I have webpage with a button. when user pressing on button he get email with the current time. i need to send him another message after 60 sec async .. [he can still press the button how many times he wants]
how can i do it ?
after looking it up here is the answer
// Wait X Sec and then try to send message
System.Timers.Timer t = new System.Timers.Timer();
t.Interval = Convert.ToDouble(ConfigurationManager.AppSettings["timer"]);
t.Elapsed += delegate { /*your function here */};
t.Start();
t.AutoReset = false; // do it once
You can do it in the client side, as #Holystream suggested, but that will fail if the user leaves your page in thsoe 60 seconds, let alone close the browser.
If you don't want to create your own queuing mechanism, you can try using the Windows Scheduler. Just create a task that will access a URL in your application that will send that email. It'll work with you don't have a lot of such requests, and if the minute is not absolutely crucial (you can miss it a little, the scheduler isn't designed for such resolutions).
You should store data for schedule in DB with schedule time-stamp.
If user press button multiple times that time you can validate in DB if a scheduled email is already exists for the criteria ignore it.
You need to set Cron Job (Scheduler) service to call you page which will send emails from the data in DB if scheduled time is elapsed.
Based on accuracy you need, you need to set shorter duration for Cron Job to send emails.
If you want to set own scheduler service one good C# library is http://csharp-source.net/open-source/job-schedulers/quartz-net.
Hope this helps.
Related
So I have a verify channel on my discord server which verifies you if you type in //verify , but I want to make it so all messages are automatically deleted every minute on that channel. How do I do that?
One minute delay
Well if you really need that 1 Minute delay you can have a List of Message Id's (ulongs). On your MessageReceived method you can do something like if(message.Channel.Id == YOURCHANNELID) YOURMESSAGELIST.Add(message.Id); On your Client Ready event you would start an async Timer (from System.Threading) with a delay on 1 Minute. So always on your Timer Tick:
var guild = MainClass.DiscordClient.GetGuild(YOURCHANNELID);
var channel = guild.GetTextChannel(YOURCHANNELID);
await channel.DeleteMessagesAsync(YOURMESSAGELIST);
YOURMESSAGELIST.Clear();
Delete message when receiving
What would be way easier and probaply cleaner is deleting every message from that channel as soon as you receive it which mean that you have an if in your MessageReceived method similar to this: if(message.Channel.Id == YOURCHANNELID) await message.DeleteAsync();
I hope that helps you.
I am working on an assignment in asp.net to send notification email to users at specific intervals.
But the problem is that since the server is not privately owned i cannot implement a windows service on it.
Any ideas?
There's no reliable way to achieve that. If you cannot install a Windows Service on the host you could write a endpoint (.aspx or .ashx) that will send the email and then purchase on some other site a service which will ping this endpoint at regular intervals by sending it HTTP request. Obviously you should configure this endpoint to be accessible only from the IP address of the provider you purchase the service from, otherwise anyone could send an HTTP request to the endpoint and trigger the process which is probably undesirable.
Further reading: The Dangers of Implementing Recurring Background Tasks In ASP.NET.
There are several ways to get code executing on an interval that don't require a windows service.
One option is to use the Cache class - use one of the Insert overloads that takes a CacheItemRemovedCallback - this will be called when the cache item is removed. You can re-add the cache item with this callback again and again...
Though, the first thing you need to do is contact the hosting company and find out if they already have some sort of solution for you.
You could set up a scheduled task on the server to invoke a program with the desired action.
You can always use a System.Timer and create a call at specific intervals. What you need to be careful is that this must be run one time, eg on application start, but if you have more than one pools, then it may run more times, and you also need to access some database to read the data of your actions.
using System.Timers;
var oTimer = new Timer();
oTimer.Interval = 30000; // 30 second
oTimer.Elapsed += new ElapsedEventHandler(MyThreadFun);
oTimer.Start();
private static void MyThreadFun(object sender, ElapsedEventArgs e)
{
// inside here you read your query from the database
// get the next email that must be send,
// you send them, and mark them as send, log the errors and done.
}
why I select system timer:
http://msdn.microsoft.com/en-us/magazine/cc164015.aspx
more words
I use this in a more complex class and its work fine. What are the points that I have also made.
Signaling the application stop, to wait for the timer to end.
Use mutex and database for synchronize the works.
Easiest solution is to exploit global.asax application events
On application startup event, create a thread (or task) into a static singleton variable in the global class.
The thread/task/workitem will have an endless loop while(true) {...} with your "service like" code inside.
