Gremlin is a simple, safe and secure service for performing Chaos Engineering experiments through a SaaS-based platform. Memcache is general-purpose distributed memory caching system. Datadog is a monitoring service for cloud-scale applications, providing monitoring of servers, databases, tools, and services, through a SaaS-based data analytics platform. Datadog provides an integration to monitor Memcache.
For the purposes of this tutorial we will run Chaos Engineering experiments for Memcache on Kubernetes. We will use Gremlin to run Chaos Engineering experiments on our cluster where run an IO attack to increase the number of reads. This will give us confidence in the reliability and resiliency of our memcached cluster. Additional experiments that are recommended to run include shutting down Memcache instances and pods and insuring this does not take down your database/storage layer.
To complete this tutorial you will need the following:
- 4 cloud infrastructure hosts running Ubuntu 16.04 with 4GM RAM and private networking enabled
- A Gremlin account (sign up here)
- A Datadog account (sign up here)
You will need to install the following on each of your 4 cloud infrastructure hosts. This will enable you to run your Chaos Engineering experiments.
This tutorial will walk you through the required steps to run the Memcache IO Chaos Engineering experiment.
- Step 1 - Creating a Kubernetes cluster with 3 nodes
- Step 2 - Installing Memcache
- Step 3 - Installing Helm
- Step 4 - Installing Gremlin
- Step 5 - Installing Datadog
- Step 6 - Performing Chaos Engineering experiments on Memcache
- Step 7 - Installing mcrouter
- Step 8 - Performing Chaos Engineering experiments on mcrouter
We will start with creating three Ubuntu 16.04 servers. This will give you four servers to configure. Create 4 hosts and call them kube-01, kube-02, kube-03 and kube-04. You need to be running hosts with a minimum of 4GB RAM.
Set your hostnames for your servers as follows:
- Server 1 - Hostname: k8-01
- Server 2 - Hostname: k8-02
- Server 3 - Hostname: k8-03
- Server 4 - Hostname: k8-04
Kubernetes will need to assign specialized roles to each server. We will setup one server to act as the master:
- k8-01 - role: master
- k8-02 - role: node
- k8-03 - role: node
- k8-04 - role: node
On each of the three Ubuntu 16.04 servers run the following commands as root:
apt-get update && apt-get install -y apt-transport-httpscurl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -cat <<EOF >/etc/apt/sources.list.d/kubernetes.listdeb http://apt.kubernetes.io/ kubernetes-xenial mainEOFapt-get updateapt-get install -y kubelet kubeadm kubectl docker.io
On the kube-01 node run the following command:
To start using your cluster, you need to run the following as a regular user:
mkdir -p $HOME/.kubesudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/configsudo chown $(id -u):$(id -g) $HOME/.kube/config
Your Kubernetes master has initialized successfully!
You can now join any number of machines by running the kubeadm join command on each node as root. This command will be created for you as displayed in your terminal for you to copy and run. An example of what this looks like is below:
kubeadm join --token 702ff6.bc7aacff7aacab17 188.8.131.52:6443 --discovery-token-ca-cert-hash sha256:68bc22d2c631800fd358a6d7e3998e598deb2980ee613b3c2f1da8978960c8ab
When you join your kube-02 and kube-01 nodes you will see the following on the node:
This node has joined the cluster:* Certificate signing request was sent to master and a response was received.* The Kubelet was informed of the new secure connection details.
To check that all nodes are now joined to the master run the following command on the Kubernetes master kube-01:
kubectl get nodes
The successful result will look like this:
NAME STATUS ROLES AGE VERSIONk8-01 NotReady master 111s v1.12.2k8-03 NotReady <none> 14s v1.12.2k8-04 NotReady <none> 12s v1.12.2
Kubernetes Add-Ons are pods and services that implement cluster features. Pods extend the functionality of Kubernetes. You can install addons for a range of cluster features including Networking and Visualization.
We are going to install the Weave Net Add-On on the kube-01 master which provides networking and network policy. It will continue working on both sides of a network partition and does not require an external database.
