This is perhaps more then you asked for but I have a snipplet (even though it's quite long) for doing RPC using node-amqp instead of REQ/RES with rabbit.js. What I have done is similar to what you could find in the RabbitMQ tutorial about RPC
For the moment the content in the message should be an object (hash) that will get transformed by the amqp module to json.
The AmqpRpc class take an amqp connection when initialized then it should only be a matter of calling makeRequest and wait for a response in the callback.
The response have the form of function(err, response) where err might be a timeout error
I'm sorry its not exactly what you asked for but it's maybe close enough.
I also posted the code as a gist on github: https://gist.github.com/2720846
Edit:
Samples changed to support multiple outstanding requests.
amqprpc.js
var amqp = require('amqp')
, crypto = require('crypto')
var TIMEOUT=2000; //time to wait for response in ms
var CONTENT_TYPE='application/json';
exports = module.exports = AmqpRpc;
function AmqpRpc(connection){
var self = this;
this.connection = typeof(connection) != 'undefined' ? connection : amqp.createConnection();
this.requests = {}; //hash to store request in wait for response
this.response_queue = false; //plaseholder for the future queue
}
AmqpRpc.prototype.makeRequest = function(queue_name, content, callback){
var self = this;
//generate a unique correlation id for this call
var correlationId = crypto.randomBytes(16).toString('hex');
//create a timeout for what should happen if we don't get a response
var tId = setTimeout(function(corr_id){
//if this ever gets called we didn't get a response in a
//timely fashion
callback(new Error("timeout " + corr_id));
//delete the entry from hash
delete self.requests[corr_id];
}, TIMEOUT, correlationId);
//create a request entry to store in a hash
var entry = {
callback:callback,
timeout: tId //the id for the timeout so we can clear it
};
//put the entry in the hash so we can match the response later
self.requests[correlationId]=entry;
//make sure we have a response queue
self.setupResponseQueue(function(){
//put the request on a queue
self.connection.publish(queue_name, content, {
correlationId:correlationId,
contentType:CONTENT_TYPE,
replyTo:self.response_queue});
});
}
AmqpRpc.prototype.setupResponseQueue = function(next){
//don't mess around if we have a queue
if(this.response_queue) return next();
var self = this;
//create the queue
self.connection.queue('', {exclusive:true}, function(q){
//store the name
self.response_queue = q.name;
//subscribe to messages
q.subscribe(function(message, headers, deliveryInfo, m){
//get the correlationId
var correlationId = m.correlationId;
//is it a response to a pending request
if(correlationId in self.requests){
//retreive the request entry
var entry = self.requests[correlationId];
//make sure we don't timeout by clearing it
clearTimeout(entry.timeout);
//delete the entry from hash
delete self.requests[correlationId];
//callback, no err
entry.callback(null, message);
}
});
return next();
});
}
A small example on how to use it can be found below. Save both code parts and just run with...
node client.js
If you don't have a server to provide the reply the request will time out.
client.js
//exmaple on how to use amqprpc
var amqp = require('amqp');
var connection = amqp.createConnection({host:'127.0.0.1'});
var rpc = new (require('./amqprpc'))(connection);
connection.on("ready", function(){
console.log("ready");
var outstanding=0; //counter of outstanding requests
//do a number of requests
for(var i=1; i<=10 ;i+=1){
//we are about to make a request, increase counter
outstanding += 1;
rpc.makeRequest('msg_queue', {foo:'bar', index:outstanding}, function response(err, response){
if(err)
console.error(err);
else
console.log("response", response);
//reduce for each timeout or response
outstanding-=1;
isAllDone();
});
}
function isAllDone() {
//if no more outstanding then close connection
if(outstanding === 0){
connection.end();
}
}
});
I'll even throw in a sample server for good measure
server.js
//super simple rpc server example
var amqp = require('amqp')
, util = require('util');
var cnn = amqp.createConnection({host:'127.0.0.1'});
cnn.on('ready', function(){
console.log("listening on msg_queue");
cnn.queue('msg_queue', function(q){
q.subscribe(function(message, headers, deliveryInfo, m){
util.log(util.format( deliveryInfo.routingKey, message));
//return index sent
cnn.publish(m.replyTo, {response:"OK", index:message.index}, {
contentType:'application/json',
contentEncoding:'utf-8',
correlationId:m.correlationId
});
});
});
});
Your issue is that SSRS IIf
expressions do not short circuit, so whenever you have a blank string your code will still be trying the FormatDateTime
conversion, so you get this error even with your check.
You can add some logic to stop the empty string being evaluated in the FormatDateTime
expression by using another IIf
to change it to a NULL value, which won't fail:
=IIF(Fields!DiscontinuedDate.Value = ""
, ""
, FormatDateTime(IIf(Fields!DiscontinuedDate.Value = ""
, Nothing
, Fields!DiscontinuedDate.Value)
, DateFormat.ShortDate))
That solves your immediate issue, but assuming the underlying data is text based, I would also recommend looking at your underlying data and using explicit DateTime type data types instead of strings to prevent these at the lowest possible level.
Best Answer
The first thing you do, wherever you have used the "Paid" parameter, set it to allow null value. Allow null only not blank.
The second thing about the expression, use something like this,