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Media Service

Service Type: Deployable backend service Language: Kotlin / Micronaut Database: No persistent database Messaging: Apache Kafka External Integrations: S3-compatible object storage, Kafka Status: Implemented; currently focused on image thumbnail processing

Summary & Purpose​

whitelabel/media-service is an asynchronous media-processing service. Its currently implemented capability is image thumbnail generation: it consumes resize requests from Kafka, downloads source images from S3-compatible storage, generates thumbnails, uploads the results, and publishes processing outcomes.

Business Responsibilities​

  • Process image resize requests.
  • Download source images from object storage.
  • Generate fixed-size 100×100 pixel thumbnails.
  • Upload generated thumbnails.
  • Notify requesting services about processing results.
  • Report download, resize, and upload failures.

Owned Data​

The service does not own persistent business data. It temporarily processes image content and stores generated thumbnails in S3-compatible object storage. The service owns the generated file path convention, including the miniatures directory and PNG thumbnail output.

Interfaces​

Inbound Interfaces​

Kafka​

  • Consumes media.resizing.requested.
  • Requests contain:
    • Source S3 key
    • Requesting service name No REST or GraphQL API was verified.

Outbound Interfaces​

Object Storage​

  • Downloads the original image.
  • Uploads the generated thumbnail.

Kafka​

  • Publishes the result to:
    • {requestingService}.resizing.result The result contains the generated S3 key and processing status.

Kafka Producers & Consumers​

Producers​

  • {requestingService}.resizing.result
    • Notifies the requesting service that processing completed.
    • Returns the generated thumbnail key.
    • Reports success or a processing error.

Consumers​

  • media.resizing.requested
    • Requests image thumbnail generation.

External Integrations​

S3-Compatible Object Storage​

The service uses the shared file-manager abstraction to download source images and upload generated thumbnails. The configured storage can be AWS S3 or an S3-compatible service such as MinIO.

Kafka​

Kafka is used for asynchronous request processing and result notification.

ImageIO​

Java ImageIO is used to read supported image formats and generate PNG thumbnails.

Business Rules​

  • Each resize request is processed using the source S3 key and requesting service.

  • Generated thumbnails have a fixed size of 100×100 pixels.

  • Thumbnails are stored under:

          • The requesting service determines the result topic.

  • Processing results distinguish between:

    • Success
    • Download failure
    • Resize failure
    • Upload failure

  • Requests are processed by a single Kafka listener thread.

Processing & Error Handling​

The processing flow consists of three steps:

  1. Download the original image from object storage.
  2. Resize the image to 100×100 pixels.
  3. Upload the generated PNG thumbnail. If any step fails, the service publishes an error result with the expected thumbnail key and an appropriate error status.

Observability​

  • Uses the common DEUSS logging framework.
  • Logs received resize requests.
  • Logs successful processing.
  • Logs download, resize, upload, and Kafka publishing failures.
  • No dedicated metrics, tracing, or alerting configuration was verified.

Relationships to Other Components​

  • Other backend services publish resize requests to Kafka.
  • media-service processes the image and stores the thumbnail.
  • The requesting service receives the result through its service-specific Kafka topic.
  • Other services can subsequently use the generated S3 key.

Deployment Topology​

  • Independent Kotlin/Micronaut application.
  • Runs as a Kafka consumer and producer.
  • Uses the Kafka consumer group media-service by default.
  • Does not own a PostgreSQL database.
  • Does not use Flyway.
  • Uses S3-compatible object storage.
  • Does not expose a verified REST or GraphQL API.
  • Does not directly integrate with blockchain services.

Architecture Notes & Inconsistencies​

  • The service currently implements image resizing only; broader media capabilities are not verified.
  • The README describes the service as standalone and states that no environment variables are required, while application.yaml defines AWS/S3 configuration. The runtime configuration should be treated as authoritative.
  • The resize implementation produces a fixed 100×100 image and does not preserve the original aspect ratio.

Source References​

  • whitelabel/media-service/src/main/kotlin/cz/deuss/mediaservice/kafka/ResizeEventsListener.kt
  • whitelabel/media-service/src/main/kotlin/cz/deuss/mediaservice/kafka/ResizedEventsProducer.kt
  • whitelabel/media-service/src/main/kotlin/cz/deuss/mediaservice/service/ImageResizeService.kt
  • whitelabel/media-service/src/main/kotlin/cz/deuss/mediaservice/service/ImageIOResizeService.kt
  • whitelabel/media-service/src/main/kotlin/cz/deuss/mediaservice/service/S3ImageService.kt
  • whitelabel/media-service/src/main/resources/application.yaml
  • whitelabel/media-service/README.md