registry/docs/configuration.md

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title = "Configure a Registry"
description = "Explains how to deploy a registry"
keywords = ["registry, service, images,  repository"]
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parent="smn_registry"
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<![end-metadata]-->



# Registry Configuration Reference

The Registry configuration is based on a YAML file, detailed below. While it comes with sane default values out of the box, you are heavily encouraged to review it exhaustively before moving your systems to production.

## Override configuration options

In a typical setup where you run your Registry from the official image, you can specify any configuration variable from the environment by passing `-e` arguments to your `docker run` stanza, or from within a Dockerfile using the `ENV` instruction.

To override a configuration option, create an environment variable named
`REGISTRY_variable` where *`variable`* is the name of the configuration option
and the `_` (underscore) represents indention levels. For example, you can
configure the `rootdirectory` of the `filesystem` storage backend:

    storage:
      filesystem:
        rootdirectory: /var/lib/registry

To override this value, set an environment variable like this:

    REGISTRY_STORAGE_FILESYSTEM_ROOTDIRECTORY=/somewhere

This variable overrides the `/var/lib/registry` value to the `/somewhere`
directory.

>**Note**: If an environment variable changes a map value into a string, such
>as replacing the storage driver type with `REGISTRY_STORAGE=filesystem`, then
>all sub-fields will be erased. As such, specifying the storage type in the
>environment will remove all parameters related to the old storage
>configuration.



## List of configuration options

This section lists all the registry configuration options. Some options in
the list are mutually exclusive. So, make sure to read the detailed reference
information about each option that appears later in this page.

    version: 0.1
    log:
      level: debug
      formatter: text
      fields:
        service: registry
        environment: staging
      hooks:
        - type: mail
          disabled: true
          levels:
          - panic
          options:
            smtp:
              addr: mail.example.com:25
              username: mailuser
              password: password
              insecure: true
            from: sender@example.com
            to: 
              - errors@example.com
    loglevel: debug # deprecated: use "log"
    storage:
      filesystem:
        rootdirectory: /var/lib/registry
      azure:
        accountname: accountname
        accountkey: base64encodedaccountkey
        container: containername
      s3:
        accesskey: awsaccesskey
        secretkey: awssecretkey
        region: us-west-1
        bucket: bucketname
        encrypt: true
        secure: true
        v4auth: true
        chunksize: 5242880
        rootdirectory: /s3/object/name/prefix
      rados:
        poolname: radospool
        username: radosuser
        chunksize: 4194304
      cache:
        blobdescriptor: redis
      maintenance:
        uploadpurging:
          enabled: true
          age: 168h
          interval: 24h
          dryrun: false
    auth:
      silly:
        realm: silly-realm
        service: silly-service
      token:
        realm: token-realm
        service: token-service
        issuer: registry-token-issuer
        rootcertbundle: /root/certs/bundle
      htpasswd:
        realm: basic-realm
        path: /path/to/htpasswd
    middleware:
      registry:
        - name: ARegistryMiddleware
          options:
            foo: bar
      repository:
        - name: ARepositoryMiddleware
          options:
            foo: bar
      storage:
        - name: cloudfront
          options:
            baseurl: https://my.cloudfronted.domain.com/
            privatekey: /path/to/pem
            keypairid: cloudfrontkeypairid
            duration: 3000
    reporting:
      bugsnag:
        apikey: bugsnagapikey
        releasestage: bugsnagreleasestage
        endpoint: bugsnagendpoint
      newrelic:
        licensekey: newreliclicensekey
        name: newrelicname
        verbose: true
    http:
      addr: localhost:5000
      prefix: /my/nested/registry/
      secret: asecretforlocaldevelopment
      tls:
        certificate: /path/to/x509/public
        key: /path/to/x509/private
        clientcas:
          - /path/to/ca.pem
          - /path/to/another/ca.pem
      debug:
        addr: localhost:5001
    notifications:
      endpoints:
        - name: alistener
          disabled: false
          url: https://my.listener.com/event
          headers: <http.Header>
          timeout: 500
          threshold: 5
          backoff: 1000
    redis:
      addr: localhost:6379
      password: asecret
      db: 0
      dialtimeout: 10ms
      readtimeout: 10ms
      writetimeout: 10ms
      pool:
        maxidle: 16
        maxactive: 64
        idletimeout: 300s

In some instances a configuration option is **optional** but it contains child
options marked as **required**. This indicates that you can omit the parent with
all its children. However, if the parent is included, you must also include all
the children marked **required**.



