How to make GCE instance stop when its deployed container finishes? - containers

Question

I have a Docker container that performs a single large computation. This computation requires lots of memory and takes about 12 hours to run.
I can create a Google Compute Engine VM of the appropriate size and use the "Deploy a container image to this VM instance" option to run this job perfectly. However once the job is finished the container quits but the VM is still running (and charging).
How can I make the VM exit/stop/delete when the container exits?
When the VM is in its zombie mode only the stackdriver containers are left running:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
bfa2feb03180 gcr.io/stackdriver-agents/stackdriver-logging-agent:0.2-1.5.33-1-1 "/entrypoint.sh /u..." 17 hours ago Up 17 hours stackdriver-logging-agent
161439a487c2 gcr.io/stackdriver-agents/stackdriver-metadata-agent:0.2-0.0.17-2 "/bin/sh -c /opt/s..." 17 hours ago Up 17 hours 8000/tcp stackdriver-metadata-agent
I create the VM like this:
gcloud beta compute --project=abc instances create-with-container vm-name \
--zone=us-central1-c --machine-type=custom-1-65536-ext \
--network=default --network-tier=PREMIUM --metadata=google-logging-enabled=true \
--maintenance-policy=MIGRATE \
--service-account=xyz \
--scopes=https://www.googleapis.com/auth/cloud-platform \
--image=cos-stable-69-10895-71-0 --image-project=cos-cloud --boot-disk-size=10GB \
--boot-disk-type=pd-standard --boot-disk-device-name=vm-name \
--container-image=gcr.io/abc/my-image --container-restart-policy=on-failure \
--container-command=python3 \
--container-arg="a" --container-arg="b" --container-arg="c" \
--labels=container-vm=cos-stable-69-10895-71-0

Answer 1

When you create the VM, you'll need to give it write access to compute so you can delete the instance from within. You should also set container environment variables like gce_zone and gce_project_id at this time. You'll need them to delete the instance.
gcloud beta compute instances create-with-container {NAME} \
--container-env=gce_zone={ZONE},gce_project_id={PROJECT_ID} \
--service-account={SERVICE_ACCOUNT} \
--scopes=https://www.googleapis.com/auth/compute,...
...
Then within the container, whenever YOU determine your task is finished:
request an api token (im using curl for simplicity and DEFAULT gce service account)
curl "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token" -H "Metadata-Flavor: Google"
This will respond with json that looks like
{
"access_token": "foobarbaz...",
"expires_in": 1234,
"token_type": "Bearer"
}
Take that access token and hit the instances.delete api endpoint (notice the environment variables)
curl -XDELETE -H 'Authorization: Bearer {TOKEN}' https://www.googleapis.com/compute/v1/projects/$gce_project_id/zones/$gce_zone/instances/$HOSTNAME

Answer 2

Having grappled with the problem for some time, here's a full solution that works pretty well.
This solution doesn't use the "start machine with a container image" option. Instead it uses a startup script, which is more flexible. You still use a Container-Optimized OS instance.
Create a startup script:
#!/usr/bin/env bash
# get image name and container parameters from the metadata
IMAGE_NAME=$(curl http://metadata.google.internal/computeMetadata/v1/instance/attributes/image_name -H "Metadata-Flavor: Google")
CONTAINER_PARAM=$(curl http://metadata.google.internal/computeMetadata/v1/instance/attributes/container_param -H "Metadata-Flavor: Google")
# This is needed if you are using a private images in GCP Container Registry
# (possibly also for the gcp log driver?)
sudo HOME=/home/root /usr/bin/docker-credential-gcr configure-docker
# Run! The logs will go to stack driver
sudo HOME=/home/root docker run --log-driver=gcplogs ${IMAGE_NAME} ${CONTAINER_PARAM}
# Get the zone
zoneMetadata=$(curl "http://metadata.google.internal/computeMetadata/v1/instance/zone" -H "Metadata-Flavor:Google")
# Split on / and get the 4th element to get the actual zone name
IFS=$'/'
zoneMetadataSplit=($zoneMetadata)
ZONE="${zoneMetadataSplit[3]}"
# Run compute delete on the current instance. Need to run in a container
# because COS machines don't come with gcloud installed
docker run --entrypoint "gcloud" google/cloud-sdk:alpine compute instances delete ${HOSTNAME} --delete-disks=all --zone=${ZONE}
Put the script somewhere public. For example put it on Cloud Storage and create a public URL. You can't use a gs:// URI for a COS startup script.
Start an instance using a startup-script-url, and passing the image name and parameters, e.g.:
gcloud compute --project=PROJECT_NAME instances create INSTANCE_NAME \
--zone=ZONE --machine-type=TYPE \
--metadata=image_name=IMAGE_NAME,\
container_param="PARAM1 PARAM2 PARAM3",\
startup-script-url=PUBLIC_SCRIPT_URL \
--maintenance-policy=MIGRATE --service-account=SERVICE_ACCUNT \
--scopes=https://www.googleapis.com/auth/cloud-platform --image-family=cos-stable \
--image-project=cos-cloud --boot-disk-size=10GB --boot-disk-device-name=DISK_NAME
(You probably want to limit the scopes, the example uses full access for simplicity)

