sanic/guide/content/en/plugins/sanic-ext/health-monitor.md

Health monitor

The health monitor requires both sanic>=22.9 and sanic-ext>=22.9.

You can setup Sanic Extensions to monitor the health of your worker processes. This requires that you not be in single process mode.

Setup

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Out of the box, the health monitor is disabled. You will need to opt-in if you would like to use it.

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```python
app.config.HEALTH = True
```

How does it work

The monitor sets up a new background process that will periodically receive acknowledgements of liveliness from each worker process. If a worker process misses a report too many times, then the monitor will restart that one worker.

Diagnostics endpoint

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The health monitor will also enable a diagnostics endpoint that outputs the [worker state](../../guide/deployment/manager.md#worker-state). By default is id disabled.

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    The diagnostics endpoint is not secured. If you are deploying it in a production environment, you should take steps to protect it with a proxy server if you are using one. If not, you may want to consider disabling this feature in production since it will leak details about your server state.

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```
$ curl http://localhost:8000/__health__
{
    'Sanic-Main': {'pid': 99997},
    'Sanic-Server-0-0': {
        'server': True,
        'state': 'ACKED',
        'pid': 9999,
        'start_at': datetime.datetime(2022, 10, 1, 0, 0, 0, 0, tzinfo=datetime.timezone.utc),
        'starts': 2,
        'restart_at': datetime.datetime(2022, 10, 1, 0, 0, 12, 861332, tzinfo=datetime.timezone.utc)
    },
    'Sanic-Reloader-0': {
        'server': False,
        'state': 'STARTED',
        'pid': 99998,
        'start_at': datetime.datetime(2022, 10, 1, 0, 0, 0, 0, tzinfo=datetime.timezone.utc),
        'starts': 1
    }
}
```

Configuration

Key	Type	Default	Description
HEALTH	bool	False	Whether to enable this extension.
HEALTH_ENDPOINT	bool	False	Whether to enable the diagnostics endpoint.
HEALTH_MAX_MISSES	int	3	The number of consecutive misses before a worker process is restarted.
HEALTH_MISSED_THRESHHOLD	int	10	The number of seconds the monitor checks for worker process health.
HEALTH_MONITOR	bool	True	Whether to enable the health monitor.
HEALTH_REPORT_INTERVAL	int	5	The number of seconds between reporting each acknowledgement of liveliness.
HEALTH_URI_TO_INFO	str	""	The URI path of the diagnostics endpoint.
HEALTH_URL_PREFIX	str	"/__health__"	The URI prefix of the diagnostics blueprint.