## version

    version: 0.1

The `version` option is **required**. It specifies the configuration's version.
It is expected to remain a top-level field, to allow for a consistent version
check before parsing the remainder of the configuration file.

## log

The `log` subsection configures the behavior of the logging system. The logging
system outputs everything to stdout. You can adjust the granularity and format
with this configuration section.

    log:
      level: debug
      formatter: text
      fields:
        service: registry
        environment: staging

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>level</code>
    </td>
    <td>
      no
    </td>
    <td>
      Sets the sensitivity of logging output. Permitted values are
      <code>error</code>, <code>warn</code>, <code>info</code> and
      <code>debug</code>. The default is <code>info</code>.
    </td>
  </tr>
  <tr>
    <td>
      <code>formatter</code>
    </td>
    <td>
      no
    </td>
    <td>
      This selects the format of logging output. The format primarily affects how keyed
      attributes for a log line are encoded. Options are <code>text</code>, <code>json</code> or
      <code>logstash</code>. The default is <code>text</code>.
    </td>
  </tr>
    <tr>
    <td>
      <code>fields</code>
    </td>
    <td>
      no
    </td>
    <td>
      A map of field names to values. These are added to every log line for
      the context. This is useful for identifying log messages source after
      being mixed in other systems.
    </td>
</table>

## hooks

    hooks:
      - type: mail
        levels:
          - panic
        options:
          smtp:
            addr: smtp.sendhost.com:25
            username: sendername
            password: password
            insecure: true
          from: name@sendhost.com
          to:
            - name@receivehost.com

The `hooks` subsection configures the logging hooks' behavior. This subsection
includes a sequence handler which you can use for sending mail, for example.
Refer to `loglevel` to configure the level of messages printed.

## loglevel

> **DEPRECATED:** Please use [log](#logs) instead.

    loglevel: debug

Permitted values are `error`, `warn`, `info` and `debug`. The default is
`info`.

## storage

    storage:
      filesystem:
        rootdirectory: /var/lib/registry
      azure:
        accountname: accountname
        accountkey: base64encodedaccountkey
        container: containername
      s3:
        accesskey: awsaccesskey
        secretkey: awssecretkey
        region: us-west-1
        bucket: bucketname
        encrypt: true
        secure: true
        v4auth: true
        chunksize: 5242880
        rootdirectory: /s3/object/name/prefix
      rados:
        poolname: radospool
        username: radosuser
        chunksize: 4194304
      cache:
        blobdescriptor: inmemory
      maintenance:
        uploadpurging:
          enabled: true
          age: 168h
          interval: 24h
          dryrun: false

The storage option is **required** and defines which storage backend is in use.
You must configure one backend; if you configure more, the registry returns an error.

If you are deploying a registry on Windows, be aware that a Windows volume mounted from the host is not recommended. Instead, you can use a S3, or Azure, backing data-store. If you do use a Windows volume, you must ensure that the `PATH` to the mount point is within Window's `MAX_PATH` limits. Failure to do so can result in the following error message: 

    mkdir /XXX protocol error and your registry will not function properly.

### cache

Use the `cache` subsection to enable caching of data accessed in the storage
backend. Currently, the only available cache provides fast access to layer
metadata. This, if configured, uses the `blobdescriptor` field.

You can set `blobdescriptor` field to `redis` or `inmemory`.  The `redis` value uses
a Redis pool to cache layer metadata.  The `inmemory` value uses an in memory
map.

>**NOTE**: Formerly, `blobdescriptor` was known as `layerinfo`. While these
>are equivalent, `layerinfo` has been deprecated, in favor or
>`blobdescriptor`.

