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@adobe/asset-compute-sdk
Adobe Asset Compute Worker SDK
Last updated 14 days ago by tmathern .
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Adobe Asset Compute Worker SDK

This library is required for all custom workers for the Adobe Asset Compute Service. It provides an easy to use framework and takes care of common things like asset & rendition access, validation and type checks, event notification, error handling and more.

Installation

npm install @adobe/asset-compute-sdk

Overview

These are the high-level steps done by the Adobe Asset Compute Worker SDK:

  1. Setup
    • Initiates the metrics agent and Adobe IO Events handler (see asset-compute-commons for more information)
    • Sets up the proper directories for local access to source and rendition
  2. Download source file from url in source object
  3. Run renditionCallback function for each rendition (worker) or for all the renditions at once (batch worker)
    • The rendition callback is where you put your worker logic. At the minimum, this function needs to convert the local source file into a local rendition file
  4. Notify the client via Adobe IO Events after each rendition
    • It sends a rendition_created or rendition_failed event depending on the outcome (see Asset Compute API asynchronous events for more information)
    • If the worker is part of a chain of workers, it will only send successful rendition events after the last worker in the chain

Examples

Simple javascript worker

Calls rendition function (renditionCallback) for each rendition

const { worker } = require('@adobe/asset-compute-sdk');

async function renditionCallback(source, rendition, params) => {
	// ... worker logic
}
const main = worker(renditionCallback, options);
await main(params);

Batch processing javascript worker

Calls rendition function once with all the renditions

const { batchWorker } = require('@adobe/asset-compute-sdk');

async function batchRenditionCallback(source, rendition, outdir, params) => {
	// ... worker logic
}
const main = batchWorker(batchRenditionCallback, options);
await main(params);

ShellScript worker

Processes renditions using from a worker written in shellscript

const { shellScriptWorker } = require('../lib/api');

const main = shellScriptWorker(); // assumes script is in `worker.sh`
await main(params);

Shellscript worker with custom script name

const { shellScriptWorker } = require('../lib/api');

const main = shellScriptWorker('custom-worker-name.sh'); // assumes script is in `custom-worker-name.sh`
await main(params);

API details

The worker and batchWorker take two parameters: renditionCallback and options as described below.

Rendition Callback for worker (required)

The renditionCallback function is where you put your custom worker code. The basic expectation of this function is to look at parameters from rendition.instructions and convert it into a rendition, then write this rendition to rendition.path.

Producing the rendition may involve external libraries or APIs. These steps should also be accomplished inside your renditionCallback function.

Parameters

The parameters for the rendition callback function are: source, rendition, and params

source

Object containing the following attributes:

Name Type Description Example
url string URL pointing to the source binary. "http://example.com/image.jpg"
path string Absolute path to local copy of source file "/tmp/image.jpg"
name string File name. File extension in the name might be used if no mime type can be detected. Takes precedence over filename in URL path or filename in content-disposition header of the binary resource. Defaults to "file". "image.jpg"
headers object Object containining additional headers to use when doing a HTTP(S) request towards the url headers: { 'Authorization': 'auth-headers' }
rendition

Object containing the following attributes:

Name Type Description
instructions object rendition parameters from the worker params (e.g. quality, dpi, format, height etc. See full list here
directory string directory to put the renditions
name string filename of the rendition to create
path string Absolute path to store rendition locally (must put rendition here in order to be uploaded to cloud storage)
index number number used to identify a rendition
params

Original parameters passed into the worker (see full Asset Compute prcoessing API Doc)

Note: This argument is usually not needed, as a callback should take its information from the rendition.instructions which are the specific rendition parameters from the request.

Examples

At the bare minimum, the rendition callback function must write something to the rendition.path.

Simplest example (copying the source file):

async function renditionCallback(source, rendition) => {
    // Check for unsupported file
    const stats = await fs.stat(source.path);
    if (stats.size === 0) {
        throw new SourceUnsupportedError('source file is unsupported');
    }
    // process infile and write to outfile
    await fs.copyFile(source.path, rendition.path);
}

Rendition Callback for batchWorker (required)

The renditionCallback function in batchWorker is where you put your custom worker code. It works similarly to the renditionCallback function in worker with slightly different parameters. The main difference is it only gets called once per worker (instead of for each rendition).

The basic expectation of this function is to go through each of the renditions and using the rendition's instructions convert the it into a rendition, then write this rendition to it's corresponding rendition.path.

Parameters

The parameters for the rendition callback function are: source, renditions, outdir, and params

source

Source is the exact same as for renditionCallback in worker

renditions

Renditions is an array of rendition objects. Each rendition object has the same structure as for renditionCallback in worker

outdir

directory to put renditions produced in batch workers

params

params is the exact same as for renditionCallback in worker

Examples

At the bare minimum, the rendition callback function must write something to the rendition.path.

Simplest example (copying the source file):

async function renditionCallback(source, renditions, outdir, params) => {
    // Check for unsupported file
    const stats = await fs.stat(source.path);
    if (stats.size === 0) {
        throw new SourceUnsupportedError('source file is unsupported');
    }
    // process infile and write to outfile
    renditions.forEach(rendition, () => {
        await fs.copyFile(source.path, outdir + rendition.path);
    })
}

Worker Options (optional)

Optional parameters to pass into workers

  • disableSourceDownload: Boolean used to disable the source download (defaults to false).

  • disableRenditionUpload: Boolean used to disable the rendition upload (defaults to false).

    WARNING: Use this flag only if no rendition should be uploaded. This will make the worker activation fail since the asset compute SDK expects a rendition output.

Disable source download example:

const { worker } = require('@adobe/asset-compute-sdk');

async function renditionCallback(source, rendition, params) => {
	// downloads source inside renditionCallback so does not need asset-compute-sdk to download source file
	await fetch(source.url);
}
const options = {
	disableSourceDownload: true
};
const main = worker(renditionCallback, options);
await main(params);

Disable rendition upload example:

const { worker } = require('@adobe/asset-compute-sdk');
const options = {
	disableRenditionUpload: true
};
const main = worker(renditionCallback, options);
await main(params);

Post processing

Note: this feature is not available for custom workers of the Adobe Asset Compute service.

Image post processing is available since version 2.4.0 and must be enabled by the worker by setting

rendition.postProcess = true;

in the processing callback.

For shell script workers, they can create a JSON file whose path is given to the script by the env var optionsfile and include this in the file:

{
    "postProcess": true
}

Post processing features

These instructions are supported:

  • fmt with png, jpg/jpeg, tif/tiff and gif
  • width and height
  • quality for jpeg and gif
  • interlace for png
  • jpegSize for jpeg
  • dpi
  • convertToDpi
  • crop

Contribution guidelines

Asset Compute Service has repository modularity and naming guidelines. It is modular to the extent possible, as fostered by the serverless concept and OpenWhisk framework. It means having small and focused GitHub repositories that support decoupled development and deployment lifecycles. One repository for one action is OK if it represents its own small services such as a worker. If you want to create a separate repository, log an issue in Asset Compute SDK repository.

For detailed guidelines, see the contribution guidelines. Also, follow these Git commit message guidelines.

Available resources and libraries

The open-sourced libraries of Asset Compute Service are:

Licensing

This project is licensed under the Apache V2 License. See LICENSE for more information.

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