Get metric promises (#12)

* Update to promises

* Minor cleanup

* NIO 2

* Byte Buffers & no promises

* Move ByteBuffer methods to extensions and (temp) remove Swift 4 tests

* NIO Bump & docs

* Add some helpers & update test wording

Author: MrLotU

Package.resolved

@@ -14,12 +14,12 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-metrics.git", from: "1.0.0"),
-        .package(url: "https://github.com/apple/swift-nio.git", Version("1.0.0") ..< Version("3.0.0")),
+        .package(url: "https://github.com/apple/swift-nio.git", from: "2.0.0"),
     ],
     targets: [
         .target(
             name: "Prometheus",
-            dependencies: ["CoreMetrics", "NIOConcurrencyHelpers"]),
+            dependencies: ["CoreMetrics", "NIOConcurrencyHelpers", "NIO"]),
         .target(
             name: "PrometheusExample",
             dependencies: ["Prometheus", "Metrics"]),

Package.swift

@@ -67,7 +67,6 @@ public class PromCounter<NumType: Numeric, Labels: MetricLabels>: PromMetric, Pr
         }
     }
 
-    
     /// Increments the Counter
     ///
     /// - Parameters:

Sources/Prometheus/MetricTypes/Counter.swift

@@ -1,3 +1,5 @@
+import NIO
+
 /// Different types of metrics supported by SwiftPrometheus
 public enum PromMetricType: String {
     /// See `PromCounter`
@@ -34,6 +36,16 @@ public protocol PromMetric {
     func collect() -> String
 }
 
+extension PromMetric {
+    /// Helper method to record metrics into a `ByteBuffer` directly
+    ///
+    /// - Parameters:
+    ///     - buffer: `ByteBuffer` to collect into
+    func collect(into buffer: inout ByteBuffer) {
+        buffer.writeString(collect())
+    }
+}
+
 /// Adding a prometheus instance to all metrics
 internal protocol PrometheusHandled {
     /// Promtheus client handling this metric

Sources/Prometheus/MetricTypes/PromMetric.swift

@@ -1,4 +1,5 @@
 import NIOConcurrencyHelpers
+import NIO
 
 /// Prometheus class
 ///
@@ -22,14 +23,47 @@ public class PrometheusClient {
         self.lock = Lock()
     }
 
+    // MARK: - Collection
+    
     /// Creates prometheus formatted metrics
     ///
-    /// - Returns: Newline separated string with metrics for all Metric Trackers of this Prometheus instance
-    public func collect() -> String {
-        return self.lock.withLock {
-            return self.metrics.map { $0.collect() }.joined(separator: "\n")
+    /// - Parameters:
+    ///     - succeed: Closure that will be called with a newline separated string with metrics for all Metrics this PrometheusClient handles
+    public func collect(_ succeed: (String) -> ()) {
+        self.lock.withLock {
+            succeed(self.metrics.map { $0.collect() }.joined(separator: "\n"))
+        }
+    }
+    
+    /// Creates prometheus formatted metrics
+    ///
+    /// - Parameters:
+    ///     - promise: Promise that will succeed with a newline separated string with metrics for all Metrics this PrometheusClient handles
+    public func collect(into promise: EventLoopPromise<String>) {
+        collect(promise.succeed)
+    }
+    
+    /// Creates prometheus formatted metrics
+    ///
+    /// - Parameters:
+    ///     - succeed: Closure that will be called with a `ByteBuffer` containing a newline separated string with metrics for all Metrics this PrometheusClient handles
+    public func collect(_ succeed: (ByteBuffer) -> ()) {
+        self.lock.withLock {
+            var buffer = ByteBufferAllocator().buffer(capacity: 0)
+            self.metrics.forEach {
+                $0.collect(into: &buffer)
+            }
+            succeed(buffer)
         }
     }
+
+    /// Creates prometheus formatted metrics
+    ///
+    /// - Parameters:
+    ///     - promise: Promise that will succeed with a `ByteBuffer` containing a newline separated string with metrics for all Metrics this PrometheusClient handles
+    public func collect(into promise: EventLoopPromise<ByteBuffer>) {
+        collect(promise.succeed)
+    }
 
     // MARK: - Metric Access
 

Sources/Prometheus/Prometheus.swift

@@ -1,5 +1,6 @@
 import Prometheus
 import Metrics
+import NIO
 
 let myProm = PrometheusClient()
 
@@ -111,5 +112,11 @@ for _ in 0...Int.random(in: 100...1000) {
    summary.observe(Double.random(in: 0...10000), SummaryThing("/test"))
 }
 
-let metrics = try! MetricsSystem.prometheus().collect()
-print(metrics)
+let elg = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+let prom = elg.next().makePromise(of: String.self)
+
+prom.futureResult.whenSuccess {
+    print($0)
+}
+
+try! MetricsSystem.prometheus().collect(prom.succeed)

