---
layout: docs
page_title: Vault Proxy Caching
description: |-
  Vault Proxy Caching allows client-side caching of responses containing newly
  created tokens and responses containing leased secrets generated off of these
  newly created tokens.
---

# Vault Proxy caching

Vault Proxy caching allows client-side caching of responses containing newly
created tokens and responses containing leased secrets generated off of these
newly created tokens. The renewals of the cached tokens and leases are also
managed by the proxy. Additionally, with `cache_static_secrets` set to `true`,
Vault Proxy [can be configured to cache KVv1 and KVv2 secrets][static-secret-caching].

## Caching and renewals

Response caching and renewals for dynamic secrets are managed by Proxy only under these
specific scenarios.

1. Token creation requests are made through the proxy. This means that any
   login operations performed using various auth methods and invoking the token
   creation endpoints of the token auth method via the proxy will result in the
   response getting cached by the proxy. Responses containing new tokens will
   be cached by the proxy only if the parent token is already being managed by
   the proxy or if the new token is an orphan token.

2. Leased secret creation requests are made through the proxy using tokens that
   are already managed by the proxy. This means that any dynamic credentials
   that are issued using the tokens managed by the proxy, will be cached and
   its renewals are taken care of.

## Static secret caching

You can configure Vault Proxy to cache dynamic secrets and static (KVv1 and KVv2)
secrets. When you enable caching for static secrets. Proxy keeps a cached entry
of the secret but only provides the cached response to requests made with tokens
that can access the secret. As a result, multiple requests to Vault Proxy for
the same KV secret only require a single, initial request to be forwarded to Vault.

Static secret caching is disabled by default. To enable caching for static secrets you must
configure [auto-auth](/vault/docs/agent-and-proxy/autoauth) and ensure the
auto-auth token has permission to subscribe to KV
[event](/vault/docs/concepts/events) updates.

Once configured, Proxy uses the auto-auth token to subscribe to KV events, and
monitors the subscription feed to know when to update the secrets in its cache.

For more information on static secret caching, refer to the
[Vault Proxy static secret caching][static-secret-caching] overview.

## Persistent cache

Vault Proxy can restore secrets, such as, tokens, leases, and static secrets, from a persistent
cache file created by a previous Vault Proxy process.

Refer to the [Vault Proxy Persistent
Caching](/vault/docs/agent-and-proxy/proxy/caching/persistent-caches) page for more information on
this functionality.

## Cache evictions

The eviction of cache entries pertaining to dynamic secrets will occur when the proxy
can no longer renew them. This can happen when the secrets hit their maximum
TTL or if the renewals result in errors.

Vault Proxy does some best-effort cache evictions by observing specific request types
and response codes. For example, if a token revocation request is made via the
proxy and if the forwarded request to the Vault server succeeds, then proxy
evicts all the cache entries associated with the revoked token. Similarly, any
lease revocation operation will also be intercepted by the proxy and the
respective cache entries will be evicted.

Note that while proxy evicts the cache entries upon secret expirations and upon
intercepting revocation requests, it is still possible for the proxy to be
completely unaware of the revocations that happen through direct client
interactions with the Vault server. This could potentially lead to stale cache
entries. For managing the stale entries in the cache, an endpoint
`/proxy/v1/cache-clear`(see below) is made available to manually evict cache
entries based on some of the query criteria used for indexing the cache entries.

## Request uniqueness

In order to detect repeat requests and return cached responses, Proxy needs
to have a way to uniquely identify the requests. This computation as it stands
today takes a simplistic approach (may change in future) of serializing and
hashing the HTTP request along with all the headers and the request body. This
hash value is then used as an index into the cache to check if the response is
readily available. The consequence of this approach is that the hash value for
any request will differ if any data in the request is modified. This has the
side-effect of resulting in false negatives if say, the ordering of the request
parameters are modified. As long as the requests come in without any change,
caching behavior should be consistent. Identical requests with differently
ordered request values will result in duplicated cache entries. A heuristic
assumption that the clients will use consistent mechanisms to make requests,
thereby resulting in consistent hash values per request is the idea upon which
the caching functionality is built upon.

## Renewal management

The tokens and leases are renewed by the proxy using the secret renewer that is
made available via the Vault server's [Go
API](https://godoc.org/github.com/hashicorp/vault/api#Renewer). Proxy performs
all operations in memory and does not persist anything to storage. This means
that when the proxy is shut down, all the renewal operations are immediately
terminated and there is no way for the proxy to resume renewals after the fact.
Note that shutting down the proxy does not indicate revocations of the secrets,
instead it only means that renewal responsibility for all the valid unrevoked
secrets are no longer performed by the Vault proxy.

