0g-chain/x/metrics/spec/README.md
Robert Pirtle 9a0aed7626
feat(x/metrics): add module for emiting custom chain metrics (#1668)
* initialize x/metrics with metrics collection

* include global labels in x/metrics metrics

* add x/metrics spec

* add x/metrics test coverage

* update changelog
2023-08-25 12:23:53 -07:00

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<!--
order: 0
title: "Metrics Overview"
parent:
title: "metrics"
-->
# `metrics`
## Abstract
`x/metrics` is a stateless module that does not affect consensus. It captures chain metrics and emits them when the `instrumentation.prometheus` option is enabled in `config.toml`.
## Precision
The metrics emitted by `x/metrics` are `float64`s. They use `github.com/go-kit/kit/metrics` Prometheus gauges. Cosmos-sdk's `telemetry` package was not used because, at the time of writing, it only supports `float32`s and so does not maintain accurate representations of ints larger than ~16.8M. With `float64`s, integers may be accurately represented up to ~9e15.
## Metrics
The following metrics are defined:
* `cometbft_blocksync_latest_block_height` - this emulates the blocksync `latest_block_height` metric in CometBFT v0.38+. The `cometbft` namespace comes from the `instrumentation.namespace` config.toml value.
## Metric Labels
All metrics emitted have the labels defined in app.toml's `telemetry.global-labels` field. This is the same field used by cosmos-sdk's `telemetry` package.
example:
```toml
# app.toml
[telemetry]
global-labels = [
["chain_id", "kava_2222-10"],
["my_label", "my_value"],
]
```