Checkpoints
Create a new Cluster
/ 25
Create the StorageClass
/ 25
Deploying the Headless Service and StatefulSet
/ 25
Scaling the MongoDB replica set
/ 25
Running a MongoDB Database in Kubernetes with StatefulSets
This lab was developed with our partner, MongoDB. Your personal information may be shared with MongoDB, the lab sponsor, if you have opted-in to receive product updates, announcements, and offers in your Account Profile.
GSP022
Overview
Kubernetes is an open source container orchestration tool that handles the complexities of running containerized applications. You can run Kubernetes applications with Kubernetes Engine
—a Google Cloud computing service that offers many different customizations and integrations. In this lab, you will get some practical experience with Kubernetes by learning how to set up a MongoDB database with a StatefulSet. Running a stateful application (a database) on a stateless service (container) may sound contradictory. However, after getting hands-on practice with this lab you will quickly see how that's not the case. In fact, by using a few open-source tools you will see how Kubernetes and stateless services can go hand-in-hand.
What you'll learn
In this lab, you will learn the following:
- How to deploy a Kubernetes cluster, a headless service, and a StatefulSet.
- How to connect a Kubernetes cluster to a MongoDB replica set.
- How to scale MongoDB replica set instances up and down.
- How to clean up your environment and shutdown the above services.
Prerequisites
This is an advanced level lab. Familiarity with Kubernetes or containerized applications is suggested. Experience with the Google Cloud Shell/SDK and MongoDB is also recommended. If you are looking to get up to speed in these services, be sure to check out the following labs:
Once you're ready, scroll down to get your lab environment set up.
Setup
Before you click the Start Lab button
Read these instructions. Labs are timed and you cannot pause them. The timer, which starts when you click Start Lab, shows how long Google Cloud resources will be made available to you.
This hands-on lab lets you do the lab activities yourself in a real cloud environment, not in a simulation or demo environment. It does so by giving you new, temporary credentials that you use to sign in and access Google Cloud for the duration of the lab.
To complete this lab, you need:
- Access to a standard internet browser (Chrome browser recommended).
- Time to complete the lab---remember, once you start, you cannot pause a lab.
How to start your lab and sign in to the Google Cloud console
-
Click the Start Lab button. If you need to pay for the lab, a pop-up opens for you to select your payment method. On the left is the Lab Details panel with the following:
- The Open Google Cloud console button
- Time remaining
- The temporary credentials that you must use for this lab
- Other information, if needed, to step through this lab
-
Click Open Google Cloud console (or right-click and select Open Link in Incognito Window if you are running the Chrome browser).
The lab spins up resources, and then opens another tab that shows the Sign in page.
Tip: Arrange the tabs in separate windows, side-by-side.
Note: If you see the Choose an account dialog, click Use Another Account. -
If necessary, copy the Username below and paste it into the Sign in dialog.
{{{user_0.username | "Username"}}} You can also find the Username in the Lab Details panel.
-
Click Next.
-
Copy the Password below and paste it into the Welcome dialog.
{{{user_0.password | "Password"}}} You can also find the Password in the Lab Details panel.
-
Click Next.
Important: You must use the credentials the lab provides you. Do not use your Google Cloud account credentials. Note: Using your own Google Cloud account for this lab may incur extra charges. -
Click through the subsequent pages:
- Accept the terms and conditions.
- Do not add recovery options or two-factor authentication (because this is a temporary account).
- Do not sign up for free trials.
After a few moments, the Google Cloud console opens in this tab.
Activate Cloud Shell
Cloud Shell is a virtual machine that is loaded with development tools. It offers a persistent 5GB home directory and runs on the Google Cloud. Cloud Shell provides command-line access to your Google Cloud resources.
- Click Activate Cloud Shell at the top of the Google Cloud console.
When you are connected, you are already authenticated, and the project is set to your Project_ID,
gcloud
is the command-line tool for Google Cloud. It comes pre-installed on Cloud Shell and supports tab-completion.
- (Optional) You can list the active account name with this command:
- Click Authorize.
