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Development Specifications on Custom Functions

When developing a custom function, the input and output parameters of the function must comply with the specifications in this section.

For details about how to compile a custom function, see Developing Functions.

Function Input Parameters

The following tables define the JSON structure and environment variables of input parameters of a custom function executed by a Data+ workflow:
Table 1 JSON format of the function input parameters

Parameter

Mandatory

Type

Description

Records

Yes

Array

Message records of an event source triggered by a workflow

inputs

No

Map[String]String

List of modifiable parameters

dynamic_source

No

Map

Parameter required for function execution, which can be used to pass to the service to be invoked.

execution_name

Yes

String

Workflow instance name

graph_name

Yes

String

Workflow name
Table 2 Function environment variables

Parameter

Mandatory

Type

Description

region

No

String

Name of the current region

Function Output Parameters

The following table defines the JSON structure of a custom function's output parameters:

Table 3 JSON format of the function output parameters

Parameter

Mandatory

Type

Description

Constraint

Records

Yes

Array

Message records of an event source triggered by a workflow

If there is no change, the output records are the same as the input records.

inputs

No

Map[String]String

List of modifiable parameters

If there are no new parameters, this will be the same as the input value.

dynamic_source

No

Map

Output parameter of a function. It can be passed to the next function to be executed.

-

execution_name

Yes

String

Workflow instance name

Inherits the execution_name value of the input parameter.

graph_name

Yes

String

Workflow name

Inherits the graph_name value of the input parameter.

operation_name

No

String

Operation name of a function

Operation names of built-in workflow functions are as follows:

  • Video parsing: MPC.Metadata
  • Frame capturing: MPC.Thumbnail
  • Video transcoding: MPC.Transcode
  • SMN message noticing: SMN.Publish

Implementing a Function that Interconnects with the Built-in Frame Capturing Function (for GO Language)

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package main

import (
	"encoding/json"
	"errors"
	"go-runtime/go-api/context"
)

func DemoHandler(jsonData []byte, ctx context.RuntimeContext) (interface{}, error) {
	var eventMsg Payload
	err := json.Unmarshal(jsonData, &eventMsg)
	if err != nil {
		return nil, errors.New("not correct format")
	}
        // Store the input bucket and object values.
	record := eventMsg.Records[0]

        // Output definitions.
	resp := struct {
		OBSMessages
		Inputs        map[string]interface{} `json:"inputs"`
		ExecutionName string                 `json:"execution_name"`
		GraphName     string                 `json:"graph_name"`
		DynamicSource struct {
			*CreateThumbnailDynamicSourceBody
		} `json:"dynamic_source"`
	}{}
        // Configure frame capturing parameters to provide parameter settings for downstream capturing tasks.
	resp.DynamicSource.CreateThumbnailDynamicSourceBody = &CreateThumbnailDynamicSourceBody{
		Thumbnails: []*ThumbnailCreateTaskBody{
			&ThumbnailCreateTaskBody{
                               // Storage location of an input file
				Input: &FileAddr{
					Location:   "cn-north-1",
					BucketName: record.Obs.Bucket.Name,
					Object:     record.Obs.Object.Key,
				},
                                // Storage location of an output file
				Output: &FileAddr{
					Location:   "cn-north-1",
					BucketName: record.Obs.Bucket.Name,
					Object:     "thumb_out",
				},
                                // Whether to compress captured snapshots to a TAR package
				Tar: 0,
                                // Whether to enable synchronous processing. Synchronous processing refers to quickly locating the snapshot position to take a snapshot.
				Mode: 0,
                               // Frame capturing parameters
				ThumbnailParam: &ThumbnailParam{
					Type:           "DOTS",
					MaxLength:      0,
                                        Dots:           []int64{2, 10, 14}, // Frame capturing position (s) 
					OutputFileName: "default_cover.jpg",
				},
			},
		},
	}
       // The following parameters need to be inherited and passed so that the downstream functions of the workflow can obtain the corresponding parameter values.
	resp.Inputs = eventMsg.Inputs
	resp.Records = eventMsg.Records
	resp.GraphName = eventMsg.GraphName
	resp.ExecutionName = eventMsg.ExecutionName
	return resp, nil
}

