# Google Cloud Storage

Google Cloud Storage is an Internet service to store data in Google's cloud. It
allows world-wide storage and retrieval of any amount of data and at any time,
taking advantage of Google's own reliable and fast networking infrastructure to
perform data operations in a cost effective manner.

The goal of google-cloud is to provide an API that is comfortable to Rubyists.
Your authentication credentials are detected automatically in Google Cloud
Platform environments such as Google Compute Engine, Google App Engine and
Google Kubernetes Engine. In other environments you can configure authentication
easily, either directly in your code or via environment variables. Read more
about the options for connecting in the {file:AUTHENTICATION.md Authentication
Guide}.

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new(
  project_id: "my-project",
  credentials: "/path/to/keyfile.json"
)

bucket = storage.bucket "my-bucket"
file = bucket.file "path/to/my-file.ext"
```

To learn more about Cloud Storage, read the [Google Cloud Storage Overview
](https://cloud.google.com/storage/docs/overview).

## Retrieving Buckets

A {Google::Cloud::Storage::Bucket Bucket} instance is a container for your data.
There is no limit on the number of buckets that you can create in a project. You
can use buckets to organize and control access to your data. For more
information, see [Working with
Buckets](https://cloud.google.com/storage/docs/creating-buckets).

Each bucket has a globally unique name, which is how they are retrieved: (See
{Google::Cloud::Storage::Project#bucket Project#bucket})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
```

You can also retrieve all buckets on a project: (See
{Google::Cloud::Storage::Project#buckets Project#buckets})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

all_buckets = storage.buckets
```

If you have a significant number of buckets, you may need to fetch them in
multiple service requests.

Iterating over each bucket, potentially with multiple API calls, by invoking
{Google::Cloud::Storage::Bucket::List#all Bucket::List#all} with a block:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

buckets = storage.buckets
buckets.all do |bucket|
  puts bucket.name
end
```

Limiting the number of API calls made:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

buckets = storage.buckets
buckets.all(request_limit: 10) do |bucket|
  puts bucket.name
end
```

See {Google::Cloud::Storage::Bucket::List Bucket::List} for details.

## Creating a Bucket

A unique name is all that is needed to create a new bucket: (See
{Google::Cloud::Storage::Project#create_bucket Project#create_bucket})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.create_bucket "my-todo-app-attachments"
```

## Retrieving Files

A {Google::Cloud::Storage::File File} instance is an individual data object that
you store in Google Cloud Storage. Files contain the data stored as well as
metadata describing the data. Files belong to a bucket and cannot be shared
among buckets. There is no limit on the number of files that you can create in a
bucket. For more information, see [Working with
Objects](https://cloud.google.com/storage/docs/object-basics).

Files are retrieved by their name, which is the path of the file in the bucket:
(See {Google::Cloud::Storage::Bucket#file Bucket#file})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "avatars/heidi/400x400.png"
```

You can also retrieve all files in a bucket: (See
{Google::Cloud::Storage::Bucket#files Bucket#files})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
all_files = bucket.files
```

Or you can retrieve all files in a specified path:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
avatar_files = bucket.files prefix: "avatars/"
```

If you have a significant number of files, you may need to fetch them in
multiple service requests.

Iterating over each file, potentially with multiple API calls, by invoking
{Google::Cloud::Storage::File::List#all File::List#all} with a block:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new
bucket = storage.bucket "my-todo-app"

files = storage.files
files.all do |file|
  puts file.name
end
```

Limiting the number of API calls made:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

files = storage.files
files.all(request_limit: 10) do |file|
  puts bucket.name
end
```

See {Google::Cloud::Storage::File::List File::List} for details.

## Creating a File

A new file can be uploaded by specifying the location of a file on the local
file system, and the name/path that the file should be stored in the bucket.
(See {Google::Cloud::Storage::Bucket#create_file Bucket#create_file})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
bucket.create_file "/var/todo-app/avatars/heidi/400x400.png",
                   "avatars/heidi/400x400.png"
```

