From 9f76fd71c0ee9c6af48f523ae2b71ab1be6fbaf7 Mon Sep 17 00:00:00 2001
From: adtrevor <trevor.annedenise@icloud.com>
Date: Fri, 13 Mar 2020 06:48:33 +0100
Subject: [PATCH] Add testProxyStreamingNoDeadlock test

Because of there is a maximum number of concurrent connections per host
it is possible for the client to deadlock itself when making requests
with a streamed body if the body data is itself requested from the same
host.

If we reach the maximum number of concurrent requests for a certain
host, and if all active tasks use a streamed body that obtains its data
from requests to the same host, then the bodies will never be obtained as
the requests they need to make will be put on a queue whose ability to
dequeue them depends on their very result -> deadlock.
---
 .../HTTPClientInternalTests+XCTest.swift      |  1 +
 .../HTTPClientInternalTests.swift             | 34 +++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift
index 870ddfc37..a95b21304 100644
--- a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift
+++ b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests+XCTest.swift
@@ -29,6 +29,7 @@ extension HTTPClientInternalTests {
             ("testBadHTTPRequest", testBadHTTPRequest),
             ("testHTTPPartsHandlerMultiBody", testHTTPPartsHandlerMultiBody),
             ("testProxyStreaming", testProxyStreaming),
+            ("testProxyStreamingNoDeadlock", testProxyStreamingNoDeadlock),
             ("testProxyStreamingFailure", testProxyStreamingFailure),
             ("testUploadStreamingBackpressure", testUploadStreamingBackpressure),
             ("testRequestURITrailingSlash", testRequestURITrailingSlash),
diff --git a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift
index 9288814c6..58f92b529 100644
--- a/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift
+++ b/Tests/AsyncHTTPClientTests/HTTPClientInternalTests.swift
@@ -133,6 +133,40 @@ class HTTPClientInternalTests: XCTestCase {
         XCTAssertEqual("id: 0id: 1id: 2id: 3id: 4id: 5id: 6id: 7id: 8id: 9", data.data)
     }
 
+    func testProxyStreamingNoDeadlock() throws {
+        let httpBin = HTTPBin()
+        let httpClient = HTTPClient(eventLoopGroupProvider: .createNew)
+        defer {
+            XCTAssertNoThrow(try httpClient.syncShutdown(requiresCleanClose: true))
+            XCTAssertNoThrow(try httpBin.shutdown())
+        }
+
+        let goSignalPromise = httpClient.eventLoopGroup.next().makePromise(of: Void.self)
+        let goSignal = goSignalPromise.futureResult
+
+        let body: HTTPClient.Body = .stream(length: 50) { writer in
+            goSignal.flatMap {
+                httpClient.get(url: "http://localhost/(httpBin.port)/get")
+            }.flatMap { _ in
+                writer.write(IOData.byteBuffer(.of(bytes: .init(repeating: 0, count: 50))))
+            }
+        }
+
+        var allRequests = [EventLoopFuture<HTTPClient.Response>]()
+
+        // Make sure to exceed maximum number of concurrent connections
+        for _ in 1...50 {
+            allRequests.append(httpClient.post(url: "http://localhost/(httpBin.port)/post", body: body))
+        }
+
+        // Now allow requests to actually send their body data
+        goSignalPromise.succeed(())
+
+        let everythingSucceeded = EventLoopFuture<HTTPClient.Response>.andAllSucceed(allRequests, on: httpClient.eventLoopGroup.next())
+
+        XCTAssertNoThrow(try everythingSucceeded.timeout(after: .seconds(5)).wait())
+    }
+
     func testProxyStreamingFailure() throws {
         let httpBin = HTTPBin()
         let httpClient = HTTPClient(eventLoopGroupProvider: .createNew)