I have a concurrent dictionary List on my controller that stores list of online users. For example when Client A and Client B connects there are 2 online clients present on the list, but when i disconnect B and then re- connect again it must still show 2 online clients but in my case, only Client B detected as online user(disconnected then reconnected). I am using IIS server 7.5.. Please help me with this, do i need to use a database rather than dictionary? I think it resets the dictionary to zero if one user disconnects and reconnects again.... :( Below is my hub class code
public class Chat : Hub
{
//add online client
private static ConcurrentDictionary<string, string> personLists
= new ConcurrentDictionary<string, string>();
public void Connect(string Username, int ID)
{
string id = Context.ConnectionId;
if (!personLists.ContainsKey(Username))
{
personLists.TryAdd(Username, id);
Clients.Caller.viewOnlinePersons(personLists.Where(p => p.Key != Username));
Clients.Others.enters(Username);
}
else
{
string notif = "user: "+Username+" is already used";
Clients.Caller.onUse(notif);
}
The concurrent dictionary should work just fine. It'd be good if you could post some code, but if you go this route with concurrent dictionary, make sure it's static (the Hub classes get created and destroyed per signal) and I think it'd be better suited placed on the hub itself and private (and of course static, again). You can also use Dependency Injection with SignalR which will be a lot cleaner.
You'll only need database as a backplane if you plan on running the application on multiple servers where of course a memory of a single server is not accessible by the other servers and a duplicate dictionary would be created for each server, so in that case you need to take the storage and move it up a bit in the architecture to be accessible by all the servers.
Related
We are using spring poller in our application to poll the data from mySQL DB and send to a third party.
The functionality is as such working but when we moved to PRODUCTION since we have mutiple appservers , the job is running from all servers and we need this to be run in all servers to address the request coming in.
Poller time is configured to run #every 5 secs.
But even if we added the update statement, a particular record is being picked up in multiple servers since both are running at the same time.
We have the below configurations
<int-jdbc:inbound-channel-adapter id="datachannel"
query="${sql}"
data-source="dbDataSource" max-rows-per-poll="1" row-mapper="pollerdatamapper"
update="update <table> set flag=1 where id =:Id">
<int:poller fixed-rate="${pollerinterval}">
<int:transactional/>
</int:poller>
</int-jdbc:inbound-channel-adapter>
PollerService class will be invoked as below for each record from the above poller
<int:service-activator input-channel="datachannel"
output-channel="executerchannel" ref="pollerservice" method="getRecordFromPoller">
</int:service-activator>
public class PollerService
{
private static final Logger LOGGER = Logger.getLogger(PollerService.class);
public PollerDataBO getRecordFromPoller(PollerDataBO pollerDataBO)
{
LOGGER.info("call for the Id " + Id);
}
Could you please confirm if there are any transactional setting that we can do restrict the pick of same record in other servers.
Right, SELECT ... FOR UPDATE should be great solution for you:
https://docs.oracle.com/cd/E17952_01/mysql-5.1-en/innodb-locking-reads.html
You also ca try to play with the isolation="SERIALIZABLE" for the <int:transactional/>, but I don't have too much confidence in it.
Also I think we could improve the JdbcPollingChannelAdapter in the code like:
if (this.updatePerRow) {
for (Object row : payload) {
executeUpdateQuery(row);
}
}
And skip those rows which weren't updated.
Feel free to raise a JIRA on the matter.
I'm trying to find what is the right design where a client will open 2 sessions where one is used to upload a large file and another is used to provide SignalR messaging. The goal is that when the server processes the large file, it needs to provide status messages to the SignalR channel so that the client keeps get notified about the processes going on the server during and beyond the upload itself. The assumption is that at the upload, the client will provide the SignalR identifier so that the worker working on the file upload can pass it on to the Hub but what I'm not actually sure about is how the upload worker should connect with Hub. Do I maintain a static singleton class that holds a persistent reference to the hub? Or do I just make a new HTTP session and send via loopback? Or is there a better approach I didn't even think of?
You can use dependency injection to get a reference to your hub;
public class UploadController
{
IHubContext<YourHub> _hub;
public UploadController(IHubContext<YourHub> hub)
{
_hub = hub;
}
public ActionResult Upload(SomeFile model)
{
// start upload processing
// send progress updates
var conectionId = DetermineConnectionId(); // store it in a dictionary maybe?
_hub.Clients.Client(connectionId).SendProgressUpdate();
}
}
I am creating dynamic connection strings in my project. They're created on the fly with the information provided specifically for every user. When the application first fires off, if a database doesn't exist (first time user logs on), a new database is created without problems with this initializer:
public DataContext() : base()
{
// ProxyCreation and LazyLoading doesn't affect the situation so
// comments may be removed
//this.Configuration.LazyLoadingEnabled = false;
//this.Configuration.ProxyCreationEnabled = false;
string conStr = GetDb();
this.Database.Connection.ConnectionString = conStr;
}
The problem is, with this method, I have to restart the application pool on the server and the new user should be the first accessor to the application.
