I've got a rebus server process running on one machine and an MVC website on another. I configure the message routing in the MVC website with a local input and error queue and the destination pointing to the queue myinputqueue#BusServer and when it runs it sends the subscription message without error but nothing seems to appear on the destination queue. The receiving bus never acknowledges it or creates a subscription entry.
It's using msmq as the transport and all queues have full permissions to the Everyone group.
I'm assuming I've not configured something correctly so I hope this is the right forum to raise the question.
Appreciate any help.
Even though Everyone has access to the queues, and that sounds like there's nothing in the way of communicating freely, I'm not sure that it works that way.
In any case, I suggest you make sure your IIS app pool is runnig with some dedicated service user identity, which you can also use as the user account under which your server process is running.
With MSMQ, messages are never lost - so in your case, the subscription message is most likely sitting in an outgoing queue on the web server machine, or it might have been moved to the "Transactional dead-letter queue" which is where MSMQ ends up moving stuff that it cannot find a place for.
Could you try and take a look at the outgoing MSMQ queues and/or the transactional dead-letter queue to see if it's a user rights problem that is haunting you?
Related
Our system has two servers (S1) one is running processesing and data storage (basically DB) and the other one is a webserver (WS).
There are two types of even that can happen in the system:
User A pings User B. In this case we check if user B is logged in and we push a notification to User B client throw SignalR. It works.
Services constantly running on S1 and generating new data that concenrs multiple users. My goal is as soon as a new data important for user A is generated I immediately want to dispatch a signalR notification to user A client provided he/she is logged in.
This part 2 is not quite clear for me how to design. My thought right now is to start an indefinite process on webserves that monitors our DataBase and checks if new records are generated fpr this user and then push a SignalR message.
That would be fine, but now we have 10k users logged in and I don't think the right decision would be run 10k threads monitoring activities.
Basically, my question is what would a proper way do design signalR based notification mechanism that is based on events that are not originated on our webserver.
I would use a service bus or mq, for example this Free MQ https://www.rabbitmq.com/
You can proxy the messages direcly to the Clients using this proxy library (I'm the author).
Doc's here https://github.com/AndersMalmgren/SignalR.EventAggregatorProxy/wiki
Demo https://github.com/AndersMalmgren/SignalR.EventAggregatorProxy/tree/master/SignalR.EventAggregatorProxy.Demo.MVC4
You can also set up a sql dependency that triggers a message to your signalr clients,
http://techbrij.com/database-change-notifications-asp-net-signalr-sqldependency
This link is the one that I based my code on.
couple of things to watch for, the setup of the table. You cannot use 3 part table names
"SELECT [CMRID],
[SolutionID],
[CreateDT],
[ModifyDT]
**FROM [dbo].[Case]**
WHERE [ModifyDT] > " + LastExecutionDateTime;
Also, and this is very important, you MUST reset the event handler every time the dependency triggers, if not it will work the first time and then stop working.
I hope this helps you.
I have an xmpp/ejabberdb app that uses an external service to provide eventing features, but when this service becomes unavailable, I want to disconnect/logout all of my clients. Is this possible? How?
I got it working the way I needed. In fact, I didn't find any simple way to make my own server logout all connected users given some kind of situation, so I dug into ejabberd's code and figured out a way to do it myself.
In ejabberd_c2s.erl module, when a client logs out or it's socket is dropped for some reason, the FSM is terminated, doing all necessary clean up to maintain ejabberd's consistency.
What I had to do was just create an exported function shutdown/1 in this module that calls gen_fsm:send_all_state_event/2 sending a signal for it to terminate.
As for each connection there's one c2s process, I need to call this function for each user.
---UPDATING---
Actually there's no need to create this shutdown function, as ejabber_c2s already has the ability to process 'closed' signal, which does the same thing. So, instead of creating the shutdown function, simply doing ge_fsm:send_event(C2SPid, closed) might be enough.
---UPDATING---
To discover the user's c2s process PID I just use ejabberd_sm:get_session_pid/1 or ejabberd_sm:dirty_get_sessions_list/0 (for all sessions).
This worked fine for me, but if anyone has a better idea, please add here.
