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What is a workflow? Wikipedia says "A workflow consists of an orchestrated and repeatable pattern of activity, enabled by the systematic organization of resources into processes that transform materials, provide services, or process information."
None of that is incorrect. But it is certainly a mouthful. If I am asked in an elevator what a workflow orchestration is, I like to use analogies to make the point as approachable as possible:
"It's like a recipe for code. A recipe has a series of steps, that must be run in a specific order. Iyt can also have different options for food allergies, or different ingredients you might have on hand? A workflow is a recipe for your code, and can be built to handle many of the changes that might reasonably occur when the code runs."
You may have seen one of the name videos out there of parents teaching kids code by writing out the steps to create a Peanut butter and Jelly sandwich.
We're not going to be quite as silly as that Dad, but we'll run through some instructions on how to create a PB&J from Instructables..
If you look at the URL of that recipe - it appears it took 4 tries to get it right :D https://www.instructables.com/How-to-Make-a-Peanut-Butter-and-Jelly-Sandwich-4/
The steps are (skipping some substeps for clarity):
(if you read closely, I skipped 3 steps - wearing gloves, removing the crust and cutting the sandwich in half... because, well - that's all just ridiculous)
The eight steps above are a workflow. They must be performed in that order to create a sandwich - you cannot spread the PB before you lay out the bread.
We can turn these 8 steps into a Conductor workflow.
This workflow shows clear steps with arrows pointing to the next step - so it is visually possible to see how the workflow will progress.
Each task is run by a microservice, so making changes and adding tasks is easy to do. In this example - you see that the recipe calls for PB to be spread first, and then the jelly. This works for a single human - these steps each take 2 hands. But there is no reason that the jelly cannot go first, and THEN the PB. Or - if you had more hands - the PB and the Jelly could be spread simultaneously.
Let's remove the PB dependency from the jelly spreading - as the order of PB vs. jelly does not matter.
We can do this in Conductor with a Fork. A fork splits your workflow into 2 asynchronous tasks, and then a Join reconnects the the workflow into a single path.
We can now apply a fork to apply PB, and a second fork to apply the jelly:
This is version 2 of the workflow.
Now, these operations are independent, and if there is space in the jelly task queue - that can be completed ahead of the PB.
Often, recipes have variations to preparation, and they can be read like an IF statement in programming if (fresh tomatoes) do something, else if (tinned tomatoes) do somethingelse
Let's look at a common example - from a burrito in my freezer. The preparation directions vary depending on the cooking method.
We can emulate this in a workflow using a switch task. The Switch task takes in the workflow ovenType input ${workflow.input.ovenType} and based on this value will make a decision. The default case is for the microwave, and then second decisionCase is set to "oven". From that input, the different tasks can be run.
Workflows are a series of tasks that must be followed in a certain order. In this post, we used cooking recipes as an analogy to a workflow - they too are a series of tasks that must be followed in a certain order.
We created sample workflows for making a peanut and jelly sandwich version 1:
{
"name": "PBJ",
"description": "Edit or extend this sample workflow. Set the workflow name to get started",
"version": 1,
"tasks": [
{
"name": "collect_ingredients",
"taskReferenceName": "collect_ingredients",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "open_bread_bag_place_two_pieces_of_bread_on_plate",
"taskReferenceName": "open_bread_bag_place_two_pieces_of_bread_on_plate",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "open_PB_open_jelly",
"taskReferenceName": "open_PB_open_jelly",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "spread_PB_left_slice_of_bread",
"taskReferenceName": "spread_PB_left_slice_of_bread",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "spread_jelly_right_slice_of_bread",
"taskReferenceName": "spread_jelly_right_slice_of_bread",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "close_sandwich",
"taskReferenceName": "close_sandwich",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "clean_up",
