Java Function as a Service(FaaS) Tutorial

Overview

Overview

This tutorial walks you through on how to build a Java functions on a Function as a Service(FaaS) platform Apache OpenWhisk.

Prerequisites

You will need in this tutorial

Tools

minishift
docker
kubectl
oc (eval $(minishift oc-env))
Apache Maven
stern (brew install stern)
OpenWhisk CLI
curl, gunzip, tar are built-in to MacOS or part of your bash shell
git (everybody needs the git CLI)
Java 8

Setup minishift

Assumes minishift, tested with minishift v1.13.1+75352e5

Minishift Profile Setup

#!/bin/bash

# add the location of minishift executable to PATH

export MINISHIFT_HOME=~/minishift_1.13.1
export PATH=$MINISHIFT_HOME:$PATH

minishift profile set faas-tutorial
minishift config set memory 8GB
minishift config set cpus 3
minishift config set image-caching true
minishift addon enable admin-user
minishift addon enable anyuid # # (1)

minishift start

minishift ssh -- sudo ip link set docker0 promisc on # # (2)

Some images that are in Apache OpenWhisk Docker hub requires anyuid SCC in OpenShift
This is needed for pods to communicate with each other within the cluster (TODO: need to add more clear details here)

❗	`minishift ssh — sudo ip link set docker0 promisc on` command needs to be execute each and every time minishift restarted

Setup environment

#!/bin/bash

eval $(minishift oc-env) && eval $(minishift docker-env)
oc login $(minishift ip):8443 -u admin -p admin

Setup OpenWhisk

The project OpenWhisk on OpenShift provides the OpenShift templates required to deploy Apache OpenWhisk.

oc new-project faas # # (1)
oc project -q # # (2)
oc process -f https://git.io/openwhisk-template | oc create -f - # # (3)
oc adm policy add-role-to-user admin developer -n faas # # (4)

Its always better to group certain class of applications, create a new OpenShift project called faas to deploy all OpenWhisk applications
Make sure we are in right project
Deploy OpenWhisk applications to openwhisk project
(Optional) Add developer user as admin to faas project so as to allow you to login with developer user and access faas project

📎	You need to wait for sometime to have all the required OpenWhisk pods come up and the FaaS is ready for some load. You can watch the status watch -n 5 'oc logs -f controller-0 -n faas \| grep "invoker status changed"'`

Verify Deployment

Launch OpenShift console via minishift console, a successful deployment will look like:

Configure WSK CLI

Download OpenWhisk CLI and add it your PATH. Verify your path using the command wsk --help

The OpenWhisk CLI needs to be configured to know where the OpenWhisk is located and the authorization that could be used to invoke wsk commands. Run the following command to have that setup:

#!/bin/bash

AUTH_SECRET=$(oc get secret whisk.auth -o yaml | grep "system:" | awk '{print $2}' | base64 --decode)
wsk property set --auth $AUTH_SECRET --apihost $(oc get route/openwhisk --template="{{.spec.host}}")

Successful setup of WSK CLI will show output like:

In this case the OpenWhisk API Host is pointing to the local minishift nip.io address

To verify if wsk CLI is configured properly run wsk -i action list,that should list some actions which are installed as part of the OpenWhisk setup. If you see empty result then you Reinstall default Catalog

💡	The `nginx` in OpenWhisk deployment uses a self-signed certificate, to avoid certificate errors when using `wsk`, you need to add `wsk -i` to each of your `wsk` commands. For convenience you can add an alias to your profile like `alias wsk='wsk -i $@'`

Setup your Development environment

Clone the complete project from git clone https://github.com/redhat-developer-demos/faas-java-tutorial, we will refer to this location as $PROJECT_HOME through out the document for convenience.

What is Action ?

Actions are stateless code snippets that run on the OpenWhisk platform. It is analogous to Function in Java idioms. OpenWhisk Actions are thread-safe meaning at a given point of time only one invocation happens.

Fore more details refer the official documentation here.

