René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"child_process.spawn() is unreliable on Promise.all() completion","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-->\r\n\r\n* **Version**:\r\n\r\n```\r\n$ node -v\r\nv10.12.0\r\n```\r\n\r\n* **Platform**:\r\n\r\n```\r\n$ uname -a\r\nLinux ip-172-31-8-12 4.15.0-1021-aws #21-Ubuntu SMP Tue Aug 28 10:23:07 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux\r\n```\r\n\r\n* **Subsystem**:\r\n\r\n```\r\n...\r\nvar spawn = require('child_process').spawn;\r\n...\r\n```\r\n\r\n\u003c!-- Please provide more details below this comment. -->\r\n\r\n* **Setup**:\r\n\r\nI have a few promises that I fulfill with `Promise.all()`. \r\n\r\nWhen fulfilled, within the `finally()` block, I try to spawn a process and detach it.\r\n\r\n```\r\nvar p1 = new Promise(function(resolve, reject) { ... });\r\nvar p2 = new Promise(function(resolve, reject) { ... });\r\nvar p3 = new Promise(function(resolve, reject) { ... });\r\n...\r\nPromise.all([p1, p2, p3, ...])\r\n    .then(function(vals) {\r\n    })\r\n    .catch(function(errs) {\r\n        if (errs)\r\n            console.log(errs);\r\n    })\r\n    .finally(function() {\r\n        var myScript = path.join(__dirname, '..', 'bin', 'myScript.js');\r\n        var myScriptSpawn = spawn(myScript\r\n            ['-a', '-b', '-c', ...],\r\n            {\r\n                stdio : 'ignore',\r\n                detached : true,\r\n                shell : '/usr/bin/node',\r\n                env : process.env\r\n            });\r\n        myScriptSpawn.unref();\r\n    })\r\n```\r\n\r\n* **Problem**:\r\n\r\nOccasionally the process is spawned, occasionally the process is not spawned. This fails approximately 33% of the time. No warning, exception, or error rises when spawn fails.\r\n\r\n* **Debugging**:\r\n\r\nThe process `myScript` always works if run manually from the `bash` shell, outside of `node`. The process does not get spawned reliably when attempted within `Promise.all()` within `node`. Moving the function out of the `Promise.all()` fulfillment completion stage seems to work consistently.","author":{"url":"https://github.com/alexpreynolds","@type":"Person","name":"alexpreynolds"},"datePublished":"2018-10-11T19:53:05Z","url":"https://github.com/nodejs/node/issues/23428"}