Plugin Ecosystem

FinFocus relies on a robust plugin ecosystem to separate the core orchestration logic from the provider-specific cost retrieval implementations. This architecture ensures the core remains lightweight and provider-agnostic.

System Overview

The system consists of three main components:

1. Core Engine: The CLI tool that parses Pulumi infrastructure plans (pulumi preview --json) and orchestrates cost retrieval.
2. Plugin Host: A gRPC server management layer that launches plugins as subprocesses and manages their lifecycle.
3. Plugins: Independent executables that implement the FinFocus Spec protocol to return pricing or usage data.

Component Roles

Core

• Responsibility: Plan parsing, plugin discovery, lifecycle management, cost aggregation, and reporting.
• Data Source: Pulumi JSON output.

Plugin Host

• Responsibility: Multiplexing gRPC calls, health checking, and version negotiation.
• Protocol: Protocol Buffers (gRPC).

Plugins

• Responsibility: Mapping cloud resources (e.g., aws:ec2/instance) to cost data.
• Types:
  • Fallback/Public: Uses embedded or public pricing APIs (list prices). No auth required.
  • Production/Live: Uses cloud provider billing APIs (Cost Explorer, Billing Conductor). Requires credentials.

Data Flow Architecture

graph TD
    User[User] -->|Run CLI| Core[FinFocus Core]
    Core -->|Parse| Plan[Pulumi Plan JSON]
    Core -->|Discover| Registry[Plugin Registry]

    subgraph "Plugin Host Layer"
        Core -->|gRPC Request| Host[Plugin Host]
    end

    subgraph "Plugin Ecosystem"
        Host -->|Spawn| P1[aws-public]
        Host -->|Spawn| P2[aws-costexplorer]
        Host -->|Spawn| P3[azure-retail]
    end

    P1 -.->|Embedded DB| ListPrice[List Prices]
    P2 -.->|AWS SDK| CostAPI[AWS Cost Explorer API]
    P3 -.->|HTTP| AzureAPI[Azure Retail API]

    P1 -->|Cost Estimate| Host
    P2 -->|Actual Cost| Host
    Host -->|Aggregated Data| Core
    Core -->|Report| User

Plugin Relationships

Public vs. Production Plugins

For AWS, FinFocus offers two distinct plugins that serve different stages of the lifecycle:

1. aws-public (The Fallback)

   • Purpose: Pre-deployment estimates (Projected Costs).
   • Data Source: Embedded pricing database (offline capable).
   • Auth: None required.
   • Accuracy: List prices (MSRP), no discounts.

2. aws-costexplorer (The Production Source)

   • Purpose: Post-deployment tracking (Actual Costs).
   • Data Source: AWS Cost Explorer API.
   • Auth: AWS Credentials required.
   • Accuracy: Real billing data, including Reserved Instances (RIs), Savings Plans, and Enterprise Discount Program (EDP) rates.

The Core engine automatically routes requests: it uses aws-public when no credentials are provided or for projected costs, and aws-costexplorer when configured for actual historical analysis.