Thanks
I don't know the ejabberd specifics, but you could write a custom XMPP component which polls the external service (or listens for presence events, if it's another XMPP component), then logs out users when the service becomes unavailable.
For my client's custom-built CRM, I want users (technicians) to be notified of changes to marked cases via email.
This warrants a simple subscription mapping table between users and cases and automated emails to be sent every time a change is made to a case from within the logging method.
How do I send 10-100 emails to subscribed users without bogging down my logging method? My SMTP server is on a peer on my LAN, so sends should be quick, but ideally this should be handled by an external queuing process.
I can have a cron job send any outstanding emails every 10 minutes, but for this specific client cases are quite time-sensitive and instant notification (as instant as email can be) would be great.
How can I send bulk notification emails from within ASP.NET MVC without bogging down my logging method?
Back in 2007 I was asked to look into a case where Web Server would suddenly freeze and start sending 503 errors and come back after a few minutes. Cutting a long story short it turned out at the end that it was sending email which was blocking the server (in addition to some bad code).
Basically Microsoft's SMTP server is implemented as a single-thread service - last I checked. This will mean that all your valuable ASP.NET threads serving requests will have to queue to a single thread monolithic application to send a not so urgent email. You need to decouple your web site from sending emails - that is what everyone does and there is a good reason for it.
Write your emails to a queue and have a process reading and sending emails.
Sending emails from an ASP.NET application is not a good idea as it might monopolize valuable server resources. A better solution would be to setup a Windows Service to perform this task or even write a Console application which could be scheduled to run with Windows Scheduler. Quartz.NET is a good solution you might take a look at allowing you to schedule jobs.
If you want those email sending to be triggered from within a particular controller action you could also have a separate WCF service which could be invoked asynchronously.
I have created a WCF service using the NetMsmq binding for which i created a private queue on my machine and executed the project. This works fine as such and my WCF service is started and accesses the message using the queue in the debugging environment. Now, I wanted to host the service using the windows service and for the same I created a new project and windows installer as well (This service runs under Local System Account). Then I tried installing this windows service using the InstallUtil command through the command prompt. When installation is happening and during the service host opening, I get an exception saying:
There was an error opening the queue. Ensure that MSMQ is installed and running, the queue exists and has proper authorization to be read from. The inner exception may contain additional information.
Inner Exception System.ServiceModel.MsmqException: An error occurred while opening the queue:Access is denied. (-1072824283, 0xc00e0025). The message cannot be sent or received from the queue. Ensure that MSMQ is installed and running. Also ensure that the queue is available to open with the required access mode and authorization.
at System.ServiceModel.Channels.MsmqQueue.OpenQueue()
at System.ServiceModel.Channels.MsmqQueue.GetHandle()
at System.ServiceModel.Channels.MsmqQueue.SupportsAccessMode(String formatName, Int32 accessType, MsmqException& msmqException)
Could anyone suggest the possible solution for the above issue? Am I missing any permissions to be set for the queue as well as the windows service, if so could you suggest where should these permissions be added?
Tom Hollander had a great three-part blog series on using MSMQ from WCF - well worth checking out!
MSMQ, WCF and IIS: Getting them to play nice (Part 1)
MSMQ, WCF and IIS: Getting them to play nice (Part 2)
MSMQ, WCF and IIS: Getting them to play nice (Part 3)
Maybe you'll find the solution to your problem mentioned somewhere!
Yes, it looks like a permissions issue.
Right click on your private queue from the Server Manager, and select Properties. Proceed to the Security tab, and make sure you have the right permissions in there for your Local System Account.
This is also confirmed in Nicholas Allen's article: Diagnosing Common Queue Errors, where the author defines the error code 0xC00E0025 as a permissions problem.
I ran into same problem, here is the solution.
Right click "My Computer" --> Manage. In Computer Management window go to "Services and Applications --> Message Queueing --> ur queue", select ur queue and access properties. Add the user running ur WCF application and give full access. This should solve the issue.
Can simple be that the service can't find the it's queue.
The queue name must exact match the endpoint address.
Example:
net.msmq://localhost/private/wf.listener_srv/service.svc
points to local queue
private$\wf.listener_srv\service.svc
If queue name and endpoint are according to each other, then is most like that the credentials defined on the IIS pool don't grant access to the queue.
