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Multi-Cluster Architecture

GKE Clusters

Kubernetes is not vendor specific; however, for the sake of providing explicit and complete instructions for deploying all elements of a multi-cluster Kubernetes Operator implementation, this section walks you through the process of deploying multiple Kubernetes clusters on GCP specifically.

Prerequisites

Before you begin, perform the following actions:

  • Create a GCP account.

  • Prepare a GCP project so that you can use it to create GKE (Google Kubernetes Engine) clusters.

  • Install the GCP CLI.

  • Authenticate with the gcloud auth login command.

  • Update as needed and set the environment variables defined in the following env_variables.sh file.

1# GCP project name - this is the only parameter that is mandatory to change here
2export MDB_GKE_PROJECT="${MDB_GKE_PROJECT:="### Set your GKE project name here ###"}"
3
4# Adjust the values for each Kubernetes cluster in your deployment.
5# The deployment script references the following variables to get values for each cluster.
6export K8S_CLUSTER_0="k8s-mdb-0${K8S_CLUSTER_SUFFIX:-""}"
7export K8S_CLUSTER_0_ZONE="europe-central2-a"
8export K8S_CLUSTER_0_NUMBER_OF_NODES=3
9export K8S_CLUSTER_0_MACHINE_TYPE="e2-standard-4"
10export K8S_CLUSTER_0_CONTEXT_NAME="gke_${MDB_GKE_PROJECT}_${K8S_CLUSTER_0_ZONE}_${K8S_CLUSTER_0}"
11
12export K8S_CLUSTER_1="k8s-mdb-1${K8S_CLUSTER_SUFFIX:-""}"
13export K8S_CLUSTER_1_ZONE="europe-central2-b"
14export K8S_CLUSTER_1_NUMBER_OF_NODES=3
15export K8S_CLUSTER_1_MACHINE_TYPE="e2-standard-4"
16export K8S_CLUSTER_1_CONTEXT_NAME="gke_${MDB_GKE_PROJECT}_${K8S_CLUSTER_1_ZONE}_${K8S_CLUSTER_1}"
17
18export K8S_CLUSTER_2="k8s-mdb-2${K8S_CLUSTER_SUFFIX:-""}"
19export K8S_CLUSTER_2_ZONE="europe-central2-c"
20export K8S_CLUSTER_2_NUMBER_OF_NODES=1
21export K8S_CLUSTER_2_MACHINE_TYPE="e2-standard-4"
22export K8S_CLUSTER_2_CONTEXT_NAME="gke_${MDB_GKE_PROJECT}_${K8S_CLUSTER_2_ZONE}_${K8S_CLUSTER_2}"
23
24# Comment out the following line so that the script does not create preemptible nodes.
25# DO NOT USE preemptible nodes in production.
26export GKE_SPOT_INSTANCES_SWITCH="--preemptible"

Source Code

You can find all included source code in the MongoDB Kubernetes Operator repository.

Procedure

1

Set your default gcloud project:

1gcloud config set project "${MDB_GKE_PROJECT}"
2

Create Kubernetes clusters.

Create three GKE (Google Kubernetes Engine) clusters:

1gcloud container clusters create "${K8S_CLUSTER_0}" \
2      --zone="${K8S_CLUSTER_0_ZONE}" \
3      --num-nodes="${K8S_CLUSTER_0_NUMBER_OF_NODES}" \
4      --machine-type "${K8S_CLUSTER_0_MACHINE_TYPE}" \
5      --tags=mongodb \
6      "${GKE_SPOT_INSTANCES_SWITCH:-""}"
1gcloud container clusters create "${K8S_CLUSTER_1}" \
2      --zone="${K8S_CLUSTER_1_ZONE}" \
3      --num-nodes="${K8S_CLUSTER_1_NUMBER_OF_NODES}" \
4      --machine-type "${K8S_CLUSTER_1_MACHINE_TYPE}" \
5      --tags=mongodb \
6      "${GKE_SPOT_INSTANCES_SWITCH:-""}"
1gcloud container clusters create "${K8S_CLUSTER_2}" \
2      --zone="${K8S_CLUSTER_2_ZONE}" \
3      --num-nodes="${K8S_CLUSTER_2_NUMBER_OF_NODES}" \
4      --machine-type "${K8S_CLUSTER_2_MACHINE_TYPE}" \
5      --tags=mongodb \
6      "${GKE_SPOT_INSTANCES_SWITCH:-""}"
3

Store credentials in your kubeconfig.

