Wednesday, December 26, 2012

Starting AppScale

This post is written assuming you already have a machine or a VM image with AppScale and AppScale-Tools installed. If you don't please refer to my previous post on "Setting Up AppScale". 
We use AppScale-Tools to start, manage and terminate AppScale instances in various environments. The inputs we should pass into the tools differ slightly based on the environment in which we want to start AppScale. If you're going to deploy AppScale without the help of an IaaS layer like EC2 or Eucalyptus, then you're responsible for manually starting up the required machines or VMs. For an example if you're going to run AppScale on the Xen hypervisor, then you should first start your AppScale Xen images manually. Similarly if you're going to run AppScale over VMWare Fusion, you should start your AppScale Fusion images manually. Once the instances are up and running note down their IP addresses (assuming that the instances obtain IP addresses from a service such as DHCP). As an example lets assume you have 3 VM instances up and running and their IP addresses are, and With this information we should compile a simple YAML configuration like this:
Lets call this file ips.yaml. This configuration instructs AppScale to use one machine as the controller and the rest as ordinary nodes. The controller (aka head node) operates as a load balancer and a ZooKeeper leader. The other nodes will assume the roles of application server and DB server. In this case both server nodes will assume the application server and DB server roles. Therefore we end up with an application server cluster (of 2) and a replicated DB cluster (of 2) fronted by a single load balancer. You can further fine tune how AppScale assigns roles to machines by changing your ips.yaml file. For more information regarding the role placement configuration please refer the "Placement Support" article on AppScale wiki.
Once you have your ips.yaml file you can start deploying AppScale on the VMs. First create a SSH key-pair so that AppScale-Tools can login to the relevant machines remotely. This is done by executing the appscale-add-keypair command.
appscale-add-keypair --ips /path/to/ips.yaml
This will prompt you to enter the root passwords for each of the machines specified in your ips.yaml. Once this step has completed you can fire off AppScale using the app scale-run-instances command.
appscale-run-instances --ips /path/to/ips.yaml
This will start the AppScale daemons on each of the machines and initialize the AppScale PaaS. At some point you will be prompted to enter an email address and a password for the AppScale admin account. Just enter any email address or password for this. You can later use these credentials to login to AppScale management console. (For more details on deploying AppScale over a virtualized cluster setup refer the AppScale wiki)
If you are deploying AppScale over an IaaS layer such as EC2 or Eucalyptus, then you don't need to start the VMs manually nor you need any ips.yaml file. All you need is the unique ID of your AMI or EMI provided by your IaaS provider and the security credentials to interact with the IaaS. In case of EC2 you will need your AWS access key, secret key, AWS private key and X509 certificate. You can get these from the security credentials page of your AWS management console. If you're on Eucalyptus you can download a zip file from Euca admin console which contains all the required credentials.
Using these credentials you should first setup some environment variables.
export EC2_CERT=~/mycert.pem 
export EC2_PRIVATE_KEY=~/mypk.pem 
export EC2_ACCESS_KEY=my-access-key 
export EC2_SECRET_KEY=my-secret-key
In case of Eucalyptus you can simply source the eucarc file found in the downloaded credentials file.
source eucarc
With these environment variables in place you're ready to go. Simply execute the app scale-run-instances command as follows.
appscale-run-instances --min 1 --max 1 --infrastructure ec2 --machine ami-52912a3b --keyname app scale_test --group app scale_test
This will start a simple 1-node AppScale cloud in EC2. If you want more instances in your PaaS, simply adjust the values of min and max flags. For deployment on Eucalyptus change the value of infrastructure flag to 'euca' and provide a valid EMI ID for the machine flag. Here's the command for a 10 node AppScale deployment over Eucalyptus.
appscale-run-instances --min 10 --max 10 --infrastructure euca --machine emi-12345678 --keyname app scale_test --group app scale_test
The values of keyname and group flags will be used to create a keypair and a security group in the respective IaaS environment. Therefore make sure they are unique for your EC2/Eucalyptus account. Note that when running in a billed environment such as EC2, the machines spawned by AppScale are billed against the EC2 credentials provided (the credentials that we set as environment variables). AppScale spawns m1.large instances which cost about 26 cents an hour.
An AppScale deployment could take several minutes to complete. In environments like EC2 and Eucaplyptus, deployment times over 10 minutes are not uncommon. This delay is primarily due to the VM bootup and initialization overhead of IaaS environments which cannot be avoided. Once the AppScale deployment is complete AppScale-Tools will spit out a URL that you can use to check the status of the AppScale deployment:
The status of your AppScale instance is at the following URL:
Simply copy and paste the URL into your web browser to view the AppScale status page.
In my next post I'll explain how to deploy applications in an already running AppScale PaaS.

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