Your first Action

Lets quickly create a simple function in JavaScript to see if all working:

mkdir -p getstarted
cd $PROJECT_HOME/getstarted

Create a file called $PROJECT_HOME/getstarted/greeter.js and add the following content to it:

function main() {
    return {payload: 'Welcome to OpenWhisk on OpenShift'};
}

Create an action called greeter:

wsk -i action update greeter greeter.js

Lets invoke the action using command:

wsk -i action invoke greeter --result

The action invoke should respond with the following JSON:

{
    "payload": "Welcome to OpenWhisk on OpenShift"
}

Java Actions

Install Maven Archetype

Maven Archetype could be used to generate the template Java Action project, as of writing this tutorial the archetype is not maven central hence it need to install it locally,

git clone https://github.com/apache/incubator-openwhisk-devtools
cd incubator-openwhisk-devtools/java-action-archetype
mvn -DskipTests clean install
cd $PROJECT_HOME

Your first Java Action

Lets now create the first Java Action a simple "hello world" kind of function, have it deployed to OpenWhisk and finally invoke to see the result. This section will also details the complete Create-Update-Delete cycle of Java Actions on OpenWhisk.

📎	For easier jar names all the examples will be using maven `<finalName>`. If you generating new project following the instructions just be sure to update the default `<finalName>` in `pom.xml` to `${artifactId}` to make the command instructions in subsequent section work without any changes.

Create Java Action

cd $PROJECT_HOME
mvn archetype:generate \
  -DarchetypeGroupId=org.apache.openwhisk.java \
  -DarchetypeArtifactId=java-action-archetype \
  -DarchetypeVersion=1.0-SNAPSHOT \
  -DgroupId=com.example \
  -DartifactId=hello-openwhisk

Build

cd hello-openwhisk
mvn clean package

Deploy to OpenWhisk

Create

wsk -i action create hello-openwhisk target/hello-openwhisk.jar --main com.example.FunctionApp

Invoke and Verify the result

Synchronously

wsk -i action invoke hello-openwhisk --result

As all the OpenWhisk actions are asynchronous, we need to add --result to get the result shown on the console.

Successful execution of the command will show the following output:

{"greetings":  "Hello! Welcome to OpenWhisk" }

Asynchronously

wsk -i action invoke hello-openwhisk

A successful action invoke will return an activation id :

We can then use the to activation id check the response using wsk CLI:

wsk -i activation result <activation_id>

e.g.

wsk -i activation result ffb2966350904356b29663509043566e

Successful execution of the command will show the same output like Action Response.

Update

Update the FunctionApp class with code:

package com.example;

import com.google.gson.JsonObject;

/**
 * Hello FunctionApp
 */
public class FunctionApp {
  public static JsonObject main(JsonObject args) {
    JsonObject response = new JsonObject();
    response.addProperty("greetings", "Hello! Welcome to OpenWhisk on OpenShift");
    return response;
  }
}

Update the FunctionAppTest class with code:

package com.example;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

import com.google.gson.JsonObject;

import org.junit.Test;

/**
 * Unit test for simple function.
 */
public class FunctionAppTest {
  @Test
  public void testFunction() {
    JsonObject args = new JsonObject();
    JsonObject response = FunctionApp.main(args);
    assertNotNull(response);
    String greetings = response.getAsJsonPrimitive("greetings").getAsString();
    assertNotNull(greetings);
    assertEquals("Hello! Welcome to OpenWhisk on OpenShift", greetings);
  }
}

cd $PROJECT_HOME/hello-openwhisk
mvn clean package
wsk -i action update hello-openwhisk target/hello-openwhisk.jar --main com.example.FunctionApp

Successful update should show a output like:

Repeating the Invocation and Verification steps should result in the updated response like:

{
    "greetings": "Hello! Welcome to OpenWhisk on OpenShift"
}

Delete

wsk -i action delete hello-openwhisk

Successful delete should show a output like:

Web Action

WebActions allows the OpenWhisk action to be invoked via HTTP verbs like GET, POST, PUT etc., The WebActions can be enabled for any Action using the prameter --web=true during the creation of the action using WSK CLI.

cd $PROJECT_HOME
mvn archetype:generate \
  -DarchetypeGroupId=org.apache.openwhisk.java \
  -DarchetypeArtifactId=java-action-archetype \
  -DarchetypeVersion=1.0-SNAPSHOT \
  -DgroupId=com.example \
  -DartifactId=hello-web

Update the FunctionApp class with code:

package com.example;

import com.google.gson.JsonObject;

/**
 * Hello Web FunctionApp
 */
public class FunctionApp {
  public static JsonObject main(JsonObject args) {
    JsonObject response = new JsonObject();
    response.add("response", args);
    return response;
  }
}

Update the FunctionAppTest class with code:

package com.example;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

import com.google.gson.JsonObject;

import org.junit.Test;

/**
 * Unit test for simple function.
 */
public class FunctionAppTest {
  @Test
  public void testFunction() {
    JsonObject args = new JsonObject();
    args.addProperty("name", "test");
    JsonObject response = FunctionApp.main(args);
    assertNotNull(response);
    String actual = response.get("response").getAsJsonObject().get("name").getAsString();
    assertEquals("test", actual);
  }
}

