# Enabling Monitoring

## NATS Server Monitoring

To monitor the NATS messaging system, `nats-server` provides a lightweight HTTP server on a dedicated monitoring port. The monitoring server provides several endpoints, providing statistics and other information.

The [NATS monitoring endpoints](/running-a-nats-service/nats_admin/monitoring.md) support [JSONP](https://en.wikipedia.org/wiki/JSONP) and [CORS](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing#How_CORS_works), making it easy to create single page monitoring web applications.

> Warning: `nats-server` does not have authentication/authorization for the monitoring endpoint. When you plan to open your `nats-server` to the internet make sure to not expose the monitoring port as well. By default monitoring binds to every interface `0.0.0.0` so consider setting monitoring to `localhost` or have appropriate firewall rules.

### Enabling monitoring from the command line

To enable the monitoring server, start the NATS server with the monitoring flag `-m` and the monitoring port, or turn it on in the [configuration file](#enable-monitoring-from-the-configuration-file).

```
-m, --http_port PORT             HTTP PORT for monitoring
-ms,--https_port PORT            Use HTTPS PORT for monitoring
```

Example:

```bash
nats-server -m 8222
```

```
[4528] 2019/06/01 20:09:58.572939 [INF] Starting nats-server version 2.0.0
[4528] 2019/06/01 20:09:58.573007 [INF] Starting http monitor on port 8222
[4528] 2019/06/01 20:09:58.573071 [INF] Listening for client connections on 0.0.0.0:4222
[4528] 2019/06/01 20:09:58.573090 [INF] nats-server is ready
```

To test, run `nats-server -m 8222`, then go to <http://localhost:8222/>

### Enable monitoring from the configuration file

You can also enable monitoring using the configuration file as follows:

```yaml
http_port: 8222
```

Binding to `localhost` as well:

```yaml
http: localhost:8222
```

For example, to monitor this server locally, the endpoint would be <http://localhost:8222/varz>. It reports various general statistics.

## Monitoring Tools

In addition to writing custom monitoring tools, you can monitor nats-server in Prometheus. The [Prometheus NATS Exporter](https://github.com/nats-io/prometheus-nats-exporter) allows you to configure the metrics you want to observe and store in Prometheus. There's a sample [Grafana](https://grafana.com) dashboard that you can use to visualize the server metrics.


---

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