2021-04-27 08:32:47 +03:00
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// Package flow is an interface used for saga pattern microservice workflow
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2021-02-14 23:47:11 +03:00
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package flow
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import (
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"context"
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"errors"
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"github.com/unistack-org/micro/v3/metadata"
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)
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var (
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ErrStepNotExists = errors.New("step not exists")
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ErrMissingClient = errors.New("client not set")
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)
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// RawMessage is a raw encoded JSON value.
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// It implements Marshaler and Unmarshaler and can be used to delay decoding or precompute a encoding.
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type RawMessage []byte
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// MarshalJSON returns m as the JSON encoding of m.
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func (m *RawMessage) MarshalJSON() ([]byte, error) {
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if m == nil {
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return []byte("null"), nil
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}
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return *m, nil
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}
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// UnmarshalJSON sets *m to a copy of data.
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func (m *RawMessage) UnmarshalJSON(data []byte) error {
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if m == nil {
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return errors.New("RawMessage UnmarshalJSON on nil pointer")
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}
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*m = append((*m)[0:0], data...)
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return nil
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}
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type Message struct {
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Header metadata.Metadata
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Body RawMessage
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}
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// Step represents dedicated workflow step
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type Step interface {
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// ID returns step id
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ID() string
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// Endpoint returns rpc endpoint service_name.service_method or broker topic
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Endpoint() string
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// Execute step run
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Execute(ctx context.Context, req *Message, opts ...ExecuteOption) (*Message, error)
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// Requires returns dependent steps
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Requires() []string
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// Options returns step options
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Options() StepOptions
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// Require add required steps
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Require(steps ...Step) error
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// String
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String() string
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// GetStatus returns step status
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GetStatus() Status
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// SetStatus sets the step status
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SetStatus(Status)
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// Request returns step request message
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Request() *Message
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// Response returns step response message
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Response() *Message
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}
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type Status int
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const (
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StatusPending Status = iota
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StatusRunning
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StatusFailure
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StatusSuccess
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StatusAborted
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StatusSuspend
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)
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// Workflow contains all steps to execute
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type Workflow interface {
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// ID returns id of the workflow
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ID() string
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// Execute workflow with args, return execution id and error
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Execute(ctx context.Context, req *Message, opts ...ExecuteOption) (string, error)
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// RemoveSteps remove steps from workflow
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RemoveSteps(steps ...Step) error
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// AppendSteps append steps to workflow
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AppendSteps(steps ...Step) error
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// Status returns workflow status
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Status() Status
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// Steps returns steps slice where parallel steps returned on the same level
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Steps() ([][]Step, error)
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}
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// Flow the base interface to interact with workflows
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type Flow interface {
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// Options returns options
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Options() Options
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// Init initialize
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Init(...Option) error
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// WorkflowCreate creates new workflow with specific id and steps
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WorkflowCreate(ctx context.Context, id string, steps ...Step) (Workflow, error)
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// WorkflowSave saves workflow
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WorkflowSave(ctx context.Context, w Workflow) error
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// WorkflowLoad loads workflow with specific id
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WorkflowLoad(ctx context.Context, id string) (Workflow, error)
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// WorkflowList lists all workflows
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WorkflowList(ctx context.Context) ([]Workflow, error)
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}
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