Build

cd hello-web
mvn clean package

Deploy to OpenWhisk

wsk -i action update --web=true redhat-developers-demo/hello-web target/hello-web.jar --main com.example.FunctionApp

Invoke and Verify the result

WEB_URL=`wsk -i action get redhat-developers-demo/hello-web --url | awk 'FNR==2{print $1}'` # #(1)
AUTH=`oc get secret whisk.auth -o yaml | grep "system:" | awk '{print $2}'` # #(2)

Get the HTTP URL for invoking the action
Some resources requires authentication, for those requests its required to add Authorization header with value as $AUTH

curl -k $WEB_URL.json

You can also access the url via browser using $WEB_URL.json, where you can get the $WEB_URL using command wsk -i action get /whisk.system/redhat-developers-demo/hello-web --url.

📎

The following section shows some example requests and their expected responses

Without any request data

{
  "response": {
    "__ow_method": "get",
    "__ow_headers": {
      "x-forwarded-port": "443",
      "accept": "*/*",
      "forwarded": "for=192.168.64.1;host=openwhisk-faas.192.168.64.67.nip.io;proto=https",
      "user-agent": "curl/7.54.0",
      "x-forwarded-proto": "https",
      "host": "controller.faas.svc.cluster.local:8080",
      "x-forwarded-host": "openwhisk-faas.192.168.64.67.nip.io",
      "x-forwarded-for": "192.168.64.1"
    },
    "__ow_path": ""
  }
}

With any JSON request data

curl -k -X POST -H 'Content-Type: application/json' -d '{"name": "test"}' $WEB_URL.json

{
  "response": {
    "__ow_method": "post",
    "__ow_headers": {
      "x-forwarded-port": "443",
      "accept": "*/*",
      "forwarded": "for=192.168.64.1;host=openwhisk-faas.192.168.64.67.nip.io;proto=https",
      "user-agent": "curl/7.54.0",
      "x-forwarded-proto": "https",
      "host": "controller.faas.svc.cluster.local:8080",
      "content-type": "application/json",
      "x-forwarded-host": "openwhisk-faas.192.168.64.67.nip.io",
      "x-forwarded-for": "192.168.64.1"
    },
    "__ow_path": "",
    "name": "test"
  }
}

With request data and an invalid content type

curl -k -X POST -H 'Content-Type: application/something' -d '{"name": "test"}' $WEB_URL.json

Invoke via curl like above , with request data you will see the response like:

{
  "response": {
    "__ow_method": "post",
    "__ow_headers": {
      "x-forwarded-port": "443",
      "accept": "*/*",
      "forwarded": "for=192.168.64.1;host=openwhisk-faas.192.168.64.67.nip.io;proto=https",
      "user-agent": "curl/7.54.0",
      "x-forwarded-proto": "https",
      "host": "controller.faas.svc.cluster.local:8080",
      "content-type": "application/something",
      "x-forwarded-host": "openwhisk-faas.192.168.64.67.nip.io",
      "x-forwarded-for": "192.168.64.1"
    },
    "__ow_path": "",
    "__ow_body": "eyJuYW1lIjogInRlc3QifQ==" //(1)
  }
}

for unknown content-type the request body will be sent as base64 encoded string

Chaining Actions

Apache OpenWhisk allows chaining of actions which is called in sequence like how they are defined. We will now create a simple sequence of actions which will split, uppercase and sort a comma separated string.

All the three projects can be co-located in same directory for clarity and easy building:

cd ..
mkdir -p sequence-demo
cd sequence-demo
wsk -i package create redhat-developers-demo # # (1)

Create a new package to hold our actions, this gives a better clarity on which actions we add to our sequence. For more details refer Packages

Create Split Action

This Action will be first in the sequence which will receive a comma separated string as a parameter and will return a array of string as response.

cd $PROJECT_HOME
mvn archetype:generate \
  -DarchetypeGroupId=org.apache.openwhisk.java \
  -DarchetypeArtifactId=java-action-archetype \
  -DarchetypeVersion=1.0-SNAPSHOT \
  -DgroupId=com.example \
  -DartifactId=splitter

