Hello World Codelab 5
What we've covered so far:
Hello World Part 1 We created the Hello World Workflow.
Hello World Part 2 We created V2 of Hello World (Versioning) and added an HTTP Task.
Hello World Part 3 We created V3 of Hello World and introduced the concept of FORK and JOIN tasks.
Hello World Part 4 We created V4 of Hello World, adding an Inline task to calculate a formula in JavaScript.
Part 5
In part 5 of the Hello World codelab, we'll wrap up our hello_world application by adding a Switch Task and several Set a Variable Tasks.
In Part 4, we calculated the local time - based on the users' IP address and converting GMT to the local time. In Part 5, we'll wish the user a "Good [time of day]" based on the hour calculation.
Note: Clearly, this would be much easier to do in the same Inline task with just a couple of more lines of JavaScript, but why not show off the power of Conductor's Switch task?
The Switch
A Switch task takes an input value and then, based on the results, will run different workflows based on the result.
The expression below will return a different time of day based on the hour calculated.
- Before 6 AM, will return "night".
- 6-12 AM returns "morning".
- 12-18 (12 -6 PM) returns "afternoon".
- After 1800 (after 6 PM), returns "evening".
Based on this data, a different set of tasks will be run. In this case, we'll set a different variable for each time of day.
The Workflow
The workflow is getting very long, so let's just walk through the differences. Here are the basics of the Switch task:
- The
hourinput parameter comes from the calculate_local_time_ref output. - The expression is a simple if/else statement in JavaScript (and minified). It defines the periods of the day and returns the category.
- There are
decisionCasesset for each category determined in the switch case.
{
"name": "time_of_day",
"taskReferenceName": "time_of_day_ref",
"inputParameters": {
"hour": "${calculate_local_time_ref.output.result.hour}"
},
"type": "SWITCH",
"evaluatorType": "javascript",
"expression": "$.hour <= 6 ? 'night': $.hour <= 12 ? 'morning':$.hour <= 18 ? 'afternoon':$.hour <= 24 ? 'evening'}",
"defaultCase": [
{
}
],
"decisionCases": {
"night": [
{
...
}
],
"morning": [
{
...
}
],
"afternoon": [
{
...
}
],
"evening": [
{
...
}
]
}
}
What should we do in each case?
In each "case" of the switch, we'll call a Set variable task to set a variable named message.
For example, the morning task will be:
{
"name": "set_morning_variable",
"taskReferenceName": "set_morning_variable_ref",
"type": "SET_VARIABLE",
"inputParameters": {
"message": "Have a great morning!!"
}
}
We'll build a similar SET_VARIABLE task for the afternoon, evening and night - ensuring that the message has value in every possible case of the SWITCH.
Putting all of this logic together to create a Switch task with 4 cases, each with one embedded task, looks like this:
{
"name": "time_of_day",
"taskReferenceName": "time_of_day_ref",
"inputParameters": {
"hour": "${calculate_local_time_ref.output.result.hour}"
},
"type": "SWITCH",
"evaluatorType": "javascript",
"expression": "function e(){return $.hour<6?'night':$.hour<12?'morning':$.hour<18?'afternoon':'evening'}e();",
"decisionCases": {
"night": [
{
"name": "set_night_variable",
"taskReferenceName": "set_night_variable_ref",
"type": "SET_VARIABLE",
"inputParameters": {
"message": "Have a great night!!"
}
}
],
"morning": [
{
"name": "set_morning_variable",
"taskReferenceName": "set_morning_variable_ref",
"type": "SET_VARIABLE",
"inputParameters": {
"message": "Have a great morning!!"
}
}
],
"afternoon": [
{
"name": "set_afternoon_variable",
"taskReferenceName": "set_afternoon_variable_ref",
"type": "SET_VARIABLE",
"inputParameters": {
"message": "Have a great afternoon!!"
}
}
],
"evening": [
{
"name": "set_evening_variable",
"taskReferenceName": "set_evening_variable_ref",
"type": "SET_VARIABLE",
"inputParameters": {
"message": "Have a great evening!!"
}
}
]
}
}
Place this task in the JSON inside the FORK, right after the calculate_local_time task. Additionally:
- Update the version of the workflow to 5.
- Change the joinOn from
calculate_local_time_reftotime_of_day_ref - add
"hw_time_of_day": "${workflow.variables.message}"tooutputParameters.
Now the workflow diagram will look like this:
How it works
The hour is calculated in the task before. The SWITCH decides if the hour is night, morning, afternoon or evening. Based on the SWITCH decision, a different SET_VARIABLE is called to create a phrase matching that time of day. Then, we call this variable as one of the output parameters of the workflow.
Results
The input for version 5 is the same - just the ipaddress. The result of the workflow adds the variable phrase in the hw_time_of_day greeting:
{
"hw_location":"We hope the weather is nice near Bengaluru"
"hw_time":"The Local time is 23:41"
"hw_response":"Hello World!"
"hw_time_of_day":"Have a great evening!!"
}
Conclusion
Congratulations! You have completed the Hello World Codelab. You've built several iterations of the application, from V1 with just a Java worker to V5 with the Java Worker, FORK, SWITCH, VARIABLE, HTTP and INLINE tasks.
We've covered a lot of the features in Conductor workflows. If you'd like to review, here are links to earlier sections of the codelab:
Hello World Part 1 We created the Hello World Workflow.
Hello World Part 2 We created V2 of Hello World (Versioning) and added an HTTP Task.
Hello World Part 3 We created V3 of Hello World and introduced the concept of FORK and JOIN tasks.
Hello World Part 4 We created V4 of Hello World, adding an Inline task to calculate a formula in JavaScript.
Thank you. We'd love your feedback on this codelab.