Output:
- (Optional) You can list the project ID with this command:
Output:
gcloud
, in Google Cloud, refer to the gcloud CLI overview guide.
Task 1. Set a compute zone
Throughout this lab, we will be using the gcloud command line tool to provision our services.
- Before we can create our Kubernetes cluster, we will need to set a compute zone so that the virtual machines in our cluster are all created in the same region. We can do this using the
gcloud config set
command—run the following in your cloud shell to set your zone to:
Task 2. Create a new cluster
Now that our zone is set, we will create a new cluster of containers.
- Run the following command to instantiate a cluster named
hello-world
:
This command creates a new cluster with two nodes, or virtual machines. You can configure this command with additional flags to change the number of nodes, the default permissions, and other variables. Learn more from the gcloud container clusters create reference.
Launching the cluster may take a few minutes. Once it's up, you should receive a similar output:
Click Check my progress to verify the objective.
Task 3. Setting up
Now that we have our cluster up and running, it's time to integrate it with MongoDB. We will be using a replica set so that our data is highly available and redundant—a must for running production applications.
To get set up, we need to do the following:
- Download the MongoDB replica set/sidecar (or utility container in our cluster).
- Instantiate a StorageClass.
- Instantiate a headless service.
- Instantiate a StatefulSet.
- Run the following command to clone the MongoDB/Kubernetes replica set from the Github repository:
- Once it's cloned, navigate to the
StatefulSet
directory with the following command:
Once you have verified that the files have been downloaded and that you're in the right directory, let's go ahead and create a Kubernetes StorageClass
.
Create the StorageClass
A StorageClass
tells Kubernetes what kind of storage you want to use for database nodes. On the Google Cloud, you have a couple of storage choices: SSDs and hard disks.
If you take a look inside the StatefulSet
directory (you can do this by running the ls
command), you will see SSD and HDD configuration files for both Azure and Google Cloud.
- Run the following command to take a look at the
googlecloud_ssd.yaml
file:
Output:
This configuration creates a new StorageClass called "fast" that is backed by SSD volumes.
- Run the following command to deploy the StorageClass:
Now that our StorageClass is configured, our StatefulSet can now request a volume that will automatically be created.
Click Check my progress to verify the objective.
Task 4. Deploying the Headless Service and StatefulSet
Find and inspect the files
- Before we dive into what headless service and StatefulSets are, let's open up the configuration file (
mongo-statefulset.yaml
) where they are both housed in:
You should receive the following output (without the pointers to the Headless Service and StatefulSet content):
- Remove the following flags from the file (lines 49 and 50):
- Ensure that this section of your file looks like the following:
- Exit the nano editor with CTRL+X > Y > ENTER.
Headless service: overview
The first section of mongo-statefulset.yaml
refers to a headless service
. In Kubernetes terms, a service describes policies or rules for accessing specific pods. In brief, a headless service is one that doesn't prescribe load balancing. When combined with StatefulSets, this will give us individual DNSs to access our pods, and in turn a way to connect to all of our MongoDB nodes individually. In the yaml
file, you can make sure that the service is headless by verifying that the clusterIP
field is set to None
.
StatefulSet: overview
The StatefulSet configuration is the second section of mongo-statefulset.yaml.
This is the bread and butter of the application: it's the workload that runs MongoDB and what orchestrates your Kubernetes resources. Referencing the yaml
file, we see that the first section describes the StatefulSet object. Then, we move into the Metadata section, where labels and the number of replicas are specified.
Next comes the pod spec. The terminationGracePeriodSeconds
is used to gracefully shutdown the pod when you scale down the number of replicas. Then the configurations for the two containers are shown. The first one runs MongoDB with command line flags that configure the replica set name. It also mounts the persistent storage volume to /data/db
: the location where MongoDB saves its data. The second container runs the sidecar. This sidecar container will configure the MongoDB replica set automatically. As mentioned earlier, a "sidecar" is a helper container that helps the main container run its jobs and tasks.
Finally, there is the volumeClaimTemplates
. This is what talks to the StorageClass we created before to provision the volume. It provisions a 100 GB disk for each MongoDB replica.
