Node.js API pitfalls

Disclaimer ;-)
Doesn't necessarily reflect the views of IBM, or any of
my Node.js collaborators...
1

nextTick
•  [ ] in next tick of the event loop
•  [ ] immediately after A returns
2
process.nextTick(function() {
// Called ...
});

nextTick
•  [x] immediately after A returns
3
process.nextTick(function() {
// Called ...
});

setImmediate
4
setImmediate(function() {
// Called ...
});

setImmediate
•  [x] in next tick of the event loop
5
setImmediate(function() {
// Called ...
});

nextTick vs setImmediate
•  nextTick: adds callback to queue to be called immediately
•  setImmediate: adds callback to queue to be called next tick
6

worker.kill()
7
var cluster = require('cluster');
if (cluster.isMaster) {
cluster.fork()
.on('online', function() {
this.kill('SIGHUP');
})
.on('exit', function() {
console.log('Exit');
});
} else {
process.on('SIGHUP', function() {
console.log('Hup');
});
}

worker.kill()
•  [ ] "Hup"
•  [ ] "Exit"
•  [ ] "Hup" and "Exit"
•  [ ] No output
8
cluster.fork()
})
.on('exit', function() { console.log('Exit'); });
} else {
process.on('SIGHUP', function() { console.log('Hup'); });
}

worker.kill()
•  [ ] "Hup"
•  [x] "Exit"
•  [ ] "Hup" and "Exit"
•  [ ] No output
9
cluster.fork()
})
.on('exit', function() { console.log('Exit'); });
} else {
process.on('SIGHUP', function() { console.log('Hup'); });
}

worker.kill() - what is it really?
•  Use worker.process.kill() if you want to signal the worker
•  Asymetric with worker.send(), worker.on('message', ...), etc.
10
Worker.prototype.kill = function(signo) {
var proc = this.process;
this.once('disconnect', function() {
this.process.kill(signo || 'SIGTERM');
});
this.disconnect();
};

worker.suicide - kill the worker
•  [ ] true
•  [ ] false
11
cluster.fork()
this.kill('SIGTERM');
})
// this.suicide is ....
});
} else {
}

worker.suicide - kill the worker
•  [x] true
•  [ ] false
12
cluster.fork()
this.kill('SIGTERM');
})
});
} else {
}

worker.suicide - exit the worker
•  [ ] true
•  [ ] false
13
cluster.fork()
});
} else {
process.exit(0);
}

worker.suicide - exit the worker
•  [ ] true
•  [x] false
14
cluster.fork()
});
} else {
process.exit(0);
}

worker.suicide - what does it mean?
•  worker.disconnect() in parent (implicitly done by worker.kill())
•  process.disconnect() in worker
15
Actual meaning: "orderly exit"

url.parse/format
16
var url = require('url');
var uri = url.parse('http://example.com:8080/path');
uri.host = 'ibm.com';
console.log(url.format(uri));
•  [ ] yes
•  [ ] no
Prints http://ibm.com:8080/path ...

url.parse/format
17
uri.host = 'ibm.com';
•  [ ] yes
•  [x] no: http://ibm.com/path

url.parse/format
•  host is "example.com:8080"
•  hostname is "example.com"
18

url.parse/format
19
uri.hostname = 'ibm.com';
•  [ ] yes
•  [ ] no

url.parse/format
20
•  [ ] yes
•  [x] no: http://example.com:8080/path

url.parse/format
•  hostname and port are ignored if host is present...
21

url.parse/format
22
delete uri.host;
•  http://ibm.com:8080/path, finally!

url.parse/format
•  parse: "http://example:8080":
– port is 8080
– host is "example:8080"... why not hostport?
– hostname is "example"... why not host?
•  format: hostname and port are ignored if hostname is present
– shouldn't they be prefered if present?
23

path.parse/format
24
var path = require('path');
var bits = path.parse('some/dir/index.txt');
// has: .name, .ext
bits.ext = '.html';
console.log(path.format(bits));
Logs some/dir/index.html...
•  [ ] yes
•  [ ] no

path.parse/format
25
bits.ext = '.html';
•  [ ] yes
•  [x] no: some/dir/index.txt

path.parse/format
26
console.log(bits.base); // > index.txt
delete bits.base
bits.ext = '.html';
•  [ ] yes
•  [ ] no
Its probably like url...

path.parse/format
27
console.log(bits.base); // > index.txt
delete bits.base
bits.ext = '.html';
•  [ ] yes
•  [x] no: some/dir/

path.parse/format
28
bits.base = bits.name + '.html';
console.log(path.format(bits)); // > some/dir/index.html
Its just completely different, format always ignores name and ext.
Correct:

streams v1, 2, 3
29
Note that, for backwards compatibility reasons, removing 'data' event
handlers will not automatically pause the stream. Also, if there are
piped destinations, then calling pause() will not guarantee that the
stream will remain paused once those destinations drain and ask for
more data.
From https://nodejs.org/api/stream.html#stream_class_stream_readable:

streams v1, 2, 3
30
Note that, for backwards compatibility reasons, removing 'data' event
handlers will not automatically pause the stream. Also, if there are
piped destinations, then calling pause() will not guarantee that the
stream will remain paused once those destinations drain and ask for
more data.
From https://nodejs.org/api/stream.html#stream_class_stream_readable:
When can we delete backwards compat to v0.8?

Question
•  Laurie Voss (@seldo), NPM, Nov. 28, 2015
31
What kind of node do you want: a good one?
or a (mostly) v0.8 compatible one?
@octetcloud As of right now, 30.4% of registered npm
accounts are less than 6 months old.

Answer
•  github, twitter, etc..
•  Be tolerant (or intolerant) of breakages, but what
you say will effect what happens.
32
Its yours (and a lot of other people's) Node.js, speak out:

Flames to:
•  github: @sam-github
•  email: rsam@ca.ibm.com
•  twitter: @octetcloud
•  talk source: https://gist.github.com/sam-github/4c5c019b92cf95fb6571, or
https://goo.gl/2RWpqE
33

Node.js API pitfalls

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