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Setting up Autoscale

Autoscaling is basically load balancing where the number of instances used to handle your traffic is automatically adapted to match the current traffic load. On KraftCloud, scale out (the process of adding instances to cope with increased load) happens in milliseconds, so you can transparently and effortlessly handle load increase including traffic peaks. No more headaches due to slow autoscale like keeping hot instances around to deal with peaks, coming up with complex predictive algorithms, or other painful workarounds; you can just set autoscale on and let KraftCloud handle your traffic increases and peaks.

The Basics

As with load balancing, autoscaling in KraftCloud is handled via a service group. Service groups allow you to load balance traffic for an Internet-facing service like a web server by creating multiple instances within the same service group, as shown in this diagram:

Service groups in KraftCloud

While you can add or remove instances to a service group to scale your service, doing this manually makes it hard to react to changes in traffic load, and always keeping a large number of instances running just to cope with intermittent bursts would be wasteful and expensive; this is where autoscale comes into play.

With autoscale enabled, KraftCloud takes care of the heavy lifting for you by continuously monitoring the load of your service and automatically creating or deleting instances as needed.

Setting up Autoscale

First, we’ll use the kraft cloud deploy command to create an instance, in this example we’ll use NGINX:

Terminal window
git clone https://github.com/kraftcloud/examples
cd examples/nginx/
kraft cloud deploy -p 443:8080 .
Terminal window
[] Deployed successfully!
────────── name: nginx-4d7u3
────────── uuid: 8fda2a70-6a32-4b5e-8900-4395b33d02d7
───────── state: running
─────────── url: https://small-leaf-rafirkw7.fra0.kraft.host
───────── image: nginx@sha256:389bfa6be6455c92b61cfe429b50491373731dbdd8bd8dc79c08f985d6114758
───── boot time: 20.36 ms
──────── memory: 128 MiB
service group: small-leaf-rafirkw7
── private fqdn: nginx-4d7u3.internal
──── private ip: 172.16.6.5
────────── args: /usr/bin/nginx -c /etc/nginx/nginx.conf

With this single kraft cloud deploy command we’ve accomplished 3 things:

  1. Created an instance of NGINX which we will use as the autoscale master instance.
  2. Created a service group via the -p flag (named small-leaf-rafirkw7).
  3. Attached the instance to the service group (automatically done by the -p flag too).

All that’s left to do now to set up autoscale is to set an autoscale configuration policy and to set our instance as master; KraftCloud will then take care of cloning this master instance whenever load increases. To achieve this we’ll use the kraft cloud scale command:

Terminal window
kraft cloud scale init small-leaf-rafirkw7 --master nginx-4d7u3 --min-size 0 --max-size 8
kraft cloud scale add small-leaf-rafirkw7 --name scale-out-policy --metric cpu --adjustment percent --step 600:800/50 --step 800:/100
kraft cloud scale add small-leaf-rafirkw7 --name scale-in-policy --metric cpu --adjustment percent --step :50/-50

Note the following:

  • With the first command we set the master to the instance we created, and say that we want to scale up to a maximum of 8 instances and a minimum of 0 (scale to zero).
  • WIth the second command we set the scale out policy based on CPU utilization (in millicores): between 60% and 80% utilization, increase by 50% of instances. From 80% onward, double the number of instances.
  • With the third command we set the scale in policy: below 50% utilization, reduce the number of instances by half (note the - sign for scale in).

Testing it

To check it’s working, you can use the kraft cloud scale get command to list the autoscale properties of the service group:

Terminal window
kraft cloud scale get small-leaf-rafirkw7

You should see output similar to:

Terminal window
uuid: 5ca059ec-a24a-41f2-8413-f09bc58730ca
name: small-leaf-rafirkw7
enabled: true
min size: 0
max size: 8
warmup (ms): 1000
cooldown (ms): 1000
master: f840ac12-f485-4f02-9f33-6a0a7de46f1f
policies: scale-out-policy;scale-in-policy

To list an individual policy, you can further use the kraft cloud scale get command as follows:

Terminal window
kraft cloud scale get --policy scale-out-policy small-leaf-rafirkw7

You should see output similar to:

Terminal window
adjustment_type: percent
enabled: true
metric: cpu
name: scale-out-policy
status: success
steps:
- adjustment: 50
lower_bound: 600
upper_bound: 800
- adjustment: 100
lower_bound: 800
type: step

You can further check that the master instance is on standby, i.e., it has been scaled to 0 (assuming your service isn’t receiving any traffic yet). You can get the UUID of your master instance from the kraft cloud scale get command above.

Terminal window
kraft cloud inst get f840ac12-f485-4f02-9f33-6a0a7de46f1f -o list

You should see output similar to:

Terminal window
uuid: f840ac12-f485-4f02-9f33-6a0a7de46f1f
name: nginx-9mbf2
fqdn: restless-resonance-0oo7m7s8.fra0.kraft.host
private ip: 172.16.6.4
state: standby
created at: 30 minutes ago
image: felipe.unikraft.io/nginx@sha256:d4325c1f1a472c511723148adc380d491029f4c98a2367fbeff628c6456d4180
memory: 128 MiB
args: /usr/bin/nginx -c /etc/nginx/nginx.conf
env:
volumes:
service group: 5ca059ec-a24a-41f2-8413-f09bc58730ca
boot time: 19465us

Note the value of the state field. Now let’s make sure the service is up:

Terminal window
curl https://small-leaf-rafirkw7.fra0.kraft.host

You should get an immediate response, even though the instance was on standby. You can use the watch tool to see if you manage to see the instance change state from standby to running:

Terminal window
watch --color -n 0.5 kraft cloud instance list

That’s it! To test scale out send traffic to your service. Here’s a brief video showing different traffic loads and how KraftCloud’s autoscale reacts to them:

Autoscale video

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