## Host AI chat application with Flask: Postgres-backed state

### Summary
Deploy an AI chat application built with Flask on Ample using the durable job state pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, and a managed PostgreSQL 16 database is auto-provisioned and injected as `DATABASE_URL`. Verified on Flask: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true).

### Representative Queries
- Host AI chat application with Flask: Postgres-backed state
- Where can I host AI chat application built with Flask?
- I need a durable state schema and retry/recovery semantics implemented by application code.

### Resource Requirements
- Compute
- PostgreSQL

### Infrastructure Requirements
1. **Compute**
   - Status: Verified
   - Summary: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
2. **Postgres**
   - Status: Verified
   - Summary: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no `DATABASE_URL` is supplied.

### Framework
Flask

### Workload
AI chat application

### Prerequisites
- A Flask project that builds and starts with the documented commands (pip install into `.ample/python` from `requirements.txt`, then `waitress` from `app.py` reading `PORT` on the `python-3.12` template).
- A PostgreSQL driver reading `DATABASE_URL` at runtime (auto-provisioned when omitted, or supplied with `--env`).
- An Ample account token with `servers:write`, `databases:read`.

### Tested Configuration
- **Template**: python-3.12
- **Runtime**: python
- **Size**: s-1vcpu-1gb
- **Install**: `python3 -m pip install --target .ample/python -r requirements.txt`
- **Start**: `PYTHONPATH=.ample/python:${PYTHONPATH:-} python3 app.py`

### Input Schema
```json
{
  "additionalProperties": false,
  "properties": {
    "env": {
      "description": "Encrypted environment variables (bucket credentials, secrets)",
      "items": { "pattern": "^[A-Z][A-Z0-9_]*=.*$", "type": "string" },
      "maxItems": 50,
      "type": "array"
    },
    "name": {
      "description": "App name",
      "maxLength": 63,
      "minLength": 1,
      "pattern": "^[a-z0-9-]+$",
      "type": "string"
    },
    "path": {
      "description": "Project directory or ample.toml service",
      "maxLength": 512,
      "minLength": 1,
      "type": "string"
    },
    "release_command": {
      "description": "Migration command run before activation",
      "maxLength": 512,
      "type": "string"
    },
    "start": {
      "description": "Start command (Python apps pass one explicitly)",
      "maxLength": 512,
      "type": "string"
    }
  },
  "required": ["name", "path", "start"],
  "type": "object"
}
```

### Workflow Steps
1. **Build and start**: `pip install into .ample/python from requirements.txt`, then `waitress from app.py reading PORT on the python-3.12 template`. The server must bind `0.0.0.0 on PORT`.
2. **Implement the pattern on PostgreSQL**: The fixture's module implements durable job state: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). Copy the approach into your schema; keep migrations idempotent and run them with `--release-command`.
3. **Deploy**: Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op. 
   - Command: `ample deploy . --name --public --start "python3 app.py"`
4. **Verify**: Fetch the live URL and the pattern self-test route(s) (`/p/durable-job-state`) from the example; then run your own checks. On failure read `ample logs --kind build` then `--kind runtime`. 
   - Command: `ample logs --kind build`

### Success Checks
- App responds on its public URL
  - Kind: http_get
  - Path: `/`
  - Expect: `ample canary flask patterns`
- Durable-job-state self-test
  - Kind: http_get
  - Path: `/p/durable-job-state`
  - Expect: `job=done attempts=1 idempotent=true`

### Limitations
- Verified on the python-3.12 template at s-1vcpu-1gb with the example fixture; other sizes, templates, and Flask major versions are not verified.
- The AI chat application itself (your job types, payload schema, and retry policy) is application code and was not separately tested; the pattern checks are what was verified.
- Region, compliance attestations and request-duration limits are unknown and not claimed.
- Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
- Managed PostgreSQL 16 only; extensions, connection limits, and backup or restore procedures are not verified; apps and their databases are placed together.

### Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0
- **Authoritative**: true
- **Basis**: size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty
- **Components**:
  - App server: s-1vcpu-1gb (quantity: 1.0, monthlyAmount: 5.0)
  - Managed PostgreSQL database: s-1vcpu-1gb (quantity: 1.0, monthlyAmount: 5.0)
- **Note**: Always-on monthly price of the tested sizes; apps and databases auto-pause when idle.

### Evidence Summary
1. **Canary Run**
   - Summary: Flask pattern fixture deployed on Ample. Checks passed for durable-job-state and configuration-secrets.
   - Observed At: 2026-09-21T01:14:18Z
   - Implementation Revision: 50dbac567d2c5cc8e55e6c748a646be0025d9cfb-dirty (CLI 0.1.21)
   - Scope: checks=`/p/durable-job-state`, pattern=`pattern:durable-job-state`, template=`python-3.12`
2. **Canary Run**
   - Summary: The same Flask app deployed with a --release-command migration; the marker it created was readable after activation.
   - Observed At: 2026-09-20T01:54:51Z
   - Implementation Revision: 199ff1dfd52683832ae75d3f98b53a7a4bff7f96-dirty (CLI e3181f5)
   - Scope: pattern=`pattern:durable-job-state`

### Last Verified At
2026-09-21T01:14:18Z

### Unknowns
- Region availability is unknown until a verified region fact is recorded.
- Compliance attestations are unknown; none are claimed.

### Formats
- HTML: [View Here](/content/recipes/ai-chat-application/flask/persistent-state/index.html)
- Markdown: [View Here](/content/recipes/ai-chat-application/flask/persistent-state.md)
- JSON: [View Here](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Aai-chat-application%3Aflask%3Apersistent-state)

### Next Actions
1. **Browse the catalog index**
2. **Search published recipes by intent, stack and constraints**
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4. **Read the existing agent authentication setup**