Cloud Emulators (GCS, S3 & more)

devx cloud spins up local cloud service emulators inside the devx VM so your application can use real cloud SDKs (Google Cloud, AWS) without touching actual cloud infrastructure during development.

Why Emulators?

• No credentials needed — no GCP project, no service account JSON
• Zero cloud costs — everything runs on your local machine
• Safe by default — data only lives in memory; no accidental production writes
• SDK compatible — GCP client libraries automatically pick up the emulator endpoint via standard env vars

Spawn an Emulator

devx cloud spawn gcs       # Google Cloud Storage (fake-gcs-server)
devx cloud spawn pubsub    # Google Cloud Pub/Sub
devx cloud spawn firestore # Google Cloud Firestore
devx cloud spawn s3        # Amazon S3 (MinIO)

On success, devx cloud spawn prints the environment variable your application needs:

✅ Google Cloud Storage emulator is running!

  Container: devx-cloud-gcs
  Port:      4443

  Add to your .env:

    STORAGE_EMULATOR_HOST=http://localhost:4443

  Or use 'devx shell' to have these injected automatically.

Auto-injection via devx shell

When you use devx shell to launch your dev container, it automatically discovers all running devx cloud emulators and injects their endpoint env vars. No manual .env changes needed.

Flags

Flag	Default	Description
--port	emulator default	Host port to bind
--runtime	auto-detected	Container runtime (podman, docker, nerdctl)

List Running Emulators

devx cloud list

Shows all running emulators and the env var keys they expose:

devx — Cloud Emulators

  Google Cloud Storage  devx-cloud-gcs  Up 5 minutes  0.0.0.0:4443->4443/tcp
    env:  STORAGE_EMULATOR_HOST  http://localhost:4443

Remove an Emulator

devx cloud rm gcs

Stops and removes the container. Since emulators run with in-memory backends, no persistent data is left behind.

Supported Services

Key	Name	Port	SDK Env Var(s)
gcs	Google Cloud Storage	4443	STORAGE_EMULATOR_HOST
pubsub	Google Cloud Pub/Sub	8085	PUBSUB_EMULATOR_HOST
firestore	Google Cloud Firestore	8080	FIRESTORE_EMULATOR_HOST
s3	Amazon S3 (MinIO)	9000	AWS_ENDPOINT_URL_S3, AWS_ENDPOINT_URL, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION

The S3 emulator pre-seeds MinIO's default credentials (minioadmin / minioadmin) into the injected env vars so the AWS SDKs work out of the box — these credentials only grant access to your local container.

Connecting from Your Code

Go (GCS)

// The GCP client library automatically reads STORAGE_EMULATOR_HOST
client, err := storage.NewClient(ctx)

Node.js (GCS via @google-cloud/storage)

// No code changes needed — just set STORAGE_EMULATOR_HOST in your env
const { Storage } = require('@google-cloud/storage');
const storage = new Storage();

Python (GCS via google-cloud-storage)

# No code changes needed when STORAGE_EMULATOR_HOST is set
from google.cloud import storage
client = storage.Client()

Go (S3 via aws-sdk-go-v2)

// AWS SDK v2 reads AWS_ENDPOINT_URL_S3 automatically from the environment.
cfg, _ := config.LoadDefaultConfig(ctx)
client := s3.NewFromConfig(cfg, func(o *s3.Options) { o.UsePathStyle = true })

Python (S3 via boto3 1.34+)

# boto3 1.34+ reads AWS_ENDPOINT_URL_S3 automatically. For older versions,
# pass endpoint_url=os.environ["AWS_ENDPOINT_URL_S3"] explicitly.
import boto3
s3 = boto3.client("s3")

Node.js (S3 via @aws-sdk/client-s3 v3)

// AWS SDK v3 reads AWS_ENDPOINT_URL_S3 automatically.
import { S3Client } from "@aws-sdk/client-s3";
const s3 = new S3Client({ forcePathStyle: true });