I have little bit knowledge of AWS EC2. Previously I have bought a mx3large instance and did all my necessary installations on the server and cloned my code there but didn't map domain to the system.
Now my client wants to implement auto scalling and load balancing. I have read about those that auto scalling is to add/subtract instances with respect to traffic and load balancing is to balance loads between instances.First correct me if I am wrong.
Now I want to ask
If I auto scale some instances, do I need to do installations on all instances or some one instance? If one then what will be my primary instance?
As mentioned above, I have already bought an instance where I did my all installations. But that instance is currently stop. Will I remove that instance when I will be using auto scaling?
What are the prices. If I bought a instance of $0.28/hour, will I have to pay number of instances * cost for number of time they are activated?
On which instance I will be cloning my code, ssh to connect and all related operations?
Load balancing will automatically start working with my auto scall instances?
Any help will be much appreciated.
Your questions make me think you still need to read a lot of "getting started" guides, but I'll do my best to answer your questions:
1) If I auto scale some instances, do I need to do installations on all instances or some one instance? If one then what will be my primary instance?
R: All instances, none will be a "primary instance". They will all be treated equally
2) As mentioned above, I have already bought an instance where I did my all installations. But that instance is currently stop. Will I remove that instance when I will be using auto scaling?
R: The Elastic Load Balancer (ELB) will detect that your instance is not healthy and will stop sending request to that instance
3) What are the prices. If I bought a instance of $0.28/hour, will I have to pay number of instances * cost for number of time they are activated?
R: You pay for the time they are in running state and for the time the ELB is running (it can't be stopped, only deleted)
4) On which instance I will be cloning my code, ssh to connect and all related operations?
R: On every instance. The ideal case is when all of them are identical
5) Load balancing will automatically start working with my auto scall instances?
R: yes, assuming you have correctly configured the autoscaling group with the ELB
Related
I'm using AWS cloudwatch for scaling my application. I created launch configuration, autoscaling group, upscaling and downscaling alarm and policies. The problem is it is taking 5 mins to launch an instance from an AMI. Is there a way to reduce the start-up time from 5 to 2-3 mins?
No, it isn't possible to speed up the provisioning of a new EC2 instance by an AutoScaling scale up action.
I think it's important to appreciate all that EC2 is doing in those 5 minutes. It's building a new virtual machine, installing an image of an operating system on it, hooking it up to a network and bringing it into service. That's pretty impressive for 5 minutes work if you ask me.
If you're needing to scale up that quickly, then quite frankly you're doing it wrong. Even with autoscaling, you should always be a little over provisioned for your expected load. If you start getting close to that over scaled limit, then it's time to autoscale up. Don't provision exactly what you need, it won't work well.
The start up time depends on a few things:
The availability of resources for your instance type within the
availability zone.
The size of the AMI. In the case of a custom AMI image, it may need to be copied to the correct internal storage for the VM.
Initialization procedures. For windows, some images with user-data scripts can require a reboot to join the domain.
This is an old question, and as I have seen. Start times have improved for EC2 over the past years. Some providers like Google Cloud can provide servers in under a minute. So if your workload is that demanding, you may research the available providers and their operational differences.
I want to maintain a pool of stopped amazon ec2 instances. Whenever the amount is below the threshold, I would like to be able to create new instances and then immediately stop them once they are running. Is this possible within the amazon infrastructure alone?
You can certainly create Amazon EC2 instances and then Stop them, making the available to Start later. As you point out, this has the benefit that instances will Start faster than they take to Launch a new instance.
There is no automated method to assist with this. You could have to code a solution that does the following:
Monitor the number of Stopped instances
If the quantity is below the threshold, launch a new instance
The new instance could automatically stop itself via User Data (either via a Shutdown command to the Operating System, or via a StopInstances call to EC2)
Some things you would have to consider:
What triggers the monitoring? Would it be on a schedule?
The task that launches a new instance would need to wait for the new instance to Launch & Stop before launching any more instances
What Starts the instances when they are needed?
