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test: refactor flaky net-error-twice #4062

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test: refactor flaky net-error-twice #4062

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test: refactor flaky net-error-twice
Trott Nov 28, 2015
c30dc10
fixup: windows-specific handling
Trott Nov 29, 2015
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32 changes: 18 additions & 14 deletions test/parallel/test-net-error-twice.js
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Original file line number Diff line number Diff line change
@@ -1,33 +1,37 @@
'use strict';
var common = require('../common');
var assert = require('assert');
var net = require('net');
const common = require('../common');
const assert = require('assert');
const net = require('net');

var buf = new Buffer(10 * 1024 * 1024);
const buf = new Buffer(10 * 1024 * 1024);

buf.fill(0x62);

var errs = [];

var srv = net.createServer(function onConnection(conn) {
conn.write(buf);
const srv = net.createServer(function onConnection(conn) {
if (common.isWindows) {
// Windows-specific handling. See:
// * https://github.com/nodejs/node/pull/4062
// * https://github.com/nodejs/node/issues/4057
setTimeout(() => { conn.write(buf); }, 100);
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@bnoordhuis bnoordhuis Nov 30, 2015

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Why is the delay necessary?

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@Trott Trott Nov 30, 2015

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@bnoordhuis Concise-but-naive answer: Without the delay, the test is flaky on Windows 2012 r2 on the CI infrastructure.

Less concise and marginally less naive: In this test, conn.write(buf) is supposed to get an error (either EPIPE or ECONNRESET depending on timing). Unfortunately, on Windows 2012 r2 only, it appears that the call to client.destroy() often returns before the socket is set to emit the error. UPDATE: Actually, I think the problem is that the client connection and server connection callbacks fire in an unpredictable order. On Windows 2012 r2 only, the conn.write() would often not trigger an error and the result was assert.equal(errs.length, 1) firing (because errs.length is 0). I tried setImmediate() and that may have improved things but it did not resolve the flakiness. Using the timeout resolved the flakiness. (I did not experiment with a timeout of less than 100 milliseconds.)

As for the cause of this on Windows 2012 r2, I don't know and would certainly be receptive to some guidance on figuring it out (or someone simply doing the work and identifying the source of the issue). Operating system limitation? Bug in libuv? Bug in socket.destroy? I don't know. I don't have easy access to a Windows 2012 r2 machine. (I could try to run one via VirtualBox, but my laptop resources are kind of limited right now and my weak excuse is that it would probably fill up my disk.)

} else {
conn.write(buf);
}

conn.on('error', function(err) {
errs.push(err);
if (errs.length > 1 && errs[0] === errs[1])
assert(false, 'We should not be emitting the same error twice');
if (errs.length > 1)
assert(errs[0] !== errs[1], 'Should not get the same error twice');
});
conn.on('close', function() {
srv.unref();
});
}).listen(common.PORT, function() {
var client = net.connect({ port: common.PORT });

client.on('connect', function() {
client.destroy();
});
const client = net.connect({ port: common.PORT });
client.on('connect', client.destroy);
});

process.on('exit', function() {
console.log(errs);
assert.equal(errs.length, 1);
});