SWIFT-1015 Only create monitoring events if they are being consumed (#531)

Author: kmahar

Sources/MongoSwift/APM.swift

@@ -24,11 +24,18 @@ private protocol MongoSwiftEvent {
     associatedtype MongocEventType: MongocEvent
     associatedtype PublishableEventType: Publishable
 
+    static var monitoringComponent: MonitoringComponent { get }
+
     init(mongocEvent: MongocEventType)
 
     func toPublishable() -> PublishableEventType
 }
 
+/// Indicates which type of monitoring an event is associated with.
+private enum MonitoringComponent {
+    case command, sdam
+}
+
 /// A protocol for libmongoc event wrappers to implement.
 private protocol MongocEvent {
     init(_ eventPtr: OpaquePointer)
@@ -117,6 +124,8 @@ public struct CommandStartedEvent: MongoSwiftEvent, CommandEventProtocol {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .command }
+
     /// The command.
     public let command: BSONDocument
 
@@ -166,6 +175,8 @@ public struct CommandSucceededEvent: MongoSwiftEvent, CommandEventProtocol {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .command }
+
     /// The execution time of the event, in microseconds.
     public let duration: Int
 
@@ -216,6 +227,8 @@ public struct CommandFailedEvent: MongoSwiftEvent, CommandEventProtocol {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .command }
+
     /// The execution time of the event, in microseconds.
     public let duration: Int
 
@@ -304,6 +317,8 @@ public struct ServerDescriptionChangedEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// The connection ID (host/port pair) of the server.
     public let serverAddress: ServerAddress
 
@@ -339,6 +354,8 @@ public struct ServerOpeningEvent: MongoSwiftEvent {
     fileprivate struct MongocServerOpeningEvent: MongocEvent {
         fileprivate let ptr: OpaquePointer
 
+        fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
         fileprivate init(_ eventPtr: OpaquePointer) {
             self.ptr = eventPtr
         }
@@ -348,6 +365,8 @@ public struct ServerOpeningEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// The connection ID (host/port pair) of the server.
     public let serverAddress: ServerAddress
 
@@ -374,6 +393,8 @@ public struct ServerClosedEvent: MongoSwiftEvent {
     fileprivate struct MongocServerClosedEvent: MongocEvent {
         fileprivate let ptr: OpaquePointer
 
+        fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
         fileprivate init(_ eventPtr: OpaquePointer) {
             self.ptr = eventPtr
         }
@@ -383,6 +404,8 @@ public struct ServerClosedEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// The connection ID (host/port pair) of the server.
     public let serverAddress: ServerAddress
 
@@ -418,6 +441,8 @@ public struct TopologyDescriptionChangedEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// A unique identifier for the topology.
     public let topologyID: BSONObjectID
 
@@ -458,6 +483,8 @@ public struct TopologyOpeningEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// A unique identifier for the topology.
     public let topologyID: BSONObjectID
 
@@ -489,6 +516,8 @@ public struct TopologyClosedEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// A unique identifier for the topology.
     public let topologyID: BSONObjectID
 
@@ -521,6 +550,8 @@ public struct ServerHeartbeatStartedEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// The address of the server.
     public let serverAddress: ServerAddress
 
@@ -548,6 +579,8 @@ public struct ServerHeartbeatSucceededEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// The execution time of the event, in microseconds.
     public let duration: Int
 
@@ -584,6 +617,8 @@ public struct ServerHeartbeatFailedEvent: MongoSwiftEvent {
         }
     }
 
+    fileprivate static var monitoringComponent: MonitoringComponent { .sdam }
+
     /// The execution time of the event, in microseconds.
     public let duration: Int
 
@@ -683,19 +718,19 @@ private func publishEvent<T: MongoSwiftEvent>(type: T.Type, eventPtr: OpaquePoin
     }
     let client = Unmanaged<MongoClient>.fromOpaque(context).takeUnretainedValue()
 
-    let event = type.init(mongocEvent: mongocEvent)
-
-    // TODO: SWIFT-524: remove workaround for CDRIVER-3256
-    if let tdChanged = event as? TopologyDescriptionChangedEvent,
-        tdChanged.previousDescription == tdChanged.newDescription {
-        return
-    }
-
-    if let sdChanged = event as? ServerDescriptionChangedEvent,
-        sdChanged.previousDescription == sdChanged.newDescription {
-        return
+    // only create Swift events if handlers are actually registered for this type of event.
+    switch type.monitoringComponent {
+    case .sdam:
+        guard !client.sdamEventHandlers.isEmpty else {
+            return
+        }
+    case .command:
+        guard !client.commandEventHandlers.isEmpty else {
+            return
+        }
     }
 
+    let event = type.init(mongocEvent: mongocEvent)
     event.toPublishable().publish(to: client)
 }
 

Tests/MongoSwiftSyncTests/SDAMTests.swift

@@ -46,23 +46,27 @@ final class SDAMTests: MongoSwiftTestCase {
             return
         }
 
-        expect(receivedEvents.count).to(equal(4))
+        expect(receivedEvents.count).to(equal(5))
         expect(receivedEvents[0].topologyOpeningValue).toNot(beNil())
-        expect(receivedEvents[1].serverOpeningValue).toNot(beNil())
-        expect(receivedEvents[2].serverDescriptionChangedValue).toNot(beNil())
-        expect(receivedEvents[3].topologyDescriptionChangedValue).toNot(beNil())
+        expect(receivedEvents[1].topologyDescriptionChangedValue).toNot(beNil())
+        expect(receivedEvents[2].serverOpeningValue).toNot(beNil())
+        expect(receivedEvents[3].serverDescriptionChangedValue).toNot(beNil())
+        expect(receivedEvents[4].topologyDescriptionChangedValue).toNot(beNil())
 
         let event0 = receivedEvents[0].topologyOpeningValue!
 
-        let event1 = receivedEvents[1].serverOpeningValue!
+        let event1 = receivedEvents[1].topologyDescriptionChangedValue!
         expect(event1.topologyID).to(equal(event0.topologyID))
-        expect(event1.serverAddress).to(equal(hostAddress))
 
-        let event2 = receivedEvents[2].serverDescriptionChangedValue!
+        let event2 = receivedEvents[2].serverOpeningValue!
         expect(event2.topologyID).to(equal(event1.topologyID))
+        expect(event2.serverAddress).to(equal(hostAddress))
 
-        let prevServer = event2.previousDescription
-        let newServer = event2.newDescription
+        let event3 = receivedEvents[3].serverDescriptionChangedValue!
+        expect(event3.topologyID).to(equal(event2.topologyID))
+
+        let prevServer = event3.previousDescription
+        let newServer = event3.newDescription
 
         expect(prevServer.address).to(equal(hostAddress))
         expect(newServer.address).to(equal(hostAddress))
@@ -73,11 +77,11 @@ final class SDAMTests: MongoSwiftTestCase {
         expect(prevServer.type).to(equal(.unknown))
         expect(newServer.type).to(equal(.standalone))
 
-        let event3 = receivedEvents[3].topologyDescriptionChangedValue!
-        expect(event3.topologyID).to(equal(event2.topologyID))
+        let event4 = receivedEvents[4].topologyDescriptionChangedValue!
+        expect(event4.topologyID).to(equal(event3.topologyID))
 
-        let prevTopology = event3.previousDescription
-        let newTopology = event3.newDescription
+        let prevTopology = event4.previousDescription
+        let newTopology = event4.newDescription
 
         expect(prevTopology.type).to(equal(.unknown))
         expect(newTopology.type).to(equal(.single))