### filesystem

The `filesystem` storage backend uses the local disk to store registry files. It
is ideal for development and may be appropriate for some small-scale production
applications.

This backend has a single, required `rootdirectory` parameter. The parameter
specifies the absolute path to a directory. The registry stores all its data
here so make sure there is adequate space available.

### azure

This storage backend uses Microsoft's Azure Blob Storage.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>accountname</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Azure account name.
    </td>
  </tr>
  <tr>
    <td>
      <code>accountkey</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Azure account key.
    </td>
  </tr>
  <tr>
    <td>
      <code>container</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Name of the Azure container into which to store data.
    </td>
  </tr>
   <tr>
    <td>
      <code>realm</code>
    </td>
    <td>
      no
    </td>
    <td>
      Domain name suffix for the Storage Service API endpoint. By default, this
      is <code>core.windows.net</code>.
    </td>
  </tr>

</table>


### rados

This storage backend uses [Ceph Object Storage](http://ceph.com/docs/master/rados/).

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>poolname</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Ceph pool name.
    </td>
  </tr>
   <tr>
    <td>
      <code>username</code>
    </td>
    <td>
      no
    </td>
    <td>
      Ceph cluster user to connect as (i.e. admin, not client.admin).
    </td>
  </tr>
   <tr>
    <td>
      <code>chunksize</code>
    </td>
    <td>
      no
    </td>
    <td>
      Size of the written RADOS objects. Default value is 4MB (4194304).
    </td>
  </tr>
</table>


### S3

This storage backend uses Amazon's Simple Storage Service (S3).

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>accesskey</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Your AWS Access Key.
    </td>
  </tr>
    <tr>
    <td>
      <code>secretkey</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Your AWS Secret Key.
    </td>
  </tr>
    <tr>
    <td>
      <code>region</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The AWS region in which your bucket exists. For the moment, the Go AWS
      library in use does not use the newer DNS based bucket routing.
    </td>
  </tr>
    <tr>
    <td>
      <code>bucket</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The bucket name in which you want to store the registry's data.
    </td>
  </tr>
    <tr>
    <td>
      <code>encrypt</code>
    </td>
    <td>
      no
    </td>
    <td>
       Specifies whether the registry stores the image in encrypted format or
       not. A boolean value. The default is false.
    </td>
  </tr>
    <tr>
    <td>
      <code>secure</code>
    </td>
    <td>
      no
    </td>
    <td>
      Indicates whether to use HTTPS instead of HTTP. A boolean value. The
      default is false.
    </td>
  </tr>
    <tr>
    <td>
      <code>v4auth</code>
    </td>
    <td>
      no
    </td>
    <td>
      Indicates whether the registry uses Version 4 of AWS's authentication.
      Generally, you should set this to <code>true</code>. By default, this is
      <code>false</code>.
    </td>
  </tr>
    <tr>
    <td>
      <code>chunksize</code>
    </td>
    <td>
      no
    </td>
    <td>
      The S3 API requires multipart upload chunks to be at least 5MB. This value
      should be a number that is larger than 5*1024*1024.
    </td>
  </tr>
   <tr>
    <td>
      <code>rootdirectory</code>
    </td>
    <td>
      no
    </td>
    <td>
      This is a prefix that will be applied to all S3 keys to allow you to segment data in your bucket if necessary.
    </td>
  </tr>
</table>

### Maintenance

Currently the registry can perform one maintenance function: upload purging.  This and future
maintenance functions which are related to storage can be configured under the maintenance section.

### Upload Purging

Upload purging is a background process that periodically removes orphaned files from the upload
directories of the registry.  Upload purging is enabled by default.  To
 configure upload directory purging, the following parameters
must be set.


| Parameter | Required | Description
  --------- | -------- | -----------
`enabled` | yes | Set to true to enable upload purging.  Default=true. |
`age` | yes | Upload directories which are older than this age will be deleted.  Default=168h (1 week)
`interval` | yes | The interval between upload directory purging.  Default=24h.
`dryrun` | yes |  dryrun can be set to true to obtain a summary of what directories will be deleted.  Default=false.

