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Generate a large volume of logs with Python on GKE to Pub/Sub

Author(s): @arieljassan ,   Published: 2020-06-08

Ariel Jassan | Data Engineer | Google

Contributed by Google employees.

One of the challenges of building scalable data-intensive applications is the ability to create tests that are representative enough to simulate the scale of the system in production. To overcome this challenge, you need tools to generate custom test data at a large scale. This tutorial makes that process easier with scripts and architecture to simulate logs published to Pub/Sub. Pub/Sub allows ingestion of high volumes of data in real time, which you can then use in data sinks and other systems.

This tutorial describes how to create a GKE (Google Kubernetes Engine) cluster, deploy a Python application that generates logs using the Faker library, and simulate load with the Python library Locust.

By the end of the tutorial, you'll be able to monitor the cluster utilization from the Kubernetes Engine dashboard in Cloud Monitoring and the arrival of the messages to Pub/Sub in the Cloud Console.

This tutorial assumes that you already have a project in Google Cloud and that you have the Cloud SDK installed in your environment. To install the Cloud SDK, see Installing the Cloud SDK.


  • Create a GKE cluster and a Pub/Sub topic.
  • Create Docker containers for the application logic and for the Locust master and workers.
  • Create service accounts with permissions to deploy Docker containers from Cloud Build on GKE and to publish to Pub/Sub.
  • Deploy the containers to GKE.
  • Monitor GKE cluster and Pub/Sub topic utilization.


You may incur costs in GKE, Compute Engine, Cloud Build, Cloud Storage, and networking. Use the Pricing Calculator to generate a cost estimation based on your projected usage.

Reference architecture

The following diagram shows the architecture components of the solution.


  1. The Kubernetes deployment locust-master is responsible for coordinating the Locust threads as defined by the end user.
  2. The Kubernetes deployment locust-worker creates HTTP requests to trigger the generation of logs by the webapp containers.
  3. The Kubernetes deployment webapp is responsible for generating dictionary-like logs, which are published to a Pub/Sub topic.
  4. Cloud Pub/Sub is the sink of the log generation process. The Pub/Sub topic captures the logs sent by the webapp containers.
  5. Cloud Monitoring samples the usage of the GKE cluster and summarizes the information in the Kubernetes Dashboard in Cloud Monitoring.
  6. The landing page of the Pub/Sub API shows the number of API requests and operations per second for the topic.

In addition to the components above, there are two Kubernetes services deployed as part of the solution:

  • The load balancer service locust-master handles the requests from the end user.
  • The cluster IP service webapp-cip serves as the interface between the Locust testing environment and the web application.

Before you begin

Clone the Google Cloud Community repository and go to the directory:

git clone https://github.com/GoogleCloudPlatform/community.git
cd community/tutorials/generate-logs-scale    

Enable relevant APIs

Run the following commands in the Cloud Console to enable APIs for GKE, Container Registry, Pub/Sub, Cloud Monitoring, and Cloud Build.

    gcloud services enable \
        container.googleapis.com \
        containerregistry.googleapis.com \
        pubsub.googleapis.com \
        stackdriver.googleapis.com \

It may take a few minutes for the APIs to be enabled.

Set environment variables

Run the following comands in the Cloud Console to set environment variables. Replace the values for PROJECT_ID, TOPIC_NAME, SUBSCRIPTION_NAME, and CLUSTER_NAME.

gcloud config set compute/zone $ZONE
gcloud config set project $PROJECT_ID

Create a service account with permissions to access Container Registry

Run the following commands to create a service account with permissions to read from Cloud Storage buckets, where Container Registry stores container images.

# Create service account.
gcloud iam service-accounts create $SA_NAME \
    --display-name "user generated service account for GKE nodes"

# Add to the service account permissions to read from Cloud Storage.
gcloud projects add-iam-policy-binding $PROJECT_ID \
    --member serviceAccount:$SA_FULL_NAME \
    --role "roles/storage.objectViewer" 

Create a GKE cluster

Run the following command to create a GKE cluster with 5 nodes of the machine type n1-standard-4 with binding to the service account. The command enables autoscaling up to 10 nodes and Horizontal Pod Autoscaling.

gcloud beta container clusters create \
    --project=$PROJECT_ID \
    --region=$REGION \
    --node-locations=$ZONE \
    --enable-ip-alias \
    --num-nodes=5 \
    --machine-type=n1-standard-4 \
    --enable-stackdriver-kubernetes \
    --metadata disable-legacy-endpoints=false \
    --service-account "$SA_FULL_NAME"  \
    --enable-autoscaling  --min-nodes=0 --max-nodes=10 \
    --addons "HorizontalPodAutoscaling"  \

Create a Pub/Sub topic and subscription

Run the following commands to create a topic and a subscription with the names set in the environment variables:

gcloud pubsub topics create $TOPIC_NAME
gcloud pubsub subscriptions create $SUBSCRIPTION_NAME \

