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Kraken Architecture


Server exposes Kraken ReST API


UI is an Angular application that can be served by NGINX. Unicorn can be used to maintain Server instances.


Controller is made of 4 services:

  • Planner - it triggers new flows based on indicated rule in given project's branch
  • Scheduler - it assigns jobs to agents
  • Watchdog - it checks runs and their jobs if they are in their time limits, it also monitors agents and their machines health
  • QNeck - it is a broker to RQ (see below) that filters out repeating the same requested background tasks


RQ executes background tasks like processing results reported by an agent. Any service in Controller or RQ tasks can enqueue new RQ tasks. Current tasks:

  • analyze_results_history
  • notify_about_completed_run
  • trigger_stages
  • job_completed
  • trigger_run
  • trigger_flow

ClickHouse & its Proxy

ClickHouse is a database that is used for storing logs from all Kraken services and from all agents, ClickHouse Proxy is used to collect logs, aggregate them and send in batches to ClickHouse database.


MinIO is an object storage database. It is used in Kraken to store artifact that are created during jobs execution, to store cache files and to store Git repository bundles.


Redis is used in various places:

  • by RQ as its backend storage;
  • by Casbin (RBAC system) for synchronizing changes
  • by Kraken CI Server for caching various data
  • by Kraken CI QNeck as pubsub for passing tasks to RQ


Agent is a service that is run on a machine that is expected to execute jobs. Agent can execute jobs directly on the system (locally), or it can encapulate them in e.g. container. Currently there are executors for:

  • local
  • Docker
  • LXD

Presentation about Kraken Architecture