Is it possible to Add a message to an Azure queue then, in the same flow, update or delete that message?
The idea would be to use the queue to ensure that some work gets done - there's a worker role monitoring that queue. But, the Web role which added the message may be able to make some progress toward (and sometimes even to complete) the transaction.
The worker would already be designed to handle double-delivery and reprocessing partially handled messages (from previous, failed worker attempts) - so there isn't a technical problem here, just time inefficiency and some superfluous storage transactions.
So far it seems like adding the message allows for a delivery delay, giving the web role some time, but doesn't give back a pop-receipt which it seems like we'd need to update/delete the message. Am I missing something?
It seems this feature was added as part of the "2016-05-31” REST API
we now make pop receipt value available in the Put Message (aka Add Message) response which allows users to update/delete a message without the need to retrieve the message first.
I suggest you follow these steps as it worked for me
How to: Create a queue
A CloudQueueClient object lets you get reference objects for queues. The following code creates a CloudQueueClient object. All code in this guide uses a storage connection string stored in the Azure application's service configuration. There are also other ways to create a CloudStorageAccount object. See CloudStorageAccount documentation for details.
// Retrieve storage account from connection string
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
CloudConfigurationManager.GetSetting("StorageConnectionString"));
// Create the queue client
CloudQueueClient queueClient = storageAccount.CreateCloudQueueClient();
Use the queueClient object to get a reference to the queue you want to use. You can create the queue if it doesn't exist.
// Retrieve a reference to a queue
CloudQueue queue = queueClient.GetQueueReference("myqueue");
// Create the queue if it doesn't already exist
queue.CreateIfNotExists();
How to: Insert a message into a queue
To insert a message into an existing queue, first create a new CloudQueueMessage. Next, call the AddMessage method. A CloudQueueMessage can be created from either a string (in UTF-8 format) or a byte array. Here is code which creates a queue (if it doesn't exist) and inserts the message 'Hello, World':
// Retrieve storage account from connection string.
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
CloudConfigurationManager.GetSetting("StorageConnectionString"));
// Create the queue client.
CloudQueueClient queueClient = storageAccount.CreateCloudQueueClient();
// Retrieve a reference to a queue.
CloudQueue queue = queueClient.GetQueueReference("myqueue");
// Create the queue if it doesn't already exist.
queue.CreateIfNotExists();
// Create a message and add it to the queue.
CloudQueueMessage message = new CloudQueueMessage("Hello, World");
queue.AddMessage(message);
For more details, refer this link.
http://azure.microsoft.com/en-us/documentation/articles/storage-dotnet-how-to-use-queues/
Girish Prajwal
Related
The documentation for Spring WebSockets states:
4.4.13. User Destinations
An application can send messages targeting a specific user, and Spring’s STOMP support recognizes destinations prefixed with "/user/" for this purpose. For example, a client might subscribe to the destination "/user/queue/position-updates". This destination will be handled by the UserDestinationMessageHandler and transformed into a destination unique to the user session, e.g. "/queue/position-updates-user123". This provides the convenience of subscribing to a generically named destination while at the same time ensuring no collisions with other users subscribing to the same destination so that each user can receive unique stock position updates.
Is this supposed to work in a multi-server environment with RabbitMQ as broker?
As far as I can tell, the queue name for a user is generated by appending the simpSessionId. When using the recommended client library stomp.js this results in the first user getting the queue name "/queue/position-updates-user0", the next gets "/queue/position-updates-user1" and so on.
This in turn means the first users to connect to different servers will subscribe to the same queue ("/queue/position-updates-user0").
The only reference to this I can find in the documentation is this:
In a multi-application server scenario a user destination may remain unresolved because the user is connected to a different server. In such cases you can configure a destination to broadcast unresolved messages to so that other servers have a chance to try. This can be done through the userDestinationBroadcast property of the MessageBrokerRegistry in Java config and the user-destination-broadcast attribute of the message-broker element in XML.
But this only makes the it possible to communicate with a user from a different server than the one where the web socket is established.
