I am in the process of QuickFix service initiator implementation in c# which needs to do the following.
Listen to incoming QuoteRequest messages and save them to a local database/queue.
Our users will have the ability to hit the Bids on these quote requests. These selections will be saved in a local queue.
Service will need to read the queue and send Quote messages back to the sender.
Listen to QuoteResponse / BusinessReject and QuoteStatus Messages from the sender and store on our end.
I'm planning to have two threads in my service.
Thread 1: This will be used to listen to incoming QuoteRequest, Quote response, Businessreject and quotestatus messages.
Outgoing ExecutionReport will be sent from OnMessage event handler while cracking QuoteResponse message.
Those messages will get stored in our system and published on our sites/queue etc.
Thread 2: This will listen to another local queue and sends out Quote(bids) messages to the acceptor. Quotes will be sent out using Session.SendToTarget.
Is there a way to configure two instances of initiators to be used in each thread ? Or do I create one initiator and add two sessions.
Would it work if both initiators are using same socket server and port ? Also if a message is not cracked by one thread would it be available for the other thread ?
I couldnt find any example of a multithreaded approach to handle both incoming and outgoing messages.
Appreciate any inputs/recommendation on a correct approach to implementation.
This is only one connection, and only one session, so there should only be one Initiator.
You can set up different worker threads, but your various OnMessage() callbacks should be a common entry point. They can dispatch their received messages to your thread (you could have them push received messages into a queue or something for your threads to consume). Your threads can do what they need to do and then call sendToTarget as appropriate.
Above all else, try not to put any expensive logic in the QF callbacks; put it in the threads. Other than that, you can do what you want.
Related
I am experiencing a racing condition issue with my rabbitmq client. My service has multiple instances listening on a single queue, storing received messages into a db.
When they all get restarted at once, i sometimes see messages being redelivered and stored in the db twice. This is normally handled on client side by checking if the correlationid has already been stored in the db. This works 99.9% of the time (i am processing 5mill messages a day, it happens once or twice a day).
So as i said, i suspect a racing condition being responsible for this. I think i receive the message again while my first message is still being processed. So when i check i dont see it stored in the db, and in the end, store it twice.
I should not that this is a non-issue, but has been bothering me because i can't really explain what happens.
I suspect that it happens when i restart the services. I think i disconnect from the queue, while i am still processing the message, triggering rabbitmq to redeliver again to another instance that is not shutdown yet.
What i want to do is when i am stopping the service is to
tell rabbitmq that i dont want to receive further messages
wait for all currently processing messages to finish
send acks / nacks
shutdown
Right now i am first deregistering the received event
_consumerServer.Received -= MessageReceived;
then i am disposing the channel and the server
if (_channel != null)
{
_channel.Close();
_channel.Dispose();
}
if (_connectionServer != null)
{
_connectionServer.Close();
_connectionServer.Dispose();
}
The RabbitMQ team monitors this mailing list and only sometimes answers questions on StackOverflow.
Rather than try and shut down a consumer so that messages won't be redelivered, you should handle redelivery correctly. Check for and handle the case where the redelivered flag is set on a message, and act appropriately. You should also try store your messages in such a way that the store operation is idempotent - i.e. it can happen multiple times and you will only have one record in your database.
Please see the guidelines that the team have provided here:
https://www.rabbitmq.com/reliability.html#consumer
I'm using SingalR in an application that sends alot messages in a short period of time.
let's say i have client A and client B.
Client A just sends messages and client B just listening to messages.
Client A sends the following messages in the following order: A->B->C->D
What i'm seeing is that Client B sometimes receives the messages in a different order, for example: B->A->C->D
It is important for maintain the same order i sent the messages.
I've looked online and i found people saying i should use async-await on the function on the hub that handles those messages.
public async Task hubMethod(msgObject msg)
{
await Clients.All.message(msg);
}
I'm not sure how that helps since each time i make a call from client A , singalR should create a new instance of the hub.
The only thing it does is wait for the singalR that it finished doing all it can do on the server in order to send the message to the other client and notifies it to client A.
So my question is this - is there a singalR or asp.net mechanism that make sure i receive the messages in the correct order on the other client or do i need to write my own mechanism (server or client) that reorders the messages if they are out of order - and if so, is there a library that already does it?