Sources/PrometheusExample/main.swift

@@ -1,27 +1,37 @@
 import XCTest
+import NIO
 @testable import Prometheus
 @testable import CoreMetrics
 
 final class PrometheusMetricsTests: XCTestCase {
 
     var prom: PrometheusClient!
+    var group: EventLoopGroup!
+    var eventLoop: EventLoop {
+        return group.next()
+    }
 
     override func setUp() {
         self.prom = PrometheusClient()
+        self.group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
         MetricsSystem.bootstrapInternal(prom)
     }
 
     override func tearDown() {
         self.prom = nil
+        try! self.group.syncShutdownGracefully()
     }
 
     func testCounter() {
         let counter = Counter(label: "my_counter")
         counter.increment(by: 10)
         let counterTwo = Counter(label: "my_counter", dimensions: [("myValue", "labels")])
         counterTwo.increment(by: 10)
-
-        XCTAssertEqual(prom.collect(), """
+        
+        let promise = self.eventLoop.makePromise(of: String.self)
+        prom.collect(promise.succeed)
+        
+        XCTAssertEqual(try! promise.futureResult.wait(), """
         # TYPE my_counter counter
         my_counter 10
         my_counter{myValue=\"labels\"} 10
@@ -38,7 +48,10 @@ final class PrometheusMetricsTests: XCTestCase {
         let gaugeTwo = Gauge(label: "my_gauge", dimensions: [("myValue", "labels")])
         gaugeTwo.record(10)
 
-        XCTAssertEqual(prom.collect(), """
+        let promise = self.eventLoop.makePromise(of: String.self)
+        prom.collect(promise.succeed)
+        
+        XCTAssertEqual(try! promise.futureResult.wait(), """
         # TYPE my_gauge gauge
         my_gauge 20.0
         my_gauge{myValue=\"labels\"} 10.0
@@ -54,7 +67,10 @@ final class PrometheusMetricsTests: XCTestCase {
         let recorderTwo = Recorder(label: "my_histogram", dimensions: [("myValue", "labels")])
         recorderTwo.record(3)
 
-        XCTAssertEqual(prom.collect(), """
+        let promise = self.eventLoop.makePromise(of: String.self)
+        prom.collect(promise.succeed)
+        
+        XCTAssertEqual(try! promise.futureResult.wait(), """
         # TYPE my_histogram histogram
         my_histogram_bucket{le="0.005"} 0.0
         my_histogram_bucket{le="0.01"} 0.0
@@ -104,7 +120,10 @@ final class PrometheusMetricsTests: XCTestCase {
         let summaryTwo = Timer(label: "my_summary", dimensions: [("myValue", "labels")])
         summaryTwo.recordNanoseconds(123)
 
-        XCTAssertEqual(prom.collect(), """
+        let promise = self.eventLoop.makePromise(of: String.self)
+        prom.collect(promise.succeed)
+        
+        XCTAssertEqual(try! promise.futureResult.wait(), """
         # TYPE my_summary summary
         my_summary{quantile="0.01"} 1.0
         my_summary{quantile="0.05"} 1.0
@@ -131,7 +150,27 @@ final class PrometheusMetricsTests: XCTestCase {
         let counter = Counter(label: "my_counter")
         counter.increment()
         counter.destroy()
-        XCTAssertEqual(prom.collect(), "")
+        let promise = self.eventLoop.makePromise(of: String.self)
+        prom.collect(promise.succeed)
+        
+        XCTAssertEqual(try! promise.futureResult.wait(), "")
+    }
+    
+    func testBuffer() {
+        let counter = Counter(label: "my_counter")
+        counter.increment(by: 10)
+        let counterTwo = Counter(label: "my_counter", dimensions: [("myValue", "labels")])
+        counterTwo.increment(by: 10)
+        
+        let promise = self.eventLoop.makePromise(of: ByteBuffer.self)
+        prom.collect(promise.succeed)
+        var buffer = try! promise.futureResult.wait()
+        
+        XCTAssertEqual(buffer.readString(length: buffer.readableBytes), """
+        # TYPE my_counter counter
+        my_counter 10
+        my_counter{myValue=\"labels\"} 10
+        """)
     }
 }
 

Tests/SwiftPrometheusTests/PrometheusMetricsTests.swift

@@ -1,14 +1,6 @@
 version: 2
 
 jobs:
-  swift4:
-    docker:
-      - image: swift:4.2
-    steps:
-      - checkout
-      - run: apt-get update; apt-get install -y libssl-dev zlib1g-dev
-      - run: swift build
-      - run: swift test
   swift5:
     docker:
       - image: swift:5.0
@@ -39,5 +31,4 @@ workflows:
     jobs:
       - bionic
       - bionic-release
-      - swift4
       - swift5