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FinFocus Documentation

Cost Calculations

Overview

Section titled “Overview”

FinFocus supports two primary workflows for analyzing infrastructure costs: Projected Costs (pre-deployment) and Actual Costs (post-deployment).

1. Projected Costs (Pre-Deployment)

Section titled “1. Projected Costs (Pre-Deployment)”

The projected cost workflow estimates monthly spending based on the resources defined in your Pulumi plan, before they are created in the cloud.

Projected Workflow

Section titled “Projected Workflow”
  1. Parse Plan: FinFocus reads the JSON output from pulumi preview --json.
  2. Map Resources: It identifies cloud resources (e.g., aws:ec2/instance) and extracts relevant properties (Type, Region, Size).
  3. Route to Plugin: The system routes the resource data to the appropriate plugin (e.g., aws-public).
  4. Lookup Pricing: The plugin queries its pricing database (usually public list prices) to find a match.
  5. Calculate: Monthly costs are calculated assuming 730 hours/month of usage (on-demand rates).
  6. Report: The Core engine aggregates these estimates into a summary table.

Projected Use Cases

Section titled “Projected Use Cases”
  • Budget approval before deployment.
  • Comparing costs between different instance types or regions.
  • CI/CD checks to prevent cost spikes.

2. Actual Costs (Post-Deployment)

Section titled “2. Actual Costs (Post-Deployment)”

The actual cost workflow retrieves historical spending data for resources that have already been deployed and are running.

Actual Workflow

Section titled “Actual Workflow”
  1. Parse Plan: FinFocus parses the Pulumi plan to identify the specific resource IDs (e.g., i-0123456789abcdef0) of deployed resources.
  2. Route to Plugin: The request is routed to a production-grade plugin (e.g., aws-costexplorer).
  3. Query Provider API: The plugin uses the cloud provider’s API to fetch billing data for those specific resource IDs over a specified time range.
  4. Return Data: The plugin returns the exact spend, including taxes, credits, and discounts (RIs/Savings Plans).
  5. Report: The Core engine presents the historical spend data.

Actual Use Cases

Section titled “Actual Use Cases”
  • Chargeback/showback reports.
  • Validating that reserved instances are being applied.
  • Monitoring daily spend trends.

Key Differences

Section titled “Key Differences”
Feature Projected Costs Actual Costs
Timing Before Deployment After Deployment
Data Source Public List Prices (MSRP) Billing API (Real Invoices)
Accuracy Estimate Precise
Auth Usually None Required (API Keys)
Plugin aws-public aws-costexplorer
Section titled “Related Documentation”

For more details on the plugins referenced above (aws-public, aws-costexplorer) and related topics: