open-vault/website/source/docs/configuration/storage/dynamodb.html.md
James Nugent 65e7a2660d docs: Clarify the utility of DynamoDB capacities
When configuring DynamoDB, the read and write capacities configured only
have any effect if the table does not exist. As per the comment in the
code [1], the configuration of an existing table is never modified. This
was not previously reflected in the documentation - this commit
rectifies that.

[1]: https://github.com/hashicorp/vault/blob/master/physical/dynamodb/dynamodb.go#L743-L745
2018-12-03 17:55:18 -06:00

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---
layout: "docs"
page_title: "DynamoDB - Storage Backends - Configuration"
sidebar_title: "DynamoDB"
sidebar_current: "docs-configuration-storage-dynamodb"
description: |-
The DynamoDB storage backend is used to persist Vault's data in DynamoDB
table.
---
# DynamoDB Storage Backend
The DynamoDB storage backend is used to persist Vault's data in
[DynamoDB][dynamodb] table.
- **High Availability** the DynamoDB storage backend supports high
availability. Because DynamoDB uses the time on the Vault node to implement
the session lifetimes on its locks, significant clock skew across Vault nodes
could cause contention issues on the lock.
- **Community Supported** the DynamoDB 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 this
storage backend, you could be referred to the original author for support.
```hcl
storage "dynamodb" {
ha_enabled = "true"
region = "us-west-2"
table = "vault-data"
}
```
For more information about the read/write capacity of DynamoDB tables, please
see the [official AWS DynamoDB documentation][dynamodb-rw-capacity].
## DynamoDB Parameters
- `endpoint` `(string: "")` Specifies an alternative, AWS compatible, DynamoDB
endpoint. This can also be provided via the environment variable
`AWS_DYNAMODB_ENDPOINT`.
- `ha_enabled` `(string: "false")` Specifies whether this backend should be used
to run Vault in high availability mode. Valid values are "true" or "false". This
can also be provided via the environment variable `DYNAMODB_HA_ENABLED`.
- `max_parallel` `(string: "128")` Specifies the maximum number of concurrent
requests.
- `region` `(string "us-east-1")` Specifies the AWS region. This can also be
provided via the environment variable `AWS_DEFAULT_REGION`.
- `read_capacity` `(int: 5)` Specifies the maximum number of reads consumed
per second on the table, for use if Vault creates the DynamoDB table. This has
no effect if the `table` already exists. This can also be provided via the
environment variable `AWS_DYNAMODB_READ_CAPACITY`.
- `table` `(string: "vault-dynamodb-backend")` Specifies the name of the
DynamoDB table in which to store Vault data. If the specified table does not
yet exist, it will be created during initialization. This can also be
provided via the environment variable `AWS_DYNAMODB_TABLE`. See the
information on the table schema below.
- `write_capacity` `(int: 5)` Specifies the maximum number of writes performed
per second on the table, for use if Vault creates the DynamoDB table. This value
has no effect if the `table` already exists. This can also be provided via the
environment variable `AWS_DYNAMODB_WRITE_CAPACITY`.
The following settings are used for authenticating to AWS. If you are
running your Vault server on an EC2 instance, you can also make use of the EC2
instance profile service to provide the credentials Vault will use to make
DynamoDB API calls. Leaving the `access_key` and `secret_key` fields empty will
cause Vault to attempt to retrieve credentials from the AWS metadata service.
- `access_key` `(string: <required>)` Specifies the AWS access key. This can
also be provided via the environment variable `AWS_ACCESS_KEY_ID`.
- `secret_key` `(string: <required>)` Specifies the AWS secret key. This can
also be provided via the environment variable `AWS_SECRET_ACCESS_KEY`.
- `session_token` `(string: "")` Specifies the AWS session token. This can
also be provided via the environment variable `AWS_SESSION_TOKEN`.
## Required AWS Permissions
The governing policy for the IAM user or EC2 instance profile that Vault uses
to access DynamoDB must contain the following permissions for Vault to perform
the required operations on the DynamoDB table:
```javascript
"Statement": [
{
"Action": [
"dynamodb:DescribeLimits",
"dynamodb:DescribeTimeToLive",
"dynamodb:ListTagsOfResource",
"dynamodb:DescribeReservedCapacityOfferings",
"dynamodb:DescribeReservedCapacity",
"dynamodb:ListTables",
"dynamodb:BatchGetItem",
"dynamodb:BatchWriteItem",
"dynamodb:CreateTable",
"dynamodb:DeleteItem",
"dynamodb:GetItem",
"dynamodb:GetRecords",
"dynamodb:PutItem",
"dynamodb:Query",
"dynamodb:UpdateItem",
"dynamodb:Scan",
"dynamodb:DescribeTable"
],
"Effect": "Allow",
"Resource": [ "arn:aws:dynamodb:us-east-1:... dynamodb table ARN" ]
},
```
## Table Schema
If you are going to create the DynamoDB table prior to the execution and
initialization of Vault, you will need to create a table with these attributes:
* Primary partition key: "Path", a string
* Primary sort key: "Key", a string
You might create the table via Terraform, with a configuration similar to this:
```
resource "aws_dynamodb_table" "dynamodb-table" {
name = "${var.dynamoTable}"
read_capacity = 1
write_capacity = 1
hash_key = "Path"
range_key = "Key"
attribute [
{
name = "Path"
type = "S"
},
{
name = "Key"
type = "S"
}
]
tags {
Name = "vault-dynamodb-table"
Environment = "prod"
}
}
```
If a table with the configured name already exists, Vault will not modify it -
and the Vault configuration values of `read_capacity` and `write_capacity` have
no effect.
If the table does not already exist, Vault will try to create it, with read and
write capacities set to the values of `read_capacity` and `write_capacity`
respectively.
## DynamoDB Examples of Vault Configuration
### Custom Table and Read-Write Capacity
This example shows using a custom table name and read/write capacity.
```hcl
storage "dynamodb" {
table = "my-vault-data"
read_capacity = 10
write_capacity = 15
}
```
### Enabling High Availability
This example show enabling high availability for the DynamoDB storage backend.
```hcl
api_addr = "https://vault-leader.my-company.internal"
storage "dynamodb" {
ha_enabled = "true"
...
}
```
[dynamodb]: https://aws.amazon.com/dynamodb/
[dynamodb-rw-capacity]: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/WorkingWithTables.html#ProvisionedThroughput