I feel I'm missing something? Is there anyway to configure Spring to be able to safely use MessagingTemplate.convertAndSendToUser(principal.getName(), destination, payload) in a multi-server environment?
If they need to be authenticated (I assume their credentials are stored in a database) you can always use their database unique user id to subscribe to.
What I do is when a user logs in they are automatically subscribed to two topics an account|system topic for system wide broadcasts and account|<userId> topic for specific broadcasts.
You could try something like notification|<userid> for each person to subscribe to then send messages to that topic and they will receive it.
Since user Ids are unique to each user you shouldn't have an issue within a clustered environment as long as each environment is hitting the same database information.
Here is my send method:
public static boolean send(Object msg, String topic) {
try {
String destination = topic;
String payload = toJson(msg); //jsonfiy the message
Message<byte[]> message = MessageBuilder.withPayload(payload.getBytes("UTF-8")).build();
template.send(destination, message);
return true;
} catch (Exception ex) {
logger.error(CommService.class.getName(), ex);
return false;
}
}
My destinations are preformatted so if i want to send a message to user with id of one the destinations looks something like /topic/account|1.
Ive created a ping pong controller that tests websockets for users who connect to see if their environment allows for websockets. I don't know if this will help you but this does work in my clustered environment.
/**
* Play ping pong between the client and server to see if web sockets work
* #param input the ping pong input
* #return the return data to check for connectivity
* #throws Exception exception
*/
#MessageMapping("/ping")
#SendToUser(value="/queue/pong", broadcast=false) // send only to the session that sent the request
public PingPong ping(PingPong input) throws Exception {
int receivedBytes = input.getData().length;
int pullBytes = input.getPull();
PingPong response = input;
if (pullBytes == 0) {
response.setData(new byte[0]);
} else if (pullBytes != receivedBytes) {
// create random byte array
byte[] data = randomService.nextBytes(pullBytes);
response.setData(data);
}
return response;
}
I am creating utiltiy which send mail using my outlook account, to do so I am creating object of javax.mail.Message and send it, if message sending is failed due to SendingFailedException, I want to add those messages into jms queue, and at the other end listener will run at every 10 min interval to consume these messages from the queue and try to resend those messages.
I have gone through some of the stackoverflow topics related to same, they instructed to change message into xml or in JSON, I just want to know how to deal with it, if that would be the way to implement this.
Thanks in advance
Using the MimeMessage.writeTo method you can turn the message into a byte stream. Collect it in a ByteArrayOutputStream and then include the bytes in the JMS message. At the other end, you can reconstitute the message using the MimeMessage constructor that takes an InputStream.
For example:
ByteArrayOutputStream bos = new ByteArrayOutputStream();
msg.writeTo(bos);
byte[] data = bos.toByteArray();
// put the data in a JMS message
// in the receiver, extract the byte array from the message
byte[] data = ...
MimeMessage msg = new MimeMessage(session, data);
Sorry, I can't help you with the JMS part.
I am having a great experience with ServiceStack & Redis, but I'm confused by ThreadPool and Pub/Sub within a thread, and an apparent limitation for accessing Redis within a message callback. The actual error I get states that I can only call "Subscribe" or "Publish" within the "current context". This happens when I try to do another Redis action from the message callback.
I have a process that must run continuously. In my case I can't just service a request one time, but must keep a thread alive all the time doing calculations (and controlling these threads from a REST API route is ideal). Data must come in to the process on a regular basis, and data must be published. The process must also store and retrieve data from Redis. I am using routes and services to take data in and store it in Redis, so this must take place async from the "calculation" process. I thought pub/sub would be the answer to glue the pieces together, but so far that does not seem possible.