Do instances ever get Stopped when they are no longer required?
The much better choice would be to use Auto Scaling, with a scale-out alarm based on some metric that says your fleet is busy, and a scale-in alarm to remove instances when the fleet is not busy. The scale-out alarm could be set to launch instances once a threshold is passed (eg 80% CPU) that should allow the new instance(s) to launch before things are 100% busy. The time difference between launching a new instance and starting an existing instance is quite small (at least for Linux).
If you're using Windows, the biggest time delay when launching a new instance is due to Sysprep, which makes a "clean" machine with new Unique IDs. You could cheat by creating an AMI without Sysprep, which would boot faster.
Perhaps I am misunderstanding your objective... you can't "ensure availability" of instances without paying for them.
Instances in the stopped state are only logical entities that don't physically exist anywhere -- hardware is allocated on launch, deallocated on stop, reallocated on the next start. In the unlikely condition where an availability zone is exhausted of capacity for given instance class, stopped instances of that class won't start, because there is no hardware available for them to be deployed onto.
To ensure that instances are always available, you have to reserve them, and you have to specify the reservations in a specific availability zone:
Amazon EC2 Reserved Instances provide a significant discount (up to 75%) compared to On-Demand pricing and provide a capacity reservation when used in a specific Availability Zone. [emphasis added]
https://aws.amazon.com/ec2/pricing/reserved-instances/
Under most plans, reserved instances are billed the same rate whether they are running or not, so there would be little point in stopping them.
I'm writing the backend for a mobile app that does some cpu intensive work. We anticipate the app will not have heavy usage most of the time, but will have occasional spikes of high demand. I was thinking what we should do is reserve a couple of 24/7 servers to handle the steady-state of low demand traffic and then add and remove EC2 instances as needed to handle the spikes. The mobile app will first hit a simple load balancing server that does a simple round-robin user distribution among all the available processing servers. The load balancer will handle bringing new EC2 instances up and turning them back off as needed.
Some questions:
I've never written something like this before, does this sound like a good strategy?
What's the best way to handle bringing new EC2 instances up and back down? I was thinking I could just create X instances ahead of time, set them up as needed (install software, etc), and then stop each instance. The load balancer will then start and stop the instances as needed (eg through boto). I think this should be a lot faster and easier than trying to create new instances and install everything through a script or something. Good idea?
One thing I'm concerned about here is the cost of turning EC2 instances off and back on again. I looked at the AWS Usage Report and had difficulty interpreting it. I could see starting a stopped instance being a potentially costly operation. But it seems like since I'm just starting a stopped instance rather than provisioning a new one from scratch it shouldn't be too bad. Does that sound right?
This is a very reasonable strategy. I used it successfully before.
You may want to look at Elastic Load Balancing (ELB) in combination with Auto Scaling. Conceptually the two should solve this exact problem.
Back when I did this around 2010, ELB had some problems with certain types of HTTP requests that prevented us from using it. I understand those issues are resolved.
Since ELB was not an option, we manually launched instances from EBS snapshots as needed and manually added them to an NGinX load balancer. That certainly could have been automated using the AWS APIs, but our peaks were so predictable (end of month) that we just tasked someone to spin up the new instances and didn't get around to automating the task.
When an instance is stopped, I believe the only cost that you pay is for the EBS storage backing the instance and its data. Unless your instances have a huge amount of data associated, the EBS storage charge should be minimal. Perhaps things have changed since I last used AWS, but I would be surprised if this changed much if at all.
First with regards to costs, whether an instance is started from scratch or from a stopped state has no impact on cost. You are billed for the amount of compute units you use over time, period.
Second, what you are looking to do is called autoscaling. What you do is setup up a launch config that specifies an AMI you are going to use (along with any user-data configs you are using, the ELB and availiabilty zones you are going to use, min and max number of instances, etc. You set up a scaling group using that launch config. Then you set up scaling policies to determine what scaling actions are going to be attached to the group. You then attach cloud watch alarms to each of those policies to trigger the scaling actions.
