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In this video, we are going to do Hands on up, suck up a ten four, orchestrate distributed transactions

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using a step functions.

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So we are going to design a step functions state machine for implementing place order use cases.

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You can see the image on the slide.

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This is the place, the use cases.

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So we will create an a step function state machine for implementing order fulfillment process with creating

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these steps will be placed order after that update inventory, perform payment and if everything goes

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well, we can succeed to order.

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If something goes wrong in any step, we will revert back to payment inventory, remove order and go

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to face statement.

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For that purpose, please open the pseudocode code.

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I have created separate lecture and section folder in the command text.

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I have designed our architecture which will be state machine.

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You can see that we are starting here and there is a task which is the place order accommodate the incoming

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place order request and after that we will have a choice that explaining the is place order and we have

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yes or no.

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If yes we have separate task which is the update inventory.

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If inventory updated, we can update the make the payment.

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If payment successful, we can succeed to order with incoming request.

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So this is the pivot.

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But in every step we have, if an yes and no statement, if we can't place an order, we should go to

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the paid order statement.

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If we cannot update the inventory, we can revert back to inventory and remove the order.

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If we cannot make the payment, we can revert back the payment, revert inventory, remove order and

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fail order status.

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So now I am going to open a console and design our workflow.

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Go to step functions and state machines and click the create state machine.

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We will create standard state machines.

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So for that purpose, I'm going to select the standard and click the next button.

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Here you can see that we can design our workflow with workflow to so now we will implement our logic.

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So basically I will start with adding the lambda.

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So this is the task that we can place order.

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So that's why I'm going to say place order.

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By this way, if you open the architecture, you can see that every lambda function is a microservices.

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So we will perform distributed transaction across multiple microservices, which are the order inventory

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payment microservices.

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So these are the path from our order fulfillment process for the distributed transaction and implementing

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the setup pattern.

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So that's why we will select the lambda function as a task off to our every step.

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And these lambda functions can be interacted on databases and also payment can be interact with the

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third party services in order to perform payment operation.

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So if you come back to our designer, the first step is place order.

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So this will be placed order with lambda function.

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And after that we will go to follow section and add the choice.

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So this choice is confirmed with the is order placed or not?

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This will be checked.

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Response from the lambda function and according to response it is accommodate and redirect to this event

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to the update inventory or the fail of the order place operation.

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For that purpose we have defined two rules.

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So you can come here and now we can edit the rule one if you open the rule one so a the condition,

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we can get a condition from the dollar sign and that so is order placed.

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And we can choose that the actual 2 billion construct and true is order placed.

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Then we can continue our save this condition.

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Okay.

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And also, I have one more rule.

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We can add the new rule, add the condition, and we can copy from the condition from this state.

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You can see that we have checked the is order placed and if you come to rule two a the condition so

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what will should be is order placed and again is equal to and the value is the building constant.

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And you can see the force.

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Look, we have to enforce is order placed and is also placed to enforce.

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So now I am going to add the required steps which we can continue our support pattern implementation.

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So if you add the additional lambda function, that means microservices, this will be the ah event

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or database event or microservices.

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For that purpose I'm going to say update inventory.

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Okay.

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So this is going to update eventually and if the order placed equal force, so that means we got exception.

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I have the flow statement which is the fail I drag and drop the fail statement.

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This will be a failed order.

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Okay, so now I'm going to continue with the happy.

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Is order placed?

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Yes.

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Now we have updated the inventory.

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So now, again, I need to check the inventory update or not for that purpose.

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The choice statement.

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In the choice statement, we can add a rule definition.

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So in the rule definition we have at the assignment condition, if you condition we can we have a dollar

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sign and the.

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Is.

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Update inventory.

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You can copy paste and choose the operator equal to and again volume constant and to the end post.

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If the update inventory true, that means we will continue happy bet.

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And again I'm going to add a new choice and condition is the same and this time I'm going to set a given

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constant and say the false.

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So we have two conditions.

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Of course, we should put the dollar sign and that notation.

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By this way, we can reach the output data from the previous task set.

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Okay, click the save condition and now I'm going to remove the default result.

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We can clear this one.

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Yes.

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As you can see that we have to choose after the update inventory.

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Basically, we will use the happy pet which is the is updated one, two, three, four for the happy.

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But I'm going to add an additional Microsoft lambda function, which is the payment microservices and

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we can set the state name as a make payment.

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This will be power from payment operations and if there is any problem for that action.