Here is how my code is currently structured (the code with the above error). This is the callback for the route that starts the long term "calculation" thread:
public object Get(SystemCmd request)
{
object ctx = new object();
TradingSystemCmd SystemCmd = new TradingSystemCmd(request, ctx);
ThreadPool.QueueUserWorkItem(x =>
{
SystemCmd.signalEngine();
});
return (retVal); // retVal defined elsewhere
}
Here is the SystemCmd.signalEngine():
public void signalEngine(){
using (var subscription = Redis.CreateSubscription())
{
subscription.OnSubscribe = channel =>
{
};
subscription.OnUnSubscribe = channel =>
{
};
subscription.OnMessage = (channel, msg) =>
{
TC_CalcBar(channel, redisTrade);
};
subscription.SubscribeToChannels(dmx_key); //blocking
}
}
The "TC_CalcBar" call does processing on data as it becomes available. Within this call is a call to Redis for a regular database accesses (and the error). What I could do would be to remove the Subscription and use another method to block on data being available in Redis. But the current approach seemed quite nice until it failed to work. :-)
I also don't know if the ThreadPool has anything to do with the error, or not.
As per Redis documentation:
Once the client enters the subscribed state it is not supposed to
issue any other commands, except for additional SUBSCRIBE, PSUBSCRIBE,
UNSUBSCRIBE and PUNSUBSCRIBE commands.
Source : http://redis.io/commands/subscribe
I need to remove/delete my topic subscriber. I found this http://activemq.apache.org/manage-durable-subscribers.html
However, it's not good enough for us. We want to control the timing of removing a subscriber, and no matter there are any message or not. Besides, our program is written by C#. So the best solution for us is NMS API.
Thanks.
Here are the code,
Apache.NMS.ActiveMQ.ConnectionFactory factory = new Apache.NMS.ActiveMQ.ConnectionFactory(m_brokerURI);
m_connection = factory.CreateConnection(username, password);
Apache.NMS.ActiveMQ.Connection con = (Apache.NMS.ActiveMQ.Connection)m_connection;
ISession session = m_connection.CreateSession(AcknowledgementMode.AutoAcknowledge);
try
{
session.DeleteDurableConsumer(strQueueName);
}
catch (Exception ex)
{
// log the error message
}
Update
Our scenario is quite simple.
A client built a queue and subscribed a consumer on a topic.
the client side closed the connection.
delete the consumer on the server side(as the example code in the last update)
Here is the snapshot of activemq broker via jconsole:
jconsole snapshot
We would like to remove the subscriber “7B0FD84D-6A2A-4921-967F-92B215E22751” by following method,
But always got this error "javax.jms.InvalidDestinationException : No durable subscription exists for: 7B0FD84D-6A2A-4921-967F-92B215E22751"
strSubscriberName = “7B0FD84D-6A2A-4921-967F-92B215E22751”
session.DeleteDurableConsumer(strSubscriberName);
To delete a durable subscription from the NMS API you use the DeleteDurableConsumer method defined in ISession. You must call this method from a Connection that uses the same client Id as was used when the subscription was created and you pass the name of the subscription that is to be removed. The method will fail if there is an active subscriber though so be prepared for that exception.
In the sample code you don't set a Client Id on the connection. When working with durable subscriptions you must, must, MUST always use the same client Id and subscription name. So in you same you will get this error until you set the client Id to the same value as the connection that created the subscription in the first place.
I have a Windows service using NServiceBus to handle incoming messages.
While processing a message, I would like to check to see if there are any other remaining messages on the queue to process.
What is the best way to approach this?
For this specific scenario I'd say that a saga could be appropriate where it is created by the first message received, opens a timeout (for let's say one minute), collects all messages during that period of time, then Bus.SendLocal's a message containing all rows, for which another handler creates the spreadsheet and uploads.
Since, NServiceBus is using MSMQ, you can use the methods from System.Messaging.
Included is a modified method, I'm currently working on, to do a kind of batch processing.
using System.Messaging;
public int PeekAtQueue()
{
const string QUEUE_NAME = "private$\\you_precious_queuname";
if (!MessageQueue.Exists(".\\" + QUEUE_NAME))
return 0;
var messageQueues = MessageQueue.GetPrivateQueuesByMachine(Environment.MachineName);
var queue = messageQueues.Single(x => x.QueueName == QUEUE_NAME);
return queue.GetAllMessages().Count();
}
Modified here itself in the editor. Hope it still compiles :)
Found a similar discussion here, by the way:
http://jopinblog.wordpress.com/2008/03/12/counting-messages-in-an-msmq-messagequeue-from-c/