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Overview

The Xloud Resource Optimizer is composed of three collaborating services: the API and Decision Engine (analysis), the Planner (action plan generation), and the Applier (execution). Understanding the architecture helps administrators tune the system, diagnose failures, and integrate custom data sources or strategies.
This guide requires administrator privileges. Changes to strategy configuration and data source settings affect all ongoing and future audits platform-wide.

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Component Diagram

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Components

Decision Engine

The analytical core. On each audit, the Decision Engine:
  1. Collects the cluster data model from the Compute API (host inventory, VM placement)
  2. Fetches time-series metrics from configured data sources (Prometheus, Telemetry)
  3. Selects the strategy plugin for the requested goal
  4. Runs the strategy algorithm to identify suboptimal placements
  5. Passes the resulting recommended actions to the Planner
Deployed as: watcher_decision_engine container on controller nodes.
Receives the recommended action set from the Decision Engine and applies dependency ordering — ensuring migrations that depend on free capacity from an earlier migration execute in the correct sequence.The Planner is embedded in the Decision Engine container and does not run as a separate service.
Executes approved action plans through a Taskflow workflow engine. The Applier:
  • Processes actions in priority order
  • Handles retries for transient failures
  • Updates action state in the database in real time
  • Halts execution on non-retriable failures
Deployed as: watcher_applier container on controller nodes.
Exposes the REST API used by the Dashboard and CLI to create audits, view action plans, and execute or cancel plans.Deployed as: watcher_api container on controller nodes.

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Deployment Topology

Controller Nodes
watcher_api — REST API
watcher_decision_engine — Analysis + Planner
watcher_applier — Plan execution

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Data Flow: Audit to Execution

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Service Configuration File

Configuration file location
cat /etc/xavs/watcher/watcher.conf
Key sections:
SectionPurpose
[DEFAULT]Service identity, RPC transport, action plan expiry
[watcher_cluster_data_model_collectors]Data source configuration
[watcher_strategies.*]Per-strategy tuning parameters
[keystone_authtoken]Xloud Identity authentication
[database]Database connection

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Next Steps

Strategy Configuration

Configure and tune optimization strategy plugins.

Data Sources

Connect Prometheus and Telemetry data sources to the Decision Engine.

Scheduling

Automate recurring audits with audit templates and schedules.

Security

Configure RBAC and service account credentials for the Resource Optimizer.