Post Syndicated from Sheila Busser original https://aws.amazon.com/blogs/compute/building-a-cloud-in-the-cloud-running-apache-cloudstack-on-amazon-ec2-part-2/

This blog is written by Mark Rogers, SDE II – Customer Engineering AWS.

In part 1, I showed you how to run Apache CloudStack with KVM on a single Amazon Elastic Compute Cloud (Amazon EC2) instance. That simple setup is great for experimentation and light workloads. In this post, things will get a lot more interesting. I’ll show you how to create an overlay network in your Amazon Virtual Private Cloud (Amazon VPC) that allows CloudStack to scale horizontally across multiple EC2 instances. This same method could work with other hypervisors, too.

If you haven’t read it yet, then start with part 1. It explains why this network setup is necessary. The same prerequisites apply to both posts.

Making things easier

I wrote some scripts to automate the CloudStack installation and OS configuration on CentOS 7. You can customize them to meet your needs. I also wrote some AWS CloudFormation templates you can copy in order to create a demo environment. The README file has more details.

The scalable method

Our team started out using a single EC2 instance, as described in my last post. That worked at first, but it didn’t have the capacity we needed. We were limited to a couple of dozen VMs, but we needed hundreds. We also needed to scale up and down as our needs changed. This meant we needed the ability to add and remove CloudStack hosts. Using a Linux bridge as a virtual subnet was no longer adequate.

To support adding hosts, we need a subnet that spans multiple instances. The solution I found is Virtual Extensible LAN (VXLAN). It’s lightweight, easy to configure, and included in the Linux kernel. VXLAN creates a layer 2 overlay network that abstracts away the details of the underlying network. It allows machines in different parts of a network to communicate as if they’re all attached to the same simple network switch.

Another example of an overlay network is an Amazon VPC. It acts like a physical network, but it’s actually a layer on top of other networks. It’s networks all the way down. VXLAN provides a top layer where CloudStack can sit comfortably, handling all of your VM needs, blissfully unaware of the world below it.

An overlay network comes with some big advantages. The biggest improvement is that you can have multiple hosts, allowing for horizontal scaling. Having more hosts not only gives you more computing power, but also lets you do rolling maintenance. Instead of putting the database and file storage on the management server, I’ll show you how to use Amazon Elastic File System (Amazon EFS) and Amazon Relational Database Service (Amazon RDS) for scalable and reliable storage.

EC2 Instances

Let’s start with three Amazon EC2 instances. One will be a router between the overlay network and your Amazon VPC, the second one will be your CloudStack management server, and the third one will be your VM host. You’ll also need a way to connect to your instances, such as a bastion host or a VPN endpoint.

VXLAN must send and receive multicast traffic. Only Nitro instances can be multicast senders. As you plan, look at the list of Nitro instance types.

The router won’t need much computing power, but it will need enough network bandwidth to meet your needs. If you put Amazon EFS in the same subnet as your instances, then they’ll communicate with it directly, thereby reducing the load on the router. Decide how much network throughput you want, and then pick a suitable Nitro instance type.

After creating the router instance, configure AWS to use it as a router. Stop source/destination checking in the instance’s network settings. Then update the applicable AWS route tables to use the router as the target for the overlay network. The router’s security group needs to allow ingress to the CloudStack UI (TCP port 8080) and any services you plan to offer from VMs.

For the management server, you’ll want a Nitro instance type. It’s going to use more CPU than your router, so plan accordingly.

In addition to being a Nitro type, the host instance must also be a metal type. Metal instances have hardware virtualization support, which is needed by KVM. If you have a new AWS account with a low on-demand vCPU limit, then consider starting with an m5zn.metal, which has 48 vCPUs. Otherwise, I suggest going directly to a c5.metal because it provides 96 vCPUs for a similar price. There are bigger types available depending on your compute needs, budget, and vCPU limit. If your account’s on-demand vCPU limit is too low, then you can file a support ticket to have it raised.