Implementing a Function that Interconnects with the Built-in Transcoding Function (for GO Language)

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package main

import (
	"encoding/json"
	"errors"
	"go-runtime/go-api/context"
)

func DemoTranscodeHandler(jsonData []byte, ctx context.RuntimeContext) (interface{}, error) {
	var eventMsg Payload
	err := json.Unmarshal(jsonData, &eventMsg)
	if err != nil {
		return nil, errors.New("not correct format")
	}
        // Store the input bucket and object values.
	record := eventMsg.Records[0]

        // Output definitions.
	resp := struct {
		OBSMessages
		Inputs        map[string]interface{} `json:"inputs"`
		ExecutionName string                 `json:"execution_name"`
		GraphName     string                 `json:"graph_name"`
		DynamicSource struct {
			*CreateTranscodeDynamicSourceBody
		} `json:"dynamic_source"`
	}{}
        // Configure frame capturing parameters to provide parameter settings for downstream capturing tasks.
	resp.DynamicSource.CreateTranscodeDynamicSourceBody = &CreateTranscodeDynamicSourceBody{
		Transcodes: []*CreateTranscodeTaskBody{
			&CreateTranscodeTaskBody{
                               // Storage location of an input file
				Input: &FileAddr{
					Location:   "cn-north-4",
					BucketName: record.Obs.Bucket.Name,
					Object:     record.Obs.Object.Key,
				},
                                // Storage location of an output file
				Output: &FileAddr{
					Location:   "cn-north-4",
					BucketName: record.Obs.Bucket.Name,
					Object:     "transcode_out",
				},
				TransTemplateID: []int{7000523, 7000524, 7000526, 7000528, 7000530, 7000538},
				OutputFilenames: []string{"out_file1", "out_file2", "out_file3", "out_file4", "out_file5", "out_file6"},
			},
		},
	}
       // The following parameters need to be inherited and passed so that the downstream functions of the workflow can obtain the corresponding parameter values.
	resp.Inputs = eventMsg.Inputs
	resp.Records = eventMsg.Records
	resp.GraphName = eventMsg.GraphName
	resp.ExecutionName = eventMsg.ExecutionName
	return resp, nil
}

Structure Example in Go

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package main

type CreateTranscodeDynamicSourceBody struct {
	Transcodes []*CreateTranscodeTaskBody `json:"transcodes"`
}

type CreateTranscodeTaskBody struct {
       // Storage location of an input file
	Input *FileAddr `json:"input,omitempty"`
        // Storage location of an output file
	Output *FileAddr `json:"output"`
        //Transcoding template ID, which is an array.
	TransTemplateID []int `json:"trans_template_id,omitempty"`
        // A maximum of 20 watermarks (images and texts) are supported.
	Watermarks []*Watermark `json:"watermarks,omitempty"`
        // Task priority.
	Priority string `json:"priority,omitempty"`
        // Output file name. Each output file has a name. If there are multiple output files, their names must be in sequence of the template ID array.
	OutputFilenames []string `json:"output_filenames,omitempty"`
}
type Watermark struct {
	Input          *FileAddr       `json:"input,omitempty"`
	TemplateID     int             `json:"template_id,omitempty"`
	TextContext    string          `json:"text_context,omitempty"`
	ImageWatermark *ImageWatermark `json:"image_watermark,omitempty"`
	TextWatermark  *TextWatermark  `json:"text_watermark,omitempty"`
}
type TextWatermark struct {
	Dx               string `json:"dx,omitempty"`
	Dy               string `json:"dy,omitempty"`
	ReferPos         string `json:"referpos,omitempty"`
	TimelineStart    string `json:"timeline_start,omitempty"`
	TimelineDuration string `json:"timeline_duration,omitempty"`
	FontName         string `json:"font_name,omitempty"`
	FontSize         string `json:"font_size,omitempty"`
	FontColor        string `json:"font_color,omitempty"`
	Base             string `json:"base,omitempty"`
}
type ImageWatermark struct {
	Dx               string `json:"dx,omitempty"`
	Dy               string `json:"dy,omitempty"`
	ReferPos         string `json:"referpos,omitempty"`
	TimelineStart    string `json:"timeline_start,omitempty"`
	TimelineDuration string `json:"timeline_duration,omitempty"`
	ImageProcess     string `json:"image_process,omitempty"`
	Width            string `json:"width,omitempty"`
	Height           string `json:"height,omitempty"`
	Base             string `json:"base,omitempty"`
}

type CreateThumbnailDynamicSourceBody struct {
	Thumbnails []*ThumbnailCreateTaskBody `json:"thumbnails"`
}

