CTE015 – Subscribe to the LANSA Image
In this exercise you will subscribe to the LANSA Image in the AWS (Amazon Web Services) Marketplace so that the LANSA Stack may use that image. This image is called an Amazon Machine Image or AMI.
Note 1: This step is not required when using the LANSA Product Centre AWS account.
To achieve this objective, you must complete the following:
Step 1. Locate the LANSA Scalable AMI
Before You Begin
Obtain access to the AWS console to use AWS Marketplace
Review the performance and pricing examples provided below.
Review, also, the
LANSA WAM Performance and Pricing Guidelines
The Cloud Formation template instantiates a number of AWS resources into the LANSA Stack. There are a myriad number of ways you may configure your Stack but here are a few examples from which you may calculate approximately how much your stack will cost per hour.
- A rule of thumb is that each m3.medium Web server may handle 10 concurrent users.
- Keep the maximum CPU % utilization below 80%. Add more webservers if it'sgreater than this.
- When the CPU % utilization is below 50%, the average response time will depend on the RDS instance type.
- And your application will perform differently...maybe radically differently. It is very important to load test your application. The Cloud makes this easy to do. So do it!
- A multi-AZ deployment is the recommended architecture so that there are the fewest single points of failure. The cost is 20% slower performance as half the transactions must travel outside the datacentre (AZ) to the other AZ to connect to the RDS. Although that is not strictly true... the same performance may be achieved by using more EC2 instances or a larger RDS instance and thus the cost of fault tolerance is increased hourly charges.
- Adding in a Multi-AZ RDS may slow it further as the RDS must take time to keep the Slave up to date.
- It is useful to keep the EC2 instance type small so that scaling out may be more finely adjusted. The EC2 instance type size may need to be increased if the CPU requirement for typical transactions is higher than the benchmark test. This is where it's very useful to be using a load testing tool which mimics your expected transaction workload. You can gain insights ahead of time as to how your application may behave under various loads. And you may easily adjust the instance sizes to gauge the best combination for your application's needs.
- Starting many instances at once takes much longer to complete the MSI install as the DB access part has contention from so many instances publishing weblets at once. It is best not to do this. Specify 1 or 2 web servers and use the auto scaling group to scale up more instances as necessary.
- It is very important to ensure that all instances have reached a steady state CPU % of 0 before using the instances. Use the AWS console to list in created time order, then select the last 12 or so and graph the CPU time - click on the small image to get more detail.
- Micro instances e.g. t2.micro are a good solution if the application load is sporadic.