Networking

All of the instances should be on a dedicated subnet. Sharing the subnet with other instances can cause communication issues. For an example, refer to the following figure. The subnet has an instance named TroubleMaker that’s not on the overlay network. If TroubleMaker sends a request to the management instance’s overlay network address, then here’s what happens:

1. The request goes through the AWS subnet to the router.
2. The router forwards the request via the overlay network.
3. The CloudStack management instance has a connection to the same AWS subnet that TroubleMaker is on. Therefore, it responds directly instead of using the router. This isn’t the return path that AWS is expecting, so the response is dropped.

If you move TroubleMaker to a different subnet, then the requests and responses will all go through the router. That will fix the communication issues.

The instances in the overlay network will use special interfaces that serve as VXLAN tunnel endpoints (VTEPs). The VTEPs must know how to contact each other via the underlay network. You could manually give each instance a list of all of the other instances, but that’s a maintenance nightmare. It’s better to let the VTEPs discover each other, which they can do using multicast. You can add multicast support using AWS Transit Gateway.

Here are the steps to make VXLAN multicasts work:

1. Enable multicast support when you create the transit gateway.
2. Attach the transit gateway to your subnet.
3. Create a transit gateway multicast domain with IGMPv2 support enabled.
4. Associate the multicast domain with your subnet.
5. Configure the eth0 interface on each instance to use IGMPv2. The following sample code shows how to do this.
6. Make sure that your instance security groups allow ingress for IGMP queries (protocol 2 traffic from 0.0.0.0/32) and VXLAN traffic (UDP port 4789 from the other instances).

CloudStack VMs must connect to the same bridge as the VXLAN interface. As mentioned in the previous post, CloudStack cares about names. I recommend giving the interface a name starting with “eth”. Moreover, this naming convention tells CloudStack which bridge to use, thereby avoiding the need for a dummy interface like the one in the simple setup.

The following snippet shows how I configured the networking in CentOS 7. You must provide values for these variables:

• $overlay_host_ip_address, $overlay_netmask, and $overlay_gateway_ip: Use values for the overlay network that you’re creating.
• $dns_address: I recommend using the base of the VPC IPv4 network range, plus two. You shouldn’t use 169.654.169.253 because CloudStack reserves link-local addresses for its own use.
• $multicast_address: The multicast address that you want VXLAN to use. Pick something in the multicast range that won’t conflict with anything else. I recommend choosing from the IPv4 local scope (239.255.0.0/16).
• $interface_name: The name of the interface VXLAN should use to communicate with the physical network. This is typically eth0.

A couple of the steps are different for the router instance than for the other instances. Pay attention to the comments!

yum install -y bridge-utils net-tools

# IMPORTANT: Omit the GATEWAY setting on the router instance!
cat << EOF > /etc/sysconfig/network-scripts/ifcfg-cloudbr0
DEVICE=cloudbr0
TYPE=Bridge
ONBOOT=yes
BOOTPROTO=none
IPV6INIT=no
IPV6_AUTOCONF=no
DELAY=5
STP=no
USERCTL=no
NM_CONTROLLED=no
IPADDR=$overlay_host_ip_address
NETMASK=$overlay_netmask
DNS1=$dns_address
GATEWAY=$overlay_gateway_ip
EOF

cat << EOF > /sbin/ifup-local
#!/bin/bash
# Set up VXLAN once cloudbr0 is available.
if [[ \$1 == "cloudbr0" ]]
then
    ip link add ethvxlan0 type vxlan id 100 dstport 4789 group "$multicast_address" dev "$interface_name"
    brctl addif cloudbr0 ethvxlan0
    ip link set up dev ethvxlan0
fi
EOF

chmod +x /sbin/ifup-local

# Transit Gateway requires IGMP version 2
echo "net.ipv4.conf.$interface_name.force_igmp_version=2" >> /etc/sysctl.conf
sysctl -p

# Enable IPv4 forwarding
# IMPORTANT: Only do this on the router instance!
echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
sysctl -p

# Restart the network service to make the changes take effect.
systemctl restart network

Storage

Let’s look at storage. Create an Amazon RDS database using the MySQL 8.0 engine, and set a master password for CloudStack’s database setup tool to use. Refer to the CloudStack documentation to find the MySQL settings that you’ll need. You can put the settings in an RDS parameter group. In case you’re wondering why I’m not using Amazon Aurora, it’s because CloudStack needs the MyISAM storage engine, which isn’t available in Aurora.

