Remove unneeded assertion (#169)

* Remove activity assertion in prepareForClose

motivation: assertion on activity sometimes fails but it turns out it is overly restrictive

changes:
- remove assertion and accept any given activity in prepareForClose

* test closing connections whilst syncShutdown

Co-authored-by: Johannes Weiss <johannesweiss@apple.com>

Author: Trevör

Sources/AsyncHTTPClient/ConnectionPool.swift

@@ -414,7 +414,6 @@ final class ConnectionPool {
             assert(MultiThreadedEventLoopGroup.currentEventLoop == nil,
                    "HTTPClient shutdown on EventLoop unsupported") // calls .wait() so it would crash later anyway
             let (waitersFutures, closeFutures) = self.stateLock.withLock { () -> ([EventLoopFuture<Connection>], [EventLoopFuture<Void>]) in
-                assert(self.state.activity == .opened, "Invalid activity: \(self.state.activity)")
                 // Fail waiters
                 let waitersCopy = self.state.waiters
                 self.state.waiters.removeAll()

Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift

@@ -35,6 +35,7 @@ extension HTTPClientInternalTests {
             ("testChannelAndDelegateOnDifferentEventLoops", testChannelAndDelegateOnDifferentEventLoops),
             ("testResponseConnectionCloseGet", testResponseConnectionCloseGet),
             ("testWeNoticeRemoteClosuresEvenWhenConnectionIsIdleInPool", testWeNoticeRemoteClosuresEvenWhenConnectionIsIdleInPool),
+            ("testWeTolerateConnectionsGoingAwayWhilstPoolIsShuttingDown", testWeTolerateConnectionsGoingAwayWhilstPoolIsShuttingDown),
         ]
     }
 }

Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift

@@ -581,4 +581,46 @@ class HTTPClientInternalTests: XCTestCase {
         XCTAssertEqual(2, sharedStateServerHandler.connectionNumber.load())
         XCTAssertEqual(2, sharedStateServerHandler.requestNumber.load())
     }
+
+    func testWeTolerateConnectionsGoingAwayWhilstPoolIsShuttingDown() {
+        struct NoChannelError: Error {}
+
+        let client = HTTPClient(eventLoopGroupProvider: .createNew)
+        var maybeServersAndChannels: [(HTTPBin, Channel)]?
+        XCTAssertNoThrow(maybeServersAndChannels = try (0..<10).map { _ in
+            let web = HTTPBin()
+            defer {
+                XCTAssertNoThrow(try web.shutdown())
+            }
+
+            let req = try! HTTPClient.Request(url: "http://localhost:\(web.serverChannel.localAddress!.port!)/get",
+                                              method: .GET,
+                                              body: nil)
+            var maybeConnection: ConnectionPool.Connection?
+            XCTAssertNoThrow(try maybeConnection = client.pool.getConnection(for: req,
+                                                                             preference: .indifferent,
+                                                                             on: client.eventLoopGroup.next(),
+                                                                             deadline: nil).wait())
+            guard let connection = maybeConnection else {
+                XCTFail("couldn't make connection")
+                throw NoChannelError()
+            }
+
+            let channel = connection.channel
+            client.pool.release(connection)
+            return (web, channel)
+        })
+
+        guard let serversAndChannels = maybeServersAndChannels else {
+            XCTFail("couldn't open servers")
+            return
+        }
+
+        DispatchQueue.global().async {
+            serversAndChannels.forEach { serverAndChannel in
+                serverAndChannel.1.close(promise: nil)
+            }
+        }
+        XCTAssertNoThrow(try client.syncShutdown())
+    }
 }