I have an ESB (Aqualogic) that have a proxy.
This proxy will call 3 different services, and i have to put those 3 services in a transaction scope...
ESB doesn't have support to transactions...
Someone know any solution to that?
I am not familiar with Aqualogic, but in general I can say that what you want to do is very, very difficult.
If Aqualogic uses MSMQ for transport then you may have some form of support for transactions by using transactional queues. But that's only the start.
If you want to integrate WCF services with a transactional context, you need to set up support for the WS-Atomic protocol (see http://msdn.microsoft.com/en-us/library/ms729784.aspx and http://social.msdn.microsoft.com/Forums/en/wcf/thread/cae32545-6536-4631-b89f-54f55da62199). This is a serious pain in the butt.
Not just to configure it, but also to use it. Using WS-Atomic across servers means you need to activate MSDTC on all machines, and coordination between these MSDTC's is very slow and prone to long timeouts.
It's a better bet to not expect to run everything in a single transaction, but to use a workflow that compensates for partial success/partial failure of your operation. See also http://msdn.microsoft.com/en-us/library/dd483319.aspx for an example.
Related
I was trying to get some info on WCF transactions, and I did manage to get info on how to use them. What I didn't get much info on is Why/When to use them.
What is the difference between database transactions and WCF transactions? Is there any specific case when either of these approach is preferred over the other?
By WCF transactions what you are really asking about is Microsoft's implementation of the WS-AtomicTransaction web service extension standard.
Why/When to use them
Similar to using a database transaction to guarantee consistency within the database, WS-AtomicTransaction is used to guarantee consistency within a larger, distributed system, based on communication over SOAP 1.2 services. This distributed system may or may not include database writes, but more often than not it will do.
Transactions propagated to the service from clients will cause the internal code of the service to execute within the context of the clients transaction.
So, in that same way a database transaction can wrap multiple database writes into a single unit of work, a WCF transaction can wrap multiple service calls into a single unit of work, so that a failure in one will roll back the others.
This, as you can imagine, is hugely costly from a resource perspective, so these kinds of cross-network transactions should be rarely (if ever) used unless absolutely necessary.
I was assigned to update existing system of gathering data coming from points of sale and inserting it into central database. The one that is working now is based on FTP/SFTP transmission, where the information is sent once a day, usually at night. Unfortunately, because of unstable connection links (low quality 2G/3G modems), some of the files appear to be broken. With just a few shops connected that way everything was working smooth, but along with increasing number of shops, errors became more often. What is worse, the time needed to insert data into central database is taking up to 12 - 14h (including waiting for the data to be downloaded from all of the shops) and that cannot happen during the working day as it would block the process of creating sale reports and other activities with the database - so we are really tight with processing time here.
The idea my manager suggested is to send the data continuously, during the day. Data packages would be significantly smaller, so their transmission and insertion would be much faster, central server would contain actual (almost real time) data and night could be used for long running database activities like creating backups, rebuilding indexes etc.
After going through many websites, I found that:
using ASMX web service is now obsolete and WCF should be used instead
WCF with MSMQ or System Messaging could be used to safely transmit data, where I don't have to care that much about acknowledging delivery of data, consistency, nodes going offline etc.
according to http://blogs.msdn.com/b/motleyqueue/archive/2007/09/22/system-messaging-versus-wcf-queuing.aspx WCF queuing is better
there are also other technologies for implementing message queue, like RabbitMQ, ZeroMQ etc.
And that is where I become confused. With so many options, do you have any pros and cons of these technologies?
We were using .NET with Windows Forms and SQL Server, but if it would be necessary, we could change to something more suitable. I am also a bit afraid of server efficiency. After some calculations, server would be receiving about 15 packages of data per second (peak). Is it much? I know there are many websites without serious server infrastructure, that handle hundreds of visitors online and still run smooth, but the website mainly uploads data to the client, and here we would download it from the client.
I also found somewhat similar SO question: Middleware to build data-gathering and monitoring for a distributed system
where DDS was mentioned. What do you think about introducing some middleware servers that would cope with low quality links to points of sale, so the main server would not be clogged with 1KB/s transmission?
I'd be grateful with all your help. Thank you in advance!
Rabbitmq can easily cope with thousands of 1kb messages per second.
As your use case is not about processing real time data, I'd say you should combine few messages and send them as a batch. That would be good enough in order to spread load over the day.
As the motivation here is not to process the data in real time, then any transport layer would do the job. Even ftp/sftp. As rabbitmq will work fine here, it's not the typical use case for it.
As you mentioned that one of your concerns is slow/unreliable network, I'd suggest to compress the files before sending them, and on the receiving end, immediately verify their integrity. Rsync or similar will probably do great job in doing that.
