Advanced Guide

Publishing Custom Metrics

GoFr publishes some default metrics.

GoFr can handle multiple different metrics concurrently, each uniquely identified by its name during initialization. It supports the following metrics types in Prometheus format:

  1. Counter
  2. UpDownCounter
  3. Histogram
  4. Gauge

If any custom metric is required, it can be created by using custom metrics as shown below:

Usage

1. Counter Metrics

Counter is a synchronous Instrument which supports non-negative increments.

Usage

package main

import (
	"gofr.dev/pkg/gofr"
)

func main() {
	// initialise gofr object
	app := gofr.New()

	app.Metrics().NewCounter("transaction_success", "used to track the count of successful transactions")

	app.POST("/transaction", func(ctx *gofr.Context) (interface{}, error) {
		ctx.Metrics().IncrementCounter(ctx, "transaction_success")

		return "Transaction Successful", nil
	})

	app.Run()
}

2. UpDown Counter Metrics

UpDownCounter is a synchronous Instrument which supports increments and decrements. Note: If the value is monotonically increasing, use Counter instead.

Usage

package main

import (
	"gofr.dev/pkg/gofr"
)

func main() {
	// initialise gofr object
	app := gofr.New()

	app.Metrics().NewUpDownCounter("total_credit_day_sale", "used to track the total credit sales in a day")

	app.POST("/sale", func(ctx *gofr.Context) (interface{}, error) {
		ctx.Metrics().IncrementCounter(ctx, "total_credit_day_sale")

		return "Sale Completed", nil
	})

	app.Run()
}

3. Histogram Metrics

Histogram is a synchronous Instrument which can be used to report arbitrary values that are likely to be statistically meaningful. It is intended for statistics such as histograms, summaries, and percentile.

Usage

package main

import (
	"gofr.dev/pkg/gofr"
)

func main() {
	// initialise gofr object
	app := gofr.New()

	app.Metrics().NewHistogram("transaction_time", "used to track the time taken by a transaction",
		5, 10, 15, 20, 25, 35)

	app.POST("/transaction", func(ctx *gofr.Context) (interface{}, error) {
		transactionStartTime := time.Now()

		// transaction logic

		tranTime := time.Now().Sub(transactionStartTime).Milliseconds()

		ctx.Metrics().RecordHistogram(ctx, "transaction_time", float64(tranTime))

		return "Transaction Completed", nil
	})

	app.Run()
}

4. Gauge Metrics

Gauge is a synchronous Instrument which can be used to record non-additive value(s) when changes occur.

Usage

package main

import (
	"gofr.dev/pkg/gofr"
)

func main() {
	// initialise gofr object
	app := gofr.New()

	app.Metrics().NewGauge("product_stock", "used to track the number of products in stock")

	app.POST("/sale", func(ctx *gofr.Context) (interface{}, error) {
		ctx.Metrics().SetGauge("product_stock", 10)

		return "Sale Completed", nil
	})

	app.Run()
}

Good To Know

While registering a metrics 2 key pieces of information of required:
- Name
- Description

When a registered metrics has to be used 3 key pieces of information are required:
- Name
- Value
- A set of key-value pairs called tags or labels.

A permutation of these key-value values provides the metric cardinality.
Lower the cardinality, faster the query performance and lower the monitoring resource utilisation.