Note: `age` and `interval` are strings containing a number with optional fraction and a unit suffix: e.g. 45m, 2h10m, 168h (1 week).

## auth

    auth:
      silly:
        realm: silly-realm
        service: silly-service
      token:
        realm: token-realm
        service: token-service
        issuer: registry-token-issuer
        rootcertbundle: /root/certs/bundle
      htpasswd:
        realm: basic-realm
        path: /path/to/htpasswd

The `auth` option is **optional**. There are
currently 2 possible auth providers, `silly` and `token`. You can configure only
one `auth` provider.

### silly

The `silly` auth is only for development purposes. It simply checks for the
existence of the `Authorization` header in the HTTP request. It has no regard for
the header's value. If the header does not exist, the `silly` auth responds with a
challenge response, echoing back the realm, service, and scope that access was
denied for.

The following values are used to configure the response:

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>realm</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The realm in which the registry server authenticates.
    </td>
  </tr>
    <tr>
    <td>
      <code>service</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The service being authenticated.
    </td>
  </tr>
</table>



### token

Token based authentication allows the authentication system to be decoupled from
the registry. It is a well established authentication paradigm with a high
degree of security.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>realm</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The realm in which the registry server authenticates.
    </td>
  </tr>
    <tr>
    <td>
      <code>service</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The service being authenticated.
    </td>
  </tr>
    <tr>
    <td>
      <code>issuer</code>
    </td>
    <td>
      yes
    </td>
    <td>
The name of the token issuer. The issuer inserts this into
the token so it must match the value configured for the issuer.
    </td>
  </tr>
    <tr>
    <td>
      <code>rootcertbundle</code>
    </td>
    <td>
      yes
     </td>
    <td>
The absolute path to the root certificate bundle. This bundle contains the
public part of the certificates that is used to sign authentication tokens.
     </td>
  </tr>
</table>

For more information about Token based authentication configuration, see the [specification](spec/auth/token.md).

### htpasswd

The _htpasswd_ authentication backed allows one to configure basic auth using an
[Apache HTPasswd File](https://httpd.apache.org/docs/2.4/programs/htpasswd.html).
Only [`bcrypt`](http://en.wikipedia.org/wiki/Bcrypt) format passwords are
supported. Entries with other hash types will be ignored. The htpasswd file is
loaded once, at startup. If the file is invalid, the registry will display and
error and will not start.

> __WARNING:__ This authentication scheme should only be used with TLS
> configured, since basic authentication sends passwords as part of the http
> header.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>realm</code>
    </td>
    <td>
      yes
    </td>
    <td>
      The realm in which the registry server authenticates.
    </td>
  </tr>
    <tr>
    <td>
      <code>path</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Path to htpasswd file to load at startup.
    </td>
  </tr>
</table>

## middleware

The `middleware` option is **optional**. Use this option to inject middleware at
named hook points. All middlewares must implement the same interface as the
object they're wrapping. This means a registry middleware must implement the
`distribution.Namespace` interface, repository middleware must implement
`distribution.Respository`, and storage middleware must implement
`driver.StorageDriver`.

Currently only one middleware, `cloudfront`, a storage middleware, is supported
in the registry implementation.

    middleware:
      registry:
        - name: ARegistryMiddleware
          options:
            foo: bar
      repository:
        - name: ARepositoryMiddleware
          options:
            foo: bar
      storage:
        - name: cloudfront
          options:
            baseurl: https://my.cloudfronted.domain.com/
            privatekey: /path/to/pem
            keypairid: cloudfrontkeypairid
            duration: 3000

Each middleware entry has `name` and `options` entries. The `name` must
correspond to the name under which the middleware registers itself. The
`options` field is a map that details custom configuration required to
initialize the middleware. It is treated as a `map[string]interface{}`. As such,
it supports any interesting structures desired, leaving it up to the middleware
initialization function to best determine how to handle the specific
interpretation of the options.

