Merge pull request #78 from Sam-Amin/sam-fixconcurrency-gh

Author: ktoso

Sources/Prometheus/MetricTypes/Histogram.swift

@@ -221,7 +221,7 @@ public class PromHistogram<NumType: DoubleRepresentable>: PromMetric {
             return histogram
         } else {
             return lock.withLock {
-                if let histogram = subHistograms[labels] {
+                if let histogram = self.subHistograms[labels] {
                     precondition(histogram.name == self.name,
                                  """
                                  Somehow got 2 subHistograms with the same data type  / labels 

Tests/SwiftPrometheusTests/HistogramTests.swift

@@ -29,7 +29,7 @@ final class HistogramTests: XCTestCase {
                                              helpText: "Histogram for testing",
                                              buckets: Buckets.exponential(start: 1, factor: 2, count: 63))
         let elg = MultiThreadedEventLoopGroup(numberOfThreads: 8)
-        let semaphore = DispatchSemaphore(value: 2)
+        let semaphore = DispatchSemaphore(value: 0)
         _ = elg.next().submit {
             for _ in 1...1_000 {
                 let labels = DimensionLabels([("myValue", "1")])
@@ -51,9 +51,18 @@ final class HistogramTests: XCTestCase {
             semaphore.signal()
         }
         semaphore.wait()
+        semaphore.wait()
         try elg.syncShutdownGracefully()
-        XCTAssertTrue(histogram.collect().contains("my_histogram_count 4000.0"))
-        XCTAssertTrue(histogram.collect().contains("my_histogram_sum 4000.0"))
+
+        let output = histogram.collect()
+        XCTAssertTrue(output.contains("my_histogram_count 4000.0"))
+        XCTAssertTrue(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"#))
+
+        XCTAssertTrue(output.contains(#"my_histogram_count{myValue="2"} 2000.0"#))
+        XCTAssertTrue(output.contains(#"my_histogram_sum{myValue="2"} 2000.0"#))
     }
 
     func testHistogramSwiftMetrics() {