"taskReferenceName": "clean_up",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "eat",
"taskReferenceName": "eat",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
}
],
"inputParameters": [],
"schemaVersion": 2
}
and version 2:
{
"name": "PBJ",
"description": "Edit or extend this sample workflow. Set the workflow name to get started",
"version": 2,
"tasks": [
{
"name": "collect_ingredients",
"taskReferenceName": "collect_ingredients",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "open_bread_bag_place_two_pieces_of_bread_on_plate",
"taskReferenceName": "open_bread_bag_place_two_pieces_of_bread_on_plate",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "fork_join",
"taskReferenceName": "my_fork_join_ref",
"inputParameters": {},
"type": "FORK_JOIN",
"forkTasks": [
[
{
"name": "open_PB",
"taskReferenceName": "open_PB",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "spread_PB_left_slice_of_bread",
"taskReferenceName": "spread_PB_left_slice_of_bread",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
}
],
[
{
"name": "open_jelly",
"taskReferenceName": "open_jelly",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "spread_jelly_right_slice_of_bread",
"taskReferenceName": "spread_jelly_right_slice_of_bread",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
}
]
]
},
{
"name": "notification_join",
"taskReferenceName": "notification_join_ref",
"inputParameters": {},
"type": "JOIN",
"joinOn": ["email_notification_ref", "sms_notification_ref"]
},
{
"name": "close_sandwich",
"taskReferenceName": "close_sandwich",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "clean_up",
"taskReferenceName": "clean_up",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "eat",
"taskReferenceName": "eat",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
}
],
"schemaVersion": 2
}
and another workflow to cook a frozen burrito with microwave or oven instructions:
{
"name": "burrito",
"version": 1,
"tasks": [
{
"name": "remove_overwrap",
"taskReferenceName": "remove_overwrap",
"inputParameters": {
"evaluatorType": "javascript",
"expression": "function e() { if (true){return {\"result\": true}} else { return {\"result\": false}}} e();"
},
"type": "INLINE"
},
{
"name": "order_checking",
"taskReferenceName": "switch_task",
"inputParameters": {
"switchCaseValue": "${workflow.input.ovenType}"
},
"type": "SWITCH",
"decisionCases": {
"oven": [
{
"name": "preheat_oven",
"taskReferenceName": "preheat_oven",
"inputParameters": {
"temp": "400",
"units": "F"
},
"type": "INLINE"
},
{
"name": "wrap_burrito_in_foil",
"taskReferenceName": "wrap_burrito_in_foil",
"inputParameters": {
"temp": "400",
"units": "F"
},
"type": "INLINE"
},
{
"name": "bake",
"taskReferenceName": "initial_bake",
"inputParameters": {
"time": "20"
},
"type": "INLINE"
},
{
"name": "flip",
"taskReferenceName": "flip_burrito_oven",
"inputParameters": {},
"type": "INLINE"
},
{
"name": "bake",
"taskReferenceName": "second_bake",
"inputParameters": {
"time": "20"
},
"type": "INLINE"
},
{
"name": "remove_foil",
"taskReferenceName": "remove_foil",
"inputParameters": {
"temp": "400",
"units": "F"
},
"type": "INLINE"
}
]
},
"defaultCase": [
{
"name": "place_burrito_on_plate",
"taskReferenceName": "place_burrito_on_plate",
"inputParameters": {},
"type": "INLINE"
},
{
"name": "cover_burrito_with_plate",
"taskReferenceName": "cover_burrito_with_plate",
"inputParameters": {},
"type": "INLINE"
},
{
"name": "zap",
"taskReferenceName": "initial_zap",
"inputParameters": {
"time": "1.5"
},
"type": "INLINE"
},
{
"name": "flip",
"taskReferenceName": "flip_burrito_zap",
"inputParameters": {},
"type": "INLINE"
},
{
"name": "zap",
"taskReferenceName": "second_zap",
"inputParameters": {
"time": "1.5"
},
"type": "INLINE"
}
],
"evaluatorType": "value-param",
"expression": "switchCaseValue",
"decisionCases": {},
"defaultExclusiveJoinTask": [],
"forkTasks": []
},
{
"name": "let_sit",
"taskReferenceName": "let_sit",
"inputParameters": {
"time": "1"
},
"type": "INLINE"
}
],
"schemaVersion": 2
}
We are able to reuse a number of tasks:
zap task is used twice in the microwave branch.bake task in the oven branch.flip task is used in both branches.When reusing tasks, the taskReferenceName (shown at the top of the box) must be unique.
If you're curious about how to build a workflow orchestration - it might be a fun exercise to try your favorite recipe as a workflow. You can build on the workflows from this post in our Developer Edition. Feel free to share what you came up with in our community Slack. We love seeing creative uses of workflows!