### cloudfront

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>baseurl</code>
    </td>
    <td>
      yes
    </td>
    <td>
      <code>SCHEME://HOST[/PATH]</code> at which Cloudfront is served.
    </td>
  </tr>
    <tr>
    <td>
      <code>privatekey</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Private Key for Cloudfront provided by AWS.
    </td>
  </tr>
    <tr>
    <td>
      <code>keypairid</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Key pair ID provided by AWS.
    </td>
  </tr>
    <tr>
    <td>
      <code>duration</code>
    </td>
    <td>
      no
    </td>
    <td>
      Duration for which a signed URL should be valid.
    </td>
  </tr>
</table>


## reporting

    reporting:
      bugsnag:
        apikey: bugsnagapikey
        releasestage: bugsnagreleasestage
        endpoint: bugsnagendpoint
      newrelic:
        licensekey: newreliclicensekey
        name: newrelicname
        verbose: true

The `reporting` option is **optional** and configures error and metrics
reporting tools. At the moment only two services are supported, [New
Relic](http://newrelic.com/) and [Bugsnag](http://bugsnag.com), a valid
configuration may contain both.

### bugsnag

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>apikey</code>
    </td>
    <td>
      yes
    </td>
    <td>
      API Key provided by Bugsnag
    </td>
  </tr>
  <tr>
    <td>
      <code>releasestage</code>
    </td>
    <td>
      no
    </td>
    <td>
      Tracks where the registry is deployed, for example,
      <codde>production</code>,<codde>staging</code>, or
      <codde>development</code>.
    </td>
  </tr>
  <tr>
    <td>
      <code>endpoint</code>
    </td>
    <td>
      no
    </td>
    <td>
      Specify the enterprise Bugsnag endpoint.
    </td>
  </tr>
</table>


### newrelic

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>licensekey</code>
    </td>
    <td>
      yes
    </td>
    <td>
      License key provided by New Relic.
    </td>
  </tr>
   <tr>
    <td>
      <code>name</code>
    </td>
    <td>
      no
    </td>
    <td>
      New Relic application name.
    </td>
  </tr>
     <tr>
    <td>
      <code>verbose</code>
    </td>
    <td>
      no
    </td>
    <td>
      Enable New Relic debugging output on stdout.
    </td>
  </tr>
</table>

## http

    http:
      addr: localhost:5000
      net: tcp
      prefix: /my/nested/registry/
      secret: asecretforlocaldevelopment
      tls:
        certificate: /path/to/x509/public
        key: /path/to/x509/private
        clientcas:
          - /path/to/ca.pem
          - /path/to/another/ca.pem
      debug:
        addr: localhost:5001

The `http` option details the configuration for the HTTP server that hosts the registry.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>addr</code>
    </td>
    <td>
      yes
    </td>
    <td>
     The address for which the server should accept connections. The form depends on a network type (see <code>net</code> option):
     <code>HOST:PORT</code> for tcp and <code>FILE</code> for a unix socket.
    </td>
  </tr>
  <tr>
    <td>
      <code>net</code>
    </td>
    <td>
      no
    </td>
    <td>
     The network which is used to create a listening socket. Known networks are <code>unix</code> and <code>tcp</code>.
     The default empty value means tcp.
    </td>
  </tr>
    <tr>
    <td>
      <code>prefix</code>
    </td>
    <td>
      no
    </td>
    <td>
If the server does not run at the root path use this value to specify the
prefix. The root path is the section before <code>v2</code>. It
should have both preceding and trailing slashes, for example <code>/path/</code>.
    </td>
  </tr>
  <tr>
    <td>
      <code>secret</code>
    </td>
    <td>
      yes
    </td>
    <td>
A random piece of data. This is used to sign state that may be stored with the
client to protect against tampering. For production environments you should generate a
random piece of data using a cryptographically secure random generator.
    </td>
  </tr>
</table>


### tls

The `tls` struct within `http` is **optional**. Use this to configure TLS
for the server. If you already have a server such as Nginx or Apache running on
the same host as the registry, you may prefer to configure TLS termination there
and proxy connections to the registry server.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>certificate</code>
    </td>
    <td>
      yes
    </td>
    <td>
       Absolute path to x509 cert file
    </td>
  </tr>
    <tr>
    <td>
      <code>key</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Absolute path to x509 private key file.
    </td>
  </tr>
  <tr>
    <td>
      <code>clientcas</code>
    </td>
    <td>
      no
    </td>
    <td>
      An array of absolute paths to a x509 CA file
    </td>
  </tr>
</table>


