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Clientside Prometheus library in Swift
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Build Status Swift 5.0

SwiftPrometheus, Prometheus client for Swift

A prometheus client for Swift supporting counters, gauges, histograms, summaries and info.


For examples, see main.swift


Counters go up, and reset when the process restarts.

let prom = PrometheusClient()

let counter = prom.createCounter(forType: Int.self, named: "my_counter") // Increment by 1 // Increment by given value 


Gauges can go up and down

let prom = PrometheusClient()

let gauge = prom.createGauge(forType: Int.self, named: "my_gauge") // Increment by 1
gauge.dec(19) // Decrement by given value
gauge.set(12) // Set to a given value


Histograms track the size and number of events in buckets. This allows for aggregatable calculation of quantiles.

let prom = PrometheusClient()

let histogram = prom.createHistogram(forType: Double.self, named: "my_histogram")
histogram.observe(4.7) // Observe the given value


Summaries track the size and number of events

let prom = PrometheusClient()

let summary = prom.createSummary(forType: Double.self, named: "my_summary")
summary.observe(4.7) // Observe the given value


Info tracks key-value information, usually about a whole target.

struct MyInfoStruct: MetricLabels {
   let value: String
   init() {
       self.value = "abc"
   init(_ v: String) {
       self.value = v

let prom = PrometheusClient()

let info = prom.createInfo(named: "my_info", helpText: "Just some info", labelType: MyInfoStruct.self)"def"))


All metric types support adding labels, allowing for grouping of related metrics.

Example with a counter:

struct RouteLabels: MetricLabels {
   var route: String = "*"

let prom = PrometheusClient()

let counter = prom.createCounter(forType: Int.self, named: "my_counter", helpText: "Just a counter", withLabelType: RouteLabels.self), .init(route: "/"))


To keep SwiftPrometheus as clean and lightweight as possible, there is no way of exporting metrics directly to Prometheus. Instead, retrieve a formatted string that Prometheus can use, so you can integrate it in your own Serverside Swift application

This could look something like this:

router.get("/metrics") { request -> Future<String> in
    let promise = req.eventLoop.newPromise(String.self)
    prom.getMetrics {
        promise.succeed(result: $0)
    return promise.futureResult

Here, I used Vapor syntax, but this will work with any web framework, since it's just returning a plain String.


All contributions are most welcome!

If you think of some cool new feature that should be included, please create an issue. Or, if you want to implement it yourself, fork this repo and submit a PR!

If you find a bug or have issues, please create an issue explaining your problems. Please include as much information as possible, so it's easier for me to reproduce (Framework, OS, Swift version, terminal output, etc.)

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