Next you will deploy a pod network to the cluster. The options are listed at: https://kubernetes.io/docs/concepts/cluster-administration/addons/
Get the Weave Net yaml:
curl -o weave.yaml https://cloud.weave.works/k8s/v1.8/net.yaml
Inspect the yaml contents:
On the kube-01 Kubernetes master node run the following commands:
kubectl apply -f weave.yaml
The result will look like this:
serviceaccount/weave-net createdclusterrole.rbac.authorization.k8s.io/weave-net createdclusterrolebinding.rbac.authorization.k8s.io/weave-net createdrole.rbac.authorization.k8s.io/weave-net createdrolebinding.rbac.authorization.k8s.io/weave-net createddaemonset.extensions/weave-net created
It may take a minute or two for DNS to be ready. Continue to check for DNS to be ready before moving on by running the following command:
kubectl get pods --all-namespaces
The successful result will look like this, every container should be running:
NAMESPACE NAME READY STATUS RESTARTS AGEkube-system coredns-576cbf47c7-gm6kt 1/1 Running 0 3m20skube-system coredns-576cbf47c7-h5v5k 1/1 Running 0 3m20skube-system etcd-k8-01 1/1 Running 0 2m14skube-system kube-apiserver-k8-01 1/1 Running 0 2m14skube-system kube-controller-manager-k8-01 1/1 Running 0 2m18skube-system kube-proxy-7m87q 1/1 Running 0 111skube-system kube-proxy-mk9h9 1/1 Running 0 113skube-system kube-proxy-wkxxm 1/1 Running 0 3m20skube-system kube-scheduler-k8-01 1/1 Running 0 2m35skube-system weave-net-lvp6x 2/2 Running 0 34skube-system weave-net-pjxk2 2/2 Running 0 34skube-system weave-net-qrrvl 2/2 Running 0 34s
Congratulations, now your Kubernetes cluster running on Ubuntu 16.04 is up and ready for you to deploy a microservices application.
First download the helm binary on your Kubernetes master, kube-01:
Create a helm directory and unzip the helm binary to your local system:
mkdir helm-v2.6.0tar zxfv helm-v2.6.0-linux-amd64.tar.gz -C helm-v2.6.0
Add the helm binary's directory to your PATH environment variable:
export PATH="$(echo ~)/helm-v2.6.0/linux-amd64:$PATH"
Create a service account with the cluster admin role for Tiller, the Helm server:
kubectl create serviceaccount --namespace kube-system tillerkubectl create clusterrolebinding tiller --clusterrole=cluster-admin --serviceaccount=kube-system:tiller
Initialize Tiller in your cluster, and update information of available charts:
helm init --service-account tillerhelm repo update
You will need to wait until the tiller deploy pod is ready before proceeding. Use the following command to check for when the tiller deploy pod is ready:
kubectl -n kube-system get pods
You will see the following output:
NAME READY STATUS RESTARTS AGEcoredns-576cbf47c7-gm6kt 1/1 Running 0 14mcoredns-576cbf47c7-h5v5k 1/1 Running 0 14metcd-k8-01 1/1 Running 0 13mkube-apiserver-k8-01 1/1 Running 0 13mkube-controller-manager-k8-01 1/1 Running 0 13mkube-proxy-7m87q 1/1 Running 0 12mkube-proxy-mk9h9 1/1 Running 0 12mkube-proxy-wkxxm 1/1 Running 0 14mkube-scheduler-k8-01 1/1 Running 0 13mtiller-deploy-9cfccbbcf-6f8j9 1/1 Running 0 93sweave-net-lvp6x 2/2 Running 0 11mweave-net-pjxk2 2/2 Running 0 11mweave-net-qrrvl 2/2 Running 0 11m
Check the logs for the tiller pod, run the following command replacing _tiller-deploy-9cfccbbcf-kflph _with your pod name:
kubectl logs --namespace kube-system tiller-deploy-9cfccbbcf-kflph
You will see the following output:
[main] 2018/11/20 20:00:41 Starting Tiller v2.6.0 (tls=false)[main] 2018/11/20 20:00:41 GRPC listening on :44134[main] 2018/11/20 20:00:41 Probes listening on :44135[main] 2018/11/20 20:00:41 Storage driver is ConfigMap
Install a new Memcached Helm chart release with three replicas, one for each node:
helm install stable/memcached --name mycache --set replicaCount=3
You will see the folllowing output:
NAME READY STATUS RESTARTS AGEmycache-memcached-0 1/1 Running 0 89smycache-memcached-1 1/1 Running 0 61smycache-memcached-2 0/1 Pending 0 48s
Execute the following command to see the running pods:
kubectl get pods
You should see the following:
NAME READY STATUS RESTARTS AGEmycache-memcached-0 1/1 Running 0 3m54smycache-memcached-1 1/1 Running 0 3m26smycache-memcached-2 0/1 Pending 0 3m13s
First, run the following command to retrieve the endpoints' IP addresses:
kubectl get endpoints mycache-memcached
The output should be similar to the following:
NAME ENDPOINTS AGEmycache-memcached 10.40.0.1:11211,10.46.0.4:11211 4m10s
Test the deployment by opening a telnet session with one of the running Memcached servers on port 11211:
kubectl run -it --rm alpine --image=alpine:3.6 --restart=Never telnet mycache-memcached-0.mycache-memcached.default.svc.cluster.local 11211
At the telnet prompt, run these commands using the Memcached ASCII protocol:
set mykey 0 0 5helloget mykeyquit
The resulting output is shown here in bold:
If you don't see a command prompt, try pressing enter.set mykey 0 0 5helloSTOREDget mykeyVALUE mykey 0 5helloENDquitConnection closed by foreign host
Next we will implement service discovery logic with Python. Run the following command to create a python pod in your Kubernetes cluster:
