---
layout: docs
page_title: Google Cloud Spanner - Storage Backends - Configuration
description: |-
  The Google Cloud Spanner storage backend is used to persist Vault's data in
  Spanner, a fully managed, mission-critical, relational database service that
  offers transactional consistency at global scale.
---

# Google Cloud spanner storage backend

The Google Cloud Spanner storage backend is used to persist Vault's data in
[Spanner][spanner-docs], a fully managed, mission-critical, relational database
service that offers transactional consistency at global scale, schemas, SQL, and
automatic, synchronous replication for high availability.

- **High Availability** – the Google Cloud Spanner storage backend supports high
  availability. Because the Google Cloud Spanner storage backend uses the system
  time on the Vault node to acquire sessions, clock skew across Vault servers
  can cause lock contention.

- **Community Supported** – the Google Cloud Spanner storage backend is
  supported by the community. While it has undergone review by HashiCorp
  employees, they may not be as knowledgeable about the technology. If you
  encounter problems with them, you may be referred to the original author.

```hcl
storage "spanner" {
  database = "projects/my-project/instances/my-instance/databases/my-database"
}
```

For more information on schemas or Google Cloud Spanner, please see the [Google
Cloud Spanner documentation][spanner-docs].

## `spanner` setup

To use the Google Cloud Spanner Vault storage backend, you must have a Google
Cloud Platform account. Either using the API or web interface, create a database
and the following tables:

-> You can choose "Edit as text" and copy-paste the following as the schema.
These are the default table names. If you choose to use different table names,
you will need to update the configuration accordingly.

```sql
CREATE TABLE Vault (
  Key       STRING(MAX) NOT NULL,
  Value     BYTES(MAX),
) PRIMARY KEY (Key);

CREATE TABLE VaultHA (
  Key           STRING(MAX) NOT NULL,
  Value         STRING(MAX),
  Identity      STRING(36) NOT NULL,
  Timestamp     TIMESTAMP NOT NULL,
) PRIMARY KEY (Key);
```

The Google Cloud Spanner storage backend does not support creating the table
automatically at this time, but this could be a future enhancement. For more
information on schemas or Google Cloud Spanner, please see the [Google Cloud
Spanner documentation][spanner-docs].

## `spanner` authentication

The Google Cloud Spanner Vault storage backend uses the official Google Cloud
Golang SDK. This means it supports the common ways of [providing credentials to
Google Cloud][cloud-creds].

1. The environment variable `GOOGLE_APPLICATION_CREDENTIALS`. This is specified
   as the **path** to a Google Cloud credentials file, typically for a service
   account. If this environment variable is present, the resulting credentials are
   used. If the credentials are invalid, an error is returned.

1. Default instance credentials. When no environment variable is present, the
   default service account credentials are used.

For more information on service accounts, please see the [Google Cloud Service
Accounts documentation][service-accounts].

To use this storage backend, the service account must have the following
minimum scope(s):

```text
https://www.googleapis.com/auth/google-cloud-spanner.data
```

## `spanner` parameters

- `database` `(string: <required>)` – Specifies the name of the database. Note
  that this is specified as a "path" including the project ID and instance, for
  example:

  ```text
  projects/my-project/instances/my-instance/databases/my-database
  ```

- `table` `(string: "Vault")` - Specifies the name of the table where
  data will be stored and retrieved.

- `max_parallel` `(int: 128)` - Specifies the maximum number of parallel
  operations to take place.

### High availability parameters

- `ha_enabled` `(string: "false")` - Specifies if high availability mode is
  enabled. This is a boolean value, but it is specified as a string like "true"
  or "false".

- `ha_table` `(string: "VaultHA")` - Specifies the name of the table to use for
  storing high availability information. By default, this is the name of the
  `table` suffixed with "HA".

## `spanner` examples

### High availability

This example shows configuring Google Cloud Spanner with high availability
enabled.

```hcl
api_addr = "https://vault-leader.my-company.internal"

storage "spanner" {
  database   = "projects/demo/instances/abc123/databases/vault-data"
  ha_enabled = "true"
}
```

### Custom tables

This example shows listing custom table names for data and HA with the Google
Cloud Spanner Vault storage backend.

```hcl
storage "spanner" {
  database = "projects/demo/instances/abc123/databases/vault-data"
  table    = "VaultData"
  ha_table = "VaultLeader"
}
```

[cloud-creds]: https://cloud.google.com/docs/authentication/production#providing_credentials_to_your_application
[service-accounts]: https://cloud.google.com/compute/docs/access/service-accounts
[spanner-docs]: https://cloud.google.com/spanner/docs/
