Getting Started with node.js and CouchDB

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Tonight, I would like to get started with node.js. First downloading and installing:

cstrom@whitefall:~/tmp$ wget http://nodejs.org/dist/node-v0.1.33.tar.gz
--2010-03-24 20:51:40--  http://nodejs.org/dist/node-v0.1.33.tar.gz
Resolving nodejs.org... 97.107.132.72
Connecting to nodejs.org|97.107.132.72|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 4016600 (3.8M) [application/octet-stream]
Saving to: `node-v0.1.33.tar.gz'

100%[======================================================================================================>] 4,016,600    142K/s   in 26s     

2010-03-24 20:52:07 (151 KB/s) - `node-v0.1.33.tar.gz' saved [4016600/4016600]

I store source code repositories in the repos directory, but code without source code management (e.g. tarballs) in my src directory:

cstrom@whitefall:~/tmp$ cd /home/cstrom/src/
cstrom@whitefall:~/src$ tar zxf ../tmp/node-v0.1.33.tar.gz 
tar: Ignoring unknown extended header keyword `SCHILY.dev'
tar: Ignoring unknown extended header keyword `SCHILY.ino'
tar: Ignoring unknown extended header keyword `SCHILY.nlink'
tar: Ignoring unknown extended header keyword `SCHILY.dev'
tar: Ignoring unknown extended header keyword `SCHILY.ino'
tar: Ignoring unknown extended header keyword `SCHILY.nlink'

Not sure what's up with the "unknown extended header keyword", but stuff was created:

cstrom@whitefall:~/src/node-v0.1.33$ ls
AUTHORS  benchmark  bin  ChangeLog  configure  deps  doc  lib  LICENSE  Makefile  README  src  test  tools  wscript

Since I am just messing around, I do not want to use sudo to install. For now, I will install into my "local" directory:

cstrom@whitefall:~/src/node-v0.1.33$ ./configure --prefix=/home/cstrom/local
Check for program g++ or c++             : /usr/bin/g++
Check for program cpp                    : /usr/bin/cpp
Check for program ar                     : /usr/bin/ar
Check for program ranlib                 : /usr/bin/ranlib
Checking for g++                         : ok 
...

There were a few missing development libraries. Configure completed OK without them, but I note them for later:

...
Checking for library execinfo            : not found
Checking for gnutls >= 2.5.0             : fail
...
--- libev ---
...
Checking for header port.h               : not found
Checking for header poll.h               : ok
Checking for function poll               : ok
Checking for header sys/event.h          : not found
Checking for header sys/queue.h          : ok
Checking for function kqueue             : not found
...

I would not expect them to matter because configure completes successfully:

...
creating config.h... ok
creating Makefile... ok
creating config.status... ok
all done.
'configure' finished successfully (9.562s)

With that, I can build the executables:

cstrom@whitefall:~/src/node-v0.1.33$ make
Waf: Entering directory `/home/cstrom/src/node-v0.1.33/build'
...
[22/23] cxx: src/node_idle_watcher.cc -> build/default/src/node_idle_watcher_7.o
[23/23] cxx_link: build/default/src/node_7.o build/default/src/node_child_process_7.o build/default/src/node_constants_7.o build/default/src/node_dns_7.o build/default/src/node_events_7.o build/default/src/node_file_7.o build/default/src/node_http_7.o build/default/src/node_net_7.o build/default/src/node_signal_watcher_7.o build/default/src/node_stat_watcher_7.o build/default/src/node_stdio_7.o build/default/src/node_timer_7.o build/default/src/node_idle_watcher_7.o build/default/deps/libev/ev_1.o build/default/deps/libeio/eio_1.o build/default/deps/evcom/evcom_3.o build/default/deps/http_parser/http_parser_4.o build/default/deps/coupling/coupling_5.o -> build/default/node
Waf: Leaving directory `/home/cstrom/src/node-v0.1.33/build'
'build' finished successfully (9m21.816s)

