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Charl•se
⏯️

Schedule start and stop for a GCP VM

Category
Google Cloud Platform
Published on
June 2, 2020

👉
March 2021 update: you can now easily schedule VM instances start and/or stop with the Instances Schedule feature (see documentation).

Cronjobs are a simple and reliable way to periodically execute scripts on a virtual machine. However, to avoid having your virtual instance running all the time - and being charged for it - we can configure Google Cloud to start the GCE instance a few minute before the cronjob are executed, and to power it off afterwards.

We will use the following architecture:

image

Instructions for this architecture come from the GCP support website.

Configure cron jobs on the GCE instance

  1. Edit the crontab file:
    2. crontab -e
  2. Schedule your script to run every day at a specific time (05:35 GMT in this example). Be careful with possible timezone differences between the VM and the Google schedule job.
    3. 35 05 * * * python3 /home/sweethome/my_script.py

    See unix-cron format for more info on scheduling cron tasks.

  3. Verify that the cronjob has been saved with: crontab -l

Add label to the Google Compute Engine instance

In the Google Cloud Console, go to Compute Engines > VM Instances. Edit the VM instance that will be used for the scheduled reporting, and add the following label (for example): - key: update - value: daily

Set up the Cloud Functions

In the Console, go to Cloud Functions.

Create the start function

  1. Create a new function and name it startInstancePubSub
  2. For Trigger, select Cloud Pub/Sub
  3. For Topic, create a new topic and call it start-vm
  4. For Runtime, select Node.js 8
  5. On the index.js tab, copy and paste this code
  6. On the package.json tab, copy and paste this code
  7. For Function to execute, enter startInstancePubSub.
  8. Click Create

Create the stop function:

  1. Create a new function and name it stopInstancePubSub
  2. For Trigger, select Cloud Pub/Sub
  3. For Topic, create a new topic and call it stop-vm
  4. For Runtime, select Node.js 8
  5. On the index.js tab, copy and paste this code
  6. On the package.json tab, copy and paste this code
  7. For Function to execute, enter stopInstancePubSub.
  8. Click Create

Verify that the functions work with these instructions

Set up the Cloud Scheduler jobs

In the Console, go to Cloud Scheduler.

Create the start job

  1. Create a new Job and name it start-rmn-vm
  2. For Frequency, enter a time ~5 minutes before the cronjob time on the GCE instance For example, if the cronjob is defined at 06:35, enter 30 6 * * *
  3. For Target select Pub/Sub, and for Topic enter start-vm
  4. For Payload, enter the following: {"zone":"europe-west1-d","label":"update=daily"}
  5. Click Create

Create the stop job

  1. Create a new Job and name it stop-rmn-vm
  2. For Frequency, enter a time sufficiently after the cronjob time on the GCE instance. For example, if the cronjob is defined at 06:35, enter 0 7 * * * to schedule the shutdown 25 minutes afterwards.
  3. For Target select Pub/Sub, and for Topic enter stop-vm
  4. For Payload, enter the following: {"zone":"europe-west1-d","label":"update=daily"}
  5. Click Create

Verify that the events work correctly with these instructions