I recommend Amazon EFS for file storage. For efficiency, create a mount target in the subnet with your EC2 instances. That will enable them to communicate directly with the mount target, thereby bypassing the overlay network and router. Note that the system VMs will use Amazon EFS via the router.

If you want, you can consolidate your CloudStack file systems. Just create a single file system with directories for each zone and type of storage. For example, I use directories named /zone1/primary, /zone1/secondary, /zone2/primary, etc. You should also consider enabling provisioned throughput on the file system, or you may run out of bursting credits after booting a few VMs.

One consequence of the file system’s scalability is that the amount of free space (8 exabytes) will cause an integer overflow in CloudStack! To avoid this problem, reduce storage.overprovisioning.factor in CloudStack’s global settings from 2 to 1.

When your environment is ready, install CloudStack. When it asks for a default gateway, remember to use the router’s overlay network address. When you add a host, make sure that you use the host’s overlay network IP address.

Cleanup

If you used my CloudFormation template, delete the stack and remove any route table entries you added.

If you didn’t use CloudFormation, here are the things to delete:

1. The CloudStack EC2 instances
2. The Amazon RDS database and parameter group
3. The Amazon EFS file system
4. The transit gateway multicast domain subnet association
5. The transit gateway multicast domain
6. The transit gateway VPC attachment
7. The transit gateway
8. The route table entries that you created
9. The security groups that you created for the instances, database, and file system

Conclusion

The approach I shared has many steps, but they’re not bad when you have a plan. Whether you need a simple setup for experiments, or you need a scalable environment for a data center migration, you now have a path forward. Give it a try, and comment here about the things you learned. I hope you find it useful and fun!

“Apache”, “Apache CloudStack”, and “CloudStack” are trademarks of the Apache Software Foundation.

Post Syndicated from Sheila Busser original https://aws.amazon.com/blogs/compute/building-a-cloud-in-the-cloud-running-apache-cloudstack-on-amazon-ec2-part-1/

This blog is written by Mark Rogers, SDE II – Customer Engineering AWS.

How do you put a cloud inside another cloud? Some features that make Amazon Elastic Compute Cloud (Amazon EC2) secure and wonderful also make running CloudStack difficult. The biggest obstacle is that AWS and CloudStack both want to manage network resources. Therefore, we must keep them out of each other’s way. This requires some steps that aren’t obvious, and it took a long time to figure out. I’m going to share what I learned, so that you can navigate the process more easily.

Apache CloudStack is an open-source platform for deploying and managing virtual machines (VMs) and the associated network and storage infrastructure. You would normally run it on your own hardware to create your own cloud. But there can be advantages to running it inside of an Amazon Virtual Private Cloud (Amazon VPC), including how it could help you migrate out of a data center. It’s a great way to create disposable environments for experiments or training. Furthermore, it’s a convenient way to test-drive the new CloudStack support in Amazon Elastic Kubernetes Service (Amazon EKS) Anywhere. In my case, I needed to create development and test environments for a project that uses the CloudStack API. The environments needed to be shared and scalable. Our build pipelines were already in AWS, so it made sense to put the new environments there, too.

CloudStack can work with a number of hypervisors. The instructions in this article will use Kernel-based Virtual Machine (KVM) on Linux. KVM will manage the VMs at a low level, and CloudStack will manage KVM.