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So in that case, if we cannot update the inventory again, I am going to add additional lambda function.

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But this time this lambda function performed the revert back to inventory.

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So that means what that means when we update the inventory, if there is a problem, that means if it

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is cannot update the inventory, we should revert back to change from the dynamo db.

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Think about that.

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These microservices is communicate with the its database dynamo DB database table and it is updating

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the status.

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But this should be revert back to the statement.

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So that's why we should additional lambda function in the choice statement.

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We should give the name as to choice statement is inventory updated?

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Okay.

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So as you can see that we have implement the inventory part now focus on the payment part.

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This is the last step in the distributed transaction, which is the order fulfillment for that purpose.

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I am going to add a choice statement again.

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This statement name is a, is payment done?

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Immense success.

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Okay.

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So according to payment success operation, we can put a rule definition upon the rule, add the condition.

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Again, I'm going to set a dollar sign.

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That is payment.

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Success.

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And copy paste this variable we can choose is equal to and value is boolean construct and give as a

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true.

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So this is the first condition.

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And the second condition is add a new choice, add condition and choose is equal to boolean constant.

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And this time we will select the false.

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And now I'm going to remove the default one.

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Okay.

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Very good.

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So as you can see that we have set the payment success operation.

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If payment success is correct and true, we basically make it success.

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So if you drag and drop the success order, we will succeed the order.

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That means order created successfully with full operations.

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But when it comes to the fail is if the payment is the fail, we should also revert back to payment

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operation for that purpose.

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Drag and drop the lambda function.

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And so this time we are going to revert back to payment.

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So you can think about that in the payment operation, we can integrate with the third party system.

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So even we perform the operation.

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If we got an exception in our business logic or in our microservices, we should again go back to our

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third party system and revert back to payment.

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It is very important and critical when it comes to business related use cases, so that's why we add

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additional lambda function, which is revert back to payment.

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Okay.

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After that, we perform the operation of the removing to order.

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You can see that we will continue to our fail statement.

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So basically before fail statement, we will one by one revert back the payment and revert back to inventory

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for that purpose.

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I'm going to add additional step in here after the revert.

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Eventually we should remove the order.

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As you know, that made me place an order.

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We are creating an order in the automotive table.

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By this way, if there is an exception, we should remove the order.

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But after the payment, actually, we should not go to the directly end statement because this will

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be also update the inventory for that purpose.

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Select this task, which is the word payment.

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If you go to the scroll down and next date, the next step should be the revert inventory.

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You can scroll down and select the revert inventory.

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Okay, very good.

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So this time we are also design our worst case.

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So if we over with our architecture, we can come to our first place.

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And if I make it zoom out.

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Okay, very good.

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So basically we are accommodate to place order in the lambda function and these will be interact with

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the Dynamo DB and insert a new order item in our database which is status of the creating.

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So after that we are looking to is order placed correct or true or false according to these value.

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If there is a force and that means the exception, we directly go to face statement and closed and to

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this workflow.

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If order placed successfully, that means create order successfully.

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We go to the update inventory part.

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We will update the inventory and deduct the item in Dynamo DV database.

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And after that we will check that is matter updated.

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If there is a problem when we updating inventory, then we will go to the full statement and go to revert

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inventory face.

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We will revert back to the our database and consistent make consistent data and after that remove order

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because in the first place we will create an order.

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In this phase we will create and remove an order and finish the workflow.

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And if the inventory update successfully, we go for the payment operation and perform the payment.

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If the payment is failed, we will revert payment and after the revert inventory, remove order.

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And these are the compensated steps in the step function that we design and implement such a pattern.

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If the payment is done, we will go to the success statement and finish the order.

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So basically we will implement and design our order or according to our architecture that we see on

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the image.

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So as you can see that I have designed the workflow with the implementing saga pattern, but we don't

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develop our order, inventory and payment microservice lambda functions.

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So please take these as an assignment that will connect to your Dynamo DV databases and perform record

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actions to complete this flow.

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For now, I am not going to proceed this flow to create state machine.

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Before that we should develop these order monetary and payment microservice lambda functions with rollback

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methods.

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So for that purpose please take an assignment and try to implement this logic before closing section.

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Make sure that you have the all resources, AWG resources on your Atlas Cloud environment.

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So as you can see that we don't create any state machine.

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So that's why I don't expect any state mission or state function.

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Please go to state function and make sure that you don't have any state machine on your environment.