Deus - Hosting Backends and Budget Controls

Overview

The hosting layer provisions, updates, and removes Appwrite-backed function deployments. A budget gate decides whether a new allocation can proceed based on kill-switch state and always-warm capacity limits.

Hosting Contract

Source: deus/internal/hosting/backend.go

DeployInput

DeployResult

Backend interface

type Backend interface {
    Deploy(ctx context.Context, in DeployInput) (DeployResult, error)
    Delete(ctx context.Context, functionID string) error
}

Appwrite Backend

Source: deus/internal/hosting/appwrite.go

The Appwrite backend validates configuration, reads the artifact from object storage, creates an Appwrite function, pushes variables, uploads the code bundle, and returns the execution endpoint.

Deploy flow

1. Validate Endpoint, ProjectID, APIKey are set
2. Load artifact bytes from BlobReader.Get
3. Package as code.tar.gz (gzip passthrough if already gzipped)
4. POST /functions with {name, runtime: "node-20.0", execute: ["any"], enabled: true, entrypoint: "src/main.js", commands: "npm install"}
5. If AlwaysWarm, add specification: "s-1vcpu-512mb"
6. POST /variables one at a time in deterministic key order
7. POST /deployments as multipart form data with activate: true
8. Return {FunctionID, DeploymentID, ExecEndpoint}

Key parameters

Hosted service HTTP routes

Orchestrator

The Orchestrator ties the Backend, Budget, and Store together. The Deploy method:

1. Checks budget via Budget.AllowNewDeployment(alwaysWarm)
2. Calls Backend.Deploy
3. Records the deployment in the store

Budget Controls

Source: deus/internal/hosting/budget.go

Budget gate flow

AllowNewDeployment(alwaysWarm)
  ├── alwaysWarm=true → AllowAlwaysWarm
  │     ├── KillSwitch active? → reject
  │     ├── CountAlwaysWarmDeployments >= MaxAlwaysWarm? → reject
  │     └── allow
  └── alwaysWarm=false
        ├── KillSwitch active? → reject
        └── allow

The kill-switch short-circuits before any store lookup. BudgetWei parses limits.BudgetPAXWei as base-10 text.

Error cases

Handler error mapping