Add Meter for in-progress jobs (#139)

* Add Gauge for in-progress jobs

* Whitespace nit

* Move the gauge to the right place

* Make `Gauge` a `Meter` and add test

* Change back job duration timer label

Sources/Queues/QueueWorker.swift

@@ -65,6 +65,11 @@ public struct QueueWorker: Sendable {
             try await $0.didDequeue(jobId: id.string, eventLoop: self.queue.eventLoop).get()
         }
 
+        Meter(
+            label: "jobs.in.progress.meter", 
+            dimensions: [("queueName", self.queue.queueName.string)]
+        ).increment()
+
         try await self.runOneJob(id: id, job: job, jobData: data, logger: logger)
         return true
     }
@@ -122,17 +127,15 @@ public struct QueueWorker: Sendable {
         queue: any Queue,
         error: (any Error)? = nil
     ) {
-        // Checks how long the job took to complete
         Timer(
             label: "\(jobName).jobDurationTimer",
             dimensions: [
                 ("success", error == nil ? "true" : "false"),
                 ("jobName", jobName),
             ],
-            preferredDisplayUnit: .seconds
+            preferredDisplayUnit: .milliseconds
         ).recordNanoseconds(DispatchTime.now().uptimeNanoseconds - startTime)
 
-        // Adds the completed job to a different counter depending on its result
         if error != nil {
             Counter(
                 label: "error.completed.jobs.counter",
@@ -144,5 +147,10 @@ public struct QueueWorker: Sendable {
                 dimensions: [("queueName", queue.queueName.string)]
             ).increment()
         }
+
+        Meter(
+            label: "jobs.in.progress.meter",
+            dimensions: [("queueName", queue.queueName.string)]
+        ).decrement()
     }
 }

Tests/QueuesTests/MetricsTests.swift

@@ -66,6 +66,7 @@ final class MetricsTests: XCTestCase {
         let counter = try XCTUnwrap(self.metrics.counters.first(where: { $0.label == "success.completed.jobs.counter" }))
         let queueNameDimension = try XCTUnwrap(counter.dimensions.first(where: { $0.0 == "queueName" }))
         XCTAssertEqual(queueNameDimension.1, self.app.queues.queue.queueName.string)
+        XCTAssertEqual(counter.lastValue, 1)
     }
 
     func testErroringJobsCounter() async throws {
@@ -86,6 +87,7 @@ final class MetricsTests: XCTestCase {
         let counter = try XCTUnwrap(self.metrics.counters.first(where: { $0.label == "error.completed.jobs.counter" }))
         let queueNameDimension = try XCTUnwrap(counter.dimensions.first(where: { $0.0 == "queueName" }))
         XCTAssertEqual(queueNameDimension.1, self.app.queues.queue.queueName.string)
+        XCTAssertEqual(counter.lastValue, 1)
     }
 
     func testDispatchedJobsCounter() async throws {
@@ -110,5 +112,28 @@ final class MetricsTests: XCTestCase {
         let jobNameDimension = try XCTUnwrap(counter.dimensions.first(where: { $0.0 == "jobName" }))
         XCTAssertEqual(queueNameDimension.1, self.app.queues.queue.queueName.string)
         XCTAssertEqual(jobNameDimension.1, MyAsyncJob.name)
+        XCTAssertEqual(counter.totalValue, 2)
+    }
+
+    func testInProgressJobsGauge() async throws {
+        let promise = self.app.eventLoopGroup.next().makePromise(of: Void.self)
+        self.app.queues.add(MyAsyncJob(promise: promise))
+
+        self.app.get("foo") { req async throws in
+            try await req.queue.dispatch(MyAsyncJob.self, .init(foo: "bar"))
+            return "done"
+        }
+
+        try await self.app.testable().test(.GET, "foo") { res async in
+            XCTAssertEqual(res.status, .ok)
+            XCTAssertEqual(res.body.string, "done")
+        }
+
+        try await self.app.queues.queue.worker.run()
+
+        let meter = try XCTUnwrap(self.metrics.meters.first(where: { $0.label == "jobs.in.progress.meter" }))
+        let queueNameDimension = try XCTUnwrap(meter.dimensions.first(where: { $0.0 == "queueName" }))
+        XCTAssertEqual(queueNameDimension.1, self.app.queues.queue.queueName.string)
+        XCTAssertEqual(meter.values, [1, 0])
     }
 }