node.js asynchronous initialization issue

Question

I am creating a node.js module which communicates with a program through XML-RPC. The API for this program changed recently after a certain version. For this reason, when a client is created (createClient) I want to ask the program its version (through XML-RPC) and base my API definitions on that.

The problem with this is that, because I do the above asynchronously, there exists a possibility that the work has not finished before the client is actually used. In other words:

var client = program.createClient();
client.doSomething();

doSomething() will fail because the API definitions have not been set, I imagine because HTTP XML-RPC response has not returned from the program.

What are some ways to remedy this? I want to be able to have a variable named client and work with that, as later I will be calling methods on it to get information (which will be returned via a callback).

score 4 · Accepted Answer · answered Aug 03 '11 at 07:20

4

Set it up this way:

program.createClient(function (client) {
  client.doSomething()
})

Any time there is IO, it must be async. Another approach to this would be with a promise/future/coroutine type thing, but imo, just learning to love the callback is best :)

answered Aug 03 '11 at 07:20

isaacs

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I went with the suggestion you gave on IRC, to queue the requests until the configuration was finished. Thanks a lot! – Jorge Israel Peña Aug 03 '11 at 07:27
Here is the gist isaacs showed me on IRC, for anyone else interested: https://gist.github.com/1122098 – Jorge Israel Peña Aug 03 '11 at 07:31
He also linked a snippet of his npm project in which he does something similar: https://github.com/isaacs/npm/blob/master/npm.js#L161-232 – Jorge Israel Peña Aug 03 '11 at 07:33

node.js asynchronous initialization issue

1 Answers1