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Command Dispatch

1. What is Command Dispatch?

Command Dispatch is the bidirectional control channel that enables:

• Users (via dashboard) to send real‑time commands to any edge device.
• Automated cloud services (schedulers, optimizers) to issue setpoints.
• Edges to acknowledge execution and report status.

It transforms the EMS from a passive monitoring system into an active control system.

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Command Flow (Step‑by‑Step)

Step 1: User Initiates Command

• Operator clicks "Set Battery Charge 50kW" in Next.js dashboard.
• Dashboard validates input (range, syntax).
• Sends JSON payload over WebSocket:

{
  "command_id": "cmd_12345",
  "command_type": "setpoint",
  "target": {
    "edge_id": "site1_edge_prod",
    "device_id": "bms_main",
    "channel": "SetActivePower"
  },
  "value": 50000,
  "unit": "W",
  "expiry_sec": 300,
  "source": "user_456",
  "timestamp": "2026-02-15T14:30:00Z"
}

Step 2: Cloud Authentication & Authorization

• FastAPI WebSocket server receives payload.
• Validates:
• Authentication: User session/JWT valid.
• Authorization: User has can_control permission for this edge.
• Rate limiting: Not exceeding commands/sec.
• If invalid → error response to dashboard.

Step 3: Command Routing

• FastAPI looks up edge's active WebSocket connection (from connection registry).
• If edge online → forward command immediately.
• If edge offline:
• Store in Redis command queue (persistent).
• Set expiry (configurable, default 24h).
• Edge will fetch on reconnect.

Step 4: Edge Receives & Executes

• Edge agent receives command via its persistent WebSocket.
• Immediate validation:
• Device exists? Channel writable? Value within limits?
• If invalid → reject with reason.
• If valid:
• Place command into Core Cycle execution queue.
• Core Cycle will apply at next cycle (or immediately if flagged priority: emergency).

Step 5: Execution & Acknowledgment

• Core Cycle executes command (writes setpoint to Modbus device).
• Result (success/failure) captured.
• Edge sends acknowledgment back to cloud:

{
  "command_id": "cmd_12345",
  "status": "executed",
  "executed_at": "2026-02-15T14:30:01.050Z",
  "error": null
}

Step 6: Cloud Notifies Dashboard

• FastAPI receives acknowledgment.
• Broadcasts to dashboard (if still connected) or stores in history.
• Dashboard shows "Command Executed" with timestamp.

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Command Types (MVP)

Type	Description	Example
Setpoint	Write a value to a device channel	SetActivePower = 50kW
Mode change	Switch controller mode	Enable Peak Shaving
Configuration override	Temporary parameter change	Override MinSoc = 15% for 1 hour
Scheduler control	Start/stop controllers	Disable Balancing Controller
System command	Edge lifecycle	Restart, Sync config now

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Technical Requirements (MVP)

Cloud Side (FastAPI)

S No	Requirement
01	Maintain persistent WebSocket connections to all online edges.
02	Registry mapping edge_id → active WebSocket connection.
03	Authenticate all incoming commands (user JWT).
04	Authorize per edge (check user permissions).
05	Queue commands for offline edges (Redis).
06	Rate limiting per user/edge.
07	Full audit log: who sent what command, when, result.
08	Timeout handling: if no acknowledgment within 10s, mark as failed.

Edge Side (Python Agent)

S No	Requirement
01	Maintain persistent WebSocket connection to cloud.
02	Auto‑reconnect with exponential backoff.
03	Validate incoming commands against device capabilities.
04	Queue commands if Core Cycle busy (bounded queue).
05	Execute commands in Core Cycle order (preserving priority).
06	Send acknowledgment (success/failure) back to cloud.
07	Log all commands locally (for audit when cloud unreachable).

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Integration with Existing Components

Component	Role in Command Dispatch
Next.js Dashboard	Command UI; real‑time feedback.
Django Auth	User authentication & permissions.
FastAPI WebSocket	Primary command router.
Redis	Offline queue & rate limiting store.
Edge Core Cycle	Actual command execution (writes setpoints).
Modbus Adapter	Physical device communication.
TimescaleDB	Command audit log storage.
Edge Config Sync	Provides device capability definitions.

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