### debug

The `debug` option is **optional** . Use it to configure a debug server that
can be helpful in diagnosing problems. The debug endpoint can be used for
monitoring registry metrics and health, as well as profiling. Sensitive
information may be available via the debug endpoint. Please be certain that
access to the debug endpoint is locked down in a production environment.

The `debug` section takes a single, required `addr` parameter. This parameter
specifies the `HOST:PORT` on which the debug server should accept connections.


## notifications

    notifications:
      endpoints:
        - name: alistener
          disabled: false
          url: https://my.listener.com/event
          headers: <http.Header>
          timeout: 500
          threshold: 5
          backoff: 1000

The notifications option is **optional** and currently may contain a single
option, `endpoints`.

### endpoints

Endpoints is a list of named services (URLs) that can accept event notifications.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>name</code>
    </td>
    <td>
      yes
    </td>
    <td>
A human readable name for the service.
</td>
  </tr>
  <tr>
    <td>
      <code>disabled</code>
    </td>
    <td>
      no
    </td>
    <td>
A boolean to enable/disable notifications for a service.
    </td>
  </tr>
  <tr>
    <td>
      <code>url</code>
    </td>
    <td>
    yes
    </td>
    <td>
The URL to which events should be published.
    </td>
  </tr>
   <tr>
    <td>
      <code>headers</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Static headers to add to each request.
    </td>
  </tr>
  <tr>
    <td>
      <code>timeout</code>
    </td>
    <td>
      yes
    </td>
    <td>
      An HTTP timeout value. This field takes a positive integer and an optional
      suffix indicating the unit of time. Possible units are:
      <ul>
        <li><code>ns</code> (nanoseconds)</li>
        <li><code>us</code> (microseconds)</li>
        <li><code>ms</code> (milliseconds)</li>
        <li><code>s</code> (seconds)</li>
        <li><code>m</code> (minutes)</li>
        <li><code>h</code> (hours)</li>
      </ul>
    If you omit the suffix, the system interprets the value as nanoseconds.
    </td>
  </tr>
  <tr>
    <td>
      <code>threshold</code>
    </td>
    <td>
      yes
    </td>
    <td>
      An integer specifying how long to wait before backing off a failure.
    </td>
  </tr>
  <tr>
    <td>
      <code>backoff</code>
    </td>
    <td>
      yes
    </td>
    <td>
      How long the system backs off before retrying. This field takes a positive
      integer and an optional suffix indicating the unit of time. Possible units
      are:
      <ul>
        <li><code>ns</code> (nanoseconds)</li>
        <li><code>us</code> (microseconds)</li>
        <li><code>ms</code> (milliseconds)</li>
        <li><code>s</code> (seconds)</li>
        <li><code>m</code> (minutes)</li>
        <li><code>h</code> (hours)</li>
      </ul>
    If you omit the suffix, the system interprets the value as nanoseconds.
    </td>
  </tr>
</table>


## redis

    redis:
      addr: localhost:6379
      password: asecret
      db: 0
      dialtimeout: 10ms
      readtimeout: 10ms
      writetimeout: 10ms
      pool:
        maxidle: 16
        maxactive: 64
        idletimeout: 300s

