Badges

Simple Employees access control system capable of:

• Ingesting employee information about badge-in and badge-out events
• Letting single employees access their own ingested data
  • Badge events areee aggregated by year, month and day
  • The employee is able to receive the updated aggregation in case new badge events are received
• Letting managers access both their own ingested data and the data of her/his direct reports

Events

Badge events are intended as simple structured data events containing:

• a reference to the employee,
• the kind of badge event (in or out)
• when it occurred by means of a timestamp

Architecture

API

GraphQL was used. There are two queries and one subscription available:

• query events: returns all the events related to a user id passed as parameter

  query GetEventsList {
      events(id:"5f05a5adad8d849ccafee4b1") {
          years {
          year
              months {
                  month
                  days {
                  day
                      events {
                          id
                          uid
                          type
                          date
                      }
                  }
              }
          }
      }
  }

• query reportsEvents: returns all the events related to the users maneged by the manager id passed as parameter

  query GetManagerEventsList {
      reportsEvents(mid:"5f05a5adad8d849ccafee4b1") {
          years {
              year
              months {
                  month
                  days {
                  day
                  events {
                      id
                      uid
                      type
                      date
                  }
                  }
              }
          }
      }
  }

• subscription events: returns a stream of the events with a userid equals to the one passed as parameter

  subscription SubscribeToEvents{
      events(id: "5f05a5adad8d849ccafee4b3") {
          id
          uid
          type
          date
      }
  }

Events ingestion

Events ingestion is implemented using Kafka. This allows to have a reliable system wich allows fault tolerance to both publisher and consumer sides.

One consumer group is always consuming events and saving them on DB and always starts reading from the last saved event, while other ones get instantiated at each new stream, starting to read from the last published message.

Persistence

Mongo DB was chosen as database as there were not complicated relations.

Two collections are used:

• users, containing documents with the following fields:
  • _id: objectID
  • mid: objectID (nullable) - used to reference the _id field of the manager user
• events, containing documents with the following fields:
  • _id: objectID
  • id: string - used to reference the id wich identifies the event externally (a badge machine for example)
  • uid: objectID - reference to the _id field of the user
  • type: string (IN | OUT)
  • ts: date

Setup

The project can be executed with go run ./cmd.

Configurations can be set using the config.yaml file. In particular, mongo connection string and kafka need to be setted up.

To simulate badge events, the script scripts/kafka_publisher.go can be used.