Prerequisites

Most of the information in this article should be applicable to a range of CloudStack versions. I targeted CloudStack 4.14 on CentOS 7. I also tested CloudStack versions 4.16 and 4.17, and I recommend them.

The official CentOS 7 x86_64 HVM image works well. If you use a different Linux flavor or version, then you might have to modify some of the implementation details.

You’ll need to know the basics of CloudStack. The scope of this article is making CloudStack and AWS coexist peacefully. Once CloudStack is running, I’m assuming that you’ll handle things from there.  Refer to the AWS documentation and CloudStack documentation for information on security and other best practices.

Making things easier

I wrote some scripts to automate the installation. You can run them on EC2 instances with CentOS 7, and they’ll do all the installation and OS configuration for you. You can use them as they are, or customize them to meet your needs. I also wrote some AWS CloudFormation templates you can copy in order to create a demo environment. The README file has more details.

Amazon EC2 instance types

KVM requires hardware virtualization support. Most EC2 instances are VMs that don’t support nested virtualization. To get access to the bare hardware, you need a metal instance type.

I like c5.metal because it’s one of the least expensive metal types, and has a low cost per vCPU. It has 96 vCPUs and 192 GiB of memory. If you run 20 VMs on it, with 4 CPU cores and 8 GiB of memory each, then you’d still have 16 vCPUs and 32 GiB to share between the operating system, CloudStack, and MySQL. Using CloudStack’s overprovisioning feature, you could fit even more VMs if they’re running light loads.

Networking

The biggest challenge is the network. AWS knows which IP and MAC addresses should exist, and it knows the machines to which they should belong. It blocks any traffic that doesn’t fit its idea of how the network should behave. Simultaneously, CloudStack assumes that any IP or MAC address it invents should work just fine. When CloudStack assigns addresses to VMs on an AWS subnet, their network traffic gets blocked.

You could get around this by enabling network address translation (NAT) on the instance running CloudStack. That’s a great solution if it fits your needs, but it makes it hard for other machines in your Amazon VPC to contact your VMs. I recommend a different approach.

Although AWS restricts what you can do with its layer 2 network, it’s perfectly happy to let you run your own layer 3 router. Your EC2 instance can act as a router to a new virtual subnet that’s outside of the jurisdiction of AWS. The instance integrates with AWS just like a VPN appliance, routing traffic to wherever it needs to go. CloudStack can do whatever it wants in the virtual subnet, and everybody’s happy.

What do I mean by a virtual subnet? This is a subnet that exists only inside the EC2 instance.  It consists of logical network interfaces attached to a Linux bridge. The entire subnet exists inside a single EC2 instance. It doesn’t scale well, but it’s simple. In my next post, I’ll cover a more complicated setup with an overlay network that spans multiple instances to allow horizontal scaling.

The simple way

The simple way is to put everything in one EC2 instance, including the database, file storage, and a virtual subnet. Because everything’s stored locally, allocate enough disk space for your needs. 500 GB will be enough to support a few basic VMs. Create or select a security group for your instance that gives users access to the CloudStack UI (TCP port 8080). The security group should also allow access to any services that you’ll offer from your VMs.

When you have your instance, configure AWS to treat it as a router.

1. Go to Amazon EC2 in the AWS Management Console.
2. Select your instance, and stop source/destination checking.

3. Update the subnet route tables.

a. Go to the VPC settings, and select Route Tables.

b. Identify the tables for subnets that need CloudStack access.

c. In each of these tables, add a route to the new virtual subnet. The route target should be your EC2 instance.

4. Depending on your network needs, you may also need to add routes to transit gateways, VPN endpoints, etc.

Because everything will be on one server, creating a virtual subnet is simply a matter of creating a Linux bridge. CloudStack must find a network adapter attached to the bridge. Therefore, add a dummy interface with a name that CloudStack will recognize.

