Running NServiceBus on Amazon EC2 - amazon-ec2

So I have seen a number of references and links from a year +/- ago asking about support for NServiceBus on Amazon EC2. Wondering if anyone out there has attempted to do anything with this recently?
I have seen the following articles/posts but fear the information and related links are dated.
A Less Than Positive Experience w/NServiceBus on Amazon EC2
The right idea, any movement on this?
Azure Love, but no Amazon?
I see a lot of chatter on the NServiceBus forums about the "next version" having a big focus on support for the cloud (at the time the current version was 2.5). I have a scenario where I would like to run NServiceBus w/MSMQ or RabbitMQ on a cluster of Amazon EC2 instances but it concerns me that there is not more discussion around people actually using NServiceBus on Amazon.
Anyone doing it successfully or have reasons to avoid considering it?
[EDIT] - Does anyone know if using reserved instances gets around the issue with EC2 restarts described in the article above?

There are different ways to successfully run NServiceBus on EC2. Picking which option to go with requires weighing the balance of cost, scalability, & operational overhead.
MSMQ
NServiceBus runs fine on EC2 with MSMQ, but there are a few obstacles that need attention. The main issue is that the computer names / DNS names on EC2 instances change during each restart. This is an issue because the computer name is used when sending messages to endpoint as well when subscribing to messages. One simple option to overcome this overhead is to attach an elastic IP to the instance & use its DNS name. The benefit is that it's pretty easy to do this. The downside is that you're only given 5 Elastic IPs by default. You can ask for more & Amazon is usually pretty liberal with handing out extra Elastic IPs. You will also be limited in how you scale. For instance, you won't be able to simply plug into the elastic scaling features of AWS. You also have to deal with backups. I would put the queues on a separate EBS volume & take snapshots on an interval.
I'd pick this option if you want to use messaging, but you don't have really crazy SLA's, you don't need to scale up and down machines quickly, & you don't need to deal with high message volumes. This is the case with most projects.
Amazon SQS
You could write a custom transport for SQS. The benefit of using NSB with SQS remote queues is that you get highly available queues, you don't have to manage them on your EC2 instances & you don't have to worry about backups. It's also easier to leverage elastic scaling with this approach. The downside is that each read costs $$$, so it may not be economically feasible to read at the same speeds as MSMQ or RabbitMQ - although this problem is mitigated by support for long polling and the ability to download many messages in a single call. Another downside is that it doesn't support distributed transactions with DTC. If you're using NServiceBus 5 or later, you could implement the Outbox pattern in your transport as described here, to ensure your messages are still processed only once. Otherwise it's up to you to ensure that your endpoints and handlers have idempotency solutions in place. You can play around with speed vs cost by adjusting the polling intervals of each of your endpoints & perhaps even have a back-off strategy where you decrease your polling intervals if you haven't received messages in a while. You will also have to worry about the size of your messages, as SQS has a small size limitation (256 K). You don't hit this in most messages.
I'd pick this option if read / write speeds aren't an issue, but you don't want to worry about operationally supporting your queuing infrastructure.
RabbitMQ
I haven't personally played with RabbitMQ on EC2, but a quick search came up with a few articles on how to get it up and running on an EC2 instance. There is a mature RabbitMQ transport available and it supports guaranteed once-only processing of messages as of NServiceBus version 5, as described in the link above. This would be cheaper to operate than SQS & I've heard that it's easier to cluster than MSMQ. Finally, like MSMQ, you would have to come up with a backup strategy (probably using snapshots).
Mixed
Nobody says that you have to pick one queuing system. You could use SQS for endpoints that need high availability & you don't mind paying the $$$, then use MSMQ / RabbitMQ for the rest of your system.