You'll also want to put a Thread.Sleep(60000) in the loop so it doesn't eat unnecessary CPU cycles.
static void FakeService(object obj) {
while(true) {
try {
// - get a list of users to send emails to
// - check the current time and compare it to the interval to send a new email
// - send emails
// - update the last_email_sent time for the users
} catch (Exception ex) {
// - log any exceptions
// - choose to keep the loop (fake service) running or end it (return)
}
Thread.Sleep(60000); //run the code in this loop every ~60 seconds
}
}
EDIT Because your task is more or less a simple timer job any of the ACID type concerns from an app pool reset or other error don't really apply, because it can just start up again and keep trucking along with any data corruption. But you could also use the thread to simply execute a request to an aspx or ashx that would hold your logic.
new WebClient().DownloadString("http://localhost/EmailJob.aspx");
My application could have up to roughly 100 requests for a batch job within a few milliseconds but in actuality, these job requests are being masked as one job request.
To fix this issue so that only one job request is just not feasible at the moment.
A workaround that I have thought is to program my application to fulfill only 1 batch job every x milliseconds, in this case I was thinking of 200 milliseconds, and ignore any other batch job that may come in within those 200 milliseconds or when my batch job have completed. After those 200 milliseconds are up or when the batch job is completed, my application will wait and accept 1 job request from that time on and it will not process any requests that may have been ignored before. Once my application accepts another job requests, it will repeat the cycle above.
What's the best way of doing this using .Net 4.0? Are there any boiler plate code that I can simply follow as a guide?
Update
Sorry for being unclear. I have added more details about my scenario. Also I just realized that my proposed workaround above will not work. Sorry guys, lol. Here's some background information.
I have an application that builds an index using files in a specified directory. When a file is added, deleted or modified in this directory, my application listens for these events using a FileSystemWatcher and re-indexes these files. The problem is that around 100 files can be added, deleted or modified by an external process and they occur very quickly, ie: within a few milliseconds. My end goal is to re-index these files after the last file change have occurred by the external process. The best solution is to modify the external process to signal my application when it has finished modifying the files I'm listening to but that's not feasible at the moment. Thus, I have to create a workaround.
A workaround that may solve my problem is to wait for the first file change. When the first file change have occurred, wait 200 milliseconds for any other subsequent file changes. Why 200 milliseconds? Because I'm hoping and confident that the external process can perform its file changes within 200 milliseconds. Once my application have waited for 200 milliseconds, I would like it to start a task that will re-index the files and go through another cycle of listening to a file change.
What's the best way of doing this?
Again, sorry for the confusion.
This question is a bit too high level to guess at.
My guess is your application is run as a service, you have your requests come into your application and arrive in a queue to be processed. And every 200 ms, you wake the queue and pop and item off for processing.
I'm confused about the "masked as one job request". Since you mentioned you will "ignore any other batch job", my guess is you haven't arranged your code to accept the incoming requests in a queue.
Regardless, you will generally always have one application process running (your service) and if you choose you could spawn a new thread for each item you process in the queue. You can monitor how much cpu/memory utilization this required and adjust the firing time (200ms) accordingly.
I may not be accurately understanding the problem, but my recommendation is to use the singleton pattern to work around this issue.
With the singleton approach, you can implement a lock on an object (the access method could potentially be something along the lines of BatchProcessor::GetBatchResults) that would then lock all requests to the batch job results object. Once the batch has finished, the lock will be released, and the underlying object, will have the results of the batch job available.
Please keep in mind that this is a "work around". There may be a better solution that involves looking into and changing the underlying business logic that causes multiple requests to come in for a job that's processing on demand.
Update:
Here is a link for information regarding Singleton (includes code examples): http://msdn.microsoft.com/en-us/library/ff650316.aspx
It is my understanding that the poster has some sort of an application that sits and waits for incoming requests to perform a batch job. The problem that he is receiving multiple requests within a short period of time that should actually have come in as just a single request. And, unfortunately, he is not able to solve this problem.
So, his solution is to assume that all requests received within a 200 ms timespan are the same, and to only process these once. My concern with this would be whether this assumption is correct or not? This entirely depends on the sending systems and the environment in which this is being used. The general idea to be able to do this would be to update a lastReceived date/time when a request is processed. Then when a new request comes in, compare the current date/time to the lastReceived date/time and only process it if the difference is greater than 200 ms.
Other possible solutions:
You said you could not modify the sending application so only one job request was sent, but could you add additional information to it, for instance a unique identifier?
Could you store the parameters from the last job request and compare it with the next job request and only process them if they are different?