kubectl run -it --rm python --image=python:3.6-alpine --restart=Never sh
Install the pymemcache library:
pip install pymemcache
You will see the following output
Collecting pymemcache Downloading https://files.pythonhosted.org/packages/91/14/f4fb51de1a27b12df6af42e6ff794a13409bdca6c8880e562f7486e78b5b/pymemcache-2.0.0-py2.py3-none-any.whlCollecting six (from pymemcache) Downloading https://files.pythonhosted.org/packages/67/4b/141a581104b1f6397bfa78ac9d43d8ad29a7ca43ea90a2d863fe3056e86a/six-1.11.0-py2.py3-none-any.whlInstalling collected packages: six, pymemcacheSuccessfully installed pymemcache-2.0.0 six-1.11.0
Start a Python interactive console by running the following command:
In the Python console, run these commands:
import socketfrom pymemcache.client.hash import HashClient_, _, ips = socket.gethostbyname_ex('mycache-memcached.default.svc.cluster.local')servers = [(ip, 11211) for ip in ips]client = HashClient(servers, use_pooling=True)client.set('mykey', 'hello')client.get('mykey')
You will see the following output:
Exit the Python console:
Exit the pod's shell session by pressing Control+D. You will see the following:
/ # pod "python" deleted
After you have created your Gremlin account (sign up here) you will need to find your Gremlin Daemon credentials. Login to the Gremlin App using your Company name and sign-on credentials. These were emailed to you when you signed up to start using Gremlin. Navigate to Company Teams Settings and click on your Team. Click the blue Download button to get your Team Certificate. The downloaded certificate.zip contains both a public-key certificate and a matching private key.
Unzip the certificate.zip and save it to your gremlin folder on your desktop. Rename your certificate and key files to gremlin.cert and gremlin.key.
Next create your secret as follows:
kubectl create secret generic gremlin-team-cert --from-file=./gremlin.cert --from-file=./gremlin.key
Before installing with Helm, be sure to configure your team secret as described in the section above.
The simplest way to install the Gremlin client on your Kubernetes cluster is to use helm. If you do not already have Helm installed, go here to get started. Once helm is installed and configured, add the gremlin repo and install the client:
helm repo add gremlin https://helm.gremlin.com
helm install --set gremlin.teamID=YOUR-TEAM-ID gremlin/gremlin
For more information on the Gremlin Helm chart, including more configuration options, check out the chart on Github.
By definition, containers of a Kubernetes Pod all share a network interface. This means when Gremlin applies a network impact to one container within a Kubernetes pod, the impact will be observed for all containers in the Pod. Note that this does not apply to containers in Pod replicas. If you attack a specific Pod replica, the effect applies to containers within that replica only, and does not apply to the rest of the replicas.
It is always recommended to target only a single container of a Pod. If you wish to exclude some containers from the network impact, reduce your blast radius by specifying ports relevant to the containers you wish to see impact.
To install Datadog in a Kubernetes pod you can use the Datadog Kubernetes easy one-step install. It will take a few minutes for Datadog to spin up the Datadog container, collect metrics on your existing containers and display them in the Datadog App.
You will simple copy the Kubernetes DaemonSet, save it as datadog-agent.yaml and then run the following command:
kubectl apply -f datadog-agent.yaml
Next install the Memcached Datadog Integration by clicking Install Integration:
You will see that following notification in your event stream:
You can read more about setting up Memcache monitoring in Datadog.
We will use the Gremlin Web App to create an IO attack on a specific memcache pod. The purpose of this experiment will be to ensure that we are able to identify an increase in IO for our memcache cluster. We will also use this attack to understand how the pod and server handles an increase in IO.
First click to create a new attack. Then click the container tab to view all the available containers you can run Chaos Engineering experiments on.
Select the _mycache-memcached-0 pods:
Next, select the Resource Gremlin and then choose IO. Click to unleash the Gremlin.
You can now monitor your IO attack using Datadog.
There are many Chaos Engineering experiments you could possibly run on your Memcache infrastructure:
- Shutdown Gremlin - will shutting down a memcache node cause unexpected issues?
- Latency & Packet Loss Gremlins - will they impact the ability to use the Memcache API endpoints?
- Disk Gremlin - will filling up the disk crash the host? We encourage you to run these Chaos Engineering experiments and share your findings! To get access to Gremlin, sign up here.
This tutorial has explored how to install Memcache and Gremlin with Kubernetes for your Chaos Engineering experiments. We then ran a CPU Chaos Engineering experiment on the Memcache using the Gremlin CPU attack.