@corva/node-task-lambda v5.0.1

node-task-lambda

Task lambda class for constructing task data apps.

ToC

• node-task-lambda
  • ToC
  • Requirements
  • Getting started
    • Installation
  • Features
  • Workflow
    • Pre-process
    • Post-process
    • Examples
  • API docs

Requirements

• node.js - >=12.0.0

Getting started

Installation

npm i @corva/node-task-lambda

Features

• Defines task workflow
• Get task info
• Updates task status

Workflow

Task lambda has 3 phases:

• pre-process (gets task info)
• process
• post-process (updates task status)

@startuml
(*) -->[{event}] "preProcess"

if "Exception?" then
  -->[true, {error}] "postProcess"
else
  -->[false, {event}] "process"
  -->[{data, error}] "postProcess"
endif
-->[End] (*)
@enduml

Usually you need to define process function to handle the data. Pre-process is used to modify incoming data in some way. Post-process is used to handle processed data or/and handle and log errors that were thrown during pre-process or process.

Also it expose .run method that is used to launch processing.

Pre-process

For task lambdas event that's passed to pre-process handler usually looks like:

{
  "task_id": "dc5c16e4-c0e3-43fc-85b2-83b08b9da7d0",
  "version": 2
}

And pre-process handler automatically will fetch task data from Corva API. As a result task event will be passed to process handler and it will have following structure:

{
  "app_key": "tasks.my-task-app",
  "provider": "corva",
  "asset_id": 1,
  "properties": {
    "foo": "bar",
    "bar": "baz"
  },
  "payload": {}
}

Post-process

Task app post-process handler will mark task as succeeded or failed depending on what will be passed to it. If error parameter will not be falsy, then task will be considered as failed, otherwise it will be succeeded.

If process handler returns data object, it will be saved to task as well and will be stored in payload field in task.

NOTE: Avoid returning and storing too much data in it, for big volumes use saveData from API instead.

Examples

const { TaskLambda } = require('@corva/node-task-lambda');

// you may need api client and other libs
const { ApiClient } = require('@corva/node-api-client');
const apiClient = new ApiClient();

const lambda = new TaskLambda({
  apiClient,
  process: async ({ event, context }) => {
    const result = event.a + event.b;
    // Don't return too large results
    // Returned result will be saved in task object
    return result;
  },
});