## Effortless orchestration with
---
# The problem
--
Long running, complex interactions... <!-- .element: class="fragment" -->
...in distributed systems... <!-- .element: class="fragment" -->
...with transactional characteristics. <!-- .element: class="fragment" -->
--
## Example
<img src="assets/img/interaction.svg" alt="Interaction example" class="stretch">
--
## Failure
<img src="assets/img/interaction-failure.svg" alt="Interaction failure" class="stretch">
--
## Queues FTW
<img src="assets/img/interaction-with-queues.svg" alt="Interaction with queues" class="stretch">
--
## Status?
- **User:** what's going on with my order?
- **Seller:** incoming orders?
- **Developer:** debug a single execution?
<img src="assets/img/interaction-with-queues-status.svg" alt="Interaction with queues status" class="stretch">
--
## Cancellation?
- **User:** I changed my mind, give me my money back!
- **Payment failed:** User failed to pay the order, cancel it!
<img src="assets/img/interaction-with-queues-cancellation.svg" alt="Interaction with queues cancellation" class="stretch">
--
## State!
<img src="assets/img/interaction-state.svg" alt="Interaction state" class="stretch">
--
## Reinventing wheels
<img src="assets/img/reinventing-wheels.png" alt="Reinventing wheels" class="stretch">
*Source: [StackOverflow Blog](https://stackoverflow.blog/2020/11/23/the-macro-problem-with-microservices/)* <!-- .element style="font-size: 13px" -->
<!-- .element style="margin-top: -30px;" -->
--
## Lessons learnt
- No *one size fits all* solution (yet)
- Fragile systems
- Lack of orchestration
--
## Lack of orchestration
- Fractured business processes
- Tight coupling between components
- Cancellations?
- Compensating actions?
- Additional interactions?
- Troubleshooting?
---
# Temporal
--
## What is Temporal?
- Temporal service
- Temporal SDK *(insert your programming language here)*
--
## Orchestration as code
- Write business logic as plain code
- Orchestration framework
- Durability and reliability out-of-the-box
--
## Concepts
- Workflow
- Activity
- Worker
_[Documentation](https://docs.temporal.io/concepts)_
--
## Workflow
- Encapsulates business logic
- Required to be **deterministic**
- Implemented in and executed by the _Worker_
_[Documentation](https://docs.temporal.io/workflows)_
--
## Determinism
> Output is based entirely on the input.
```go
func add(a, b int) int {
return a + b
}
```
```go
func add(a, b int) int {
// This is not deterministic
resp := http.Get(fmt.Sprintf("https://add.com/%d/%d", a, b))
return decodeBody(resp.Body)
}
```
--
## Activity
- Building blocks for _Workflows_
- Asynchronously executed
- Generally **idempotent**
- Runs to completion or exhausts timeouts/retries
_[Documentation](https://docs.temporal.io/activities)_
--
## Idempotence
> Applying an operation multiple times does not change the result beyond the initial application.
--
## Example
```go
// workflow type: "placeOrder"
func placeOrder(o Order) {
for _, item := range o.Items {
err := temporal.ExecuteActivity("warehouse.ReserveItem", item)
// handle error
}
// ...
}
// activity type: "warehouse.ReserveItem"
func reserveItem(item OrderItem) error {
if !items.IsAvailable(item.Quantity) { return ErrItemNotAvailable }
// ..
return nil
}
```
--
## Worker
- Implemented and operated by the user
- Executes _Workflows_ and _Activities_
- Listens to _Task Queues_
_[Documentation](https://docs.temporal.io/workers)_
--
<!-- .slide: data-visibility="hidden" -->
<img src="assets/img/worker-queues.svg" alt="Worker queues" class="stretch">
--
<img src="assets/img/temporal-high-level.svg" alt="Temporal highlevel" class="stretch">
---
# Further reading
--
https://github.com/sagikazarmark/temporal-intro-workshop
--
https://stackoverflow.blog/2020/11/23/the-macro-problem-with-microservices/
--
[Documentation: Concepts](https://docs.temporal.io/concepts)
[Documentation: Glossary](https://docs.temporal.io/glossary)
--
[Documentation: Developer's guide](https://docs.temporal.io/application-development/)
--
[Temporal learning materials](https://learn.temporal.io/)
---
# The End