singleton in azure queuetrigger not working as expected - azure

Question

My understanding of this is obviously wrong, any clarification would be helpful.
I thought that adding [Singleton] to a web job would force it to run one after another.
This does not seem to be the case.
This is my very basic test code (against a queue with about 149 messages)
[Singleton] //just run one at a time
public static void ProcessQueueMessage([QueueTrigger("datatrac-stops-to-update")] string message, TextWriter log)
{
monitorEntities mDb = new monitorEntities();
//go get the record
int recordToGet = Convert.ToInt32(message);
var record = (from r in mDb.To_Process where r.Id == recordToGet select r).FirstOrDefault();
record.status = 5;
mDb.SaveChanges();
Console.WriteLine($"Finished record {message}");
}
When it runs I get this on the console:
and as I step though it I am getting conflict errors.
What am I not understanding?
RESOLVED - MORE INFO
Here is what I did to address this, like Haitham said in his answer [Singleton] refers to how many instances of the webjob itself is running -- not how many items are processed per instance.
That was addressed by modifying my Main like:
static void Main(string[] args)
{
var config = new JobHostConfiguration();
config.Queues.BatchSize = 2;
Which when set to 1 only ran 1 at a time.
When set to 2 like above then modifying the below code:
public static void ProcessQueueMessage([QueueTrigger("datatrac-stops-to-update")] string message, TextWriter log)
{
var threadID = Thread.CurrentThread.ManagedThreadId;
Console.WriteLine($"{threadID} : started record {message}");
Produces this behavior (which is what was expected):
Link where I found documentation on above:
https://github.com/Azure/azure-webjobs-sdk/wiki/Queues#config

Answer 1

Singleton does not mean it will run it one after another but mainly about instantiation the instance for the web job class.
If you need to run just one at a time, you can use locks on a static variable to prevent the code to execute more than one time.
But I would not recommend that anyway and you have to see why there are conflict errors