `json:"etag,omitempty"`
	Metadata map[string]string `json:"metadata"`
}

GetResponse is the response object for getting state.

type GetStateOption

type GetStateOption struct {
	Consistency string `json:"consistency"` // "eventual, strong"
}

GetStateOption controls how a state store reacts to a get request.

type KeyInt

type KeyInt interface {
	GetKey() string
	GetMetadata() map[string]string
}

KeyInt is an interface that allows gets of the Key and Metadata inside requests.

type Metadata

type Metadata struct {
	Properties map[string]string `json:"properties"`
}

Metadata contains a state store specific set of metadata properties.

type OperationType

type OperationType string

OperationType describes a CRUD operation performed against a state store.

const Delete OperationType = "delete"

Delete is a delete operation.

const Upsert OperationType = "upsert"

Upsert is an update or create operation.

type Querier

type Querier interface {
	Query(req *QueryRequest) (*QueryResponse, error)
}

Querier is an interface to execute queries.

type QueryItem

type QueryItem struct {
	Key   string  `json:"key"`
	Data  []byte  `json:"data"`
	ETag  *string `json:"etag,omitempty"`
	Error string  `json:"error,omitempty"`
}

QueryItem is an object representing a single entry in query results.

type QueryRequest

type QueryRequest struct {
	Query    query.Query       `json:"query"`
	Metadata map[string]string `json:"metadata,omitempty"`
}

type QueryResponse

type QueryResponse struct {
	Results  []QueryItem       `json:"results"`
	Token    string            `json:"token,omitempty"`
	Metadata map[string]string `json:"metadata,omitempty"`
}

QueryResponse is the response object for querying state.

type SetRequest

type SetRequest struct {
	Key      string            `json:"key"`
	Value    interface{}       `json:"value"`
	ETag     *string           `json:"etag,omitempty"`
	Metadata map[string]string `json:"metadata,omitempty"`
	Options  SetStateOption    `json:"options,omitempty"`
}

SetRequest is the object describing an upsert request.

func (SetRequest) GetKey

func (r SetRequest) GetKey() string

GetKey gets the Key on a SetRequest.

func (SetRequest) GetMetadata

func (r SetRequest) GetMetadata() map[string]string

GetMetadata gets the Key on a SetRequest.

type SetStateOption

type SetStateOption struct {
	Concurrency string `json:"concurrency,omitempty"` // first-write, last-write
	Consistency string `json:"consistency"`           // "eventual, strong"
}

SetStateOption controls how a state store reacts to a set request.

type Store

type Store interface {
	BulkStore
	Init(metadata Metadata) error
	Features() []Feature
	Delete(req *DeleteRequest) error
	Get(req *GetRequest) (*GetResponse, error)
	Set(req *SetRequest) error
	Ping() error
}

Store is an interface to perform operations on store.

type TransactionalStateOperation

type TransactionalStateOperation struct {
	Operation OperationType `json:"operation"`
	Request   interface{}   `json:"request"`
}

TransactionalStateOperation describes operation type, key, and value for transactional operation.

type TransactionalStateRequest

type TransactionalStateRequest struct {
	Operations []TransactionalStateOperation `json:"operations"`
	Metadata   map[string]string             `json:"metadata,omitempty"`
}

TransactionalStateRequest describes a transactional operation against a state store that comprises multiple types of operations The Request field is either a DeleteRequest or SetRequest.

type TransactionalStore

type TransactionalStore interface {
	Init(metadata Metadata) error
	Multi(request *TransactionalStateRequest) error
}

TransactionalStore is an interface for initialization and support multiple transactional requests.