Before connecting your app to the Cloud Storage for Firebase emulator, make sure
that you
understand the overall Firebase Local Emulator Suite workflow
,
and that you
install and configure
the Local Emulator Suite and review its
CLI commands
.
Choose a Firebase project
The Firebase Local Emulator Suite emulates products for a single Firebase project.
To select the project to use, before you start the emulators, in the CLI run
firebase use
in your working directory. Or, you can pass
the
--project
flag to each emulator
command.
Local Emulator Suite supports emulation of
real
Firebase projects and
demo
projects.
Project type
|
Features
|
Use with emulators
|
Real
|
A real Firebase project is one you created and configured (most likely
via the Firebase console).
Real projects have live resources, like database instances, storage
buckets, functions, or any other resource you set up for that Firebase
project.
|
When working with real Firebase projects, you can run emulators for any
or all of the supported products.
For any products you are not emulating, your apps and code will
interact with the
live
resource (database instance, storage
bucket, function, etc.).
|
Demo
|
A demo Firebase project has no
real
Firebase configuration and
no live resources. These projects are usually accessed via codelabs or
other tutorials.
Project IDs for demo projects have the
demo-
prefix.
|
When working with demo Firebase projects, your apps and code interact with
emulators
only
. If your app attempts to interact with a resource
for which an emulator isn't running, that code will fail.
|
We recommend you use demo projects wherever possible. Benefits include:
- Easier setup, since you can run the emulators without ever creating a
Firebase project
- Stronger safety, since if your code accidentally invokes non-emulated
(production) resources, there is no chance of data change, usage and billing
- Better offline support, since there is no need to access the internet to
download your SDK configuration.
Instrument your app to talk to the emulators
Set up your in-app configuration or test classes to interact with the
Cloud Storage for Firebase emulator as follows.
Kotlin+KTX
// 10.0.2.2 is the special IP address to connect to the 'localhost' of
// the host computer from an Android emulator.
val storage = Firebase.storage
storage.useEmulator("10.0.2.2", 9199)
Java
// 10.0.2.2 is the special IP address to connect to the 'localhost' of
// the host computer from an Android emulator.
FirebaseStorage storage = FirebaseStorage.getInstance();
storage.useEmulator("10.0.2.2", 9199);
Swift
Storage.storage().useEmulator(withHost: "127.0.0.1", port: 9199)
Web modular API
const { getStorage, connectStorageEmulator } = require("firebase/storage");
const storage = getStorage();
if (location.hostname === "localhost") {
// Point to the Storage emulator running on localhost.
connectStorageEmulator(storage, "127.0.0.1", 9199);
}
Web namespaced API
var storage = firebase.storage();
if (location.hostname === "localhost") {
// Point to the Storage emulator running on localhost.
storage.useEmulator("127.0.0.1", 9199);
}
No additional setup is needed to test Cloud functions
triggered by Cloud Storage for Firebase events
using the emulator. When the Cloud Storage for Firebase and Cloud Functions
emulators are both running, they automatically work together.
Admin SDKs
The Firebase Admin SDKs automatically connect to the Cloud Storage for Firebase
emulator when the
FIREBASE_STORAGE_EMULATOR_HOST
environment variable is set:
export FIREBASE_STORAGE_EMULATOR_HOST="127.0.0.1:9199"
Note that the Cloud Functions emulator is automatically aware of the
Cloud Storage for Firebase emulator so you can skip this step when testing
integrations between Cloud Functions and Cloud Storage for Firebase
emulators. The environment variable will be automatically set for the Admin SDK
in Cloud Storage for Firebase.
If you want your Admin SDK code to connect to a shared emulator running in
another environment, you will need to specify the
the same project ID you set using the Firebase CLI
.
You can pass a project ID to
initializeApp
directly or set the
GCLOUD_PROJECT
environment variable.
Node.js Admin SDK
admin.initializeApp({ projectId: "your-project-id" });
Environment Variable
export GCLOUD_PROJECT="your-project-id"
Import and export data
The database and Cloud Storage for Firebase emulators allow you to export data
from a running emulator instance. Define a baseline set of data to use in your
unit tests or continuous integration workflows, then export it to be shared
among the team.
firebase emulators:export ./dir
In tests, on emulator startup, import the baseline data.
firebase emulators:start --import=./dir
You can instruct the emulator to export data on shutdown, either specifying an
export path or simply using the path passed to the
--import
flag.
firebase emulators:start --import=./dir --export-on-exit
These data import and export options work with the
firebase emulators:exec
command as well. For more, refer to the
emulator command reference
.
How the Cloud Storage for Firebase emulator differs from production
For testing of client apps, the Cloud Storage for Firebase emulator aligns to
production almost perfectly in regards to the Firebase API surface area. All
Firebase commands are expected to work between the regular Firebase SDKs (Web,
Android, and Apple platforms).
For testing of server-side apps, limitations exist. The Firebase Admin SDKs
make use the Google Cloud API surface, and not all endpoints of this API are
emulated. As a rule of thumb, anything which can be done from the client SDKs
(uploading or deleting files, getting and setting metadata) is also implemented
for use from the Admin SDKs, but anything beyond that is not. Notable exclusions
are listed below.
Differences from Google Cloud Storage
The Cloud Storage for Firebase product, including the Storage emulator, provides
a subset of Google Cloud Storage (GCS) functionality focusing on storage objects
that is very useful for developing Firebase apps. Cloud Storage for Firebase
differs from GCS in the following ways:
- Cloud Storage for Firebase does not currently support
Bucket
APIs for
creating, listing, getting, or deleting storage buckets.
- From the
Google Cloud Storage Objects API
,
the following methods are supported:
copy
,
delete
,
get
,
insert
,
list
,
patch
,
rewrite
,
update
.
Cloud IAM
The Firebase Emulator Suite does not attempt to replicate or respect any
IAM-related behavior for running. Emulators adhere to the Firebase Security
Rules provided, but in situations where IAM would normally be used, for example
to set Cloud Functions invoking service account and thus permissions, the
emulator is not configurable and will use the globally-available account on
your developer machine, similar to running a local script directly.
Pub/Sub notifications
The Cloud Storage for Firebase emulator does not integrate with the Cloud
Pub/Sub emulator and thus does not support creating
channels/notifications for storage object changes. We recommend using
Cloud Functions Storage triggers directly.
The Cloud Storage for Firebase emulator does not support any bucket-level
configuration including storage class, bucket-level CORS configuration, labels,
or retention policies. Firebase intends to improve this support over time.
What next?