I need the same thing without a requirement of restarting the app. Is that possible?
(This is a SPA using AngularJS on MVC views and WebApi as data provider - May be relevant somehow, so thought I should mention)
I already tried this, but this creates an error for EF and the application doesn't start at all...
You could try a little bit different approach to connect directly (and create) the right database.
public class DataContext : DbContext
{
public DataContext(DbConnection connection) : base(connection, true) { }
}
Here you create the DbContext already with the right connection.
Take also care because you need to specify to migrations that the right connection should be used (not the Web.Config connection but the connection that raised the database creation).
See the second overload here https://msdn.microsoft.com/en-US/library/hh829099(v=vs.113).aspx#M:System.Data.Entity.MigrateDatabaseToLatestVersion.
I'm developing an ASP.NET (Razor v2) Web Site, and using the WebMatrix.Data library to connect to a remote DB. I have the Database wrapped in a singleton, because it seemed like a better idea than constantly opening and closing DB connections, implemented like so:
public class DB
{
private static DB sInstance = null;
private Database mDatabase = null;
public static DB Instance
{
get
{
if (sInstance == null)
{
sInstance = new DB();
}
return sInstance;
}
}
private DB()
{
mDatabase = Database.Open("<Connection String name from web.config>");
return;
}
<Query Functions Go Here>
}
("Database" here refers to the WebMatrix.Data.Database class)
The first time I load my page with the form on it and submit, a watch of mDatabase's Database.Connection property shows the following: (Sorry, not enough rep to post images yet.)
http://i.stack.imgur.com/jJ1RK.png
The form submits, the page reloads, the submitted data shows up, everything is a-ok. Then I enter new data and submit the form again, and here's the watch:
http://i.stack.imgur.com/Zorv0.png
The Connection has been closed and its Connection String blanked, despite not calling Database.Close() anywhere in my code. I have absolutely no idea what is causing this, has anyone seen it before?
I'm currently working around the problem by calling Database.Open() before and Database.Close() immediately after every query, which seems inefficient.
The Web Pages framework will ensure that connections opened via the Database helper class are closed and disposed when the current page has finished executing. This is by design. It is also why you rarely see connections explicitly closed in any Web Pages tutorial where the Database helper is used.
It is very rarely a good idea to have permanently opened connections in ASP.NET applications. It can cause memory leaks. When Close is called, the connection is not actually terminated by default. It is returned to a pool of connections that are kept alive by ADO.NET connection pooling. That way, the effort required to instantiate new connections is minimised but managed properly. So all you need to do is call Database.Open in each page. It's the recommended approach.
To set the right context, let me explain the problem. Till RC1, we used to implement GenerateConnectionIdPrefix() to prefix user Id to the connection Id. Then we could retrieve user id from the connection string anytime we need.
With RC2, we now cannot inherit IConnectionIdPrefixGenerator & implement GenerateConnectionIdPrefix anymore. So I was wondering what are other avenues available to set any property on the hub with our data, that persists throughout the lifetime of the connection.
Going through documentation, I realized setting query strings is one way, but that would mean we need to set it for every call. Setting a round trip state might be another option, but it looks like even that is persistent for a single round-trip and not entire lifetime.
So my end goal is set to property once at start on SignalR connection that can be used throughout the connection lifetime.
If there is nothing available now, are there any plans to add support to achieve something similar in next version?
[Update]
As suggested below, I tried to set a state Clients.Caller.Userid in the OnConnected method, then tried to access it in the subsequent call, I found that its null. Both calls are from same connection Id.
Look at the "Round-tripping state between client and server" section on https://github.com/SignalR/SignalR/wiki/Hubs.
Basically you can read and write from dynamic properties on Clients.Caller in Hub methods such as OnConnected or anything invoked by a client. Ex:
using System;
using System.Threading.Tasks;
using Microsoft.AspNet.SignalR;
namespace StateDemo
{
public class MyHub : Hub
{
public override Task OnConnected()
{
Clients.Caller.UserId = Context.User.Identity.Name;
Clients.Caller.initialized();
return base.OnConnected();
}
public void Send(string data)
{
// Access the id property set from the client.
string id = Clients.Caller.UserId;
// ...
}
}
}
State that is stored this way will be persisted for the lifetime of the connection.
If you want to learn how to access this state using the SignalR JS client look at the "Round-tripping state" section of https://github.com/SignalR/SignalR/wiki/SignalR-JS-Client-Hubs.
There are other ways to keep track of users without IConnectionIdPrefixGenerator discussed in the following SO answer: SignalR 1.0 beta connection factory