Edit the project ID and Pub/Sub topic name in the web application

Run the following commands to set PROJECT_ID and TOPIC_NAME in the web application file.

sed -i -e "s/YOUR_PROJECT_ID/$PROJECT_ID/" webapp-docker-image/webapp/app.py
sed -i -e "s/YOUR_TOPIC_NAME/$TOPIC_NAME/" webapp-docker-image/webapp/app.py

Build the Locust and web application containers

Run the following commands to create Docker container images in Cloud Build based on the code in the directories locust-docker-image and webapp-docker-image:

gcloud builds submit --tag gcr.io/$PROJECT_ID/locust-tasks:latest locust-docker-image
gcloud builds submit --tag gcr.io/$PROJECT_ID/webapp:latest webapp-docker-image

Edit the project ID in the Kubernetes files

Run the commands below to set PROJECT_ID in the Kubernetes deployment files:

sed -i -e "s/YOUR_PROJECT_ID/$PROJECT_ID/" kubernetes-config/locust-master-controller.yaml
sed -i -e "s/YOUR_PROJECT_ID/$PROJECT_ID/" kubernetes-config/locust-worker-controller.yaml 
sed -i -e "s/YOUR_PROJECT_ID/$PROJECT_ID/" kubernetes-config/webapp-controller.yaml

Create a service account to be deployed in the Docker containers

Run the commands below to create a service account and upload the service account key as a Kubernetes secret.

# Create service account.
gcloud iam service-accounts create $SA_NAME \
    --display-name "service account for publishing to Pub/Sub"

# Add to the service account permissions to publish to Pub/Sub. 
gcloud projects add-iam-policy-binding $PROJECT_ID \
    --member serviceAccount:$SA_FULL_NAME \
    --role "roles/pubsub.publisher" 

# Create a service account key and a Kubernetes Secret.
gcloud iam service-accounts keys create $CRED_FILE \
    --iam-account=$SA_FULL_NAME --project=$PROJECT_ID
kubectl create secret generic pubsub-key --from-file=key.json=$CRED_FILE

# Delete the service account key.

Create deployments and sevices

Run the following commands to create the deployments for the web application, Locust master and workers, and the services:

kubectl apply -f kubernetes-config/locust-master-controller.yaml
kubectl apply -f kubernetes-config/locust-worker-controller.yaml
kubectl apply -f kubernetes-config/locust-master-service.yaml
kubectl apply -f kubernetes-config/webapp-controller.yaml
kubectl apply -f kubernetes-config/webapp-cip.yaml

Use port forwarding to connect from port 8888

Run the following command to forward port 8089 to port 8888:

kubectl port-forward -n default "$(kubectl get pods -l app=locust-master \
    -o jsonpath='{.items..metadata.name}')" 8888:8089

In Cloud Shell, click Web preview, and then click Preview on port 8888. If you don't see port 8888, click Change port and find port 8888.


Run a test from the Locust web interface

In a web browser showing the Locust interface, enter the value 100 in Number of users to simulate and 100 in Hatch rate. Click Start swarming.


After the test starts, you can see statistics in Locust, as shown in the following screenshot:


Monitor GKE cluster utilization

To check the utilization of you GKE cluster in the Kubenetes Monitoring dashboard, go to Menu > Monitoring > Dashboards > Kubernetes Engine.

Go to the Kubernetes Engine dashboard.


Monitor Pub/Sub API requests

Validate that the number of requests from the Locust interface are similar to those in Pub/Sub API in Cloud Monitoring.

To see the monitoring information about the Pub/Sub topic go to Menu > Monitoring > Dashboards > Pub/Sub and click the topic name.

Go to the Monitoring workspaces page..


Extensions to this tutorial

Resize your deployments and GKE cluster

One the most important benefits of GKE and containerized applications is that they can scale up and down as needed. To simulate high loads, use the following commands to generate a larger number of logs per second by adjusting the number of pods of the deployments:

kubectl scale deployment locust-worker --replicas 10
kubectl scale deployment webapp --replicas 10

Keep the deployment of locust-master to one replica.

You can also resize your GKE cluster with this command:

gcloud container clusters resize $CLUSTER_NAME --node-pool default \
    --num-nodes [NUMBER_OF_NODES]

Try out Cloud Run

You can also use Cloud Run to run the webapp containers to allow for automatic resizing of the number of containers.

Cleaning up

The easiest way to avoid incurring charges to your Google Cloud account for the resources used in this tutorial is to delete the project you created.

To delete the project, do the following:

  1. In the Cloud Console, go to the Projects page.

  2. In the project list, select the project you want to delete and click Delete project.


  3. In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

  • Try out other Google Cloud features for yourself. Have a look at our tutorials.

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