Declare parameters for constructing the redis connections. Registry instances
may use the Redis instance for several applications. The current purpose is
caching information about immutable blobs. Most of the options below control
how the registry connects to redis. You can control the pool's behavior
with the [pool](#pool) subsection.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>addr</code>
    </td>
    <td>
      yes
    </td>
    <td>
      Address (host and port) of redis instance.
    </td>
  </tr>
  <tr>
    <td>
      <code>password</code>
    </td>
    <td>
      no
    </td>
    <td>
      A password used to authenticate to the redis instance.
    </td>
  </tr>
  <tr>
    <td>
      <code>db</code>
    </td>
    <td>
      no
    </td>
    <td>
      Selects the db for each connection.
    </td>
  </tr>
  <tr>
    <td>
      <code>dialtimeout</code>
    </td>
    <td>
      no
    </td>
    <td>
      Timeout for connecting to a redis instance.
    </td>
  </tr>
  <tr>
    <td>
      <code>readtimeout</code>
    </td>
    <td>
      no
    </td>
    <td>
      Timeout for reading from redis connections.
    </td>
  </tr>
  <tr>
    <td>
      <code>writetimeout</code>
    </td>
    <td>
      no
    </td>
    <td>
      Timeout for writing to redis connections.
    </td>
  </tr>
</table>


### pool

    pool:
      maxidle: 16
      maxactive: 64
      idletimeout: 300s

Configure the behavior of the Redis connection pool.

<table>
  <tr>
    <th>Parameter</th>
    <th>Required</th>
    <th>Description</th>
  </tr>
  <tr>
    <td>
      <code>maxidle</code>
    </td>
    <td>
      no
    </td>
    <td>
      Sets the maximum number of idle connections.
    </td>
  </tr>
  <tr>
    <td>
      <code>maxactive</code>
    </td>
    <td>
      no
    </td>
    <td>
      sets the maximum number of connections that should
  be opened before blocking a connection request.
    </td>
  </tr>
  <tr>
    <td>
      <code>idletimeout</code>
    </td>
    <td>
      no
    </td>
    <td>
      sets the amount time to wait before closing
  inactive connections.
    </td>
  </tr>
</table>


## Example: Development configuration

The following is a simple example you can use for local development:

    version: 0.1
    log:
      level: debug
    storage:
        filesystem:
            rootdirectory: /var/lib/registry
    http:
        addr: localhost:5000
        secret: asecretforlocaldevelopment
        debug:
            addr: localhost:5001

The above configures the registry instance to run on port `5000`, binding to
`localhost`, with the `debug` server enabled. Registry data storage is in the
`/var/lib/registry` directory. Logging is in `debug` mode, which is the most
verbose.

A similar simple configuration is available at
[config.yml](https://github.com/docker/distribution/blob/master/cmd/registry/config.yml).
Both are generally useful for local development.


## Example: Middleware configuration

This example illustrates how to configure storage middleware in a registry.
Middleware allows the registry to serve layers via a content delivery network
(CDN). This is useful for reducing requests to the storage layer.

Currently, the registry supports [Amazon
Cloudfront](http://aws.amazon.com/cloudfront/). You can only use Cloudfront in
conjunction with the S3 storage driver.

<table>
  <tr>
    <th>Parameter</th>
    <th>Description</th>
  </tr>
  <tr>
    <td><code>name</code></td>
    <td>The storage middleware name. Currently <code>cloudfront</code> is an accepted value.</td>
  </tr>
  <tr>
    <td><code>disabled<code></td>
    <td>Set to <code>false</code> to easily disable the middleware.</td>
  </tr>
  <tr>
    <td><code>options:</code></td>
    <td>
    A set of key/value options to configure the middleware.
    <ul>
    <li><code>baseurl:</code> The Cloudfront base URL.</li>
    <li><code>privatekey:</code> The location of your AWS private key on the filesystem. </li>
    <li><code>keypairid:</code> The ID of your Cloudfront keypair. </li>
    <li><code>duration:</code> The duration in minutes for which the URL is valid. Default is 20. </li>
    </ul>
    </td>
  </tr>
</table>

The following example illustrates these values:

    middleware:
        storage:
            - name: cloudfront
              disabled: false
              options:
                 baseurl: http://d111111abcdef8.cloudfront.net
                 privatekey: /path/to/asecret.pem
                 keypairid: asecret
                 duration: 60


>**Note**: Cloudfront keys exist separately to other AWS keys.  See
>[the documentation on AWS credentials](http://docs.aws.amazon.com/AWSSecurityCredentials/1.0/AboutAWSCredentials.html#KeyPairs)
>for more information.