You need to write your own mechanism. SignalR in client B has no way to know in which order the clients messages were sent by client A because there is many things that could delay a specific message arrival, like network delay, the only thing SignalR can guarantee is the order in which the messages arrived.
If you really need to know the original order of the messages you could put a count inside the message and let client B sort them out. However i suggest you try another approach, because guaranteeing the order of delivery is not a easy task.
I'm using RabbitMQ to deliver messages to worker processes (using the official C# client). I have been running simple tests during the implementation, and all has been going swimmingly until now.
I ran a test where I queued messages for a worker process that was not listening (no connection). Once I had queued several hundred messages, I started that process. It created its IModel, declared its queue (which already existed), and began consuming messages (with BasicConsume). This went great. This process, as it processed messages, created messages for other queues. There were processes already listening to these queues (with BasicConsume), and so the messages were immediately delivered to those clients (or so the server thought...). The messages are never processed.
The server definitely believes that the messages have been delivered (the messages are all in the "unacked" bucket, not the "ready" bucket), but
IBasicConsumer.HandleBasicDeliver never got called on the client. I have tried several different techniques (using a Subscription, using QueueingBasicConsumer as well as my own custom consumer), and the outcome is exactly the same. I'm at a complete loss. If I close the connection (there is only one connection here), then the messages immediately move from the "unacked" bucket to the "ready" bucket".
Why doesn't the client get notified when messages are delivered?
Looking into the code, ModelBase.Close() calls ConsumerDispatcher.Shutdown() (ModelBase.cs line 301), and from there, it calls workService.StopWork() (ConcurrentConsumerDispatcher.cs line 27). It seems to me (by a cursory view of the code) that this stops ALL work in the connection's ConsumerWorkService. Instead, should ConcurrentConsumerDispatcher.Shutdown() be calling workService.StopWork(this) on line 27?
It's a bug in the RabbitMQ client, and a fix has already been merged in.
It should be available in the next nightly build, on 4/18/2015.
If your BasicConsume defines noAck = false, after you Dequeues a message needs to run the next code:channel.BasicAck(result.DeliveryTag, false);
If your BasicConsume defines noAck = true, after you Dequeues a message it's removed from the server automatically.
I've got a server side protocol that controls a telephony system, I've already implemented a client library that communicates with it which is in production now, however there are some problems with the system I have at the moment, so I am considering re-writing it.
My client library is currently written in Java but I am thinking of re-writing it in both C# and Java to allow for different clients to have access to the same back end.
The messages start with a keyword have a number of bytes of meta data and then some data. The messages are always terminated by an end of message character.
Communication is duplex between the client and the server usually taking the form of a request from the Client which provokes several responses from the server, but can be notifications.
The messages are marked as being on of:
C: Command
P: Pending (server is still handling the request)
D: Data data as a response to
R: Response
B: Busy (Server is too busy to handle response at the moment)
N: Notification
My current architecture has each message being parsed and a thread spawned to handle it, however I'm finding that some of the Notifications are processed out of order which is causing me some trouble as they have to be handled in the same order they arrive.
The duplex messages tend to take the following message format:
Client -> Server: Command
Server -> Client: Pending (Optional)
Server -> Client: Data (optional)
Server -> Client: Response (2nd entry in message data denotes whether this is an error or not)
I've been using the protocol for over a year and I've never seen the a busy message but that doesn't mean they don't happen.
The server can also send notifications to the client, and there are a few Response messages that are auto triggered by events on the server so they are sent without a corresponding Command being issued.
Some Notification Messages will arrive as part of sequence of messages, which are related for example:
NotificationName M00001
NotificationName M00001
NotificationName M00000
The string M0000X means that either there is more data to come or that this is the end of the messages.
At present the tcp client is fairly dumb it just spawns a thread that notifies an event on a subscriber that the message has been received, the event is specific to the message keyword and the type of message (So data,Responses and Notifications are handled separately) this works fairly effectively for Data and response messages, but falls over with the notification messages as they seem to arrive in rapid sequence and a race condition sometimes seems to cause the Message end to be processed before the ones that have the data are processed, leading to lost message data.
Given this really badly written description of how the system works how would you go about writing the client side transport code?
