# Architecture Overview

## The Central Principle

**BEDS is AMQP-first. No component in the application layer ever touches a database directly. Ever.**

This is not a guideline. It is the architectural constraint that makes everything else possible. If you find yourself writing code that calls a database adapter directly from outside the broker layer, you are breaking the framework.

## System Diagram

```
External Client
      │
      │  HTTP / WebSocket / REST
      ▼
┌─────────────┐
│  appServer  │  ← your application logic lives here
│   node      │
└──────┬──────┘
       │
       │  AMQP event  (routing key: rec.write, rel.read, log, etc.)
       ▼
┌─────────────────────────────────┐
│         RabbitMQ Broker         │
│                                 │
│  Exchange: beds.events (topic)  │
│  Exchange: beds.logs   (topic)  │
└──────┬──────────────────┬───────┘
       │                  │
       ▼                  ▼
┌────────────┐      ┌────────────┐
│  Broker    │      │   admin    │
│  Pool      │      │   node     │
│ (Tokio     │      │            │
│  tasks)    │      │ logging    │
└──────┬─────┘      │ auditing   │
       │            │ metrics    │
       ▼            └─────┬──────┘
┌────────────┐            │
│  Factory   │            ▼
│  Dispatch  │      ┌────────────┐
└──────┬─────┘      │  MongoDB   │
       │            │  msLogs    │
       ▼            └────────────┘
┌────────────────────────┐
│   NamasteCore Trait    │
│   (unified CRUD iface) │
└──────┬─────────────────┘
       │
       ├──────────────────────────┐
       ▼                          ▼
┌────────────┐            ┌────────────┐
│  MongoDB   │            │  MariaDB   │
│  Adapter   │            │  Adapter   │
│  (REC)     │            │  (REL)     │
└──────┬─────┘            └──────┬─────┘
       │                         │
       ▼                         ▼
┌────────────┐            ┌────────────┐
│  MongoDB   │            │  MariaDB   │
│  Collections│           │  Tables /  │
│            │            │  Procs /   │
│            │            │  Views     │
└────────────┘            └────────────┘
```

## Layers

### 1. Transport Layer (AMQP)

RabbitMQ is the backbone. All inter-component communication flows through it. This includes:

- Client data requests (read, write, update, delete)
- Log events from all nodes
- Audit records
- Migration jobs
- Warehouse operations

The transport layer knows nothing about databases. It routes messages. That is all.

### 2. Broker Pool (Tokio tasks)

Each node runs a pool of async broker tasks. Each task listens on one queue, processes one message at a time, and routes the result back via AMQP. The pool size is configured per broker type in `beds.toml`.

The broker pool is the throttle for the entire system. By adjusting instance counts, you control how many concurrent database operations the node performs — without changing a line of code.

Broker tasks are supervised. A panicked task is logged and replaced. The pool does not shrink on failure.

### 3. Factory Dispatch

A broker task receives an event containing a template name (e.g. `"Users"`, `"Sessions"`). The factory maps that name to the correct adapter — MongoDB for REC templates, MariaDB for REL templates. The factory does not know which template will be requested at compile time; dispatch is runtime.

### 4. NamasteCore Trait

The unified CRUD interface. Every database adapter implements it. Every template is a struct that selects an adapter and delegates to it. The application layer calls `NamasteCore` methods — it never calls adapter methods directly.

```rust
pub trait NamasteCore {
    async fn create_record(&self, payload: &Payload) -> Result<Response, BedsError>;
    async fn fetch_records(&self, query: &Query)   -> Result<Vec<Response>, BedsError>;
    async fn update_record(&self, payload: &Payload) -> Result<Response, BedsError>;
    async fn delete_record(&self, id: &str)          -> Result<Response, BedsError>;
}
```

### 5. Database Adapters

Two adapters, one interface:

- **REC adapter** — MongoDB. Document store. Schema-flexible. High-throughput appends. Used for logs, events, user profiles, audit records, anything that benefits from document structure.
- **REL adapter** — MariaDB. Relational store. SQL joins, transactions, strict schema. Used for anything that benefits from referential integrity.

Adapters do not write SQL or MongoDB queries. They call named database objects — stored procedures, views, functions — that the DBA owns. The adapter layer calls the object by name and passes parameters. It does not construct queries.

### 6. DBA-Owned Schema

The application layer never writes a query. All data access goes through named database objects. This is the separation of concerns that made Namaste maintainable across years and multiple development teams.

Adding a new data domain means:
1. DBA writes the schema (table/collection, views, stored procedures)
2. Developer writes a BEDS template (a TOML config file)
3. BEDS generates the adapter binding

Nothing else changes.

## The CALGON Pattern

Some operations cannot return an immediate result — long-running aggregations, migration jobs, warehouse operations. BEDS handles these with the **CALGON** pattern (async ticket):

1. Client submits a request
2. BEDS immediately returns a GUID ticket
3. The operation executes asynchronously
4. Client polls with the GUID to retrieve the result when ready

The client is never blocked on a long operation. The broker absorbs the work. This is the same pattern used by every major async job queue system, implemented natively in BEDS.

## Event Lineage

Every BEDS event carries a compound identifier:

```
event_id  = "{node}.{env}.{guid}"   # e.g. "ms.production.a1b2c3d4..."
parent_id = ""                       # empty string if this is a root event
depth     = 0                        # levels from the root event
```

A root event (an incoming client request) has `depth=0` and no parent. Every event it spawns (database calls, log events, audit records) carries the root's `event_id` as its `parent_id` and increments `depth`. This creates a complete, queryable tree of every operation triggered by a single client request.

Event lineage is how you answer "what actually happened when request X came in?" — without distributed tracing infrastructure.

## Configuration Drives Everything

BEDS has no node types in code. All nodes run the same binary. The configuration file determines:

- Which services this node runs (`is_local` per service)
- How many brokers of each type to spawn
- Which databases to connect to
- Whether this node is in production mode (fatal IPL failures) or development mode (non-fatal)

Changing a node's role means changing its config file and restarting. No code changes. No redeployment.