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 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 to install the package globally (with
-g option) if you intend to
deploy commands to compile and deploy compositions.
Defining a composition
const composer =moduleexports = composer
Compositions compose actions using combinator methods.
These methods implement the typical control-flow constructs of a sequential
imperative programming language. This example composition composes three actions
failure using the
combinator, which implements the usual conditional construct. It take 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 shorten to:
Deploying a composition
One way to deploy a composition is to use the
compose demo.js > demo.json deploy demo demo.json -w
ok: created /_/authenticate,/_/success,/_/failure,/_/demo
compose command compiles the composition code to a portable JSON format.
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
Running a composition
demo composition may be invoked like any action, for instance using the
wsk action invoke demo -p password passw0rd
ok: invoked /_/demo with id 4f91f9ed0d874aaa91f9ed0d87baaa07
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:
wsk activation result 4f91f9ed0d874aaa91f9ed0d87baaa07
This invocation creates a trace, i.e., a series of activation records:
wsk activation list
activations fd89b99a90a1462a89b99a90a1d62a8e demo eaec119273d94087ac119273d90087d0 failure 3624ad829d4044afa4ad829d40e4af60 demo a1f58ade9b1e4c26b58ade9b1e4c2614 authenticate 3624ad829d4044afa4ad829d40e4af60 demo 4f91f9ed0d874aaa91f9ed0d87baaa07 demo
The entry with the earliest start time (
summarizes the invocation of the composition while other entries record later
activations caused by the composition invocation. There is one entry for each
invocation of a composed action (
eaec119273d94087ac119273d90087d0). The remaining entries record the beginning
and end of the composition as well as the transitions between the composed
Compositions are implemented by means of OpenWhisk conductor actions. The documentation of conductor actions explains execution traces in greater details.