Files can also be created from an in-memory StringIO object:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
bucket.create_file StringIO.new("Hello world!"), "hello-world.txt"
```

### Customer-supplied encryption keys

By default, Google Cloud Storage manages server-side encryption keys on your
behalf. However, a [customer-supplied encryption
key](https://cloud.google.com/storage/docs/encryption#customer-supplied) can be
provided with the `encryption_key` option. If given, the same key must be
provided to subsequently download or copy the file. If you use customer-supplied
encryption keys, you must securely manage your keys and ensure that they are not
lost. Also, please note that file metadata is not encrypted, with the exception
of the CRC32C checksum and MD5 hash. The names of files and buckets are also not
encrypted, and you can read or update the metadata of an encrypted file without
providing the encryption key.

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new
bucket = storage.bucket "my-todo-app"

# Key generation shown for example purposes only. Write your own.
cipher = OpenSSL::Cipher.new "aes-256-cfb"
cipher.encrypt
key = cipher.random_key

bucket.create_file "/var/todo-app/avatars/heidi/400x400.png",
                   "avatars/heidi/400x400.png",
                   encryption_key: key

# Store your key and hash securely for later use.
file = bucket.file "avatars/heidi/400x400.png",
                   encryption_key: key
```

Use {Google::Cloud::Storage::File#rotate File#rotate} to rotate
customer-supplied encryption keys.

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new
bucket = storage.bucket "my-todo-app"

# Old key was stored securely for later use.
old_key = "y\x03\"\x0E\xB6\xD3\x9B\x0E\xAB*\x19\xFAv\xDEY\xBEI..."

file = bucket.file "path/to/my-file.ext", encryption_key: old_key

# Key generation shown for example purposes only. Write your own.
cipher = OpenSSL::Cipher.new "aes-256-cfb"
cipher.encrypt
new_key = cipher.random_key

file.rotate encryption_key: old_key, new_encryption_key: new_key
```

## Downloading a File

Files can be downloaded to the local file system. (See
{Google::Cloud::Storage::File#download File#download})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "avatars/heidi/400x400.png"
file.download "/var/todo-app/avatars/heidi/400x400.png"
```

Files can also be downloaded to an in-memory StringIO object:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "hello-world.txt"

downloaded = file.download
downloaded.rewind
downloaded.read #=> "Hello world!"
```

Download a public file with an anonymous, unauthenticated client. Use
`skip_lookup` to avoid errors retrieving non-public bucket and file metadata.

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.anonymous

bucket = storage.bucket "public-bucket", skip_lookup: true
file = bucket.file "path/to/public-file.ext", skip_lookup: true

downloaded = file.download
downloaded.rewind
downloaded.read #=> "Hello world!"
```

## Creating and downloading gzip-encoded files

When uploading a gzip-compressed file, you should pass `content_encoding:
"gzip"` if you want the file to be eligible for [decompressive
transcoding](https://cloud.google.com/storage/docs/transcoding) when it is later
downloaded. In addition, giving the gzip-compressed file a name containing the
original file extension (for example, `.txt`) will ensure that the file's
`Content-Type` metadata is set correctly. (You can also set the file's
`Content-Type` metadata explicitly with the `content_type` option.)

```ruby
require "zlib"
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

gz = StringIO.new ""
z = Zlib::GzipWriter.new gz
z.write "Hello world!"
z.close
data = StringIO.new gz.string

bucket = storage.bucket "my-bucket"

bucket.create_file data, "path/to/gzipped.txt",
                   content_encoding: "gzip"

file = bucket.file "path/to/gzipped.txt"

# The downloaded data is decompressed by default.
file.download "path/to/downloaded/hello.txt"

# The downloaded data remains compressed with skip_decompress.
file.download "path/to/downloaded/gzipped.txt",
              skip_decompress: true
```

## Using Signed URLs

Access without authentication can be granted to a file for a specified period of
time. This URL uses a cryptographic signature of your credentials to access the
file. (See {Google::Cloud::Storage::File#signed_url File#signed_url})

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "avatars/heidi/400x400.png"
shared_url = file.signed_url method: "GET",
                             expires: 300 # 5 minutes from now
```

## Controlling Access to a Bucket

Access to a bucket is controlled with {Google::Cloud::Storage::Bucket#acl
Bucket#acl}. A bucket has owners, writers, and readers. Permissions can be
granted to an individual user's email address, a group's email address, as well
as many predefined lists. See the [Access Control
guide](https://cloud.google.com/storage/docs/access-control) for more.

Access to a bucket can be granted to a user by appending `"user-"` to the email
address:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"

email = "heidi@example.net"
bucket.acl.add_reader "user-#{email}"
```