From what I understand, you have basically two problems:
Potential for loss/corruption of call data
Database write performance
The potential for loss/corruption of call data is being caused by a lack of reliability in the transmission of data from client to service.
And it's not clear what is causing the database contention/performance issues, beyond a vague reference to high volumes, so this answer will be more geared towards solving the first problem.
You have correctly identified the need for reliable asynchronous communication transport as a way to address the reliability issues in your current setup.
Looking at MSMQ to deliver this is a valid first step. MSMQ provides reliable communication via a store and forward messaging semantic which comes out of the box and requires very little in the way of configuration.
Unfortunately, while suitable for your needs, MSMQ relies on 2 things:
A reliable network protocol, and
A client service running on both sending and receiving machine.
From your description above, I don't believe 1 exists (the internet is not a reliable network), and you might well struggle with 2 - MSMQ only ships with Windows Server or business/enterprise versions of Windows on the desktop.(*see below...)
As a possible solution to the network reliability problem, you could use a WCF or a RESTful endpoint (using Nancy or WebApi) to expose a service operation(s) exposed over HTTP, which would accept the incoming calls from the client machines. These technologies are quite different, so you'll need to make sure you're making the correct choice early on.
WCF supports WS-ReliableMessaging from the SOAP 1.2 specification out of the box, which allows for reliable web service calls over http, however it's very config-heavy and not generally a nice framework to work with.
REST much simpler than WCF in .Net, is very lightweight and easy to use. However, for reliable delivery you would have to expose some kind of GET operation (in addition to a POST to allow the client to send data) to be called (within a reasonable time-frame) to verify the data was committed. The client would have to implement some kind of retry semantic if the result of the GET "acknowledgement" was negative.
Despite requiring two operations rather than one for the WCF route, I would favour the REST approach. I've done plenty of both and find REST services way nicer to work with.
(*) That's not to say that MSMQ wouldn't work in your ultimate solution, just that it would not be used to address the transmission reliability issue. However it could still be used to address another of your problems, that of database write contention. If you were to queue incoming requests once they came into the server, then these could be processed by an "offline" process, which could then perform the required database operations in a reliable manner. This could be done by using MSMQ transactional queues.
In response to comments:
99% messages are passed from shop to main server, but if some change
is needed (price correction, discounts etc.), that data has to be sent
to shop.
This kind of changes things. Had I understood from the beginning that you had a bidirectional requirement, and seeing as how you have managed to establish msmq communication, I would have nudged you towards NServiceBus, which is a really, really cool wrapper around MSMQ. The reason I would have done this is that you appear to have both a one way, and a publish-subscribe requirement, which is supported really nicely by NServiceBus.
We are currently setting up nServiceBus in a distributor/worker model and I was wondering if it is really worth it for us.
In our initial test lab, I have 2 clustered distributors and one worker (more workers in prod). What I am wondering is if it would be just as effective to leverage our high availability SQL Server for storage and rebuild the servers to all handle the work instead of having dedicated distributors and workers. All of our messages get onto the bus via a simple .Net Web API service. I could install that service on each box along with the endpoint dlls and have them all talk to SQL server which has more than enough horsepower to handle the load. We have a load balancer available to us to distribute the messages to the handlers.
What would some of the drawbacks be in taking this approach vs the distributor model?
What has me concerned is a line from David Boike's book on nServiceBus (great book BTW) that I just read...
"Using SQL Server as a transport can be a great choice for small
projects on teams that already use SQL Server"
The small projects part is what I am worried about. This is by no means a small project and it will have a pretty high volume of messages flowing through this layer as we refactor more systems to be message driven.
Has anyone been down the same road comparing SQL server to distributor and where did you come out?
Thanks
What I was referring into the book on the quote you mentioned was that there are times when you have a fairly small solution, all in a single SQL Server database, and you want to introduce some messaging around the edges. The SQL Server transport makes it easy to do that without adding a bunch of additional overhead and moving parts. If you keep everything in one database, you can even ditch the Distributed Transactions Coordinator. It can also be really useful for integrating with a legacy system where you monitor for changes via database triggers.
However, keep in mind (and if there's a next edition, I'll be sure to go into a little more detail about this) that the SQL Server transport uses a Broker pattern, that is, all communication must go through SQL Server so it becomes a central point of failure and a central bottleneck. The default MSMQ transport, on the other hand, follows the Bus architectural style, meaning it's completely decentralized. Each endpoint can run completely on its own, at least until you introduce additional dependencies.
Andreas benchmarked the new transports, and found that on V4 MSMQ was capable of roughly 6000 sends/s and 2300 receives/s, and that SqlServer was on par with that, but on MSMQ that is roughly per server (each server gets its own throughput), with the SQL Server transport that is going to be your total achievable throughput, period, and any endpoints you add will have to share it.
