Create And Expose the API with Amazon API Gateway

Create And Expose the API with Amazon API Gateway

1. Go to AWS API Gateway console.

• In the Choose an API type section, find REST API - Develop a REST API where you gain complete control over the request and response along with API management capabilities.
• Click Build

2. Click OK
3. In the Create new API section, select New API

• In the API name section, type iDevelop - Trip Search API
• In the Description section, type Allows searching ở trips from/to cities
• Click Create API

4. The API will be created, and have a root path element and nothing else.

• Click Actions
• Click Create Resource

5. In the New Child Resource page

• In the Resource Name section, type trips
• Check Enable API Gateway CORS
• Click Create Resource

6. The /trips resource will be created. Click on the /trips link

• Click Actions
• Click Create Method

7. In the dropdown list that appears, select GET

• Click the grey tick next to the dropdown list to commit the change.

8. In the Lambda Region section, select your Region

• In the Lambda Function section, type idevelop and select idevelopTripSearchFull
• Click Save

9. Click OK
10. When the method is created, you will see the Method Execution panel:
11. Click Test
12. Click Test
13. After a moment or two for the Lambda function to initialise and execute, you should see an output similar to this:
14. Click /trips

• Click Actions
• Click Enable CORS

15. Click Enable CORS and replace existing CORS headers
16. Click Yes, replace existing values
17. When each of the listed items have a green tick against them, you can move on to the next section. This will only take a moment.

Expose the /tripsfromcity RESTful API endpoint

The first path we exposed was quite simple - /trips gets all the trips in the system. But we know our source code implementation allows us to specify a filter to query for trips that originate from a particular city or have a particular destination, so we want to expose this functionality to our API consumers. First, we will expose the /tripsfromcity path.

18. In the Resources section, click /

• Click Actions
• Click Create Resource

19. In the Resource Name section, type tripsfromcity

• Select Enable API Gateway CORS
• Click Create Resource

20. Our call into the Lambda function requires a city parameter. We will follow the standard pattern for RESTful interfaces, and pass this parameter in as a URL parameter. Select /tripsfromcity

• Click Actions
• Click Create Resource

21. In the Resource Name section, type {city}

• In the Resource Path section, delete the default and replace with {city}
• Click Create Resource

22. Click /{city}

• Click Actions
• Click Create Method

23. In the dropdown list that appears, select GET

• Click the grey tick next to the dropdown list to commit the change.

24. In the Lambda Region section, select your Region

• In the Lambda Function section, type idevelop and select idevelopTripSearchFromCity
• Click Save

25. Click OK
26. When the method is created, you will see the Method Execution panel. as before for the /trips resource. We can’t go ahead and test the API call just yet, because we need to transform the request through API Gateway so that the city parameter is passed through to the Lambda function correctly.

The devlounge.lambda.FindTripsFromCityHandler handler expects to see the input data in this JSON format:

{
	"payload" : 
	{
        "city": "Melbourne"
    }
}

• Click Integration Request

27. Click Mapping Templates

• Click When there are no templates defined (recommended)
• Click Add mapping template
• In the Content-Type section , type application/json
• Click the grey tick icon to commit the change.

28. Scroll further down to show the mapping template entry text field. Paste in the following template:

{
    "payload" : {
        "city": "$input.params('city')"
    }
}

• Click Save

29. Click Method Execution
30. Click Test
31. In the Path section, in {city} field, type Melbourne

• Click Test

32. API Gateway will make the call into the Lambda function, passing the value Melbourne into the Body Mapping Template you have defined, which will insert the search parameter Melbourne into the JSON payload that is sent to the Lambda function. This will cause the function handler to consume the JSON and execute a search in the DynamoDB table, and return the results. You will see a result similar to this:
33. Select /{city} in /tripsfromcity section

• Click Actions
• Click Enable CORS

34. Click Enable CORS and replace existing CORS headers
35. Click Yes, replace existing values
36. When each of the listed items have a green tick against them, you can move on to the next section. This will only take a moment.
37. Click / in Resources section

