Question

We are using Node for developing and 95% of code is Async, working fine.

For some 5% (one small module), which is sync in nature [and depends on other third party software],

and we are looking for
1. “Code to block until call back is finished”
2. At a time only one instance of function1 + its callback should be executed.

PS 1: I do completely agree, Node is for async work, We should avoid that, but this is separate non-realtime process.

PS 2: If not with Node any other Serverside JS framework? Last option is to use other lang like python, but if anything in JS possible, we are ready to give it a shot!

Answer 1

SEQ should solve your problem.

For an overview about sync modules please look at http://nodejsrocks.blogspot.de/2012/05/how-to-avoid-nodejs-spaghetti-code-with.html

Seq()
 .seq(function () {
   mysql.query("select * from foo",[], function(err,rows,fields) {

        this(null, rows);
   });
 })
 .seq(function(mysqlResult) {
     console.log("mysql callback returnes:"+mysqlResult);
 })