The co-parallel from tj

Can't run example: SyntaxError: Unexpected token *

Not sure what I did wrong, but I can't run the example...

[email protected] node_modules/co

[email protected] node_modules/should

[email protected] node_modules/co-request
└── [email protected] ([email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected])

[email protected] node_modules/mocha
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected] ([email protected], [email protected], [email protected])
└── [email protected] ([email protected], [email protected])
mdesales@Marcello-Work ~/dev/github/co-parallel (master) $ node example.js

/Users/mdesales/dev/github/co-parallel/example.js:22
function *status(url) {
^
SyntaxError: Unexpected token *
at Module._compile (module.js:439:25)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:902:3

Add support for non-array objects

It would be great if this followed the co API and allowed parallelism of objects other than arrays. I could tee up a PR if you think this is reasonable.

Can't run example: SyntaxError: Unexpected token *

Not sure what I did wrong, but I can't run the example...

[email protected] node_modules/co

[email protected] node_modules/should

[email protected] node_modules/co-request
└── [email protected] ([email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected])

[email protected] node_modules/mocha
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected] ([email protected], [email protected], [email protected])
└── [email protected] ([email protected], [email protected])
mdesales@Marcello-Work ~/dev/github/co-parallel (master) $ node example.js

/Users/mdesales/dev/github/co-parallel/example.js:22
function *status(url) {
^
SyntaxError: Unexpected token *
at Module._compile (module.js:439:25)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:902:3

dont wait for all to return

need to queue, might as well use batch

Document why this is better than yield array

Why is co-parallel better than simply yielding an array within co? I can't find any documentation about that, and my tests don't show any particular advantage:

// tasks is an array of 200 async tasks simulated by setTimeout, cf #3
var start = Date.now();
yield parallel(tasks, 10);
console.log('total used %dms', Date.now() - start);

This takes 170ms on average, while:

// tasks is an array of 200 async tasks simulated by setTimeout, cf #3
var start = Date.now();
yield tasks;
console.log('total used %dms', Date.now() - start);

This takes 117ms on average

"object is not a function" in example code

co(function *(){
  var reqs = urls.map(status);
  var res = yield parallel(reqs, 2);
  console.log(res);
})();

It looks like the last parenthesis do not belong.

Understanding error handling

If I run the code as shown on the README at https://github.com/tj/co-parallel#example (I've removed the .() at the end of the co function since I'm using co version 4, on node with --harmony flag), the output is as I'd expect, with the seven 200 messages (status codes) appearing for each of the requests.

GET http://google.com
GET http://yahoo.com
GET http://ign.com
GET http://cloudup.com
GET http://myspace.com
GET http://facebook.com
GET http://segment.io
[ 200, 200, 200, 200, 200, 200, 200 ]

I'm trying to understand how error handling works. If I change the demo in the README to throw Errors (first 3 lines under status function) and add an error handler to the main co function (last 3 lines below), I get some behaviour I don't understand as I'm new to generators and asychronous.

function *status(url) {
  if (url.contains('yahoo')) {
      throw Error('my error');
  }
  console.log('GET %s', url);
  return (yield request(url)).statusCode;
}

...

co(function *(){
  var reqs = urls.map(status);
  var res = yield parallel(reqs, 2);
  console.log(res);
}).catch(function(e) {
  console.log(e);
});

If I run it with the above code, the output becomes the following. Instead of yahoo.com appearing I get the error message in its place, which makes sense. But I don't get the final array of any 200 messages appearing.

GET http://google.com
[Error: my error]
GET http://ign.com
GET http://cloudup.com
GET http://myspace.com
GET http://facebook.com
GET http://segment.io

And if I add another url to the error condition, changing it to if (url.contains('yahoo') || url.contains('cloudup')) { the output becomes this:

GET http://google.com
[Error: my error]
GET http://ign.com

Here the yahoo.com line is still replaced with the error message, and ign.com appears after it, but everything after that fails to appear. And the final array of any 200 messages still doesn't appear. Why does it work like this?

Can anyone share how error handling works in co with generators, etc? Am I seeing expected behaviour with both sets of modifications I've made above? I've read some articles about it but I'm unclear about it.

concurrency a little confuse

I want to use co-parallel in my project to limit the http request to a third-party server.
just like example,limie concurrency 2:
var res = yield parallel(reqs, 2);
Is it finished two request and then start another two request? till all request finshed?

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