app.yaml

AWSTemplateFormatVersion: "2010-09-09"
Description: Freifunk Monitor for your Router
Parameters:
  AccessPointName:
    Type: String
  NotificationEmail:
    Type: String
  CheckRateMinutes:
    Type: Number
    Default: 5
Resources:
  CheckProgram:
    Type: AWS::Lambda::Function
    Properties:
      Code:
        ZipFile: !Sub |
          import json
          import urllib2
          import boto3

          cw = boto3.client('cloudwatch')

          def handler(event, context):
            api_result = json.loads(urllib2.urlopen("https://api.freifunk.net/data/freifunk-karte-data.json").read())
            found_access_points = [access_point for access_point in api_result["allTheRouters"] if access_point["name"] == "${AccessPointName}"]

            if len(found_access_points) != 1:
              raise "Did not find an Access Point with the given name"

            found_access_point = found_access_points[0]

            # todo: implement other freifunk communities
            local_api_result = json.loads(urllib2.urlopen("https://map.hamburg.freifunk.net/nodes.json").read())
            access_point_is_online = local_api_result["nodes"][found_access_point["id"]]["flags"]["online"]

            cw.put_metric_data(
              Namespace="FreifunkAccessPoint",
              MetricData=[{
                "MetricName": "online",
                "Dimensions": [{
                  "Name": "AccessPointName",
                  "Value": "${AccessPointName}"
                }],
                "Value": 1 if access_point_is_online else 0
              }]
            )

      Handler: index.handler
      Role:
        Fn::GetAtt:
          - CheckProgramRole
          - Arn
      Runtime: python2.7
      Timeout: 300
      MemorySize: 256
  CheckProgramRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          Effect: Allow
          Principal:
            Service: lambda.amazonaws.com
          Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
      Policies:
        - PolicyName: WriteCustomMetric
          PolicyDocument:
            Version: "2012-10-17"
            Statement:
              - Effect: Allow
                Action:
                  - cloudwatch:PutMetricData
                Resource: "*"
  CheckProgramTrigger:
    Type: "AWS::Events::Rule"
    Properties:
      ScheduleExpression: !Sub rate(${CheckRateMinutes} minutes)
      Targets:
        - Arn:
            !GetAtt [CheckProgram, Arn]
          Id: InvokeLambda
  CheckProgramTriggerInvokePermission:
    Type: "AWS::Lambda::Permission"
    Properties:
      FunctionName: !GetAtt CheckProgram.Arn
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"
      SourceArn: !GetAtt CheckProgramTrigger.Arn
  AccessPointOfflineAlertTopic:
    Type: "AWS::SNS::Topic"
    Properties:
      Subscription:
        - Endpoint: !Ref NotificationEmail
          Protocol: email
  AccessPointOfflineAlert:
    Type: "AWS::CloudWatch::Alarm"
    Properties:
      AlarmActions:
        - !Ref AccessPointOfflineAlertTopic
      OKActions:
        - !Ref AccessPointOfflineAlertTopic
      InsufficientDataActions:
        - !Ref AccessPointOfflineAlertTopic
      ComparisonOperator: LessThanThreshold
      Dimensions:
        - Name: AccessPointName
          Value: !Ref AccessPointName
      EvaluationPeriods: 1
      MetricName: online
      Namespace: FreifunkAccessPoint
      Period: 60
      Statistic: Maximum
      Threshold: 1