• Click Actions
• Click Create Resource

38. In the Resource Name section, type tripstocity

• Select Enable API Gateway CORS
• Click Create Resource

39. Our call into the Lambda function requires a city parameter. We will follow the standard pattern for RESTful interfaces, and pass this parameter in as a URL parameter. Click /tripstocity

• Click Actions
• Click Create Resource

40. In the Resource Name section, type {city}

• In the Resource Path section, delete the default and replace with {city}
• Select Enable API Gateway CORS
• Click Create Resource

41. Click /{city} in the section /tripstocity

• Click Actions
• Click Create Method

42. In the dropdown list that appears, select GET

• Click the grey tick next to the dropdown list to commit the change.

43. In the Lambda Region section, select your Region

• In the Lambda Function section, type idevelop and select idevelopTripSearchToCity
• Click Save

44. Click OK
45. When the method is created, you will see the Method Execution panel, as before for the /tripsfromcity resource. We again need to transform the request through API Gateway so that the city parameter is passed through to the Lambda function correctly, before we can test this API call.

The devlounge.lambda.FindTripsToCityHandler handler expects to see the input data in this JSON format:

{
	"payload" : 
	{
        "city": "Melbourne"
    }
}

• Click Integration Request

46. Click Mapping Templates

• Select When there are no templates defined (recommended)
• Click Add mapping template
• In the Content-Type section, type application/json
• Click the grey tick to commit the change

47. Scroll further down to show the mapping template entry text field. Paste in the following template:

{
    "payload" : {
        "city": "$input.params('city')"
    }
}

• Click Save

49. Click Method Execution
50. Click Test
51. In the Path section, in the {city} field, type Melbourne

• Click Test

52. API Gateway will make the call into the Lambda function, passing the value Melbourne into the Body Mapping Template you have defined, which will insert the search parameter Melbourne into the JSON payload that is sent to the Lambda function. This will cause the function handler to consume the JSON and execute a search in the DynamoDB table, and return the results. You will see a result similar to this:
53. Click /{city} in /tripstocity section

• Click Actions
• Click Enable CORS

54. Click Enable CORS and replace existing CORS headers
55. Click Yes, replace existing values
56. When each of the listed items have a green tick against them, you can move on to the next section. This will only take a moment.
57. If you have completed the steps above as described, you will have a resources tree that looks like this:

Deploy the API and test

58. Now that you have confirmed that the microservices are functioning correctly, you are ready to deploy the API and test it from the publicly available endpoint. In the Resources section, click /

• Click Actions
• Click Deploy API

59. In the Deployment stage section, select [New Stage] to create a new deployment stage.

• In the Stage name section, type prod
• In the Stage description section, type Trips API
• In the Deployment description section, type Initial deployment
• Click Deploy

60. The new stage prod will be created and you will see the prod Stage Editor

• Click Invoke URL

61. A new window will open and hit the stage endpoint. You will see an error message stating {“message”:“Missing Authentication Token”}. This is because there is no handler for the root of the stage - you have only defined resources/methods beneath the /trips, /tripsfromcity and /tripstocitypaths.
62. Edit the URL in the URL bar of the browser and append /trips then press Enter. The page will refresh, and then display all of the available trips as JSON. The output will be similar to this:
63. Test the /tripsfromcity method, use /tripsfromcity/Melbourne to search for all trips that leave from Melbourne.
64. Test the /tripstocity method, use /tripstocity/Melbourne to search for all trips that go to Melbourne.

NIf the data looks right, and there are no errors, you are ready to move on to the next exercise.

Use CloudFormation/SAM via the AWS CLI to deploy the HotelSearch microservice

In the previous steps, you manually deployed and configured the TripSearch microservice, including the Lambda functions and API Gateway resources. You will have noticed that there are quite a few steps required, and doing this manually is time consuming and prone to errors. In this step, you will use the AWS CLI and CloudFormation/SAM to deploy the HotelSearch microservice, instead of manually deploying the resources.