Related

Basic AWS questions

I'm newbie on AWS, and it has so many products (EC2, Load Balancer, EBS, S3, SimpleDB etc.), and so many docs, that I can't figure out where I must start from.
My goal is to be ready for scalability.
Suppose I want to set up a simple webserver, which access a database in mongolab. I suppose I need one EC2 instance to run it. At this point, do I need something more (EBS, S3, etc.)?
At some point of time, my app has reached enough traffic and I must scale it. I was thinking of starting a new copy (instance) of my EC2 machine. But then it will have another IP. So, how traffic is distributed between both EC2 instances? Is that did automatically? Must I hire a Load Balancer service to distribute the traffic? And then will I have to pay for 2 EC2 instances and 1 LB? At this point, do I need something more (e.g.: Elastic IP)?
Welcome to the club Sony Santos,
AWS is a very powerfull architecture, but with this power comes responsibility. I and presumably many others have learned the hard way building applications using AWS's services.
You ask, where do I start? This is actually a very good question, but you probably won't like my answer. You need to read and do research about all the technologies offered by amazon and even other providers such as Rackspace, GoGrid, Google's Cloud and Azure. Amazon is not easy to get going but its not meant to be really, its focus is more about being very customizable and have a very extensive api. But lets get back to your question.
To run a simple webserver you would need to start an EC2 instance this instance by default runs on a diskdrive called EBS. Essentially an EBS drive is a normal harddrive except that you can do lots of other cool stuff with it like take it off one server and move it to another. S3 is really more of a file storage system its more useful if you have a bunch of images or if you want to store a lot of backups of your databases etc, but its not a requirement for a simple webserver. Just running an EC2 instance is all you need, everything else will happen behind the scenes.
If you app reaches a lot of traffic you have two options. You can scale your machine up by shutting it off and starting it with a larger instance. Generally speaking this is the easiest thing to do, but you'll get to a point where you either cannot handle all the traffic with 1 instance even at the larger size and you'll decide you need two OR you'll want a more fault tolerant application that will still be online in the event of a failure or update.
If you create a second instance you will need to do some form of loadbalancing. I recommend using amazons Elastic Load Balancer as its easy to configure and its integration with the cloud is better than using Round Robin DNS or a application like haproxy. Elastic Load Balancers are not expensive, I believe they cost around $18 / month + data that's passed between the loadbalancer.
But no, you don't need anything else to do scale up your site. 2 EC2 instances and a ELB will do the trick.
Additional questions you didn't ask but probably should have.
How often does an EC2 instance experience hardware failure and crash my server. What can I do if this happens?
It happens frequently, usually in batches. Sometimes I go months without any problems then I will get a few servers crash at a time. But its defiantly something you should plan for I didn't in the beginning and I paid for it. Make sure you create scripts and have backups and a backup plan ready incase your server fails. Be ok with it being down or have a load balanced solution from day 1.
Whats the hardest part about scalabilty?
Testing testing testing testing... Don't ever assume anything. Also be prepared for sudden spikes in your traffic. You have to be prepared for anything if you page goes from 1 to 1000 people over night are you prepared to handle it? Have you tested what you "think" will happen?
Best of luck and have fun... I know I have :)

