Make AppMetrics dependency based

Author: finestructure

Sources/App/Core/AppMetrics.swift

@@ -21,20 +21,6 @@ import Vapor
 
 enum AppMetrics {
 
-    static let initialized = Mutex(false)
-
-    static func bootstrap() {
-        // prevent tests from boostrapping multiple times
-        guard !initialized.withLock({ $0 }) else { return }
-        initialized.withLock {
-            let client = PrometheusClient()
-            MetricsSystem.bootstrap(PrometheusMetricsFactory(client: client))
-            $0 = true
-        }
-    }
-
-    // metrics
-
     static var analyzeCandidatesCount: PromGauge<Int>? {
         gauge("spi_analyze_candidates_count")
     }
@@ -155,13 +141,13 @@ enum AppMetrics {
 extension AppMetrics {
 
     static func counter<V: Numeric>(_ name: String) -> PromCounter<V>? {
-        try? MetricsSystem.prometheus()
-            .createCounter(forType: V.self, named: name)
+        @Dependency(\.prometheus) var prometheus
+        return prometheus?.createCounter(forType: V.self, named: name)
     }
 
     static func gauge<V: DoubleRepresentable>(_ name: String) -> PromGauge<V>? {
-        try? MetricsSystem.prometheus()
-            .createGauge(forType: V.self, named: name)
+        @Dependency(\.prometheus) var prometheus
+        return prometheus?.createGauge(forType: V.self, named: name)
     }
 
 }
@@ -176,14 +162,19 @@ extension AppMetrics {
     static func push(client: Client, jobName: String) async throws {
         @Dependency(\.environment) var environment
         @Dependency(\.logger) var logger
+        @Dependency(\.prometheus) var prometheus
+
+        guard let prometheus else {
+            throw AppError.genericError(nil, "Prometheus client unavailable (nil)")
+        }
 
         guard let pushGatewayUrl = environment.metricsPushGatewayUrl() else {
             throw AppError.envVariableNotSet("METRICS_PUSHGATEWAY_URL")
         }
         let url = URI(string: "\(pushGatewayUrl)/metrics/job/\(jobName)")
 
         do {
-            let metrics: String = try await MetricsSystem.prometheus().collect()
+            let metrics: String = await prometheus.collect()
             _ = try await client.post(url) { req in
                 // append "\n" to avoid
                 //   text format parsing error in line 4: unexpected end of input stream

Sources/App/Core/Dependencies/AppMetricsClient.swift

@@ -0,0 +1,54 @@
+// Copyright Dave Verwer, Sven A. Schmidt, and other contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Dependencies
+import Metrics
+import Synchronization
+@preconcurrency import Prometheus
+
+
+enum AppMetricsClient {
+    private static let initialized = Mutex(false)
+
+    static func bootstrap() {
+        guard !initialized.withLock({ $0 }) else { return }
+        initialized.withLock {
+            let client = PrometheusClient()
+            MetricsSystem.bootstrap(PrometheusMetricsFactory(client: client))
+            $0 = true
+        }
+    }
+}
+
+
+extension AppMetricsClient: DependencyKey {
+    static var liveValue: PrometheusClient? {
+        try? MetricsSystem.prometheus()
+    }
+}
+
+
+extension AppMetricsClient: TestDependencyKey {
+    static var testValue: PrometheusClient? {
+        unimplemented("testValue"); return nil
+    }
+}
+
+
+extension DependencyValues {
+    public var prometheus: PrometheusClient? {
+        get { self[AppMetricsClient.self] }
+        set { self[AppMetricsClient.self] = newValue }
+    }
+}

Sources/App/configure.swift

@@ -365,7 +365,7 @@ public func configure(_ app: Application, databasePort: Int? = nil) async throws
     try routes(app)
 
     // bootstrap app metrics
-    AppMetrics.bootstrap()
+    AppMetricsClient.bootstrap()
 
     return host
 }

Sources/App/routes.swift

@@ -211,7 +211,8 @@ func routes(_ app: Application) throws {
 
     do {  // Metrics
         app.get("metrics") { req -> String in
-            try await MetricsSystem.prometheus().collect()
+            @Dependency(\.prometheus) var prometheus
+            return await prometheus?.collect() ?? ""
         }
     }
 }

Tests/AppTests/AllTests.swift

@@ -16,7 +16,10 @@ import Testing
 import Dependencies
 
 
-@Suite(.dependency(\.date.now, .t0)) struct AllTests { }
+@Suite(
+    .dependency(\.date.now, .t0),
+    .dependency(\.prometheus, .init())
+) struct AllTests { }
 
 
 extension AllTests {

Tests/AppTests/MetricsTests.swift

@@ -164,7 +164,6 @@ extension AllTests.MetricsTests {
 
                 // validation
                 #expect((AppMetrics.buildTriggerDurationSeconds?.get()) ?? 0 > 0)
-                print(AppMetrics.buildTriggerDurationSeconds!.get())
             }
         }
     }