Fix behaviour for all metric types when only calls with labels are made

.github/workflows/test.yml

@@ -13,6 +13,7 @@ jobs:
           - swift:5.4
           - swift:5.5
           - swift:5.6
+          - swift:5.7
           - swiftlang/swift:nightly-main
         swiftos:
           - focal

Package.swift

@@ -10,7 +10,7 @@ let package = Package(
             targets: ["Prometheus"])
     ],
     dependencies: [
-        .package(url: "https://github.com/apple/swift-metrics.git", from: "2.2.0"),
+        .package(url: "https://github.com/apple/swift-metrics.git", from: "2.3.2"),
         .package(url: "https://github.com/apple/swift-nio.git", from: "2.0.0"),
     ],
     targets: [

Sources/Prometheus/MetricTypes/Counter.swift

@@ -17,6 +17,9 @@ public class PromCounter<NumType: Numeric>: PromMetric {
 
     /// Initial value of the counter
     private let initialValue: NumType
+
+    /// Indicates wether or not metric has been used without labels
+    private var usedWithoutLabels: Bool
 
     /// Storage of values that have labels attached
     internal var metrics: [DimensionLabels: NumType] = [:]
@@ -36,6 +39,7 @@ public class PromCounter<NumType: Numeric>: PromMetric {
         self.help = help
         self.initialValue = initialValue
         self.value = initialValue
+        self.usedWithoutLabels = initialValue != 0
         self.lock = Lock()
     }
 
@@ -44,8 +48,8 @@ public class PromCounter<NumType: Numeric>: PromMetric {
     /// - Returns:
     ///     Newline separated Prometheus formatted metric string
     public func collect() -> String {
-        let (value, metrics) = self.lock.withLock {
-            (self.value, self.metrics)
+        let (value, metrics, usedWithoutLabels) = self.lock.withLock {
+            (self.value, self.metrics, self.usedWithoutLabels)
         }
         var output = [String]()
 
@@ -54,7 +58,9 @@ public class PromCounter<NumType: Numeric>: PromMetric {
         }
         output.append("# TYPE \(self.name) \(self._type)")
 
-        output.append("\(self.name) \(value)")
+        if usedWithoutLabels {
+            output.append("\(self.name) \(value)")
+        }
 
         metrics.forEach { (labels, value) in
             let labelsString = encodeLabels(labels)
@@ -79,6 +85,7 @@ public class PromCounter<NumType: Numeric>: PromMetric {
                 self.metrics[labels] = val
                 return val
             } else {
+                self.usedWithoutLabels = true
                 self.value += amount
                 return self.value
             }

Sources/Prometheus/MetricTypes/Gauge.swift

@@ -19,7 +19,10 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
 
     /// Initial value of the Gauge
     private let initialValue: NumType
-
+
+    /// Indicates wether or not metric has been used without labels
+    private var usedWithoutLabels: Bool
+
     /// Storage of values that have labels attached
     private var metrics: [DimensionLabels: NumType] = [:]
 
@@ -39,6 +42,7 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
         self.help = help
         self.initialValue = initialValue
         self.value = initialValue
+        self.usedWithoutLabels = initialValue != 0
         self.lock = Lock()
     }
 
@@ -47,8 +51,8 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
     /// - Returns:
     ///     Newline separated Prometheus formatted metric string
     public func collect() -> String {
-        let (value, metrics) = self.lock.withLock {
-            (self.value, self.metrics)
+        let (value, metrics, usedWithoutLabels) = self.lock.withLock {
+            (self.value, self.metrics, self.usedWithoutLabels)
         }
         var output = [String]()
 
@@ -57,7 +61,9 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
         }
         output.append("# TYPE \(self.name) \(self._type)")
 
-        output.append("\(self.name) \(value)")
+        if usedWithoutLabels {
+            output.append("\(self.name) \(value)")
+        }
 
         metrics.forEach { (labels, value) in
             let labelsString = encodeLabels(labels)
@@ -129,6 +135,7 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
                 self.metrics[labels] = amount
                 return amount
             } else {
+                self.usedWithoutLabels = true
                 self.value = amount
                 return self.value
             }
@@ -151,6 +158,7 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
                 self.metrics[labels] = val
                 return val
             } else {
+                self.usedWithoutLabels = true
                 self.value += amount
                 return self.value
             }
@@ -184,6 +192,7 @@ public class PromGauge<NumType: DoubleRepresentable>: PromMetric {
                 self.metrics[labels] = val
                 return val
             } else {
+                self.usedWithoutLabels = true
                 self.value -= amount
                 return self.value
             }

