Connection doesn't update status.

[manhha1006]

I have validate function in Pool to check connection lost

    myPool.prototype.validate  = function(connection){
      return connection["connected"]
    }
    var connected  = pool.validate(conn) // true    
    // lost connect to db (lost network, db crashed ...) 
    // but connection doesn't update connected.
    connected = pool.validate(conn) // true.
   // so, how to know connection lost

[wankdanker]

Internally we keep track of "connected" based on if a connection has been successfully opened or closed. It is really never updated asynchronously if a plug is pulled. See this related SO question:

http://stackoverflow.com/questions/3438167/why-isnt-odbcconnection-state-reliable

My suggestion would be to actually do a simple query in the validate function to test if the server is still up:

myPool.prototype.validate  = function(connection){
  try {
    connection.querySync("select 1+1 as test");
  }
  catch (error) {
    //TODO: check the error is really because server failure
    return false;
  }

  return true;
}

Note that that is blocking because of the call to querySync. If there is an asynchronous version of the validate function, I would do this:

myPool.prototype.validate  = function(connection, cb){
  connection.querySync("select 1+1 as test", function (error, result) {
      if (error) {
        //TODO: check the error is really because server failure
        return cb(false);
      }
      return cb(true);
  });
}

This makes me realize that I am doing the same exact unhelpful thing in my odbc-pool module: