Is it possible to start PubSub Emulator from Cloud Build step - continuous-integration

Question

As the title mentions, I would like to know if, from a Cloud Build step, I can start and use the pubsub emulator?
options:
env:
- GO111MODULE=on
- GOPROXY=https://proxy.golang.org
- PUBSUB_EMULATOR_HOST=localhost:8085
volumes:
- name: "go-modules"
path: "/go"
steps:
- name: "golang:1.14"
args: ["go", "build", "."]
# Starts the cloud pubsub emulator
- name: 'gcr.io/cloud-builders/gcloud'
entrypoint: 'bash'
args: [
'-c',
'gcloud beta emulators pubsub start --host-port 0.0.0.0:8085 &'
]
- name: "golang:1.14"
args: ["go", "test", "./..."]
For a test I need it, it works locally and instead of using a dedicated pubsub from cloud build, I want to use an emulator.
Thanks

Answer 1

As I found a workaround and an interesting git repository, I wanted to share with you the solution.
As required, you need a cloud-build.yaml and you want to add a step where the emulator will get launched:
options:
env:
- GO111MODULE=on
- GOPROXY=https://proxy.golang.org
- PUBSUB_EMULATOR_HOST=localhost:8085
volumes:
- name: "go-modules"
path: "/go"
steps:
- name: "golang:1.14"
args: ["go", "build", "."]
- name: 'docker/compose'
args: [
'-f',
'docker-compose.cloud-build.yml',
'up',
'--build',
'-d'
]
id: 'pubsub-emulator-docker-compose'
- name: "golang:1.14"
args: ["go", "test", "./..."]
As you can see, I run a docker-compose command which will actually start the emulator.
version: "3.7"
services:
pubsub:
# Required for cloudbuild network access (when external access is required)
container_name: pubsub
image: google/cloud-sdk
ports:
- '8085:8085'
command: ["gcloud", "beta", "emulators", "pubsub", "start", "--host-port", "0.0.0.0:8085"]
network_mode: cloudbuild
networks:
default:
external:
name: cloudbuild
It is important to set the container name as well as the network, otherwise you won't be able to access the pubsub emulator from another cloud build step.

Answer 2

It is possible since every step on Cloud Build is executed in a docker container, but the image gcr.io/cloud-builders/gcloud only has a minimum installation of the gcloud components, before start the emulator your need to install the pubsub emulator via gcloud command
gcloud components install pubsub-emulator
Also it is necessary to install Open JDK7 since most of the Gcloud emulators needs java to operate.