You don't have servers in reserve that you attach to the ELB or anything like that. Everything is based on creating a single AMI that is used as the template for the servers you need.
You should read up on autoscaling at the link below:
http://aws.amazon.com/autoscaling/
I've been looking at high availability solutions such as heartbeat, and keepalived to failover when an haproxy load balancer goes down. I realised that although we would like high availability it's not really a requirement at this point in time to do it to the extent of the expenditure on having 2 load balancer instances running at any one time so that we get instant failover (particularly as one lb is going to be redundant in our setup).
My alternate solution is to fire up a new load balancer EC2 instance from an AMI if the current load balancer has stopped working and associate it to the elastic ip that our domain name points to. This should ensure that downtime is limited to the time it takes to fire up the new instance and associate the elastic ip, which given our current circumstance seems like a reasonably cost effective solution to high availability, particularly as we can easily do it multi-av zone. I am looking to do this using the following steps:
Prepare an AMI of the load balancer
Fire up a single ec2 instance acting as the load balancer and assign the Elastic IP to it
Have a micro server ping the current load balancer at regular intervals (we always have an extra micro server running anyway)
If the ping times out, fire up a new EC2 instance using the load balancer AMI
Associate the elastic ip to the new instance
Shut down the old load balancer instance
Repeat step 3 onwards with the new instance
I know how to run the commands in my script to start up and shut down EC2 instances, associate the elastic IP address to an instance, and ping the server.
My question is what would be a suitable ping here? Would a standard ping suffice at regular intervals, and what would be a good interval? Or is this a rather simplistic approach and there is a smarter health check that I should be doing?
Also if anyone foresees any problems with this approach please feel free to comment
I understand exactly where you're coming from, my company is in the same position. We care about having a highly available fault tolerant system however the overhead cost simply isn't viable for the traffic we get.
One problem I have with your solution is that you're assuming the micro instance and load balancer wont both die at the same time. With my experience with amazon I can tell you it's defiantly possible that this could happen, however unlikely, its possible that whatever causes your load balancer to die also takes down the micro instance.
Another potential problem is you also assume that you will always be able to start another replacement instance during downtime. This is simply not the case, take for example an outage amazon had in their us-east-1 region a few days ago. A power outage caused one of their zones to loose power. When they restored power and began to recover the instances their API's were not working properly because of the sheer load. During this time it took almost 1 hour before they were available. If an outage like this knocks out your load balancer and you're unable to start another you'll be down.
That being said. I find the ELB's provided by amazon are a better solution for me. I'm not sure what the reasoning is behind using HAProxy but I recommend investigating the ELB's as they will allow you to do things such as auto-scaling etc.
For each ELB you create amazon creates one load balancer in each zone that has an instance registered. These are still vulnerable to certain problems during severe outages at amazon like the one described above. For example during this downtime I could not add new instances to the load balancers but my current instances ( the ones not affected by the power outage ) were still serving requests.
UPDATE 2013-09-30
Recently we've changed our infrastructure to use a combination of ELB and HAProxy. I find that ELB gives the best availability but the fact that it uses DNS load balancing doesn't work well for my application. So our setup is ELB in front of a 2 node HAProxy cluster. Using this tool HAProxyCloud I created for AWS I can easily add auto scaling groups to the HAProxy servers.
I know this is a little old, but the solution you suggest is overcomplicated, there's a much simpler method that does exactly what you're trying to accomplish...
Just put your HAProxy machine, with your custom AMI in an auto-scaling group with a minimum AND maximum of 1 instance. That way when your instance goes down the ASG will bring it right back up, EIP and all. No external monitoring necessary, same if not faster response to downed instances.
We're running a lightweight web app on a single EC2 server instance, which is fine for our needs, but we're wondering about monitoring and restarting it if it goes down.
We have a separate non-Amazon server we'd like to use to monitor the EC2 and start a fresh instance if necessary and shut down the old one. All our user data is on Elastic Storage, so we're not too worried about losing anything.
