Node.js API pitfalls

Disclaimer ;-)

Doesn't necessarily reflect the views of IBM, or any of my Node.js collaborators...

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nextTick

•  [ ] in next tick of the event loop •  [ ] immediately after A returns

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process.nextTick(function() { // Called ... });

nextTick

•  [ ] in next tick of the event loop •  [x] immediately after A returns

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process.nextTick(function() { // Called ... });

setImmediate

•  [ ] in next tick of the event loop •  [ ] immediately after A returns

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

setImmediate

•  [x] in next tick of the event loop •  [ ] immediately after A returns

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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

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worker.kill()

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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

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} else { process.on('SIGHUP', function() { console.log('Hup'); }); }

worker.kill()

•  [ ] "Hup" •  [x] "Exit" •  [ ] "Hup" and "Exit" •  [ ] No output

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} 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.

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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

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cluster.fork() .on('online', function() { this.kill('SIGTERM'); }) .on('exit', function() { // this.suicide is .... });

} else { }

worker.suicide - kill the worker

•  [x] true •  [ ] false

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cluster.fork() .on('online', function() { this.kill('SIGTERM'); }) .on('exit', function() { // this.suicide is .... });

} else { }

worker.suicide - exit the worker

•  [ ] true •  [ ] false

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cluster.fork() .on('exit', function() { // this.suicide is .... });

} else { process.exit(0); }

worker.suicide - exit the worker

•  [ ] true •  [x] false

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cluster.fork() .on('exit', function() { // this.suicide is .... });

} else { process.exit(0); }

worker.suicide - what does it mean?

•  worker.disconnect() in parent (implicitly done by worker.kill()) •  process.disconnect() in worker

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Actual meaning: "orderly exit"

url.parse/format

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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

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var url = require('url'); var uri = url.parse('http://example.com:8080/path'); uri.host = 'ibm.com'; console.log(url.format(uri));

•  [ ] yes •  [x] no: http://ibm.com/path


url.parse/format

•  host is "example.com:8080" •  hostname is "example.com"

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url.parse/format

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var url = require('url'); var uri = url.parse('http://example.com:8080/path'); uri.hostname = 'ibm.com'; console.log(url.format(uri));

•  [ ] yes •  [ ] no


url.parse/format

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var url = require('url'); var uri = url.parse('http://example.com:8080/path'); uri.hostname = 'ibm.com'; console.log(url.format(uri));

•  [ ] yes •  [x] no: http://example.com:8080/path


url.parse/format

•  hostname and port are ignored if host is present...

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url.parse/format

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var url = require('url'); var uri = url.parse('http://example.com:8080/path'); delete uri.host; uri.hostname = 'ibm.com'; console.log(url.format(uri));

•  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?

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path.parse/format

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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

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var path = require('path'); var bits = path.parse('some/dir/index.txt'); bits.ext = '.html'; console.log(path.format(bits));


•  [ ] yes •  [x] no: some/dir/index.txt

path.parse/format

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var path = require('path'); var bits = path.parse('some/dir/index.txt'); console.log(bits.base); // > index.txt delete bits.base bits.ext = '.html'; console.log(path.format(bits));

Logs some/dir/index.html... •  [ ] yes •  [ ] no

Its probably like url...

path.parse/format

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var path = require('path'); var bits = path.parse('some/dir/index.txt'); console.log(bits.base); // > index.txt delete bits.base bits.ext = '.html'; console.log(path.format(bits));


•  [ ] yes •  [x] no: some/dir/

path.parse/format

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var path = require('path'); var bits = path.parse('some/dir/index.txt'); 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

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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

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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

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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.

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Its yours (and a lot of other people's) Node.js, speak out:

Flames to:

•  github: @sam-github •  email: [email protected] •  twitter: @octetcloud •  talk source: https://gist.github.com/sam-github/4c5c019b92cf95fb6571, or

https://goo.gl/2RWpqE

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Technology

Node.js API pitfalls