I am to build a web application which will accept different events from external sources and present them quickly to the user for further actions. I want to use Ruby on Rails for the web application. This project is a internal development project. I would prefer simple and easy to use solutions for rapid development over high reliable and complex systems.
What it should do
The user has the web application opened in his browser. Now an phone call comes is. The phone call is registered by a PBX monitoring daemon. In this case via the Asterisk Manager Interface. The daemon sends the available information (remote extension, local extension, call direction, channel status, start time, end time) somehow to the web application. Next the user receives a notified about the phone call event. The user now can work with this. For example by entering a summary or by matching the call to a customer profile.
The duration from the first event on the PBX (e.g. the creation of a new channel) to the popup notification in the browser should be short. Given a fast network I would like to be within two seconds. The single pieces of information about an event are created asynchronously. The local extension may be supplied separate from the remote extension. The user can enter a summary before the call has ended. The end time, new status etc. will show up on the interface as soon as one party has hung up.
The PBX monitor is just one data source. There will be more monitors like email or a request via a web form. The monitoring daemons will not necessarily run on the same host as the database or web server. I do not image the application will serve thousands of logged in users or concurrent requests soon. But from the design 200 users with maybe about the same number of events per minute should not be a scalability issue.
How should I do?
I am interested to know how you would design such an application. What technologies would you suggest? How do the daemons communicate their information? When and by whom is the data about an event stored into the main database? How does the user get notified? Should the browser receive a complete dataset on behalf of a daemon or just a short note that new data is available? Which JS library to use and how to create the necessary code on the server side?
On my research I came across a lot of possibilities: Message brokers, queue services, some rails background task solutions, HTTP Push services, XMPP and so on. Some products I am going to look into: ActiveMQ, Starling and Workling, Juggernaut and Bosh.
Maybe I am aiming too hight? If there is a simpler or easier way, like just using the XML or JSON interface of Rails, I would like to read this even more.
I hope the text is not too long :)
Thanks.
If you want to skip Java and Flash, perhaps it makes sense to use a technology in the Comet family to do the push from the server to the browser?
http://en.wikipedia.org/wiki/Comet_%28programming%29
For the sake of simplicity, for notifications from daemons to the Web browser, I'd leave Rails in the middle, create a RESTful interface to that Rails application, and have all of the daemons report to it. Then in your daemons you can do something as simple as use curl or libcurl to post the notifications. The Rails app would then be responsible for collecting the incoming notifications from the various sources and reporting them to the browser, either via JavaScript using a Comet solution or via some kind of fatter client implemented using Flash or Java.
You could approach this a number of ways but my only comment would be: Push, don't pull. For low latency it's not only quicker it's more efficient, as your server now doesn't have to handle n*clients once a second polling the db/queue. ActiveMQ is OK, but Starling will probably serve you better if you're not looking for insane levels of persistence.
You'll almost certainly end up using Flash on the client side (Juggernaut uses it last time I checked) or Java. This may be an issue for your clients (if they don't have Flash/Java installed) but for most people it's not an issue; still, a fallback mechanism onto a pull notification system might be prudent to implement.
Perhaps http://goldfishserver.com might be of some use to you. It provides a simple API to allow push notifications to your web pages. In short, when your data updates, send it (some payload data) to the Goldfish servers and your client browsers will be notified, with the same data.
Disclaimer: I am a developer working on goldfish.
The problem
There is an event - either external (or perhaps internally within your app).
Users should be notified.
One solution
I am myself facing this problem. I haven't solved it yet, but this is how I intend to do it. It may help you too:
(A) The app must learn about the event (via an exposed end point)
Expose an end point by which you app can be notified about external events.
When the end point is hit (and after authentication then users need to be notified).
(B) Notification
You can notify the user directly by changing the DOM on the current web page they are on.
You can notify users by using the Push API (but you need to make sure your browsers can target that).
All of these notification features should be able to be handled via Action Cable: (i) either by updating the DOM to notify you when a phone call comes in, or (ii) via a push notification that pops up in your browser.
Summary: use Action Cable.
(Also: why use an external service like Pusher, when you have ActionCable at your disposal? Some people say scalability, and infrastructure management. But I do not know enough to comment on these issues. )