Function Development Overview

Function Syntax

FunctionGraph supports Go 1.x. The following shows the function syntax.

func Handler (payload []byte, ctx context.RuntimeContext)

• Handler: name of the handler function.
• payload: event parameter defined for the function. The parameter is in JSON format.
• ctx: runtime information provided for executing the function. For details, see SDK APIs.

The format of the Go function handler is the same as the name of the executable file in the code package. Ensure that the name of the dynamic library file is consistent with the plug-in name of the handler. For example, if the name of the dynamic library file is testplugin.so, set the handler name to testplugin.Handler. You can configure or modify the handler on the function details page on the FunctionGraph console.

SDK APIs

The Go SDK provides event, context, and logging APIs. Download the Go SDK (Go SDK.sha256).

• Event APIs

  Event structure definitions are added to the Go SDK. Currently, DIS, DDS, SMN, Timer, and APIG triggers are supported. The definitions make coding much simpler when triggers are required.

  1. APIG trigger field description
     1. APIGTriggerEvent fields

        Table 1 APIGTriggerEvent fields

        Field	Description
        IsBase64Encoded	Whether the body of an event is encoded using Base64.
        HttpMethod	HTTP request method.
        Path	HTTP request path.
        Body	HTTP request body.
        PathParameters	All path parameters.
        RequestContext	API Gateway configurations (APIGRequestContext object).
        Headers	HTTP request header.
        QueryStringParameters	Query parameters.
        UserData	User data set in the APIG custom authorizer.

        Table 2 APIGRequestContext fields

        Field	Description
        ApiId	API ID.
        RequestId	API request ID.
        Stage	Name of the environment in which an API has been published.

     2. APIGTriggerResponse fields

        Table 3 APIGTriggerResponse fields

        Field	Description
        Body	Message body.
        Headers	HTTP response header to be returned.
        StatusCode	HTTP status code. Type: int.
        IsBase64Encoded	Whether the body has been encoded using Base64. Type: bool.

        

        APIGTriggerEvent provides the GetRawBody() method to obtain the body decoded using Base64. APIGTriggerResponse provides the SetBase64EncodedBody() method to set the body encoded using Base64.

  2. DIS trigger field description

     Table 4 DISTriggerEvent fields

     Field	Description
     ShardID	Partition ID.
     Message	DIS message body (DISMessage structure).
     Tag	Function version.
     StreamName	Stream name.

     Table 5 DISMessage fields

     Field	Description
     NextPartitionCursor	Next partition cursor.
     Records	Message records (DISRecord structure).
     MillisBehindLatest	Reserved parameter.

     Table 6 DISRecord fields

     Field	Description
     PartitionKey	Data partition.
     Data	Data.
     SequenceNumber	Sequence number (ID of each record).

  3. Kafka trigger field description

     Table 7 KAFKATriggerEvent fields

     Field	Description
     InstanceId	Instance ID.
     Records	Message records (Table 8).
     TriggerType	Trigger type (Kafka).
     Region	Region.
     EventTime	Time when an event occurred (seconds).
     EventVersion	Event version.

     Table 8 KAFKARecord parameters

     Field	Description
     Messages	DMS message body.
     TopicId	Topic ID.

  4. SMN trigger field description

     Table 9 SMNTriggerEvent fields

     Field	Description
     Record	Message records (SMNRecord structure).

     Table 10 SMNRecord fields

     Field	Description
     EventVersion	Event version. (Currently, the version is 1.0.)
     EventSubscriptionUrn	Subscription URN.
     EventSource	Event source.
     Smn	Message body (SMNBody structure).

     Table 11 SMNBody fields

     Field	Description
     TopicUrn	Topic URN.
     TimeStamp	Message timestamp.
     MessageAtrributes	Message attribute set.
     Message	Message body.
     Type	Message format.
     MessageId	Message ID.
     Subject	Message topic.

  5. Timer trigger field description

     Table 12 TimerTriggerEvent fields

     Field	Description
     Version	Version. (Currently, the version is v1.0.)
     Time	Current time.
     TriggerType	Trigger type (Timer).
     TriggerName	Trigger name.
     UserEvent	Additional information about the trigger.

  

  1. When using an APIG trigger, set the first parameter of the handler function (for example, handler) to handler(APIGTriggerEvent event, Context context). For details about the constraints, see Base64 Decoding and Response Structure.
  2. The preceding TriggerEvent methods have corresponding set methods, which are recommended for local debugging. DIS and LTS triggers have getRawData() methods, but do not have setRawData() methods.
• Context APIs

  The context APIs are used to obtain the context, such as agency AK/SK, current request ID, allocated memory space, and number of CPUs, required for executing a function.

  Table 13 describes the context APIs provided by FunctionGraph.

  Table 13 Context methods

  Method	Description
  getRequestID( )	Obtains a request ID.
  getRemainingTimeInMilligetRunningTimeInSecondsSeconds ( )	Obtains the remaining running time of a function.
  getAccessKey( )	Obtains the AK (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function. FunctionGraph has stopped maintaining the getAccessKey API in the Runtime SDK. You cannot use this API to obtain a temporary AK.
  getSecretKey( )	Obtains the SK (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function. FunctionGraph has stopped maintaining the getSecretKey API in the Runtime SDK. You cannot use this API to obtain a temporary SK.
  getSecurityAccessKey( )	Obtains the SecurityAccessKey (valid for 24 hours) with an agency. The cache duration is 10 minutes. That is, the same content is returned within 10 minutes. To use this method, you need to configure an agency for the function.
  getSecuritySecretKey( )	Obtains the SecuritySecretKey (valid for 24 hours) with an agency. The cache duration is 10 minutes. That is, the same content is returned within 10 minutes. To use this method, you need to configure an agency for the function.
  getSecurityToken( )	Obtains the SecurityToken (valid for 24 hours) with an agency. The cache duration is 10 minutes. That is, the same content is returned within 10 minutes. To use this method, you need to configure an agency for the function.
  getUserData(string key)	Uses keys to obtain the values passed by environment variables.
  getFunctionName( )	Obtains the name of a function.
  getRunningTimeInSeconds ( )	Obtains the timeout of a function.
  getVersion( )	Obtains the version of a function.
  getMemorySize( )	Obtains the allocated memory.
  getCPUNumber( )	Obtains CPU usage of a function.
  getPackage( )	Obtains a function group.
  getToken( )	Obtains the token (valid for 24 hours) with an agency. If you use this method, you need to configure an agency for the function.
  getLogger( )	Obtains the logger method provided by the context. By default, information such as the time and request ID is output.
  getAlias()	Obtains function alias.

• Table 14 describes the logging API provided in the Go SDK.

  Table 14 Logging API

  Method	Description
  RuntimeLogger()	Records user input logs by using the method Logf(format string, args ...interface{}). This method outputs logs in the format of Time-Request ID-Output, for example, 2017-10-25T09:10:03.328Z 473d369d-101a-445e-a7a8-315cca788f86 test log output.