Scaling Tigase XMPP server on Amazon EC2

Does anyone have an experience running clustered Tigase XMPP servers on Amazon's EC2, primarily I wish to know about anything that might trip me up that is non-obvious. (For example apparently running Ejabberd on EC2 can cause issues due to Mnesia.)
Or if you have any general advice to installing and running Tigase on Ubuntu.
Extra information:
The system I’m developing uses XMPP just to communicate (in near real-time) between a mobile app and the server(s).
The number of users will initially be small, but hopefully will grow. This is why the system needs to be scalable. Presumably for a just a few thousand users you wouldn’t need a cc1.4xlarge EC2 instance? (Otherwise this is going to be very expensive to run!)
I plan on using a MySQL database hosted in Amazon RDS for the XMPP server database.
I also plan on creating an external XMPP component written in Python, using SleekXMPP. It will be this external component that does all the ‘work’ of the server, as the application I’m making is quite different from instant messaging. For this part I have not worked out how to connect an external XMPP component written in Python to a Tigase server. The documentation seems to suggest that components are written specifically for Tigase - and not for a general XMPP server, using XEP-0114: Jabber Component Protocol, as I expected.
With this extra information, if you can think of anything else I should know about I’d be glad to know.
Thank you :)
I have lots of experience. I think there is a load of non-obvious problems. Like the only reliable instance to run application like Tigase is cc1.4xlarge. Others cause problems with CPU availability and this is just a lottery whether you are lucky enough to run your service on a server which is not busy with others people work.
Also you need an instance with the highest possible I/O to make sure it can cope with network traffic. The high I/O applies especially to database instance.
Not sure if this is obvious or not, but there is this problem with hostnames on EC2, every time you start instance the hostname changes and IP address changes. Tigase cluster is quite sensitive to hostnames. There is a way to force/change the hostname for the instance, so this might be a way around the problem.
Of course I am talking about a cluster for millions of online users and really high traffic 100k XMPP packets per second or more. Generally for large installation it is way cheaper and more efficient to have a dedicated servers.
Generally Tigase runs very well on Amazon EC2 but you really need the latest SVN code as it has lots of optimizations added especially after tests on the cloud. If you provide some more details about your service I may have some more suggestions.
More comments:
If it comes to costs, a dedicated server is always cheaper option for constantly running service. Unless you plan to switch servers on/off on hourly basis I would recommend going for some dedicated service. Costs are lower and performance is way more predictable.
However, if you really want/need to stick to Amazon EC2 let me give you some concrete numbers, below is a list of instances and how many online users the cluster was able to reliably handle:
5*cc1.4xlarge - 1mln 700k online users
1*c1.xlarge - 118k online users
2*c1.xlarge - 127k online users
2*m2.4xlarge (with 5GB RAM for Tigase) - 236k online users
2*m2.4xlarge (with 20GB RAM for Tigase) - 315k online users
5*m2.4xlarge (with 60GB RAM for Tigase) - 400k online users
5*m2.4xlarge (with 60GB RAM for Tigase) - 312k online users
5*m2.4xlarge (with 60GB RAM for Tigase) - 327k online users
5*m2.4xlarge (with 60GB RAM for Tigase) - 280k online users
A few more comments:
Why amount of memory matters that much? This is because CPU power is very unreliable and inconsistent on all but cc1.4xlarge instances. You have 8 virtual CPUs but if you look at the top command you often see one CPU is working and the rest is not. This insufficient CPU power leads to internal queues grow in the Tigase. When the CPU power is back Tigase can process waiting packets. The more memory Tigase has the more packets can be queued and it better handles CPU deficiencies.
Why there is 5*m2.4xlarge 4 times? This is because I repeated tests many times at different days and time of the day. As you can see depending on the time and date the system could handle different load. I guess this is because Tigase instance shared CPU power with some other services. If they were busy Tigase suffered from CPU under power.
That said I think with installation of up to 10k online users you should be fine. However, other factors like roster size greatly matter as they affect traffic, and load. Also if you have other elements which generate a significant traffic this will put load on your system.
In any case, without some tests it is impossible to tell how really your system behaves or whether it can handle the load.
And the last question regarding component:
Of course Tigase does support XEP-0114 and XEP-0225 for connecting external components. So this should not be a problem with components written in different languages. On the other hand I recommend using Tigase's API for writing component. They can be deployed either as internal Tigase components or as external components and this is transparent for the developer, you do not have to worry about this at development time. This is part of the API and framework.
Also, you can use all the goods from Tigase framework, scripting capabilities, monitoring, statistics, much easier development as you can easily deploy your code as internal component for tests.
You really do not have to worry about any XMPP specific stuff, you just fill body of processPacket(...) method and that's it.
There should be enough online documentation for all of this on the Tigase website.
Also, I would suggest reading about Python support for multi-threading and how it behaves under a very high load. It used to be not so great.

