Modifying the Application Code

Importing Dependencies

  1. Open the Lambda function located on /serverless-observability-workshop/code/sample-app/src/handlers/get-all-items.js and start by importing the required dependencies in the beginning of the file and initializing a log variable to be used in our lambda executions:

    const AWS = require('aws-sdk')
const docClient = new AWS.DynamoDB.DocumentClient()
const { logger_setup } = require('../lib/logging/logger')
let log

    Instrumenting Logs

  2. Now, inside the getAllItemsHandler() we are going to initialize our log variable and print both event and context objects for later analysis.

    exports.getAllItemsHandler = async (event, context) => {
  log = logger_setup()
  let response

  log.info(event)
  log.info(context)

  3. Still inside our getAllItemsHandler(), we are going to capture logs for UnsupportedHTTPMethod, instrumenting the log.error() method call if our if (event.httpMethod !== 'GET') evaluates true.

    if (event.httpMethod !== 'GET') {
    // Logging
    log.error({ "operation": "get-all-items", 'method': 'getAllItemsHandler', "details": `getAllItems only accept GET method, you tried: ${event.httpMethod}` })
    throw new Error(`getAllItems only accept GET method, you tried: ${event.httpMethod}`)
}

  4. Next, we are ready to log error entries for item list retrievals and info entries for the final execution details. Still inside your getAllItemsHandler(), find and add in the beginning of your catch block and right before the return statement the log.error() and log.info() method calls, respectively:

        try{
        //After Sucessful Response Composition
    } catch (err) {
        // Logging
        log.error({ "operation": "get-all-items", 'method': 'getAllItemsHandler', "details": err })
    }
// Logging
log.info({ operation: 'get-all-items', 'method': 'getAllItemsHandler', eventPath: event.path, statusCode: response.statusCode, body: JSON.parse(response.body) })
return response

  5. Save your changes to the serverless-observability-workshop/code/sample-app/src/handlers/get-all-items.js file.

    Your getAllItemsHandler method should look like the one below

    Full getAllItemsHandler method (expand for code)

Deploy the application

cd ~/environment/serverless-observability-workshop/code/sample-app
sam build && sam deploy

Export the stack output variables

To invoke our API’s, we first need to fetch the ApiUrl output variable that our CloudFormation stack gives us. So let us iterate through our stack and export all output variables as environment variables:

export ApiUrl=$(aws cloudformation describe-stacks --stack-name monitoring-app --output json | jq '.Stacks[].Outputs[] | select(.OutputKey=="ApiUrl") | .OutputValue' | sed -e 's/^"//'  -e 's/"$//')
echo "export ApiUrl="$ApiUrl

Test the Get All Items operation

curl -X GET $ApiUrl/items/ | jq