Access to a bucket can be granted to a group by appending `"group-"` to the
email address:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"

email = "authors@example.net"
bucket.acl.add_reader "group-#{email}"
```

Access to a bucket can also be granted to a predefined list of permissions:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"

bucket.acl.public!
```

## Controlling Access to a File

Access to a file is controlled in two ways, either by the setting the default
permissions to all files in a bucket with
{Google::Cloud::Storage::Bucket#default_acl Bucket#default_acl}, or by setting
permissions to an individual file with {Google::Cloud::Storage::File#acl
File#acl}.

Access to a file can be granted to a user by appending `"user-"` to the email
address:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "avatars/heidi/400x400.png"

email = "heidi@example.net"
file.acl.add_reader "user-#{email}"
```

Access to a file can be granted to a group by appending `"group-"` to the email
address:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "avatars/heidi/400x400.png"

email = "authors@example.net"
file.acl.add_reader "group-#{email}"
```

Access to a file can also be granted to a predefined list of permissions:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-todo-app"
file = bucket.file "avatars/heidi/400x400.png"

file.acl.public!
```

## Assigning payment to the requester

The requester pays feature enables the owner of a bucket to indicate that a
client accessing the bucket or a file it contains must assume the transit costs
related to the access.

Assign transit costs for bucket and file operations to requesting clients with
the `requester_pays` flag:

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "my-bucket"

bucket.requester_pays = true # API call
# Clients must now provide `user_project` option when calling
# Project#bucket to access this bucket.
```

Once the `requester_pays` flag is enabled for a bucket, a client attempting to
access the bucket and its files must provide the `user_project` option to
{Google::Cloud::Storage::Project#bucket Project#bucket}. If the argument given
is `true`, transit costs for operations on the requested bucket or a file it
contains will be billed to the current project for the client. (See
{Google::Cloud::Storage::Project#project Project#project} for the ID of the
current project.)

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "other-project-bucket", user_project: true

files = bucket.files # Billed to current project
```

If the argument is a project ID string, and the indicated project is authorized
for the currently authenticated service account, transit costs will be billed to
the indicated project.

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new

bucket = storage.bucket "other-project-bucket",
                        user_project: "my-other-project"
files = bucket.files # Billed to "my-other-project"
```

## Configuring Pub/Sub notification subscriptions

You can configure notifications to send Google Cloud Pub/Sub messages about
changes to files in your buckets. For example, you can track files that are
created and deleted in your bucket. Each notification contains information
describing both the event that triggered it and the file that changed.

You can send notifications to any Cloud Pub/Sub topic in any project for which
your service account has sufficient permissions. As shown below, you need to
explicitly grant permission to your service account to enable Google Cloud
Storage to publish on behalf of your account. (Even if your current project
created and owns the topic.)

```ruby
require "google/cloud/pubsub"
require "google/cloud/storage"

pubsub = Google::Cloud::Pubsub.new
storage = Google::Cloud::Storage.new

topic = pubsub.create_topic "my-topic"
topic.policy do |p|
  p.add "roles/pubsub.publisher",
        "serviceAccount:#{storage.service_account_email}"
end

bucket = storage.bucket "my-bucket"

notification = bucket.create_notification topic.name
```

## Configuring retries and timeout

You can configure how many times API requests may be automatically retried. When
an API request fails, the response will be inspected to see if the request meets
criteria indicating that it may succeed on retry, such as `500` and `503` status
codes or a specific internal error code such as `rateLimitExceeded`. If it meets
the criteria, the request will be retried after a delay. If another error
occurs, the delay will be increased before a subsequent attempt, until the
`retries` limit is reached.

You can also set the request `timeout` value in seconds.

```ruby
require "google/cloud/storage"

storage = Google::Cloud::Storage.new retries: 10, timeout: 120
```

See the [Storage status and error
codes](https://cloud.google.com/storage/docs/json_api/v1/status-codes)
for a list of error conditions.

## Additional information

Google Cloud Storage can be configured to use logging. To learn more, see the
{file:LOGGING.md Logging guide}.
