Building FunctionGraph Event Functions with NodeJS from scratch¶
Following chapter describe how to build FunctionGraph event functions using NodeJS from scratch:
Introduction¶
For general details about creating event functions from scratch and executing an event function, see Creating a Function from Scratch and Executing the Function in the user manual.
Function Development Overview¶
NodeJS 6.10¶
exports.handler = function(event, context, callback)
handler: name of the function that FunctionGraph invokes to execute your code. The name must be consistent with that you define when creating a function in FunctionGraph.
event: event parameter defined for the function. The parameter is in JSON format.
context: runtime information provided for executing the function. See Using the FunctionGraph context for details.
callback: used to return the defined err and message information to the frontend. The general syntax is callback(err, message). You can define the error or message content, for example, a character string.
NodeJS 8.10 and later¶
Node.js 8.10 and later are compatible with the APIs of Node.js 6.10, and supports an async handler. Responses are output through return.
exports.handler = async (event, context, callback [optional]) => { return data;}
handler: name of the function that FunctionGraph invokes to execute your code. The name must be consistent with that you define when creating a function in FunctionGraph.
event: event parameter defined for the function. The parameter is in JSON format.
context: runtime information provided for executing the function. See Using the FunctionGraph context for details.
Handler¶
The handler of a Node.js function is in the format of [file name].[function name]. You can configure the handler on the FunctionGraph console. For example, if you set the handler to index.handler in your function, FunctionGraph will load the handler function defined in the index.js file.
Initializer¶
For details about the initializer, see Initializer function.
The initializer is in the format of [File name].[Initializer name].
For example, if the initializer is named index.initializer, FunctionGraph loads the initializer function defined in the index.js file.
To use Node.js to build initialization logic, define a Node.js function as the initializer.
The following is a simple initializer:
exports.initializer = function (context, callback) {
const logger = context.getLogger();
logger.info("initializing :", context.getFunctionName());
callback(null, "");
};
Function name The function name exports.initializer must be the initializer function name specified for a function.
For example, if the initializer is named index.initializer, FunctionGraph loads the initializer function defined in the index.js file.
context The context parameter contains the runtime information about a function. For example, request ID, temporary AK, and function metadata. See Using the FunctionGraph context for details.
callback The callback parameter is used to return the invocation result. The signature of this parameter is function(err, data), which is the same as that of the common callback parameter used in Node.js. If the value of err is not null, the function will return HandledInitializationError. The value of data is invalid because no value will be returned for function initialization. You can set the data parameter to null by referring to the previous example.