AWS SDK for Ruby
Developer Guide

Running a Lambda Function

The following example runs the Lambda function named MyGetitemsFunction in the us-west-2 region. This function returns a list of items from a database. The input JSON looks like the following.

{ "SortBy": "name|time", "SortOrder": "ascending|descending", "Number": 50 }

where:

  • SortBy is the criteria for sorting the results. Our examples uses time, which means the returned items are sorted in the order in which they were added to the database.

  • SortOrder is the order of sorting. Our example uses descending, which means the most-recent item is last in the list.

  • Number is the maximum number of items to retrieve (the default is 50). Our example uses 10, which means get the 10 most-recent items.

The output JSON looks like the following, where:

  • STATUS-CODE is an HTTP status code, 200 means the call was successful.

  • RESULT is the result of the call, either success or failure.

  • ERROR is an error message if result is failure, otherwise an empty string

  • DATA is an array of returned results if result is success, otherwise nil.

{ "statusCode": "STATUS-CODE", "body": { "result": "RESULT", "error": "ERROR", "data": "DATA" } }

The first step is to load the modules we use:

  • aws-sdk loads the AWS SDK for Ruby module we use to invoke the Lambda function.

  • json loads the JSON module we use to marshall and unmarshall the request and response payloads.

  • os loads the OS module we use to ensure we can run our Ruby application on Microsoft Windows. If you are on a different operating system, you can remove those lines.

require 'aws-sdk-lambda' # v2: require 'aws-sdk' require 'json' # To run on Windows: require 'os' if OS.windows? Aws.use_bundled_cert! end

We then create the Lambda client we use to invoke the Lambda function.

client = Aws::Lambda::Client.new(region: 'us-west-2')

Next we create the hash for the request arguments and call MyGetItemsFunction.

req_payload = {:SortBy => 'time', :SortOrder => 'descending', :NumberToGet => 10} payload = JSON.generate(req_payload) resp = client.invoke({ function_name: 'MyGetItemsFunction', invocation_type: 'RequestResponse', log_type: 'None', payload: payload })

Finally we parse the response, and if are successful, we print out the items.

resp_payload = JSON.parse(resp.payload.string) # , symbolize_names: true) # If the status code is 200, the call succeeded if resp_payload["statusCode"] == 200 # If the result is success, we got our items if resp_payload["body"]["result"] == "success" # Print out items resp_payload["body"]["data"].each do |item| puts item end end end

See the complete example on GitHub.