This project shows how serverless, event-driven architectures can be used to execute code in response to database change events from Cloudant, thus extracting scalable and efficient analytics from both technologies.
This application shows you two IBM Cloud Functions (powered by Apache OpenWhisk) actions (written in JavaScript) that write and read text and image data to Cloudant, a hosted Apache CouchDB service. The scenario demonstrates how actions can work with data services and execute logic in response to database changes.
One action connects to Cloudant and inserts text and binary data as an attachment. The action is defined with package variables that provide it with Cloudant credentials as environment variables. This action is then uploaded to the OpenWhisk platform where it can be invoked manually to test.
A second action responds to the changes that were inserted into Cloudant by the first action. Instead of being manually invoked, the developer defines a trigger and mapping rule that binds the action to the Cloudant database and responds to changes.
- IBM Cloud Functions powered by Apache OpenWhisk
- Cloudant (CouchDB)
You should have a basic understanding of the OpenWhisk programming model. If not, try the action, trigger, and rule demo first.
Also, you'll need an IBM Cloud account and the latest OpenWhisk command line tool (wsk) installed and on your PATH.
As an alternative to this end-to-end example, you might also consider the more basic "building block" version of this sample.
- Provision Cloudant
- Create OpenWhisk actions, triggers, and rules
- Test database change events
- Delete actions, triggers, and rules
- Recreate deployment manually
Log into the IBM Cloud, provision a Cloudant database instance, and name it openwhisk-cloudant. Log into the Cloudant web console and create a database named cats.
Copy template.local.env to a new file named local.env and update the CLOUDANT_INSTANCE, CLOUDANT_DATABASE, CLOUDANT_USERNAME, and CLOUDANT_PASSWORD for your instance.
Note: The Cloudant service credentials and connectivity details can be automatically bound to the OpenWhisk context with
wsk package refresh, as they are in the simpler version of this app. However, since we are writing more than a simple JSON object back to Cloudant, we will use the Cloudant NPM client directly with the credentials, rather than through the Cloudant packaged write action.
deploy.sh is a convenience script reads the environment variables from local.env and creates the OpenWhisk actions, triggers, and rules on your behalf. Later you will run these commands yourself.
./deploy.sh --installNote: If you see any error messages, refer to the Troubleshooting section below. You can also explore Alternative deployment methods.
To test, invoke the first action manually. Open one terminal window to poll the logs:
wsk activation pollAnd in a second terminal, invoke the action:
wsk action invoke --blocking --result write-to-cloudantUse deploy.sh again to tear down the OpenWhisk actions, triggers, and rules. You will recreate them step-by-step in the next section.
./deploy.sh --uninstallThis section provides a deeper look into what the deploy.sh script executes so that you understand how to work with OpenWhisk triggers, actions, rules, and packages in more detail.
Make the Cloudant instance on the IBM Cloud available as an event source.
wsk package bind /whisk.system/cloudant "$CLOUDANT_INSTANCE" \
--param username "$CLOUDANT_USERNAME" \
--param password "$CLOUDANT_PASSWORD" \
--param host "$CLOUDANT_USERNAME.cloudant.com"Create a trigger named image-uploaded that subscribes to that Cloudant instance and specific database change events.
wsk trigger create image-uploaded \
--feed "/_/$CLOUDANT_INSTANCE/changes" \
--param dbname "$CLOUDANT_DATABASE"Upload the action code named write-to-cloudant that inserts text and an image to Cloudant which will initiate a database change event.
wsk action create write-to-cloudant actions/write-to-cloudant.js \
--param CLOUDANT_USERNAME "$CLOUDANT_USERNAME" \
--param CLOUDANT_PASSWORD "$CLOUDANT_PASSWORD" \
--param CLOUDANT_DATABASE "$CLOUDANT_DATABASE"Upload the action code named write-from-cloudant that will receive database change information and log it to the console.
wsk action create write-from-cloudant actions/write-from-cloudant.jsSpecify a linkage between the built-in Cloudant read action and the custom write-from-cloudant above in a sequence named write-from-cloudant-sequence.
wsk action create write-from-cloudant-sequence \
--sequence /_/$CLOUDANT_INSTANCE/read,write-from-cloudantDeclare a rule named echo-images that maps the trigger image-uploaded to the action sequence write-from-cloudant-sequence. Without this mapping, the trigger will fire but no logic will be executed in response.
wsk rule create echo-images image-uploaded write-from-cloudant-sequencewsk action invoke --blocking --result write-to-cloudantCheck for errors first in the OpenWhisk activation log. Tail the log on the command line with wsk activation poll or drill into details visually with the monitoring console on the IBM Cloud.
If the error is not immediately obvious, make sure you have the latest version of the wsk CLI installed. If it's older than a few weeks, download an update.
wsk property get --cliversiondeploy.sh will be replaced with wskdeploy in the future. wskdeploy uses a manifest to deploy declared triggers, actions, and rules to OpenWhisk.
You can also use the following button to clone a copy of this repository and deploy to the IBM Cloud as part of a DevOps toolchain. Supply your OpenWhisk and Cloudant credentials under the Delivery Pipeline icon, click Create, then run the Deploy stage for the Delivery Pipeline.