Amazon EC2 consideration - redundancy and elastic IPs

I've been tasked with determining if Amazon EC2 is something we should move our ecommerce site to. We currently use Amazon S3 for a lot of images and files. The cost would go up by about $20/mo for our host costs, but we could sell our server for a few thousand dollars. This all came up because right now there are no procedures in place if something happened to our server.
How reliable is Amazon EC2? Is the redundancy good, I don't see anything about this in the FAQ and it's a problem on our current system I'm looking to solve.
Are elastic IPs beneficial? It sounds like you could point DNS to that IP and then on Amazon's end, reroute that IP address to any EC2 instance so you could easily get another instance up and running if the first one failed.
I'm aware of scalability, it's the redundancy and reliability that I'm asking about.
At work, I've had something like 20-40 instances running at all times for over a year. I think we've had 1-3 alert emails come from amazon suggesting that we terminate and boot another instance (presumably because they are detecting possible failure in the underlying hardware). We've never had an instance go down suddenly, which seems rather good.
Elastic IP's are amazing and are part of the solution. The other part is being able to rapidly bring up new instances. I've learned that you shouldn't care about instances going down, that it's more important to use proper load balancing and be able to bring up commodity instances quickly.
Yes, it's very good. If you aren't able to put together a concurrent redundancy (where you have multiple servers fulfilling requests simultaneously), using the elastic IP to quickly redirect to another EC2 instance would be a way to minimize downtime.
Yeah I think moving from inhouse server to Amazon will definitely make a lot of sense economically. EBS backed instances ensure that even if the machine gets rebooted, the transient memory is not lost. And if you have a clear separation between your application and data layer and can have them on different machines, then you can build even better redundancy for your data.
For ex, if you use mysql, then you can consider using Amazon RDS service - which gives you a highly available and reliable MySQL instance, fully managed (patches and all). The application layer then can be made more resilient by having more smaller instances rather than one larger instance, through load balancing.
The cost you will save on is really hardware maintenance and the cost you would have to incur to build in disaster recovery.

High Performance Highly Available Tracking System

I currently hold a tracking service that records visits from various sources. At times we record the visits and redirect to our clients or we let clients call us to report visits. The architecture is two worker boxes configured behind a load-balancer. This system is setup using Amazon EC2 and the load-balancer used is Amazon's Elastic LB.
I did some benchmarking tests and have noticed significant network latencies. The traffic through load-balancer suffers atleast 2 times more delay than hitting any of the boxes directly.
Has anyone experienced such an issue and has attempted to solve it? Is this an Amazon EC2 specific issue?
Is there any other architecture in use that would lower my network latencies significantly. e.g. Using a HA such that traffic needn't go through a load-balancer but instead hits the end point servers directly? Before I start investing time on that I wanted to hear what others think of the same.
Thanks alot for your time,
Santosh
Change your LB and give it another try. HAProxy is great session/cookie aware L7 balancer and can be setup in Amazon cloud AFAIK. See this: http://agiletesting.blogspot.com/2009/02/load-balancing-in-amazon-ec2-with.html
You have to take into account that ELBs perform better after a while, then initially. Don't ask me why, but that's how it is -- loadbalancer warming?
It also really depends how much traffic you sent the ELB. Keep in mind that the hardware the ELB is provisioned on seems like a regular small instance. So the throughput is capped at ~25 MBit (last time I checked). If you require more, go dedicated.
In the end, I too would suggest that you look Haproxy on a dedicated instance. I'd expect some delay, 2x more delay sounds unreal. Maybe use another small instance and benchmark it directly against the ELB and then try a c1.medium.

What are the practical limitations with auto scaling EC2 or other cloud computing infrastructure?

I was curious if anyone has experimented with auto scaling web or db tier in EC2 or other cloud computing infrastructure? It seems theoretically possible, but I am curious what the practical limitations are/maybe.
Thanks!
We are also starting to look at auto-scaling.
The first candidate approach is to use Amazon's ELB (Elastic Load Balancer) and Cloud Front. However, our traffic is a web service. Caller's frequently send the 100-Continue http message, and ELB cannot understand that message. There's no word yet from Amazon on when that might be fixed. Also, there are a number of complaints in the Amazon forums about ELB not handling heavy load.
LigHTTPD 1.5 looks like a promising partial solution, in that it can detect when an instance is not functioning and transparently take it out of the rotation, and can be dynamically reconfigured without restarting the load balancer.
There are a number of commercial solutions as well. We will probably have a look at Right Scale.
This is more of a question than an answer, but I'm about to start experimenting with autoscaling myself (most likely using the Amazon CloudFront facilities) and am thinking that instance startup time will be a factor. I've noticed that a new EC2 instance can take from 5 to 20 minutes to start up, so it's not as if you can instantly add more capacity when your load increases; it seems like you would need one or more idle instances to be running and ready to pick up increased load.
Late addition:
Consider SimpleDB as well... this would eliminate the DB scaling side.
For autoscaling, we rolled our own scripts to monitor, launch, and provision servers and yes, the whole process takes about 7 minutes. We do a little predictive analysis to guess when new servers will be needed and then just break them down if they aren't. Total cost: ~10 cents.
Also, Scalr looks promising as a commercial solution (haven't used it).
Chad

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