micro/flow/flow.go

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// Package flow is an interface used for saga pattern microservice workflow
package flow // import "go.unistack.org/micro/v4/flow"
import (
"context"
"errors"
"sync"
"sync/atomic"
"go.unistack.org/micro/v4/metadata"
"go.unistack.org/micro/v4/options"
)
var (
// ErrStepNotExists returns when step not found
ErrStepNotExists = errors.New("step not exists")
// ErrMissingClient returns when client.Client is missing
ErrMissingClient = errors.New("client not set")
)
// RawMessage is a raw encoded JSON value.
// It implements Marshaler and Unmarshaler and can be used to delay decoding or precompute a encoding.
type RawMessage []byte
// MarshalJSON returns m as the JSON encoding of m.
func (m *RawMessage) MarshalJSON() ([]byte, error) {
if m == nil {
return []byte("null"), nil
}
return *m, nil
}
// UnmarshalJSON sets *m to a copy of data.
func (m *RawMessage) UnmarshalJSON(data []byte) error {
if m == nil {
return errors.New("RawMessage UnmarshalJSON on nil pointer")
}
*m = append((*m)[0:0], data...)
return nil
}
// Message used to transfer data between steps
type Message struct {
Header metadata.Metadata
Body RawMessage
}
// Step represents dedicated workflow step
type Step interface {
// ID returns step id
ID() string
// Endpoint returns rpc endpoint service_name.service_method or broker topic
Endpoint() string
// Execute step run
Execute(ctx context.Context, req *Message, opts ...options.Option) (*Message, error)
// Requires returns dependent steps
Requires() []string
// Options returns step options
Options() StepOptions
// Require add required steps
Require(steps ...Step) error
// String
String() string
// GetStatus returns step status
GetStatus() Status
// SetStatus sets the step status
SetStatus(Status)
// Request returns step request message
Request() *Message
// Response returns step response message
Response() *Message
}
// Status contains step current status
type Status int
func (status Status) String() string {
return StatusString[status]
}
const (
// StatusPending step waiting to start
StatusPending Status = iota
// StatusRunning step is running
StatusRunning
// StatusFailure step competed with error
StatusFailure
// StatusSuccess step completed without error
StatusSuccess
// StatusAborted step aborted while it running
StatusAborted
// StatusSuspend step suspended
StatusSuspend
)
var (
// StatusString contains map status => string
StatusString = map[Status]string{
StatusPending: "StatusPending",
StatusRunning: "StatusRunning",
StatusFailure: "StatusFailure",
StatusSuccess: "StatusSuccess",
StatusAborted: "StatusAborted",
StatusSuspend: "StatusSuspend",
}
// StringStatus contains map string => status
StringStatus = map[string]Status{
"StatusPending": StatusPending,
"StatusRunning": StatusRunning,
"StatusFailure": StatusFailure,
"StatusSuccess": StatusSuccess,
"StatusAborted": StatusAborted,
"StatusSuspend": StatusSuspend,
}
)
// Workflow contains all steps to execute
type Workflow interface {
// ID returns id of the workflow
ID() string
// Execute workflow with args, return execution id and error
Execute(ctx context.Context, req *Message, opts ...options.Option) (string, error)
// RemoveSteps remove steps from workflow
RemoveSteps(steps ...Step) error
// AppendSteps append steps to workflow
AppendSteps(steps ...Step) error
// Status returns workflow status
Status() Status
// Steps returns steps slice where parallel steps returned on the same level
Steps() ([][]Step, error)
// Suspend suspends execution
Suspend(ctx context.Context, id string) error
// Resume resumes execution
Resume(ctx context.Context, id string) error
// Abort abort execution
Abort(ctx context.Context, id string) error
}
// Flow the base interface to interact with workflows
type Flow interface {
// Options returns options
Options() Options
// Init initialize
Init(...options.Option) error
// WorkflowCreate creates new workflow with specific id and steps
WorkflowCreate(ctx context.Context, id string, steps ...Step) (Workflow, error)
// WorkflowSave saves workflow
WorkflowSave(ctx context.Context, w Workflow) error
// WorkflowLoad loads workflow with specific id
WorkflowLoad(ctx context.Context, id string) (Workflow, error)
// WorkflowList lists all workflows
WorkflowList(ctx context.Context) ([]Workflow, error)
}
var (
flowMu sync.Mutex
atomicSteps atomic.Value
)
// RegisterStep register own step with workflow
func RegisterStep(step Step) {
flowMu.Lock()
steps, _ := atomicSteps.Load().([]Step)
atomicSteps.Store(append(steps, step))
flowMu.Unlock()
}