Sources/Prometheus/MetricTypes/Histogram.swift

@@ -87,6 +87,9 @@ public class PromHistogram<NumType: DoubleRepresentable>: PromMetric {
     /// Total value of the Histogram
     private let sum: PromCounter<NumType>
 
+    /// Indicates wether or not metric has been used without labels
+    private var usedWithoutLabels: Bool
+
     /// Lock used for thread safety
     private let lock: Lock
 
@@ -102,6 +105,7 @@ public class PromHistogram<NumType: DoubleRepresentable>: PromMetric {
         self.help = help
 
         self.sum = .init("\(self.name)_sum", nil, 0)
+        self.usedWithoutLabels = false
 
         self.upperBounds = buckets.buckets
 
@@ -117,8 +121,8 @@ public class PromHistogram<NumType: DoubleRepresentable>: PromMetric {
     /// - Returns:
     ///     Newline separated Prometheus formatted metric string
     public func collect() -> String {
-        let (buckets, subHistograms) = self.lock.withLock {
-            (self.buckets, self.subHistograms)
+        let (buckets, subHistograms, usedWithoutLabels) = self.lock.withLock {
+            (self.buckets, self.subHistograms, self.usedWithoutLabels)
         }
 
         var output = [String]()
@@ -129,12 +133,14 @@ public class PromHistogram<NumType: DoubleRepresentable>: PromMetric {
             output.append("# HELP \(self.name) \(help)")
         }
         output.append("# TYPE \(self.name) \(self._type)")
-        collectBuckets(buckets: buckets,
-                       upperBounds: self.upperBounds,
-                       name: self.name,
-                       labels: nil,
-                       sum: self.sum.get(),
-                       into: &output)
+        if usedWithoutLabels {
+            collectBuckets(buckets: buckets,
+                           upperBounds: self.upperBounds,
+                           name: self.name,
+                           labels: nil,
+                           sum: self.sum.get(),
+                           into: &output)
+        }
 
         subHistograms.forEach { subHistogram in
             let (subHistogramBuckets, subHistogramLabels) = self.lock.withLock {
@@ -178,13 +184,17 @@ public class PromHistogram<NumType: DoubleRepresentable>: PromMetric {
         if let labels = labels {
             self.getOrCreateHistogram(with: labels)
                 .observe(value)
-        }
-        self.sum.inc(value)
-
-        for (i, bound) in self.upperBounds.enumerated() {
-            if bound >= value.doubleValue {
-                self.buckets[i].inc()
-                return
+        } else {
+            self.sum.inc(value)
+
+            self.lock.withLock {
+                self.usedWithoutLabels = true
+                for (i, bound) in self.upperBounds.enumerated() {
+                    if bound >= value.doubleValue {
+                        self.buckets[i].inc()
+                        return
+                    }
+                }
             }
         }
     }

Sources/Prometheus/MetricTypes/Summary.swift

@@ -34,6 +34,9 @@ public class PromSummary<NumType: DoubleRepresentable>: PromMetric {
 
     /// Sub Summaries for this Summary
     fileprivate var subSummaries: [DimensionLabels: PromSummary<NumType>] = [:]
+
+    /// Indicates wether or not metric has been used without labels
+    private var usedWithoutLabels: Bool
 