Of course, broker-style transports (the rest of the new transports in 4.0 are brokers too) do have some advantages over MSMQ. The biggest is that you don't need to use the Distributor to scale out. In a broker, the "queue" is centralized so you can simply spin up additional endpoints pointing at the same input queue in a competing consumers pattern.
Of course as in all things, your mileage may vary, but if you are planning an ambitious system, then the SQL Server transport may not be for you, as you will at some point get mired down in that point where your only option is to scale up your SQL Server instance.
I have created a WCF web service that will upload data from SQL Server to our ISeries. When an end user is finished with their data entry (a batch), they will "send" the batch number to the web service. The web service will then upload that data to the ISeries. It cannot be assumed that this will be a quick process and there may be many end users hitting the web service at once. Likewise, because the way the database is setup on the ISeries, I can't upload this data simultaneously because we may run into locks, misfired triggers, etc. So, I want somehow to queue these calls so that they are done in order received.
I have been searching for methods to do this and there's a lot of information in 2011 and earlier discussing MSMQ. Is that the still preferred way to do this? Would Reentrant Concurrency mode be a more "modern" option?
There are a lot of alternative queuing systems. Since you have a SQL Server in place I would recommend using MSMQ. In this combination you can use TransactionScope out-of-the-box to handle transcations spanning your DB and the Queuing system.
From my own experience, MSMQ is a proven and stable technology stack.
I've been asked by my team leader to investigate MSMQ as an option for the new version of our product. We use SQL Service Broker in our current version. I've done my fair share of experimentation and Googling to find which product is better for my needs, but I thought I'd ask the best site I know for programming answers.
Some details:
Our client is .NET 1.1 and 2.0 code; this is where the message will be sent from.
The target in a SQL Server 2005 instance. All messages end up being database updates or inserts.
We will send several updates that must be treated as a transaction.
We have to have perfect message recoverability; no messages can be lost.
We have to be asynchronous and able to accept messages even when the target SQL server is down.
Developing our own queuing solution isn't an option; we're a small team.
Things I've discovered so far:
Both MSMQ and SQL Service Broker can do the job.
It appears that service broker is faster for transactional messages.
Service Broker requires a SQL server running somewhere, whereas MSMQ needs any configured Windows machine running somewhere.
MSMQ appears to be better/faster/easier to set up/run in clusters.
Am I missing something? Is there a clear winner here? Any thoughts, experiences, or links would be valued. Thank you!
EDIT: We ended up sticking with service broker because we have a custom DB framework used in some of our client code (we handle transactions better). That code captured SQL for transactions, but not . The client code was also all version 1.1 of .NET, so we'd have to upgrade all the client code. Thanks for your help!
Having just migrated my application from Service Broker to MSMQ, I would have to vote for using MSMQ. There are several factors to take into account, but most of which have to do with how you are using your data and where the processing lives.
If processing is done in the database? Service Broker
If it is just data move? Service Broker
Is processing done in .NET/COM code? MSMQ
Do you need remote distributed transactions (for example, processing on a box different than SQL)? MSMQ
Do you need to be able to send messages while the destination is down? MSMQ
Do you want to use nServiceBus, MassTransit, Rhino-ESB, etc.? MSMQ
Things to consider no matter what you choose
How do you know the health of your queue? Both options handle failover differently. For example Service Broker will disable your queue in certain scenarios which can take down your application.
How will you perform reporting? If you already use SQL Tables in your reports, Service Broker can easily fit in as it's just another dynamic table. If you are already using Performance Monitor MSMQ may fit in nicer. Service Broker does have a lot of performance counters, so don't let this be your only factor.
How do you measure uptime? Is it merely making sure you don't lose transactions, or do you need to respond synchronously? I find that the distributed nature of MSMQ allows for higher uptime because the main queue can go offline and not lose anything. Whereas with Service Broker your database must be online or else you lose out.
Do you already have experience with one of these technologies? Both have a lot of implementation details that can come back and bite you.
No mater what choice you make, how easy is it to switch out the underlying Queueing technology? I recommend having a generic IQueue interface that you write a concrete implementation against. This way the choice you make can easily be changed later on if you find that you made the wrong one. After all, a queue is just a queue and should not lock you into a specific implementation.
I've used MSMQ before and the only item I'd add to your list is a prerequisite check for versioning. I ran into an issue where one site had Win 2000 Server and therefore MSMQ v.2, versus Win 2003 Server and MSMQ v3. All my .NET code targeted v.3 and they aren't compatible... or at least not easily so.
Just a consideration if you go the MSMQ route.
The message size limitation in MSMQ has halted my digging in that direction. I am learning Service Broker for the project.
Do you need to be able to send messages while the destination is down? MSMQ
I don't understand why? SSB can send messages to disconnected destination without any problem. All this messages going to transmission queue and would be delivered when destination stay reachable.