Composer is a new programming model for composing cloud functions built on Apache OpenWhisk. With Composer, developers can build even more serverless applications including using it for IoT, with workflow orchestration, conversation services, and devops automation, to name a few examples.
Composer synthesizes OpenWhisk conductor actions to implement compositions. Compositions have all the attributes and capabilities of an action, e.g., default parameters, limits, blocking invocation, web export.
This repository includes:
- the composer Node.js module for authoring compositions using JavaScript,
- the compose and deploy commands for compiling and deploying compositions,
- documentation, examples, and tests.
Composer is distributed as Node.js package. To install this package, use the Node Package Manager:
npm install -g @ibm-functions/composer
We recommend installing the package globally (with -g
option) if you intend to
use the compose
and deploy
commands to compile and deploy compositions.
A composition is typically defined by means of a JavaScript expression as illustrated in samples/demo.js:
const composer = require('@ibm-functions/composer')
module.exports = composer.if(
composer.action('authenticate', { action: function ({ password }) { return { value: password === 'abc123' } } }),
composer.action('success', { action: function () { return { message: 'success' } } }),
composer.action('failure', { action: function () { return { message: 'failure' } } }))
Compositions compose actions using combinator methods.
These methods implement the typical control-flow constructs of an imperative
programming language. This example composition composes three actions named
authenticate
, success
, and failure
using the composer.if
combinator,
which implements the usual conditional construct. It takes three actions (or
compositions) as parameters. It invokes the first one and, depending on the
result of this invocation, invokes either the second or third action.
This composition includes the definitions of the three composed actions. If the actions are defined and deployed elsewhere, the composition code can be shortened to:
composer.if('authenticate', 'success', 'failure')
One way to deploy a composition is to use the compose
and deploy
commands:
compose demo.js > demo.json
deploy demo demo.json -w
ok: created /_/authenticate,/_/success,/_/failure,/_/demo
The compose
command compiles the composition code to a portable JSON format.
The deploy
command deploys the JSON-encoded composition creating an action
with the given name. It also deploys the composed actions if definitions are
provided for them. The -w
option authorizes the deploy
command to overwrite
existing definitions.
The demo
composition may be invoked like any action, for instance using the
IBM Cloud CLI:
ibmcloud fn action invoke demo -p password passw0rd
ok: invoked /_/demo with id 09ca3c7f8b68489c8a3c7f8b68b89cdc
The result of this invocation is the result of the last action in the
composition, in this case the failure
action since the password in incorrect:
ibmcloud fn activation result 09ca3c7f8b68489c8a3c7f8b68b89cdc
{
"message": "failure"
}