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jorangreef/test-fs-watch-latency.js

Created November 24, 2015 10:51
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test-fs-watch-latency.js
var fs = require('fs');
var path = require('path');
/*
This test is designed for Windows, and tests whether changed folder events
are emitted on time or after several seconds delay (up to 40 seconds or more).
This requires renaming a file at least two subfolders deep relative to the
watched folder. Renaming a file only one subfolder deep will not reproduce
the slow behavior.
After renaming [watched]/a/b/source to [watched]/target we expect these path
events to be emitted fairly close in time to each other, at least a few 100ms:
null - this is for the removed source path (null for fs.watch on Windows)
target - this is for the created target path (there may be several of these)
a\b - this is for the changed subfolder path from which the source was removed
What happens instead when the bug is triggered:
"null" and "target" are emitted shortly after renaming.
"a\b" is emitted several seconds later, even tens of seconds after renaming.
Reproducible at least on Windows 10 in a Parallels VM.
On Windows 7 in a Parallels VM, only two "target" events are received.
"null" and "a\b" are never emitted.
*/
var watched = path.join(process.cwd(), 'test-fs-watch-latency-directory');
var a = path.join(watched, 'a');
var b = path.join(watched, 'a', 'b');
var source = path.join(b, 'source');
var target = path.join(watched, 'target');
function log(string) {
console.log(new Date().toISOString() + ' ' + string);
}
function relative(to) {
if (to === watched) {
var base = process.cwd();
} else {
var base = process.cwd();
}
return '.' + path.sep + path.relative(base, to);
}
function prepare(end) {
log('preparing directory structure...');
log('fs.mkdir ' + relative(watched));
fs.mkdir(watched,
function(error) {
if (error && error.code === 'EEXIST') error = null;
if (error) return end(error);
log('fs.mkdir ' + relative(a));
fs.mkdir(a,
function(error) {
if (error && error.code === 'EEXIST') error = null;
if (error) return end(error);
log('fs.mkdir ' + relative(b));
fs.mkdir(b,
function(error) {
if (error && error.code === 'EEXIST') error = null;
if (error) return end(error);
unlink(
function(error) {
if (error) return end(error);
// File size appears to be irrelevant to the test.
log('fs.writeFile ' + relative(source) + ' (0 bytes)');
fs.writeFile(source, '',
function(error) {
if (error) return end(error);
var message = '';
message += 'waiting 10 seconds before creating ';
message += 'fs.watch to prevent spurious events...';
log(message);
setTimeout(end, 10000);
}
);
}
);
}
);
}
);
}
);
}
function unlink(end) {
log('fs.unlink ' + relative(source));
fs.unlink(source,
function(error) {
if (error && error.code === 'ENOENT') error = null;
if (error) return end(error);
log('fs.unlink ' + relative(target));
fs.unlink(target,
function(error) {
if (error && error.code === 'ENOENT') error = null;
if (error) return end(error);
end();
}
);
}
);
}
function cleanup() {
function end(error) {
if (error) throw error;
process.exit();
}
log('cleaning up...');
setTimeout(
function() {
if (watch) watch.close();
unlink(
function(error) {
if (error) return end(error);
log('fs.rmdir ' + relative(b));
fs.rmdir(b,
function(error) {
if (error && error.code === 'ENOENT') error = null;
if (error) return end(error);
log('fs.rmdir ' + relative(a));
fs.rmdir(a,
function(error) {
if (error && error.code === 'ENOENT') error = null;
if (error) return end(error);
log('fs.rmdir ' + relative(watched));
fs.rmdir(watched,
function(error) {
if (error && error.code === 'ENOENT') error = null;
if (error) return end(error);
end();
}
);
}
);
}
);
}
);
},
3000 // Try not to cause an alert on Windows if user has a/b open in Explorer.
);
}
function onChange(binaryPath) {
log('change event: ' + binaryPath);
if (received === undefined) {
if (binaryPath === path.join('a', 'b') || binaryPath === path.join('a', 'b', 'source')) {
received = Date.now();
log('received "' + binaryPath + '" changed event after ' + (received - issued) + 'ms.');
cleanup();
}
}
}
var watch;
var issued;
var received;
prepare(
function(error) {
if (error) throw error;
log('creating recursive fs.watch on ' + relative(watched));
watch = fs.watch(watched, { recursive: true });
watch.on('change',
function(change, binaryPath) {
onChange(binaryPath);
}
);
watch.on('error',
function(error) {
throw error;
}
);
log('waiting 10 seconds for fs.watch to open handle...');
setTimeout(
function() {
log('renaming source > target...');
log('fs.rename ' + relative(source) + ' > ' + relative(target));
setTimeout(
function() {
if (received === undefined) {
log('still waiting for source directory/file changed event after 3 seconds...');
log('try navigating to "' + relative(b) + '" in Windows Explorer to trigger the delayed event...');
log('going to wait for at most 5 minutes...');
}
},
3 * 1000
);
setTimeout(
function() {
if (received === undefined) {
log('still waiting for source directory/file changed event after 5 minutes...');
cleanup();
}
},
5 * 60 * 1000 // It can really take this long on Windows 10 (although Windows 7 never gets it).
);
issued = Date.now();
fs.rename(source, target,
function(error) {
if (error) throw error;
}
);
},
10000
);
}
);
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