Update the FunctionApp class with code:

package com.example;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

/**
 * Splitter FunctionApp
 */
public class FunctionApp {
  public static JsonObject main(JsonObject args) {
    JsonObject response = new JsonObject();
    String text = null;
    if (args.has("text")) {
      text = args.getAsJsonPrimitive("text").getAsString();
    }
    String[] results = new String[] { text };
    if (text != null && text.indexOf(",") != -1) {
      results = text.split(",");
    }
    JsonArray splitStrings = new JsonArray();
    for (String var : results) {
      splitStrings.add(var);
    }
    response.add("result", splitStrings);
    return response;
  }
}

Update the FunctionAppTest class with code:

package com.example;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

import java.util.ArrayList;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

import org.junit.Test;

/**
 * Splitter FunctionAppTest
 */
public class FunctionAppTest {
  @Test
  public void testFunction() {
    JsonObject args = new JsonObject();
    args.addProperty("text", "apple,orange,banana");
    JsonObject response = FunctionApp.main(args);
    assertNotNull(response);
    JsonArray results = response.getAsJsonArray("result");
    assertNotNull(results);
    assertEquals(3, results.size());
    ArrayList<String> actuals = new ArrayList<>();
    results.forEach(j -> actuals.add(j.getAsString()));
    assertTrue(actuals.contains("apple"));
    assertTrue(actuals.contains("orange"));
    assertTrue(actuals.contains("banana"));
  }
}

Build Splitter Action

cd splitter
mvn clean package
wsk -i action update redhat-developers-demo/splitter target/splitter.jar --main com.example.FunctionApp

Create Uppercase Action

This Action will take the array of Strings from previous step (Splitter Action) and convert the strings to upper case

cd ..
mvn archetype:generate \
  -DarchetypeGroupId=org.apache.openwhisk.java \
  -DarchetypeArtifactId=java-action-archetype \
  -DarchetypeVersion=1.0-SNAPSHOT \
  -DgroupId=com.example \
  -DartifactId=uppercase

Update the FunctionApp class with code:

package com.example;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

/**
 * UpperCase Function
 */
public class FunctionApp {
  public static JsonObject main(JsonObject args) {
    JsonObject response = new JsonObject();
    JsonArray upperArray = new JsonArray();
    if (args.has("result")) { // // (1)
      args.getAsJsonArray("result").forEach(e -> upperArray.add(e.getAsString().toUpperCase()));
    }
    response.add("result", upperArray);
    return response;
  }
}

The function expects the previous action in sequence to send the parameter with JSON attribute called result

Update the FunctionAppTest class with code:

package com.example;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

import java.util.ArrayList;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

import org.junit.Test;

/**
 * Unit test for UpperCase Function.
 */
public class FunctionAppTest {
  @Test
  public void testFunction() {
    JsonObject args = new JsonObject();
    JsonArray splitStrings = new JsonArray();
    splitStrings.add("apple");
    splitStrings.add("orange");
    splitStrings.add("banana");
    args.add("result", splitStrings);
    JsonObject response = FunctionApp.main(args);
    assertNotNull(response);
    JsonArray results = response.getAsJsonArray("result");
    assertNotNull(results);
    assertEquals(3, results.size());
    ArrayList<String> actuals = new ArrayList<>();
    results.forEach(j -> actuals.add(j.getAsString()));
    assertTrue(actuals.contains("APPLE"));
    assertTrue(actuals.contains("ORANGE"));
    assertTrue(actuals.contains("BANANA"));
  }
}

Build Uppercase Action

cd uppercase
mvn clean package
wsk -i action update redhat-developers-demo/uppercase target/uppercase.jar --main com.example.FunctionApp

Create Sort Action

This Action will take the array of Strings from previous step (Upppercase Action) and sort them

cd ..
mvn archetype:generate \
  -DarchetypeGroupId=org.apache.openwhisk.java \
  -DarchetypeArtifactId=java-action-archetype \
  -DarchetypeVersion=1.0-SNAPSHOT \
  -DgroupId=com.example \
  -DartifactId=sorter

Update the FunctionApp class with code:

package com.example;

import java.util.ArrayList;
import java.util.Comparator;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

/**
 * Sorter FunctionApp
 */
public class FunctionApp {
  public static JsonObject main(JsonObject args) {
    JsonObject response = new JsonObject();
    ArrayList<String> upperStrings = new ArrayList<>();
    if (args.has("result")) {
      args.getAsJsonArray("result").forEach(e -> upperStrings.add(e.getAsString()));
    }

    JsonArray sortedArray = new JsonArray();
    upperStrings.stream().sorted(Comparator.naturalOrder()).forEach(s -> sortedArray.add(s));

    response.add("result", sortedArray);
    return response;
  }
}

Update the FunctionAppTest class with code:

package com.example;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

import java.util.ArrayList;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

import org.junit.Test;

