template.yml

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::Serverless-2016-10-31
Parameters:
  SearchText:
    Type: String
    Description: Non-URL-encoded search text poller should use when querying Twitter Search API.
  TweetProcessorFunctionName:
    Type: String
    Description: Name of lambda function that should be invoked to process tweets. Note, this must be a function name and not a function ARN.
  SSMParameterPrefix:
    Type: String
    Default: 'twitter-event-source'
    Description: >
      This app assumes API keys needed to use the Twitter API are stored as SecureStrings in SSM Parameter Store under the prefix defined by
      this parameter. See the app README for details.
  PollingFrequencyInMinutes:
    Type: Number
    MinValue: 1
    Default: 1
    Description: Frequency in minutes to poll for more tweets.
  BatchSize:
    Type: Number
    MinValue: 1
    Default: 15
    Description: Max number of tweets to send to the TweetProcessor lambda function on each invocation.
  StreamModeEnabled:
    Type: String
    Default: false
    AllowedValues:
      - true
      - false
    Description: If true, the app will remember the last tweet found and only invoke the tweet processor function for newer tweets. If false, the app will be stateless and invoke the tweet processor function with all tweets found in each polling cycle.

Conditions:
  IsPollingFrequencyInMinutesSingular: !Equals [!Ref PollingFrequencyInMinutes, 1]

Resources:
  TwitterSearchPoller:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: app/
      Runtime: python3.8
      Handler: poller.handler
      Tracing: Active
      MemorySize: 128
      Timeout: 60
      Policies:
        - LambdaInvokePolicy:
            FunctionName: !Ref TweetProcessorFunctionName
        - DynamoDBCrudPolicy:
            TableName: !Ref SearchCheckpoint
        - Statement:
            Effect: Allow
            Action:
              - ssm:GetParameters
            Resource: !Sub arn:${AWS::Partition}:ssm:${AWS::Region}:${AWS::AccountId}:parameter/${SSMParameterPrefix}/*
      Environment:
        Variables:
          SSM_PARAMETER_PREFIX: !Ref SSMParameterPrefix
          SEARCH_TEXT: !Ref SearchText
          SEARCH_CHECKPOINT_TABLE_NAME: !Ref SearchCheckpoint
          TWEET_PROCESSOR_FUNCTION_NAME: !Ref TweetProcessorFunctionName
          BATCH_SIZE: !Ref BatchSize
          STREAM_MODE_ENABLED: !Ref StreamModeEnabled
      Events:
        Timer:
          Type: Schedule
          Properties:
            Schedule: !If [IsPollingFrequencyInMinutesSingular, !Sub 'rate(${PollingFrequencyInMinutes} minute)', !Sub 'rate(${PollingFrequencyInMinutes} minutes)']

  SearchCheckpoint:
    Type: AWS::Serverless::SimpleTable

Outputs:
  TwitterSearchPollerFunctionName:
    Value: !Ref TwitterSearchPoller
  TwitterSearchPollerFunctionArn:
    Value: !GetAtt TwitterSearchPoller.Arn
  SearchCheckpointTableName:
    Value: !Ref SearchCheckpoint
  SearchCheckpointTableArn:
    Value: !GetAtt SearchCheckpoint.Arn