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A COMMAND PROMPT TALK. Node.js and postgres. An Introductory Glance With Live Code, Later. 2010 AURYNN SHAW, COMMAND PROMPT INC. Hi!. What is Node.js. Fast Pure event-driven server-side javascript programming environment. Ew, javascript. Built on Google’s V8

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A COMMAND PROMPT TALK

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A COMMAND PROMPT TALK


Node.js and postgres

  • An Introductory Glance

  • With Live Code, Later

2010 AURYNN SHAW, COMMAND PROMPT INC.


Hi!


What is Node.js

  • Fast

  • Pure event-driven

  • server-side

  • javascript programming environment


Ew, javascript

  • Built on Google’s V8

  • Runs on modern unix-likes (Linux, OSX, Freebsd, Cygwin)

  • Speaks network natively, and easily (Hello world is in http!)

  • Ends up Similar to Python, Perl, Ruby, ETc.


Did I mention fast?

  • Single thread can do many thousands of connections

  • standard library doesn’t block


Did I mention fast?

  • Single thread can do many thousands of connections

  • standard library doesn’t block

  • Keeps the slow tasks from blocking

  • Keeps the quick tasks quick


blocking?

# Standard synchronous processing

fh = open(“somefile”,”r”)

contents = fh.read()

# what if somefile is huge, 1GB+ ?

print contents


Every step waits


How is node different?


Did I mention fast?

  • Single thread can do many thousands of connections

  • standard library doesn’t block

  • Keeps the slow tasks from blocking

  • Keeps the quick tasks quick


Really good for anything I/O


While slow tasks run, node carries on


Non-blocking!

fs.open(“somefile”, function (fd) {

// When the file descriptor gets returned.

var buffer = null;

fs.read(fd, buffer, length, position, function (e, bytes) {

// bytes read are here.

// buffer will be not-null.

});

});


As always, there’s caveats to this


Some caveats

  • node is entirely single-threaded

  • Event-driven programming is *really* different


A maze of callbacks

fs.open(“/tmp/hello”, function (fd) {

var buffer = null;

fs.read(fd, buffer, length, position, function (e, bytes) {

// bytes read are here.

// buffer will be not-null.

});

});


Some caveats

  • node is entirely single-threaded

  • Event-driven programming is *really* different

  • Javascript’s prototype model is also really different

  • The syntax has warts


Build a bridge out of her?

/*

This allows you to kind of inherit properly.

*/

var o = function () {};

var p = function () {

/* Because ‘this’ changes */

var self = this;

o.call(this);

};

p.prototype = o;

p.prototype.constructor = p;


So why is this important?


Why is it important?

  • Javascript owns the frontend


Why is it important?

  • Javascript owns the frontend

  • More jquery and javascript programmers every day


Why is it important?

  • Javascript owns the frontend

  • More jquery and javascript programmers every day

  • Javascript is fast


Faster every day


And now, we can use postgres!


When I got here...

  • postgres.js worked.


When I got here...

  • postgres.js worked.

  • Used the simple query protocol


When I got here...

  • postgres.js worked.

  • Used the simple query protocol

  • Used SQL escape to prevent injection attacks.


whyyyy

SOURCE: http://www.flickr.com/photos/striatic/2192192956/


But it did work!


And so I wanted to make it BETTER


So, I had to ask,


How do I not allow this?


Well...


to prepare a query

  • postgres.js Didn’t use libpq.


SOURCE: http://www.flickr.com/photos/tanaka/2319325408/


to prepare a query

  • postgres.js Didn’t use libpq.

  • Speaks pure protocol


to prepare a query

  • postgres.js Didn’t use libpq.

  • Speaks pure protocol

  • ...So I had to learn the protocol.


Wax on, wax off

MONTAGE!


Sadly, reality was a lot less exciting


Complexity Abounds

  • Simple protocol sends one message to pg

  • Easy to queue, internally.


REALLY SIMPLE MESSAGE QUEUE

QUERY

QUERY

QUERY

QUERY

QUERY

QUERY

RESULTS


Really, though

  • Simple protocol sends one message to PG

  • Easy to queue, internally.