Obtain credentials and save contexts to the current kubeconfig file. By default, this file is located in the ~/.kube/config directory and referenced by the $KUBECONFIG environment variable.

1gcloud container clusters get-credentials "${K8S_CLUSTER_0}" --zone="${K8S_CLUSTER_0_ZONE}"
2gcloud container clusters get-credentials "${K8S_CLUSTER_1}" --zone="${K8S_CLUSTER_1_ZONE}"
3gcloud container clusters get-credentials "${K8S_CLUSTER_2}" --zone="${K8S_CLUSTER_2_ZONE}"

All kubectl commands reference these contexts using the following variables:

  • $K8S_CLUSTER_0_CONTEXT_NAME

  • $K8S_CLUSTER_1_CONTEXT_NAME

  • $K8S_CLUSTER_2_CONTEXT_NAME

4

Verify that kubectl has access to Kubernetes clusters.

1echo "Nodes in cluster ${K8S_CLUSTER_0_CONTEXT_NAME}"
2kubectl --context "${K8S_CLUSTER_0_CONTEXT_NAME}" get nodes
3echo; echo "Nodes in cluster ${K8S_CLUSTER_1_CONTEXT_NAME}"
4kubectl --context "${K8S_CLUSTER_1_CONTEXT_NAME}" get nodes
5echo; echo "Nodes in cluster ${K8S_CLUSTER_2_CONTEXT_NAME}"
6kubectl --context "${K8S_CLUSTER_2_CONTEXT_NAME}" get nodes
1Nodes in cluster gke_scratch-kubernetes-team_europe-central2-a_k8s-mdb-0-682f2df6e1745e000788a1d5-19985
2NAME                                                  STATUS   ROLES    AGE     VERSION
3gke-k8s-mdb-0-682f2df6e1-default-pool-68d97b7f-fct9   Ready    <none>   2m20s   v1.32.3-gke.1785003
4gke-k8s-mdb-0-682f2df6e1-default-pool-68d97b7f-k9td   Ready    <none>   2m20s   v1.32.3-gke.1785003
5gke-k8s-mdb-0-682f2df6e1-default-pool-68d97b7f-pwsw   Ready    <none>   2m19s   v1.32.3-gke.1785003
6
7Nodes in cluster gke_scratch-kubernetes-team_europe-central2-b_k8s-mdb-1-682f2df6e1745e000788a1d5-19985
8NAME                                                  STATUS   ROLES    AGE   VERSION
9gke-k8s-mdb-1-682f2df6e1-default-pool-0f84fbc8-1b4j   Ready    <none>   32s   v1.32.3-gke.1785003
10gke-k8s-mdb-1-682f2df6e1-default-pool-0f84fbc8-fn7x   Ready    <none>   32s   v1.32.3-gke.1785003
11gke-k8s-mdb-1-682f2df6e1-default-pool-0f84fbc8-k4hc   Ready    <none>   32s   v1.32.3-gke.1785003
12
13Nodes in cluster gke_scratch-kubernetes-team_europe-central2-c_k8s-mdb-2-682f2df6e1745e000788a1d5-19985
14NAME                                                  STATUS   ROLES    AGE    VERSION
15gke-k8s-mdb-2-682f2df6e1-default-pool-ff13f41c-m4f9   Ready    <none>   4m6s   v1.32.3-gke.1785003

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