René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"test-cluster-net-listen-ipv6only-none is unreliable/flaky","articleBody":"\u003c!--\r\nThank you for reporting a possible bug in Node.js.\r\n\r\nPlease fill in as much of the template below as you can.\r\n\r\nVersion: output of `node -v`\r\nPlatform: output of `uname -a` (UNIX), or version and 32 or 64-bit (Windows)\r\nSubsystem: if known, please specify the affected core module name\r\n\r\nIf possible, please provide code that demonstrates the problem, keeping it as\r\nsimple and free of external dependencies as you can.\r\n--\u003e\r\n\r\n* **Version**: 13.0.0-pre (master branch)\r\n* **Platform**: all, although observed on various Linux in CI\r\n* **Subsystem**: cluster test\r\n\r\n\u003c!-- Please provide more details below this comment. --\u003e\r\n\r\ntest-cluster-net-listen-ipv6only-none has faulty logic in its Countdown callback. The check there assumes that if a port is unavailable for IPv4 but available for IPv6, that the operating system won't supply that port for IPv6. This is apparently incorrect as seen in https://ci.nodejs.org/job/node-test-commit-linux/nodes=centos7-64-gcc6/29869/testReport/junit/(root)/test/parallel_test_cluster_net_listen_ipv6only_none/:\r\n\r\n```console\r\nError: listen EADDRINUSE: address already in use 0.0.0.0:44400\r\n    at Server.setupListenHandle [as _listen2] (net.js:1298:14)\r\n    at listenInCluster (net.js:1346:12)\r\n    at doListen (net.js:1485:7)\r\n    at processTicksAndRejections (internal/process/task_queues.js:81:21)\r\nEmitted 'error' event on Server instance at:\r\n    at emitErrorNT (net.js:1325:8)\r\n    at processTicksAndRejections (internal/process/task_queues.js:80:21) {\r\n  code: 'EADDRINUSE',\r\n  errno: -98,\r\n  syscall: 'listen',\r\n  address: '0.0.0.0',\r\n  port: 44400\r\n}\r\n```\r\n\r\nOne option to fix it would be to remove the check entirely. But then we're perhaps not checking that it's not opening the port on IPv4, which is part of the test.\r\n\r\nIn my opinion, a better option would be to switch to using `common.PORT` rather than an operating-system-allocated port. That would mean moving the test to `sequential`. \r\n\r\nWe'd also want to check the other tests in `parallel` that use `ipv6Only` to make sure they don't suffer from the same issue.","author":{"url":"https://github.com/Trott","@type":"Person","name":"Trott"},"datePublished":"2019-09-23T20:47:12.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/29679/node/issues/29679"}