  • Prepared statements require at least 5

  • Parse, describe, execute, bind, flush


THIS TYPE OF QUEUE DOESN’T WORK

SYNC

EXECUTE

BIND

DESCRIBE

PARSE

QUERY

QUERY


And while all this is happening

  • You cannot block the main thread

  • And postgres expects a synchronous request/response

  • But it does give responses...


And while all this is happening

  • You cannot block the main thread


And while all this is happening

  • You cannot block the main thread

  • And postgres expects a synchronous request/response


And while all this is happening

  • You cannot block the main thread

  • And postgres expects a synchronous request/response

  • But it does give responses...


So, we buffer message sets


KIND OF LIKE THIS

SIMPLE

PREPARED

GROUP

SIMPLE

SIMPLE

PREPARED

GROUP

SIMPLE

SIMPLE


So we never block waiting for the DB


the application keeps responding


But that’s all a bit on the technobabbly side

SO


Let’s look codE!


Using postgres.js

/* Node setup */

var pg = require(“lib/postgres-pure.js”),

sys = require(“sys”);

var db = new pg.connect("pgsql://test:[email protected]:5432/template1");

/* We now have a working DB handle.

Or, we have an error. Either way.

*/


Using postgres.js

/* We now have a working DB handle. */

/* From here, we do: */

db.query(“select 1::int;”, function (err, rs) {

// Wait, a function?

console.log(sys.inspect(rs));

});


Why a function?


What’s going on here?

/* We now have a working DB handle. */

/* From here, we do: */

db.query(“select 1::int;”, function (err, rs) {

// Wait, a function?

console.log(sys.inspect(rs));

});


What you get

1

3

// A little while later

2


It’s happening asynchronously!

  • The function argument is what’s going to happen when the DB comes back

  • db.query returns immediately

  • and your app keeps on going!


this isn’t the cool bit


Prepared queries

/* Prepared queries work the same way */

db.prepare(“select ?::int as foobar;”, function (sth) {

sth.execute(1, function (err, rs) {

console.log(sys.inspect(rs));

});

sth.execute(2, function (err, rs) {

console.log(sys.inspect(rs));

});

});


Prepared queries

/* which will return */

[ { foobar: 1 } ]

[ { foobar: 2 } ]


Or this!

/*

This becomes a prepared statement behind the scenes

*/

db.query(“select ?::int as foobar;”,

1, // A single argument

function (err, rs) {

console.log(sys.inspect(rs));

});


It would return

[ { foobar: 1 } ]


Sub-ideal Aspects


Bad, bad, bad.

  • postgres.js is still very alpha.

  • Node API is in flux

  • Learning Node takes a while


Cool bits!


Things that are pleasing

  • clean, perl DBI-based API.

  • Official support from Command prompt

  • Performance!


Vroom

[ananke:~/src/postgres-js] aurynn> time node benchmark.js 40000

[ { count: 40001 } ]

node benchmark.js 40000 18.85s user 2.75s system 87% cpu 24.602 total

Just over 2122 queries/second.


Some Stuff we can’t wait to add


Shiny things!

  • Notify support


PG notifications

/* Event-driven frameworks are ideal for this, and

the notification setup can be handled behind the

scenes.

*/

db.on(“<NOTIFYNAME>”, function (payload) {

// Do something useful as a result of

// the notification from PG

});


Payload is also arbitrary data


Shiny things!

  • Notify support

  • Stability


Shiny things!

  • Notify support

  • Stability

  • Better error handling


Shiny things!

  • Notify support

  • Stability

  • Better error handling

  • More test cases


Shiny things!

  • Notify support

  • Stability

  • Better error handling

  • More test cases

  • Better type coercion


But the most important thing we’d like?


Users.


You guys. People who care.


So that’s postgres.js.


Any questions?


Okay. LIVE CODE!Shout out ideas!


FORK IT, AND HELP!

UNSTABLE

https://github.com/commandprompt/postgres-js/

https://github.com/aurynn/postgres-js/

NOT QUITE AS UNSTABLE


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