Implement Summary?

Author: MrLotU

Sources/Prometheus/MetricTypes/Summary.swift

@@ -0,0 +1,65 @@
+public protocol SummaryLabels: MetricLabels {
+    var quantile: String { get set }
+}
+
+extension SummaryLabels {
+    init() {
+        self.init()
+        self.quantile = ""
+    }
+}
+
+public class Summary<NumType: DoubleRepresentable, Labels: SummaryLabels>: Metric {
+    public var name: String
+    
+    public var help: String?
+    
+    public var labels: Labels
+    
+    private var sum: Counter<NumType, EmptyCodable>
+    
+    private var count: Counter<NumType, EmptyCodable>
+    
+    private var values: [NumType] = []
+    
+    public init(_ name: String, _ help: String? = nil, _ labels: Labels = Labels()) {
+        self.name = name
+        self.help = help
+        
+        self.sum = .init("\(self.name)_sum")
+        
+        self.count = .init("\(self.name)_count")
+        
+        self.labels = labels
+    }
+    
+    public func getMetric() -> String {
+        var output = [String]()
+        
+        if let help = help {
+            output.append("# HELP \(name) \(help)")
+        }
+        output.append("# TYPE \(name) summary")
+        
+        let quantiles = [0.5, 0.9, 0.99]
+        
+        calculateQuantiles(quantiles: quantiles, values: values.map { $0.doubleValue }).forEach { (arg) in
+            let (q, v) = arg
+            self.labels.quantile = "\(q)"
+            let labelsString = encodeLabels(self.labels)
+            output.append("\(name)\(labelsString) \(v)")
+        }
+        
+        let labelsString = encodeLabels(self.labels, ["quantile"])
+        output.append("\(name)_count\(labelsString) \(count.get())")
+        output.append("\(name)_sum\(labelsString) \(sum.get())")
+
+        return output.joined(separator: "\n")
+    }
+    
+    public func observe(_ value: NumType) {
+        self.count.inc(1)
+        self.sum.inc(value)
+        self.values.append(value)
+    }
+}

Sources/Prometheus/Utils.swift

@@ -24,6 +24,34 @@ public func encodeLabels<Labels: MetricLabels>(_ labels: Labels, _ excludingKeys
     }
 }
 
+func calculateQuantiles(quantiles: [Double], values: [Double]) -> [Double: Double] {
+    let values = values.sorted()
+    var quantilesMap: [Double: Double] = [:]
+    quantiles.forEach { (q) in
+        quantilesMap[q] = quantile(q, values)
+    }
+    return quantilesMap
+}
+
+func quantile(_ q: Double, _ values: [Double]) -> Double {
+    if values.count == 1 {
+        return values[0]
+    }
+    
+    let n = Double(values.count)
+    if let pos = Int(exactly: n*q) {
+        if pos < 2 {
+            return values[0]
+        } else if pos == values.count {
+            return values[pos - 1]
+        }
+        return (values[pos - 1] + values[pos]) / 2.0
+    } else {
+        let pos = Int((n*q).rounded(.up))
+        return values[pos - 1]
+    }
+}
+
 extension Double {
     var description: String {
         if self == Double.greatestFiniteMagnitude {

Sources/PrometheusExample/main.swift

@@ -15,42 +15,56 @@ struct MyCodable: MetricLabels {
 let codable1 = MyCodable("Thing1")
 let codable2 = MyCodable("Thing2")
 
-let counter = Counter<Int, MyCodable>("some_test_value", "This value holds just a random imcrementer :)", 0)
-
-counter.inc(5, codable1)
-
-counter.inc(5, codable2)
-
-counter.inc(5)
-
-counter.inc(5, codable1)
-
-print(counter.getMetric())
-
-let gauge = Gauge<Int, MyCodable>("some_test_value", "This value holds a random Gauge :)")
-
-gauge.inc(codable2)
-
-gauge.dec()
-
-gauge.inc(1, codable1)
-
-let arr = [1, 2, 3, 4]
-
-gauge.set(arr.count)
-
-print(gauge.getMetric())
-
-struct HistogramCodable: HistogramLabels {
-    var le: String = ""
-}
-
-let histogram = Histogram<Int, HistogramCodable>("my_histogram", "Just a histogram")
-
-histogram.observe(6)
-histogram.observe(6)
-histogram.observe(1)
-histogram.observe(4)
-
-print(histogram.getMetric())
-
+//let counter = Counter<Int, MyCodable>("some_test_value", "This value holds just a random imcrementer :)", 0)
+//
+//counter.inc(5, codable1)
+//
+//counter.inc(5, codable2)
+//
+//counter.inc(5)
+//
+//counter.inc(5, codable1)
+//
+//print(counter.getMetric())
+//
+//let gauge = Gauge<Int, MyCodable>("some_test_value", "This value holds a random Gauge :)")
+//
+//gauge.inc(codable2)
+//
+//gauge.dec()
+//
+//gauge.inc(1, codable1)
+//
+//let arr = [1, 2, 3, 4]
+//
+//gauge.set(arr.count)
+//
+//print(gauge.getMetric())
+//
+//struct HistogramCodable: HistogramLabels {
+//    var le: String = ""
+//}
+//
+//let histogram = Histogram<Int, HistogramCodable>("my_histogram", "Just a histogram")
+//
+//histogram.observe(6)
+//histogram.observe(6)
+//histogram.observe(1)
+//histogram.observe(4)
+//
+//print(histogram.getMetric())
+
+//struct SummaryCodable: SummaryLabels {
+//    var quantile: String = ""
+//}
+//
+//let summary = Summary<Int, SummaryCodable>("my_summary", "Just a summary")
+//
+//summary.observe(4)
+//summary.observe(3)
+//summary.observe(1)
+//summary.observe(3)
+//summary.observe(9)
+//summary.observe(5)
+//
+//print(summary.getMetric())