Based on your Update
Here is an example how you could wait 200ms using a Timer:
static Timer timer;
static int waitTime = 200; //in ms
static void Main(string[] args)
{
FileSystemWatcher fsw = new FileSystemWatcher();
fsw.Path = #"C:\temp\";
fsw.Created += new FileSystemEventHandler(fsw_Created);
fsw.EnableRaisingEvents = true;
Console.ReadLine();
}
static void fsw_Created(object sender, FileSystemEventArgs e)
{
DateTime currTime = DateTime.Now;
if (timer == null)
{
Console.WriteLine("Started # " + currTime);
timer = new Timer();
timer.Interval = waitTime;
timer.Elapsed += new ElapsedEventHandler(timer_Elapsed);
timer.Start();
}
else
{
Console.WriteLine("Ignored # " + currTime);
}
}
static void timer_Elapsed(object sender, ElapsedEventArgs e)
{
//Start task here
Console.WriteLine("Elapsed # " + DateTime.Now);
timer = null;
}
I was wondering if anyone knows a good way to regulate how many emails are sent through C#?
Here is my scenario. I have a windows service that monitors three other windows services. I am using a service controller to get the status of all 3 services and if the status of any of these services change to stopped, it sends an email. My issue is, I run this on a 60 second timer so it sends an email every 60 seconds until someone starts the service back up.
My first thought was, when first email is sent, create a text file and use a counter to number it. Do this while counter < 6 so I will only receive 5 emails max. I think this will work but it seems kind of silly.
Does anyone have an alternative to this or should I just go with my first thought and perform clean up on the files?
Thank you
EDIT: The reason that I was trying to limit the number of emails sent is because the people who receive these emails do not react very quickly. At the same time, those who handle Exchange do not want the service to spam people. I felt 5 would be enough to appease both sides.
I would suggest that you should track the down time of each service.
So every 60 seconds you check, if a service is down, store the DateTime that the service is down. The on the next 60 second interval you can check to see if the service was already down. i.e. you can tell if the service just went down or has been down a while. You can also add another flag to determine if the the last check was UP or DOWN.
Then when the program first finds the service down it can send the email. Once the service is back up it can reset this flag values so the next down time it knows to send a new email.
You can then also use these flags to delay email frequency if desired. Just add a new DateTime field for LastEmailSentTime and compare that with whatever interval you want for error emails (say 10 minutes)
Hope that gives you some ideas
EDIT: Some Sample...
bool ServiceWasDown = false;
DateTime ServiceDownTime = DateTime.Now;
DateTime LastEmailTime = DateTime.Now;
void OnTimerElapsed()
{
if(IsServiceDown())
ServiceDown();
else
ServiceUp();
}
void ServiceDown()
{
if(ServiceWasDown)//already know about service
{
//if LastEmailTime more than 10 minutes ago send another email and update LastEmailTime
}
else//service just went down
{
//send new email
LastEmailTime = DateTime.Now;
ServiceWasDown = true;
ServiceDownTime = DateTime.Now;
}
}
void ServiceUp()
{
ServiceWasDown = false;
}
If you use a System.Timers.Timer then You can add a int variable for count Elapsed events.
I am using MVC 2, I have view which simply displays label with current time on it.
I want to update this View(label) every 5 seconds so time will update. I am using below (taken from here) but doesn't seem to be working.
public ActionResult Time()
{
var waitHandle = new AutoResetEvent(false);
ThreadPool.RegisterWaitForSingleObject(
waitHandle,
// Method to execute
(state, timeout) =>
{
// TODO: implement the functionality you want to be executed
// on every 5 seconds here
// Important Remark: This method runs on a worker thread drawn
// from the thread pool which is also used to service requests
// so make sure that this method returns as fast as possible or
// you will be jeopardizing worker threads which could be catastrophic
// in a web application. Make sure you don't sleep here and if you were
// to perform some I/O intensive operation make sure you use asynchronous
// API and IO completion ports for increased scalability
ViewData["Time"] = "Current time is: " + DateTime.Now.ToLongTimeString();
},
// optional state object to pass to the method
null,
// Execute the method after 5 seconds
TimeSpan.FromSeconds(5),
// Set this to false to execute it repeatedly every 5 seconds
false
);
return View();
}
Thanks for help in advance!
What you are doing won't work as once the initial response is sent to the client, the client will no longer be listening for data from your server for that request. What you want to do is have the client initiate a new request every 5 seconds, then simply return the data for each request. One way to do this is with a refresh header.
public ActionResult Time()
{
this.HttpContext.Response.AddHeader( "refresh", "5; url=" + Url.Action("time") );
return View();
}
You need to put your recurring loop on the client side so that it reloads the page every five seconds.
One way, using Javascript:
<script>setTimeout("window.location.reload();",5000);</script>
The code you provided, runs at server, and when a page (View in this case) is sent to the client, the server will forgot it! You should create a client side code for refreshing the page every 5 seconds. You can use a header command (refresh) or a script:
<script>
setTimeout("window.location.reload();", /* time you want to refresh in milliseconds */ 5000);
</script>
But if you just want to refresh the page for updating the Time, I never suggest you to refresh page completely. Instead, you can create a javascript function, to tick every 5 seconds, and calculate the current time and update the label.