The meta data does not have a message number, and I have not control over the underlying protocol as it's provided by a vendor.
The requirement that messages must be processed in the order in which they're received almost forces a producer/consumer design, where the listener gets requests from the client, parses them, and then places the parsed request into a queue. A separate thread (the consumer) takes each message from the queue in order, processes it, and sends a response to the client.
Alternately, the consumer could put the result into a queue so that another thread (perhaps the listener thread?) can send the result to the client. In that case you'd have two producer/consumer relationships:
Listener -> event queue -> processing thread -> output queue -> output thread
In .NET, this kind of thing is pretty easy to implement using BlockingCollection to handle the queues. I don't know if there is something similar in Java.
The possibility of a multi-message request complicates things a little bit, as it seems like the listener will have to buffer messages until the last part of the request comes in before placing the entire thing into the queue.
To me, the beauty of the producer/consumer design is that it forces a hard separation between different parts of the program, making each much easier to debug and minimizing the possibility of shared state causing problems. The only slightly complicated part here is that you'll have to include the connection (socket or whatever) as part of the message that gets shared in the queues so that the output thread knows where to send the response.
It's not clear to me if you have to process all messages in the order they're received or if you just need to process messages for any particular client in the proper order. For example, if you have:
Client 1 message A
Client 1 message B
Client 2 message A
Is it okay to process the first message from Client 2 before you process the second message from Client 1? If so, then you can increase throughput by using what is logically multiple queues--one per client. Your "consumer" then becomes multiple threads. You just have to make sure that only one message per client is being processed at any time.
I would have one thread per client which does the parsing and processing. That way the processing would be in the order it is sent/arrives.
As you have stated, the tasks cannot be perform in parallel safely. performing the parsing and processing in different threads is likely to add as much overhead as you might save.
If your processing is relatively simple and doesn't depend on external systems, a single thread should be able to handle 1K to 20K messages per second.
Is there any other issues you would want to fix?
I can recommend only for Java-based solution.
I would use some already mature transport framework. By "some" I mean the only one I have worked with until now -- Apache MINA. However, it works and it's very flexible.
Regarding processing messages out-of-order -- for messages which must be produced in the order they were received you could build queues and put such messages into queues.
To limit number of queues, you could instantiate, say, 4 queues, and route incoming message to particular queue depending on the last 2 bits (indeces 0-3) of the hash of the ordering part of the message (for example, on the client_id contained in the message).
If you have more concrete questions, I can update my answer appropriately.
I'm using ActiveMQ in a .Net program and I'm flooded with message-events.
In short when I get a queue-event 'onMessage(IMessage receivedMsg)' I put the message into an internal queue out of which X threads do their thing.
At first I had: 'AcknowledgementMode.AutoAcknowledge' when creating the session so I'm guessing that all the messages in the queue got sucked down and put into the memory queue (which is risky since with a crash, everything is lost).
So then I used: 'AcknowledgementMode.ClientAcknowledge' when creating the session, and when a worker was ready with the message it calls the 'commit()' method on the message. However, still all the messages get sucked down from the queue.
How can I configure it that ONLY an X amount of messages are being processed or are in an internal queue, and that not everything is being 'downloaded' right away?
Are you on .NET 4.0? You could use a BlockingCollection . Set it to the maximum amount it may contain. As soon as a thread tries to put in an excess element, the Add operation will block until the collection falls below the threshold again.
Maybe that would do it for throttling?
There is also an API for throttling in the Rx framework, but I do not know how it is implemented. If you implement your Queue source as Observable, this API would become available for you, but I don't know if this hits your needs.
You can set the client prefetch to control how many messages the client will be sent. When the Session is in Auto Ack, the client will only ack a message once its been delivered to your app via the onMessage callback or through a synchronous receive. By default the client will prefetch 1000 messages from the broker, if the client goes down these messages would be redelivered to another client it this was a Queue, otherwise for a topic they are just discarded as a topic is a broadcast based channel. If you set the prefetch to one then you client would only be sent one message from the sever, then each time your onMessage callback completes a new message would be dispatched as the client would ack that message, that is if the session is in Auto Ack mode.
Refer to the NMS configuration page for all the options:
http://activemq.apache.org/nms/configuring.html
Regards
Tim.
FuseSource.com