By using CloudFormation/SAM, many of the manual steps will be taken care of for you, streamlining the deployment process. You will still have to manually trigger the process, but the actual deployment will be automated.

The HotelSpecials microservice needs to access a MySQL database to retrieve the hotel specials data. The lab environment has automatically deployed and seeded a database for you, and the connection details are provided in Cloudformation Outputs tab with instructions below on where to update the placeholder in the template you will use to deploy the microservice. The MySQL instance has been deployed using Amazon RDS and is not publicly-accessible since it is launched in a private subnet. Therefore, for the Lambda function to be able to connect to the database, the Lambda function will also need to be deployed into a private subnet by enabling VPC Integration. The template.yml file provided has all the required setup to do this, you just need to update the placeholders as per the below instructions.

65. Download the HotelSpecials.zip file and extract
66. Open Command Prompt and navigate to the directory of the HotelSpecials project was extracted in step 65

• Execute the following command:

set AWS_PROFILE=devaxacademy
mvn package shade:shade

67. When the target JAR is built, whick is in the target folder of the project and whose name is hotelspecials-1.0.0.jar 68. Go to AWS CloudFormation Console.

• Click Stack.
• Type DevAx-06 to the search bar and press Enter.
• Click DevAx-06.

69. Click tab Output

• Save the value of DatabaseSecurityGroup, DatabaseSubnet1, DatabaseSubnet2, RDSEndpoint and S3BucketLambdaCodeBucketName to use in the next step.

70. In the Eclipse IDE, open the template.yml file
71. Replace <DatabaseSecurityGroup> by the DatabaseSecurityGroup value we saved in step 69

• Replace <DatabaseSubnet1> by the DatabaseSubnet1 value we saved in step 69
• Replace <DatabaseSubnet2> by the DatabaseSubnet2 value we saved in step 69
• Replace <RDSEndpoint> by the RDSEndpoint value we saved in step 69
• Save

72. In the Command Prompt, execute the following command to package the Lambda function

aws cloudformation package --template template.yml --s3-bucket <S3BucketLambdaCodeBucketName> --output-template template-export.yml

aws cloudformation deploy --template-file template-export.yml --stack-name HotelSpecialsAPI --capabilities CAPABILITY_IAM

74. Go to AWS CloudFormation Console.

• Click Stack.
• You will see the HotelSpecialsAPI stack. This indicates that the CloudFormation Change Set has been created. The command you issued will create the Change Set and then automatically execute the Change Set. It will take a few moments to complete the execution

75. Select HotelSpecialsAPI stack, click tab Events and eview the steps that the CloudFormation template has applied to your environment. These will match the resources and actions in the template-output.yml file.
76. Go to AWS API Gateway console

• Click iDevelop - Hotel Specials API

77. Click Get

• Click Integration Request

78. The Integration Request panel will be shown. Lambda Function specified:

The specified value is not a Lambda function, but instead, is a Stage Variable that will be replaced at runtime by API Gateway. Therefore, in order for this API call to succeed, the Stage in API Gateway must have defined a value for the envHotelSpecials stage variable.

79. Click Stages

• Click prod
• Click tab Stage Variables

  a single variable is defined - envHotelSpecials - which correlates to the stage variable name the GET method was expecting. The value of the variable is GetHotelSpecials which is the name of the Lambda function that the template created using the JAR file you built and uploaded during the package/deploy process.

Test the HotelSpecials API

80. Expand the prod root element in the Stages list to reveal the hierarchy.

• Click Get
• Click Invoke URL

81. After a moment while the Lambda function is initialised, you should see the JSON result of querying the mySQL database from the Lambda function

If you see a JSON payload with no errors, you have successfully deployed an API and supporting Lambda function that queries the mySQL database. Notice how much quicker and easier that was to deploy without any manual intervention? That is the power of automation. In the next exercise, we will take this one step further, using the (now familiar) CI/CD pipeline approach to deploy our next API.