Deploy Headless Service and the StatefulSet
Now that we have a basic understanding of what a headless service and StatefulSet are, let's go ahead and deploy them.
- Since the two are packaged in
mongo-statefulset.yaml
, we can run the following command to run both of them:
You should receive the following output:
Click Check my progress to verify the objective.
Task 5. Connect to the MongoDB Replica set
Now that we have a cluster running and our replica set deployed, let's go ahead and connect to it.
Wait for the MongoDB replica set to be fully deployed
Kubernetes StatefulSets deploys each pod sequentially. It waits for the MongoDB replica set member to fully boot up and create the backing disk before starting the next member.
- Run the following command to view and confirm that all three members are up:
Output - all three members are up:
Initiating and Viewing the MongoDB replica set
At this point, you should have three pods created in your cluster. These correspond to the three nodes in your MongoDB replica set.
- Run this command to view:
Output:
-
Wait for all three members to be created before moving on.
-
Connect to the first replica set member:
You now have a REPL
environment connected to the MongoDB.
- Let's instantiate the replica set with a default configuration by running the
rs.initiate()
command:
- Print the replica set configuration; run the
rs.conf()
command:
This outputs the details for the current member of replica set rs0
. In this lab you see only one member. To get details of all members you need to expose the replica set through additional services like nodeport or load balancer.
- Type "exit" and press enter to quit the
REPL
.
Task 6. Scaling the MongoDB replica set
A big advantage of Kubernetes and StatefulSets is that you can scale the number of MongoDB Replicas up and down with a single command!
- To scale up the number of replica set members from 3 to 5, run this command:
In a few minutes, there will be 5 MongoDB pods.
- Run this command to view them:
Your output should look like this:
- To scale down the number of replica set members from 5 back to 3, run this command:
In a few seconds, there are 3 MongoDB pods.
- Run this command to view:
Your output should look like this:
Click Check my progress to verify the objective.
Task 7. Using the MongoDB replica set
Each pod in a StatefulSet backed by a Headless Service will have a stable DNS name. The template follows this format: <pod-name>.<service-name>
This means the DNS names for the MongoDB replica set are:
You can use these names directly in the connection string URI of your app.
Using a database is outside the scope of this lab, however for this case, the connection string URI would be:
Task 8. Clean up
Because you are working in a lab environment, when you end the lab all your resources and your project will be cleaned up and discarded on your behalf. But we want to show you how to clean up resources yourself to save on cost and to be a good cloud citizen when you are in your own environment.
To clean up the deployed resources, run the following commands to delete the StatefulSet, Headless Service, and the provisioned volumes.
- Delete the StatefulSet:
- Delete the service:
- Delete the volumes:
- Finally, you can delete the test cluster:
- Press Y then Enter to continue deleting the test cluster.
Congratulations!
Kubernetes Engine provides a powerful and flexible way to run containers on Google Cloud. StatefulSets let you run stateful workloads like databases on Kubernetes. You learned about:
- Creating a MongoDB replica set with Kubernetes StatefulSets
- Connecting to the MongoDB replica set
- Scaling the replica set
Finish your quest
This self-paced lab is part of the Cloud Architecture quest. A quest is a series of related labs that form a learning path. Completing a quest earns you a badge to recognize your achievement. You can make your badge or badges public and link to them in your online resume or social media account. Enroll in any quest that contains this lab and get immediate completion credit. Refer to the Google Cloud Skills Boost catalog for all available quests.
Take your next lab
Continue your quest with the next lab, or check out these suggestions:
- Web App to Perform Real-time Data Analysis with Kubernetes, Redis, and BigQuery
- Orchestrating the Cloud with Kubernetes
Next steps / learn more
- Learn more about Kubernetes Engine.
- Read the blog post on Running MongoDB on Kubernetes with StatefulSets.
- Wondering how much it'll cost to run your workloads? Check the Pricing Calculator - you can enter the number of instances, vCPU, and memory needs.
- Get free $500 credits for MongoDB on Google Cloud Marketplace - Applicable only for new customers
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Manual Last Updated October 09, 2023
Lab Last Tested October 09, 2023
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