## API

### Cache clear

This endpoint clears the cache based on given criteria. To use this
API, some information on how the proxy caches values should be known
beforehand. Each response that is cached in the proxy will be indexed on some
factors depending on the type of request. Those factors can be the `token` that
is belonging to the cached response, the `token_accessor` of the token
belonging to the cached response, the `request_path` that resulted in the
cached response, the `lease` that is attached to the cached response, the
`namespace` to which the cached response belongs to, and a few more. This API
exposes some factors through which associated cache entries are fetched and
evicted. For listeners without caching enabled, this API will still be available,
but will do nothing (there is no cache to clear) and will return a `200` response.

| Method | Path                    | Produces               |
| :----- | :---------------------- | :--------------------- |
| `POST` | `/proxy/v1/cache-clear` | `200 application/json` |

#### Parameters

- `type` `(strings: required)` - The type of cache entries to evict. Valid
  values are `request_path`, `lease`, `token`, `token_accessor`, and `all`.
  If the `type` is set to `all`, the _entire cache_ is cleared.

- `value` `(string: required)` - An exact value or the prefix of the value for
  the `type` selected. This parameter is optional when the `type` is set
  to `all`.

- `namespace` `(string: optional)` - This is only applicable when the `type` is set to
  `request_path`. The namespace of which the cache entries to be evicted for
  the given request path.

### Sample payload

```json
{
  "type": "token",
  "value": "hvs.rlNjegSKykWcplOkwsjd8bP9"
}
```

### Sample request

```shell-session
$ curl \
    --request POST \
    --data @payload.json \
    http://127.0.0.1:1234/proxy/v1/cache-clear
```

## Configuration (`cache`)

The presence of the top level `cache` block in any way (including an empty `cache` block)  will enable the cache.
Note that either `cache_static_secrets` must be `true` and/or `disable_caching_dynamic_secrets` must
be `false`, otherwise the cache does nothing. The top level `cache` block has the following configuration entries:

- `persist` `(object: optional)` - Configuration for the persistent cache.

- `cache_static_secrets` `(bool: false)` - Enables static secret caching when
`true`.

- `disable_caching_dynamic_secrets` `(bool: false)` - Disables dynamic secret caching when
`true`.

-> **Note:** When the `cache` block is defined, a [listener][proxy-listener] must also be defined
in the config, otherwise there is no way to utilize the cache.

[proxy-listener]: /vault/docs/agent-and-proxy/proxy#listener-stanza

### Configuration (Persist)

These are common configuration values that live within the `persist` block:

- `type` `(string: required)` - The type of the persistent cache to use,
  e.g. `kubernetes`. _Note_: when using HCL this can be used as the key for
  the block, e.g. `persist "kubernetes" {...}`. Currently, only `kubernetes`
  is supported.

- `path` `(string: required)` - The path on disk where the persistent cache file
  should be created or restored from.

- `keep_after_import` `(bool: optional)` - When set to true, a restored cache file
  is not deleted. Defaults to `false`.

- `exit_on_err` `(bool: optional)` - When set to true, if any errors occur during
  a persistent cache restore, Vault Proxy will exit with an error. Defaults to `true`.

- `service_account_token_file` `(string: optional)` - When `type` is set to `kubernetes`,
this configures the path on disk where the Kubernetes service account token can be found.
Defaults to `/var/run/secrets/kubernetes.io/serviceaccount/token`.

## Configuration (`listener`)

- `listener` `(array of objects: required)` - Configuration for the listeners.

There can be one or more `listener` blocks at the top level. Adding a listener enables
the [API Proxy](/vault/docs/agent-and-proxy/proxy/apiproxy) and enables the API proxy to use the cache, if configured.
These configuration values are common to both `tcp` and `unix` listener blocks. Blocks of type
`tcp` support the standard `tcp` [listener](/vault/docs/configuration/listener/tcp)
options. Additionally, the `role` string option is available as part of the top level
of the `listener` block, which can be configured to `metrics_only` to serve only metrics,
or the default role, `default`, which serves everything (including metrics).

- `type` `(string: required)` - The type of the listener to use. Valid values
  are `tcp` and `unix`.
  _Note_: when using HCL this can be used as the key for the block, e.g.
  `listener "tcp" {...}`.

- `address` `(string: required)` - The address for the listener to listen to.
  This can either be a URL path when using `tcp` or a file path when using
  `unix`. For example, `127.0.0.1:8200` or `/path/to/socket`. Defaults to
  `127.0.0.1:8200`.

- `tls_disable` `(bool: false)` - Specifies if TLS will be disabled.

- `tls_key_file` `(string: optional)` - Specifies the path to the private key
  for the certificate.

- `tls_cert_file` `(string: optional)` - Specifies the path to the certificate
  for TLS.

### Example configuration

Here is an example of a cache configuration with the optional `persist` block,
alongside a regular listener, and a listener that only serves metrics.

```hcl
# Other Vault Proxy configuration blocks
# ...

cache {
	persist = {
		type = "kubernetes"
		path = "/vault/proxy-cache/"
		keep_after_import = true
		exit_on_err = true
		service_account_token_file = "/tmp/serviceaccount/token"
	}
}

listener "tcp" {
    address = "127.0.0.1:8100"
    tls_disable = true
}

listener "tcp" {
    address = "127.0.0.1:3000"
    tls_disable = true
    role = "metrics_only"
}
```

[static-secret-caching]: /vault/docs/agent-and-proxy/proxy/caching/static-secret-caching