Answer 3

I wrote a self-contained Python function based on Vincent's answer.
def kill_vm():
"""
If we are running inside a GCE VM, kill it.
"""
# based on https://stackoverflow.com/q/52748332/321772
import json
import logging
import requests
# get the token
r = json.loads(
requests.get("http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token",
headers={"Metadata-Flavor": "Google"})
.text)
token = r["access_token"]
# get instance metadata
# based on https://cloud.google.com/compute/docs/storing-retrieving-metadata
project_id = requests.get("http://metadata.google.internal/computeMetadata/v1/project/project-id",
headers={"Metadata-Flavor": "Google"}).text
name = requests.get("http://metadata.google.internal/computeMetadata/v1/instance/name",
headers={"Metadata-Flavor": "Google"}).text
zone_long = requests.get("http://metadata.google.internal/computeMetadata/v1/instance/zone",
headers={"Metadata-Flavor": "Google"}).text
zone = zone_long.split("/")[-1]
# shut ourselves down
logging.info("Calling API to delete this VM, {zone}/{name}".format(zone=zone, name=name))
requests.delete("https://www.googleapis.com/compute/v1/projects/{project_id}/zones/{zone}/instances/{name}"
.format(project_id=project_id, zone=zone, name=name),
headers={"Authorization": "Bearer {token}".format(token=token)})
A simple atexit hook gets me my desired behavior:
import atexit
atexit.register(kill_vm)

Answer 4

Another solution is to not use GCE and instead use AI Platform's custom job service, which automatically shuts down the VM after the Docker container exits.
gcloud ai-platform jobs submit training $JOB_NAME \
--region $REGION \
--master-image-uri $IMAGE_URI
You can specify --master-machine-type.
See the GCP documentation on custom containers.

Answer 5

The simplest way, from within the container, once it's finished:
ZONE=`gcloud compute instances list --filter="name=($HOSTNAME)" --format 'csv[no-heading](zone)'`
gcloud compute instances delete $HOSTNAME --zone=$ZONE -q
-q skips the interactive confirmation
$HOSTNAME is already exported

Answer 6

Just use curl and the local metadata server (no need for Python scripts or gcloud). Add the following to the end of your Docker Entrypoint script, so it's run when the container finishes:
# Note: inside the container the name is exposed as $HOSTNAME
INSTANCE_NAME=$(curl -sq "http://metadata.google.internal/computeMetadata/v1/instance/name" -H "Metadata-Flavor: Google")
INSTANCE_ZONE=$(curl -sq "http://metadata.google.internal/computeMetadata/v1/instance/zone" -H "Metadata-Flavor: Google")
echo "Terminating instance [${INSTANCE_NAME}] in zone [${INSTANCE_ZONE}}"
TOKEN=$(curl -sq "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token" -H "Metadata-Flavor: Google" | jq -r '.access_token')
curl -X DELETE -H "Authorization: Bearer ${TOKEN}" https://www.googleapis.com/compute/v1/$INSTANCE_ZONE/instances/$INSTANCE_NAME
For security sake, and Principle of Least Privilege, you can run the VM with a custom service account, and give that service account a role, with this permission (a custom role is best).
compute.instances.delete