The following snippet shows how I configure networking in CentOS 7. You must provide values for the variables $virutal_host_ip_address and $virtual_netmask to reflect the virtual subnet that you want to create. For $dns_address, I recommend the base of the VPC IPv4 network range, plus two. You shouldn’t use 169.654.169.253 because CloudStack reserves link-local addresses for its own use.

yum install -y bridge-utils net-tools

# The bridge must be named cloudbr0.

cat << EOF > /etc/sysconfig/network-scripts/ifcfg-cloudbr0
DEVICE=cloudbr0
TYPE=Bridge
ONBOOT=yes
BOOTPROTO=none
IPV6INIT=no
IPV6_AUTOCONF=no
DELAY=5
STP=yes
USERCTL=no
NM_CONTROLLED=no
IPADDR=$virtual_host_ip_address
NETMASK=$virtual_netmask
DNS1=$dns_address
EOF

# Create a dummy network interface.
cat << EOF > /etc/sysconfig/modules/dummy.modules
#!/bin/sh
/sbin/modprobe dummy numdummies=1
/sbin/ip link set name ethdummy0 dev dummy0
EOF

chmod +x /etc/sysconfig/modules/dummy.modules
/etc/sysconfig/modules/dummy.modules

cat << EOF > /etc/sysconfig/network-scripts/ifcfg-ethdummy0
TYPE=Ethernet
BOOTPROTO=none
NAME=ethdummy0
DEVICE=ethdummy0
ONBOOT=yes
BRIDGE=cloudbr0
NM_CONTROLLED=no
EOF

# Turn the instance into a router

echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
sysctl -p

# Must kill dhclient or the network service won't restart properly.
# A reboot would also work, if you’d rather do that.

pkill dhclient
systemctl restart network

CloudStack must know which IP addresses to use for inter-service communication. It will select by resolving the machine’s fully qualified domain name (FQDN) to an address. The following commands will make it to choose the right one. You must provide a value for $virtual_host_ip_address.

hostnamectl set-hostname cloudstack.localdomain

echo "$virtual_host_ip_address cloudstack.localdomain" >> 
/etc/hosts

You can finish the setup by following the Quick Installation Guide.

Remember that CloudStack is only directly connected to your virtual network. The EC2 instance is the router that connects the virtual subnet to the Amazon VPC. When you’re configuring CloudStack, use your instance’s virtual subnet address as the default gateway.

To access CloudStack from your workstation, you’ll need a connection to your VPC. This can be through a client VPN or a bastion host. If you use a bastion, its subnet needs a route to your virtual subnet, and you’ll need an SSH tunnel for your browser to access the CloudStack UI. The UI is at http://x.x.x.x:8080/client/, where x.x.x.x is your CloudStack instance’s virtual subnet address. Note that CloudStack’s console viewer won’t work if you’re using an SSH tunnel.

If you’re just experimenting with CloudStack, then I suggest saving money by stopping your instance when it isn’t needed. The safe way to do that is:

1. Disable your zone in the CloudStack UI.
2. Put the primary storage into maintenance mode.
3. Wait for the switch to maintenance mode to be complete.
4. Stop the EC2 instance.

When you’re ready to turn everything back on, simply reverse those steps. If you have any virtual routers in CloudStack, then you may need to start those, too.

Cleanup

If you used my CloudFormation template, then delete the stack and remove any route table entries you added. If you didn’t use CloudFormation, then terminate the EC2 instance, delete the security group you created for it, and remove any route table entries that you added.

Conclusion

Getting CloudStack to run on AWS isn’t so bad. The hardest part is simply knowing how. The setup explained here is great for small installations, but it can only scale vertically. In my next post, I’ll show you how to create an installation that scales horizontally. Instead of using a virtual subnet that exists in a single EC2 instance, we’ll build an overlay network that spans multiple instances. It will use more components and features, including some that might be new to you. I hope you find it interesting!

Now that you can create a simple setup, give it a try! I hope you have fun and learn something new along the way. Comment with the results of your experiments.

“Apache”, “Apache CloudStack”, and “CloudStack” are trademarks of the Apache Software Foundation.