Running a Lambda Function - AWS SDK for Ruby

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.

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

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

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

# Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# This file is licensed under the Apache License, Version 2.0 (the "License").
# You may not use this file except in compliance with the License. A copy of the
# License is located at
#
# http://aws.amazon.com/apache2.0/
#
# This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
# OF ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.

require 'aws-sdk-lambda'  # v2: require 'aws-sdk'
require 'json'

# To run on Windows:
require 'os'
if OS.windows?
  Aws.use_bundled_cert!
end

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

# Get the 10 most recent items
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
                       })

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.