> ## Documentation Index
> Fetch the complete documentation index at: https://optimism-373f39ad-soyboy-docs-op-supernode-guide.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Monitoring

> Set up logging, Prometheus metrics, and Grafana dashboards for kona-node.

This guide covers observability for a running `kona-node`: adjusting
log verbosity, filtering log targets, and collecting Prometheus
metrics into Grafana dashboards.

## Logging

`kona-node` provides a `-v` (or `--v`) flag as a way to set
the "verbosity" level for logs. By default, the verbosity level
is set to `3`, which is the INFO level. The level ranges from `0`
being no logs to `5` which includes trace logs. Log levels are
listed below, with each level including the one below it.

* `5`: `TRACE` - very verbose logs that provide a detailed trace
* `4`: `DEBUG` - logs meant to print debugging information
* `3`: `INFO` - informational logs
* `2`: `WARN` - includes warning and error logs
* `1`: `ERROR` - only error logs are shown
* `0`: No logs

The default verbosity level is `-vvv` which is the `3` or `INFO`
level. To set the `kona-node` to print `DEBUG` logs or level `4`,
run the node like so: `kona-node node -vvvv`.

### Filtering Log Targets

By default, the `kona-node` initializes its tracing (logging)
using the default environment variable filter [provided by the
tracing\_subscriber crate][tracing-env]. This uses the value in
the `RUST_LOG` environment variable to set the tracing level
for specific targets. Effectively, `RUST_LOG` allows you to
bypass the default log level for the whole node or specific
log targets. For example, by prepending `RUST_LOG=engine=debug`
to the `kona-node` command (or setting that as an environment
variable), only `INFO` logs will be displayed except for the
`engine` log target which will also print `DEBUG` logs.

This comes in handy say for when we would like to debug Kona's
P2P stack, we could prepend `RUST_LOG=discv5=debug,libp2p=debug`
to view debug logs from only `discv5` and `libp2p` targets.

## Metrics

The `kona-node` can serve Prometheus metrics, which are disabled
by default. To turn them on, pass the `--metrics.enabled` cli flag.

Unless otherwise specified with the `--metrics.port` flag, metrics
are exposed on port `9090`.

To grab a snapshot of the metrics, you can visit `0.0.0.0:9090`
or `curl` the url.

```
curl 0.0.0.0:9090
```

The output should be raw text mapping metrics with their values.

Remember, this is just a snapshot of the metrics at that point
in time. To record and visualize the metrics, we'll use
[Grafana and Prometheus](#grafana-and-prometheus).

## Grafana and Prometheus

Prometheus is a simple service that scrapes metrics at a predefined
interval. Grafana then uses Prometheus as a "Data Source" to
visualize the collected metrics.

The Reth book provides a great overview to setting up [Prometheus
and Grafana][setup]. Visit the Reth docs to follow along.

The `kona-node` comes shipped with a default Grafana dashboard
for the `kona-node`. To import the dashboard to grafana, click
the `+` icon > `Import Dashboard` > paste the contents of [kona's
dashboard][dashboard] in the textbox > `Load`.

[tracing-env]: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html#method.from_default_env

[setup]: https://reth.rs/run/monitoring#prometheus--grafana

[dashboard]: https://github.com/ethereum-optimism/optimism/blob/develop/rust/kona/docker/recipes/kona-node/grafana/dashboards/overview.json