     /// Lock used for thread safety
     private let lock: Lock
@@ -62,6 +65,8 @@ public class PromSummary<NumType: DoubleRepresentable>: PromMetric {
 
         self.quantiles = quantiles
 
+        self.usedWithoutLabels = false
+
         self.lock = Lock()
     }
 
@@ -70,8 +75,8 @@ public class PromSummary<NumType: DoubleRepresentable>: PromMetric {
     /// - Returns:
     ///     Newline separated Prometheus formatted metric string
     public func collect() -> String {
-        let (subSummaries, values) = lock.withLock {
-            (self.subSummaries, self.values)
+        let (subSummaries, values, usedWithoutLabels) = lock.withLock {
+            (self.subSummaries, self.values, self.usedWithoutLabels)
         }
 
         var output = [String]()
@@ -82,14 +87,17 @@ public class PromSummary<NumType: DoubleRepresentable>: PromMetric {
             output.append("# HELP \(self.name) \(help)")
         }
         output.append("# TYPE \(self.name) \(self._type)")
-        calculateQuantiles(quantiles: self.quantiles, values: values.map { $0.doubleValue }).sorted { $0.key < $1.key }.forEach { (arg) in
-            let (q, v) = arg
-            let labelsString = encodeLabels(EncodableSummaryLabels(labels: nil, quantile: "\(q)"))
-            output.append("\(self.name)\(labelsString) \(format(v))")
-        }
 
-        output.append("\(self.name)_count \(self.count.get())")
-        output.append("\(self.name)_sum \(format(self.sum.get().doubleValue))")
+        if usedWithoutLabels {
+            calculateQuantiles(quantiles: self.quantiles, values: values.map { $0.doubleValue }).sorted { $0.key < $1.key }.forEach { (arg) in
+                let (q, v) = arg
+                let labelsString = encodeLabels(EncodableSummaryLabels(labels: nil, quantile: "\(q)"))
+                output.append("\(self.name)\(labelsString) \(format(v))")
+            }
+
+            output.append("\(self.name)_count \(self.count.get())")
+            output.append("\(self.name)_sum \(format(self.sum.get().doubleValue))")
+        }
 
         subSummaries.forEach { labels, subSum in
             let subSumValues = lock.withLock { subSum.values }
@@ -138,14 +146,16 @@ public class PromSummary<NumType: DoubleRepresentable>: PromMetric {
         if let labels = labels {
             let sum = self.getOrCreateSummary(withLabels: labels)
             sum.observe(value)
-        }
-        self.count.inc(1)
-        self.sum.inc(value)
-        self.lock.withLock {
-            if self.values.count == self.capacity {
-                _ = self.values.popFirst()
+        } else {
+            self.count.inc(1)
+            self.sum.inc(value)
+            self.lock.withLock {
+                self.usedWithoutLabels = true
+                if self.values.count == self.capacity {
+                    _ = self.values.popFirst()
+                }
+                self.values.append(value)
             }
-            self.values.append(value)
         }
     }
 

Tests/SwiftPrometheusTests/GaugeTests.swift

@@ -80,4 +80,22 @@ final class GaugeTests: XCTestCase {
         my_gauge{myValue="labels"} 20
         """)
     }
+
+    func testGaugeDoesNotReportWithNoLabelUsed() {
+        let gauge = prom.createGauge(forType: Int.self, named: "my_gauge")
+        gauge.inc(1, [("a", "b")])
+
+        XCTAssertEqual(gauge.collect(), """
+        # TYPE my_gauge gauge
+        my_gauge{a="b"} 1
+        """)
+
+        gauge.inc()
+
+        XCTAssertEqual(gauge.collect(), """
+        # TYPE my_gauge gauge
+        my_gauge 1
+        my_gauge{a="b"} 1
+        """)
+    }
 }

Tests/SwiftPrometheusTests/HistogramTests.swift

@@ -55,8 +55,8 @@ final class HistogramTests: XCTestCase {
         try elg.syncShutdownGracefully()
 
         let output = histogram.collect()
-        XCTAssertTrue(output.contains("my_histogram_count 4000.0"))
-        XCTAssertTrue(output.contains("my_histogram_sum 4000.0"))
+        XCTAssertFalse(output.contains("my_histogram_count 4000.0"))
+        XCTAssertFalse(output.contains("my_histogram_sum 4000.0"))
 
