{"id":11304,"date":"2017-08-23T04:56:42","date_gmt":"2017-08-23T04:56:42","guid":{"rendered":"https:\/\/passkit.com\/blog\/?p=11304"},"modified":"2017-08-23T04:56:42","modified_gmt":"2017-08-23T04:56:42","slug":"how-to-use-golang-aws-lambda-to-build-a-scalable-barcode-generator-part-2","status":"publish","type":"post","link":"https:\/\/passkit.com\/blog\/how-to-use-golang-aws-lambda-to-build-a-scalable-barcode-generator-part-2\/","title":{"rendered":"How to use Golang & AWS Lambda to build a scalable Barcode Generator (Part 2)"},"content":{"rendered":"

Note: this is part 2 in a 2 part series. Please click here<\/a> for part 1 (running Go in an AWS Lambda).<\/em><\/p>\n

5. Setup API Gateway<\/h3>\n

Login to your AWS account, and navigate to API Gateway.
\n1. Create a new API:<\/em>
\n\"api-gateway-flow.001\"<\/a>
\n2. Name the API:<\/em>
\n\"api-gateway-flow.002\"<\/a>
\n3. Add & configure the resource:<\/em>
\n\"api-gateway-flow.003\"<\/a>
\nMake sure to check ‘Enable API Gateway CORS’. This will result in API Gateway automatically setting up an OPTIONS method with basic CORS configuration allowing all origins, all methods, and several common headers. You can manually add more strict rules to this at a later stage.<\/em>
\n\"api-gateway-flow.004\"<\/a>
\n4. Create & configure the HTTP GET method for the resource:<\/em>
\n\"api-gateway-flow.005\"<\/a>
\nPoint the method to the Lambda function created in Part 1<\/a>.<\/em>
\n\"api-gateway-flow.006\"<\/a>
\nGrant the method permissions to access your lambda.<\/em>
\n\"api-gateway-flow.007\"<\/a>
\n5. Setup the GET Parameters in the Method Request:<\/em>
\n\"api-gateway-flow.008\"<\/a>
\nAll of the parameters that are setup here can be passed into the final URL of the endpoint. In the next steps these will be mapped to the Lambda.<\/em>
\n\"api-gateway-flow.009\"<\/a>
\n6. Setup the Integration Request & Template Mapping:<\/em>
\n\"api-gateway-flow.011\"<\/a>
\n\"api-gateway-flow.012\"<\/a>
\nNext is where the JSON object is specified that is passed into the Lambda function as the eventJSON. In the integration template the request parameters can be accessed by using $json.params(‘paramName’)<\/strong>.<\/em>
\nIn our case, the first two parameters width & height are mapped as integers, and the second 2 parameters are mapped as string.<\/em>
\nFor more details on API Gateway mapping templates, have a look here<\/a>.<\/em>
\n\"api-gateway-flow.013\"<\/a>
\n7. Setup the Method Response:<\/em>
\nThis is where all the possible HTTP response codes are defined. In case of our barcode generator endpoint, we only return 200, 400 & 500.<\/em>
\n\"api-gateway-flow.015\"<\/a>
\n\"api-gateway-flow.016\"<\/a>
\nFor the 200 status we need to define 2 response headers: Allow-Access-Control-Origin & Content-Type. Content-Type is required so that the API Gateway method integration can map the Lambda base64 encoded image response to the correct image Content-Type: image\/png.<\/em>
\n\"api-gateway-flow.017\"<\/a>
\n8. Setup the Integration Response and Binary Conversion:<\/em>
\n\"api-gateway-flow.019\"<\/a>
\nIt is important to set ‘Content Handling<\/strong>‘ to ‘ CONVERT_TO_BINARY <\/strong>‘.<\/em>
\nDo not define a mapping template. When you do not define a mapping template, API Gateway invokes the passthrough template to return the Base64-decoded binary blob as the image file to the client.<\/em>
\nAPI Gateway converts results into binary content if:<\/p>\n