//FileAddr file path structure
type FileAddr struct {
	Location   string `json:"location"`
	BucketName string `json:"bucket"`
	Object     string `json:"object"`
}

type ThumbnailCreateTaskBody struct {
        // Storage location of an input file
	Input *FileAddr `json:"input"`
        // Storage location of an output file
	Output *FileAddr `json:"output"`
        // Whether to compress captured snapshots to a TAR package
	Tar int `json:"tar,omitempty"`
        // Whether to enable synchronous processing. Synchronous processing refers to quickly locating the snapshot position to take a snapshot.
	Mode int `json:"sync,omitempty"`
        // Frame capturing parameters
	ThumbnailParam *ThumbnailParam `json:"thumbnail_para"`
}

type ThumbnailParam struct {
	Type           string  `json:"type"`
	Time           int64   `json:"time,omitempty"`
	StartTime      int64   `json:"start_time,omitempty"`
	Duration       int64   `json:"duration,omitempty"`
	Dots           []int64 `json:"dots,omitempty"`
	Format         int64   `json:"format,omitempty"`
	AspectRatio    int64   `json:"aspect_ratio,omitempty"`
	Width          int64   `json:"width,omitempty"`
	Height         int64   `json:"height,omitempty"`
	MaxLength      int64   `json:"max_length,omitempty"`
	OutputFileName string  `json:"output_filename,omitempty"`
}

type OBSMessages struct {
	Records []OBSRecord `json:"Records"`
}

// OBSRecord OBS message format
type OBSRecord struct {
	EventVersion      string            `json:"eventVersion"`
	EventSource       string            `json:"eventSource"`
	EventRegion       string            `json:"eventRegion"`
	EventTime         string            `json:"eventTime"`
	EventName         string            `json:"eventName"`
	UserIdentity      UserIdentity      `json:"userIdentity"`
	RequestParameters RequestParameters `json:"requestParameters"`
	ResponseElements  ResponseElements  `json:"responseElements"`
	Obs               *OBSInfo          `json:"obs"`
}

// UserIdentity User ID
type UserIdentity struct {
	ID string `json:"ID,omitempty"`
}

//RequestParameters original request parameters
type RequestParameters struct {
	SourceIPAddress string `json:"sourceIPAddress,omitempty"`
}

//ResponseElements Response parameters
type ResponseElements struct {
	OBSRequestID string `json:"x-obs-request-id"`
	OBSID2       string `json:"x-obs-id-2"`
}

// OBSInfo OBS information
type OBSInfo struct {
	Version         string     `json:"Version"`
	ConfigurationID string     `json:"configurationId"`
	Bucket          BucketInfo `json:"bucket"`
	Object          ObjectInfo `json:"object"`
}

//BucketInfo Bucket information
type BucketInfo struct {
	Name          string       `json:"name"`
	OwnerIdentity UserIdentity `json:"ownerIdentity"`
	Bucket        string       `json:"bucket"`
}

//ObjectInfo Object information
type ObjectInfo struct {
	Key       string `json:"key"`
	Tag       string `json:"eTag"`
	Size      uint64 `json:"size"`
	VersionID string `json:"versionId"`
	Sequencer string `json:"sequencer"`
}

type Payload struct {
	ExecutionName string `json:"execution_name"`
	GraphName     string `json:"graph_name"`
	OBSMessages
	DynamicSource interface{}            `json:"dynamic_source"`
	Inputs        map[string]interface{} `json:"inputs"`
}
Parent topic: Data+ (Beta Testing)