         XCTAssertTrue(output.contains(#"my_histogram_count{myValue="1"} 2000.0"#))
         XCTAssertTrue(output.contains(#"my_histogram_sum{myValue="1"} 2000.0"#))
@@ -88,11 +88,11 @@ final class HistogramTests: XCTestCase {
         my_histogram_bucket{le="0.5"} 0.0
         my_histogram_bucket{le="1.0"} 1.0
         my_histogram_bucket{le="2.5"} 2.0
-        my_histogram_bucket{le="5.0"} 4.0
-        my_histogram_bucket{le="10.0"} 4.0
-        my_histogram_bucket{le="+Inf"} 4.0
-        my_histogram_count 4.0
-        my_histogram_sum 9.0
+        my_histogram_bucket{le="5.0"} 3.0
+        my_histogram_bucket{le="10.0"} 3.0
+        my_histogram_bucket{le="+Inf"} 3.0
+        my_histogram_count 3.0
+        my_histogram_sum 6.0
         my_histogram_bucket{myValue="labels", le="0.005"} 0.0
         my_histogram_bucket{myValue="labels", le="0.01"} 0.0
         my_histogram_bucket{myValue="labels", le="0.025"} 0.0
@@ -144,11 +144,11 @@ final class HistogramTests: XCTestCase {
         my_histogram_bucket{le="0.5"} 0.0
         my_histogram_bucket{le="1.0"} 1.0
         my_histogram_bucket{le="2.0"} 2.0
-        my_histogram_bucket{le="3.0"} 4.0
-        my_histogram_bucket{le="5.0"} 4.0
-        my_histogram_bucket{le="+Inf"} 4.0
-        my_histogram_count 4.0
-        my_histogram_sum 9.0
+        my_histogram_bucket{le="3.0"} 3.0
+        my_histogram_bucket{le="5.0"} 3.0
+        my_histogram_bucket{le="+Inf"} 3.0
+        my_histogram_count 3.0
+        my_histogram_sum 6.0
         my_histogram_bucket{myValue="labels", le="0.5"} 0.0
         my_histogram_bucket{myValue="labels", le="1.0"} 0.0
         my_histogram_bucket{myValue="labels", le="2.0"} 0.0
@@ -159,4 +159,43 @@ final class HistogramTests: XCTestCase {
         my_histogram_sum{myValue="labels"} 3.0
         """)
     }
+
+    func testHistogramDoesNotReportWithNoLabelUsed() {
+        let histogram = prom.createHistogram(forType: Double.self, named: "my_histogram", buckets: [0.5, 1, 2, 3, 5, Double.greatestFiniteMagnitude])
+        histogram.observe(3, [("a", "b")])
+
+        XCTAssertEqual(histogram.collect(), """
+        # TYPE my_histogram histogram
+        my_histogram_bucket{le="0.5", a="b"} 0.0
+        my_histogram_bucket{le="1.0", a="b"} 0.0
+        my_histogram_bucket{le="2.0", a="b"} 0.0
+        my_histogram_bucket{le="3.0", a="b"} 1.0
+        my_histogram_bucket{le="5.0", a="b"} 1.0
+        my_histogram_bucket{le="+Inf", a="b"} 1.0
+        my_histogram_count{a="b"} 1.0
+        my_histogram_sum{a="b"} 3.0
+        """)
+
+        histogram.observe(3)
+
+        XCTAssertEqual(histogram.collect(), """
+        # TYPE my_histogram histogram
+        my_histogram_bucket{le="0.5"} 0.0
+        my_histogram_bucket{le="1.0"} 0.0
+        my_histogram_bucket{le="2.0"} 0.0
+        my_histogram_bucket{le="3.0"} 1.0
+        my_histogram_bucket{le="5.0"} 1.0
+        my_histogram_bucket{le="+Inf"} 1.0
+        my_histogram_count 1.0
+        my_histogram_sum 3.0
+        my_histogram_bucket{le="0.5", a="b"} 0.0
+        my_histogram_bucket{le="1.0", a="b"} 0.0
+        my_histogram_bucket{le="2.0", a="b"} 0.0
+        my_histogram_bucket{le="3.0", a="b"} 1.0
+        my_histogram_bucket{le="5.0", a="b"} 1.0
+        my_histogram_bucket{le="+Inf", a="b"} 1.0
+        my_histogram_count{a="b"} 1.0
+        my_histogram_sum{a="b"} 3.0
+        """)
+    }
 }