> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usehasp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Maintenance Mode

> Detecting 503 maintenance responses, event handlers, write blocking, and proactive polling.

The SDK detects maintenance mode reactively via `503` responses. Write operations are blocked; reads are still allowed.

## Event Handlers

The simplest way to handle maintenance is via constructor callbacks:

```javascript theme={null}
const sdk = new HaspSDK({
  onMaintenanceStart: (status) => {
    document.getElementById('maintenance-banner').style.display = 'block';
    document.getElementById('maintenance-message').textContent =
      status.message ?? 'App is being updated.';
  },
  onMaintenanceEnd: () => {
    document.getElementById('maintenance-banner').style.display = 'none';
  },
});
```

Or attach/remove handlers dynamically:

```javascript theme={null}
// sdk.on() returns an unsubscribe function
const unsubStart = sdk.on('maintenanceStart', (status) => { /* ... */ });
const unsubEnd   = sdk.on('maintenanceEnd', () => { /* ... */ });

// Remove later:
unsubStart();
unsubEnd();
```

## Write Behavior

Write operations throw `MaintenanceError` **immediately** if the SDK is already in maintenance state — they do not hit the server:

```javascript theme={null}
try {
  await sdk.createRecord('tasks', data);
} catch (error) {
  if (error instanceof HaspSDK.MaintenanceError) {
    showMessage('App is being updated. Please try again shortly.');
  }
}
```

## Read Behavior

Read operations (`listRecords`, `getRecord`, `paginateRecords`, `getSchema`, `getBootstrap`) are allowed during maintenance and may succeed depending on server behavior.

## Automatic Recovery

Maintenance mode clears automatically — if any request succeeds after a 503, the SDK exits maintenance mode and fires `maintenanceEnd`.

## Proactive Detection

The SDK only detects maintenance reactively. For proactive detection before a write fails, implement your own status poller:

```javascript theme={null}
const poller = setInterval(async () => {
  const status = await sdk.getStatus();
  if (status.status === 'maintenance') {
    showMaintenanceBanner(status.message);
  } else {
    hideMaintenanceBanner();
  }
}, 15_000);

clearInterval(poller);
sdk.destroy();
```

## getStatus(signal?)

Fetches the current app status without triggering maintenance mode detection.

```javascript theme={null}
const status = await sdk.getStatus();
// status.status           — 'ok' | 'maintenance'
// status.message          — optional human-readable message
// status.estimatedSeconds — optional estimated downtime in seconds
```