Cool. So now a make install:

cstrom@whitefall:~/src/node-v0.1.33$ make install
Waf: Entering directory `/home/cstrom/src/node-v0.1.33/build'
* installing deps/libeio/eio.h as /home/cstrom/local/include/node/eio.h
* installing deps/libev/ev.h as /home/cstrom/local/include/node/ev.h
* installing deps/udns/udns.h as /home/cstrom/local/include/node/udns.h
...
* installing build/default/node as /home/cstrom/local/bin/node
* installing build/default/src/node_version.h as /home/cstrom/local/include/node/node_version.h
Waf: Leaving directory `/home/cstrom/src/node-v0.1.33/build'
'install' finished successfully (0.476s)

It looks as though the node.js build scripts have honored my --prefix=/home/cstrom/local and, running the node binary would seem to confirm it:

cstrom@whitefall:~$ ./local/bin/node
No script was specified.
Usage: node [options] script.js [arguments] 
Options:
  -v, --version      print node's version
  --debug[=port]     enable remote debugging via given TCP port
                     without stopping the execution
  --debug-brk[=port] as above, but break in script.js and
                     wait for remote debugger to connect
  --v8-options       print v8 command line options
  --vars             print various compiled-in variables

Enviromental variables:
NODE_PATH            ':'-separated list of directories
                     prefixed to the module search path,
                     require.paths.
NODE_DEBUG           Print additional debugging output.

Documentation can be found at http://nodejs.org/api.html or with 'man node'

Cool!

Before trying something more complicated, I will give the delayed execution example from the nodejs.org site a try. I save this in ~/tmp/delay.js and execute it with node:

cstrom@whitefall:~$ ./local/bin/node ./tmp/delay.js 
Server running at http://127.0.0.1:8000/

And, accessing this resource does incur a delay of 2 seconds:

cstrom@whitefall:~$ time curl http://127.0.0.1:8000/
Hello World
real    0m2.036s
user    0m0.012s
sys     0m0.016s

That's all well and good, but what about something a little more complex? This current chain is supposed to be about updating CouchDB. Since CouchDB is HTTP from the ground up, I ought to be able to pull data back from CouchDB inside node.js. After some fiddling, I am able to produce a list of all CouchDB databases (_all_dbs) on my local CouchDB server with this node.js script:

var sys = require('sys'),
   http = require('http');

http.createServer(function (req, res) {
  var client = http.createClient(5984, "127.0.0.1");
  var request = client.request("GET", "/_all_dbs");

  request.addListener('response', function(response) {
    var responseBody = "";

    response.addListener("data", function(chunk) {
      responseBody += chunk;
    });

    response.addListener("end", function() {
      res.writeHead(200, {'Content-Type': 'text/plain'});
      res.write(responseBody);
      res.close();
    });
  });

  request.close();

}).listen(8000);
sys.puts('Server running at http://127.0.0.1:8000/');

After running the script with node couch.js, I can indeed retrieve the list of databases with curl:

cstrom@whitefall:~$ curl http://127.0.0.1:8000/
["eee","test","seed"]

Piece by piece, this script creates a client and builds a request of the _all_dbs resource:

  var client = http.createClient(5984, "127.0.0.1");
  var request = client.request("GET", "/_all_dbs");

The request needs an event listener:

  request.addListener('response', function(response) {
// ...
  });

I turn, the response object also needs an event listener to build up the response:

    response.addListener("data", function(chunk) {
      responseBody += chunk;
    });

And to handle the end of the response from the CouchDB server (which is when the node.js action responds):

    response.addListener("end", function() {
      res.writeHead(200, {'Content-Type': 'text/plain'});
      res.write(responseBody);
      res.close();
    });

Finally, and it took me more than a little while to realize this, I need to close the request to get it processed (otherwise things just hang):

  request.close();

The rest of the script is identical to the delayed job script above.

I am quite sure that is a silly example, but it helps get me on my way with node.js. Tomorrow, I will likely play with node-couch, from which I borrowed liberally while putting this example together.

Day #52