/**
 * Unit test for Sorted Function.
 */
public class FunctionAppTest {
  @Test
  public void testFunction() {
    JsonObject args = new JsonObject();
    JsonArray splitStrings = new JsonArray();
    splitStrings.add("APPLE");
    splitStrings.add("ORANGE");
    splitStrings.add("BANANA");
    args.add("result", splitStrings);
    JsonObject response = FunctionApp.main(args);
    assertNotNull(response);
    JsonArray results = response.getAsJsonArray("result");
    assertNotNull(results);
    assertEquals(3, results.size());
    ArrayList<String> actuals = new ArrayList<>();
    results.forEach(j -> actuals.add(j.getAsString()));
    assertTrue(actuals.get(0).equals("APPLE"));
    assertTrue(actuals.get(1).equals("BANANA"));
    assertTrue(actuals.get(2).equals("ORANGE"));
  }
}

Build Sorter Action

cd sorter
mvn clean package
wsk -i action update redhat-developers-demo/sorter target/sorter.jar --main com.example.FunctionApp

Create an Action Sequence

Having created all the three actions, lets now create OpenWhisk that calls all three function split,uppercase and sort in sequence.

cd ..
wsk -i action update splitUpperAndSort --sequence redhat-developers-demo/splitter,redhat-developers-demo/uppercase,redhat-developers-demo/sorter

Invoke and Verify

wsk -i action invoke splitUpperAndSort --param text "zeebra,cat,antelope" --result

The above action invoke should result in response like:

{
    "result": [
        "ANTELOPE",
        "CAT",
        "ZEEBRA"
    ]
}

Troubleshooting

Reinstall default Catalog

If you are on a low bandwidth sometimes the default catalog will not be populated, run the following commands to have them installed

#!/bin/bash

oc delete job install-catalog (1)

cat <<EOF | oc apply -f -
apiVersion: batch/v1
kind: Job
metadata:
  name: install-catalog
spec:
  activeDeadlineSeconds: 600
  template:
    metadata:
      name: install-catalog
    spec:
      containers:
      - name: catalog
        image: projectodd/whisk_catalog:openshift-latest
        env:
          - name: "WHISK_CLI_VERSION"
            valueFrom:
              configMapKeyRef:
                name: whisk.config
                key: whisk_cli_version_tag
          - name: "WHISK_AUTH"
            valueFrom:
              secretKeyRef:
                name: whisk.auth
                key: system
          - name: "WHISK_API_HOST_NAME"
            value: "http://controller:8080"
      initContainers:
      - name: wait-for-controller
        image: busybox
        command: ['sh', '-c', 'until wget -T 5 --spider http://controller:8080/ping; do echo waiting for controller; sleep 2; done;']
      restartPolicy: Never
EOF # # (2)

Delete the old job
Run the install-catalog job again

Now when you run wsk -i action list you should see output like:

Tips and Tricks

💡

If you are going to use a lot of wsk then its worth aliasing wsk with alias wsk='wsk -i $@' to avoid SSL errors and skip adding -i for every command.
For detailed JSON output form wsk commands prefix -v. This is a great command option for troubleshooting.
Its safe to use wsk -i update [resource] when creating OpenWhisk resources like Actions, Packages etc., as this command will act like create for new resources and update for existing resources.
wsk -i [resource command ] --summary provides detailed information about a specific resource e.g. wsk -i action get foo --summary
wsk -i activation poll, a very useful command when we want to debug some error or see the exception stack traces during a funciton execution. The simple example of this could be that we star this command on one terminal and fire the action on another to see poll window showing exceptions/errors/stacktraces if any during execution.

Java Function as a Service(FaaS) Tutorial

Overview

Prerequisites

Tools

Setup minishift

Minishift Profile Setup

Setup environment

Setup OpenWhisk

Verify Deployment

Configure WSK CLI

Setup your Development environment

What is Action ?

Your first Action

Java Actions

Install Maven Archetype

Your first Java Action

Create Java Action

Build

Deploy to OpenWhisk

Create

Invoke and Verify the result

Synchronously

Asynchronously

Update

Delete

Web Action

Build

Deploy to OpenWhisk

Invoke and Verify the result

Chaining Actions

Create Split Action

Build Splitter Action

Create Uppercase Action

Build Uppercase Action

Create Sort Action

Build Sorter Action

Create an Action Sequence

Invoke and Verify

Troubleshooting

Reinstall default Catalog

Tips and Tricks

References

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