I was wondering if anyone has any experience of using EC2 in this way, and in particular of automating the process of starting the new instance? We have no problem creating something from scratch, but it seems like it should be a solved problem, so I was wondering if anyone has any tips, links, scripts, tutorials, etc to share.
Thanks.
You should have a look at puppet and its support for AWS. I would also look at the RightScale AWS library as well as this post about starting a server with the RightScale scripts. You may also find this article on web serving with EC2 useful. I have done something similar to this but without the external monitoring, the node monitored itself and shut down when it was no longer needed then a new one would start up later when there was more work to do.
Couple of points:
You MUST MUST MUST back up your Amazon EBS volume.
They claim "better" reliability, but not 100%, and it's SEVERAL orders of magnitude off of S3's "12 9's" of durability. S3 durability >> EBS durability. That's a fact. EBS supports a "snapshots" feature which backs up your storage efficiently and incrementally to S3. Also, with EBS snapshots, you only pay for the compressed deltas, which is typically far far less than the allocated volume size. In another life, I've sent lost-volume emails to smaller customers like you who "thought" that EBS was "durable" and trusted it with the only copy of a mission-critical database... it's heartbreaking.
Your Q: automating start-up of a new instance
The design path you mention is relatively untraveled; here's why... Lots of companies run redundant "hot-spare" instances where the second instance is booted and running. This allows rapid failover (seconds) in the event of "failure" (could be hardware or software). The issue with a "cold-spare" is that it's harder to keep the machine up to date and ready to pick up where the old box left off. More important, it's tricky to VALIDATE that the spare is capable of successfully recovering your production service. Hardware is more reliable than untested software systems. TEST TEST TEST. If you haven't tested your fail-over, it doesn't work.
The simple automation of starting a new EBS instance is easy, bordering on trivial. It's just a one-line bash script calling the EC2 command-line tools. What's tricky is everything on top of that. Such a solution pretty much implies a fully 100% automated deployment process. And this is all specific to your application. Can your app pull down all the data it needs to run (maybe it's stored in S3?). Can you kill you instance today and boot a new instance with 0.000 manual setup/install steps?
Or, you may be talking about a scenario I'll call "re-instancing an EBS volume":
EC2 box dies (root volume is EBS)
Force detach EBS volume
Boot new EC2 instance with the EBS volume
... That mostly works. The gotchas:
Doesn't protect against EBS failures, either total volume loss or an availability loss
Recovery time is O(minutes) assuming everything works just right
Your services need to be configured to restart automatically. It does no good to bring the box back if Nginx isn't running.
Your DNS routes or other services or whatever need to be ok with the IP-address changing. This can be worked around with ElasticIP.
How are your host SSH keys handled? Same name, new host key can break SSH-based automation when it gets the strong-warning for host-key-changed.
I don't have proof of this (other than seeing it happen once), but I believe that EC2/EBS _already_does_this_ automatically for boot-from-EBS instances
Again, the hard part here is on your plate. Can you stop your production service today and bring it up RELIABLY on a new instance? If so, the EC2 part of the story is really really easy.
As a side point:
All our user data is on Elastic Storage, so we're not too worried about losing anything.
I'd strongly suggest to regularly snapshot your EBS (Elastic Block Storage) to S3 if you are not doing that already.
You can use an autoscale group with a min/max/desired quantity of 1. Place the instance behind an ELB and have the autoscale group be triggered by the ELB healthy node count. This allows you to have built in monitoring by cloudwatch and the ELB health check. Anytime there is an issue the instance be replaced by the autoscale service.
If you have not checked 'Protect against accidental termination' you might want to do so.
Even if you have disabled 'Detailed Monitoring' for your instance you should still see the 'StatusCheckFailed' metric for your instance over which you can configure an alarm (In the CloudWatch dashboard)
Your application (hosted in a different server) should receive the alarm and start the instance using the AWS API (or CLI)
Since you have protected against accidental termination you would never need to spawn a new instance.