MykolaFedurko
Image dimensions stepping down through a scaling pipeline
View source on GitHubB1Z0N/photo-scale-microservice

projectsystemsdataweb

Photo Scale Microservice

Event-driven image-scaling microservice.
  • Java
  • Vert.x
  • Kafka
  • AWS S3
Date
September 2019
Status
Historical
Visibility
Public

A microservice from SagasLife, our university distributed-systems project — the part responsible for scaling photos to different resolutions by width.

It listens on two Kafka topics, one for userpics and one for ordinary photos, and the topic doubles as the routing key: it decides which AWS S3 bucket the original lives in. A message is just a prefix and a file name. put:pretty_woman.jpg fetches the original from S3, scales it to the sizes defined in the config, and writes the results back with suffixes — pretty_woman.jpg.sm, .md, .lg for small, medium and large. del:pretty_woman.jpg removes those same scaled files. Either way, the operation status is reported to the Sagas coordinator over its own topic.

Everything variable lives in one config.json — the scale sizes, bucket names and region, image extension, Kafka host and topic names, and even the put:/del: prefixes themselves — so behaviour changes without touching the code. The service ships with unit tests, integration tests against Kafka, and a Docker setup for running it all.