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Direct Access URLs

The main purpose of Direct Access URLs (or DAUs) is to accelerate the local download of content by allowing you to have direct content URLs for your binary content that can help with distributed content repositories in customer environments, and cloud deployments.

AWS S3 provides a way of generating pre-signed URLs for sharing objects. This feature is a perfect candidate for implementing direct access to your content.

Note: The AWS S3 pre-signed URLs are temporary links with an expiration time.

The Alfresco repository infrastructure now supports direct access URLs. This includes the ContentService and the ContentStore interface for which default methods have been provided so that ContentStore implementations for older versions of this interface throw a Not Supported exception. The new methods are auditable using the node reference and time (in seconds) for which the DAU is valid as the parameters.

REST API endpoints can be used for requesting a new DAU (i.e. a direct download link) for a specific file in the content repository.

Access to direct URLs is strictly controlled. Their expiration date is set/restricted by configurations in the repository using global and content store specific properties.

  • Values in the content store properties, default expiry time and maximum expiry time, are used in preference to the system-wide properties, if valid.
  • If invalid, an attempt is made to default to the system-wide properties.
  • However, if that still doesn’t result in a valid configuration, the DAUs for that specific content store are disabled.

Default configuration

Direct access URLs are disabled by default. This means the following configuration properties are false:

  • system.directAccessUrl.enabled
  • restApi.directAccessUrl.enabled
  • connector.s3.directAccessUrl.enabled

System-wide configuration

Below are the system-wide configuration settings required in Content Services.

Property Description
system.directAccessUrl.enabled Controls whether this feature is available, system-wide (for example false).

For DAUs to work, the feature needs to be enabled both system-wide and on the individual Content Store.
system.directAccessUrl.defaultExpiryTimeInSec Sets the default expiry time for the DAU across all Content Stores (for example 30).

Its value cannot exceed the system-wide maximum expiry time (system.directAccessUrl.maxExpiryTimeInSec) - it can only be equal or lower (otherwise all DAUs are disabled).
Note: This property is mandatory if DAUs are enabled system-wide - (otherwise all DAUs are disabled).
system.directAccessUrl.maxExpiryTimeInSec Sets the upper limit for the DAUs expiry time in seconds (for example 300, i.e. 5 minutes).

This means that a Content Store will be able to override this value but not exceed it, and the same goes for the clients. A service (Java Interface) client will be able to request a DAU for a custom expiry time but that time can’t exceed this value. If the requested time exceeds the maximum value, the expiry time reverts to the default configured one.
Note: This property is mandatory if DAUs are enabled system-wide - (otherwise all DAUs are disabled).

REST API configuration

The REST API configuration only affects the REST layer in Content Services.

Property Description
restApi.directAccessUrl.enabled Enables/disables DAU requests via the REST API (for example false).
restApi.directAccessUrl.defaultExpiryTimeInSec Sets the expiry time in seconds for all the DAUs requested via a REST call (for example 30). DAU REST API calls cannot request an explicit expiry time - unlike the service layer calls).

Its value cannot exceed the system-wide maximum expiry time configuration (system.directAccessUrl.maxExpiryTimeInSec) - it can only be equal to or lower (otherwise the REST API DAUs are disabled).

If it’s not set, the default system-wide property is used (system.directAccessUrl.defaultExpiryTimeInSec).

Storage connector content store

In the example of the S3 Connector, each content store (i.e. “final” content store, one that provides actual storage, as opposed to a caching content store), should have dedicated configuration options:

Property Description
connector.s3.directAccessUrl.enabled Controls whether DAUs are enabled on this specific content store (for example false).
connector.s3.directAccessUrl.defaultExpiryTimeInSec Sets the expiry time in seconds for the DAU in this store, by overriding the global configuration (for example 30).

If this value exceeds the content store limit (described below) or the global limit it should fallback to the global configuration. Its value cannot exceed the system-wide maximum expiry time configuration (system.directAccessUrl.maxExpiryTimeInSec) - it can only be equal or lower (otherwise DAUs for the specific content store will be disabled).

If it’s not set, the default system-wide setting is used (system.directAccessUrl.defaultExpiryTimeInSec).
connector.s3.directAccessUrl.maxExpiryTimeInSec=300 The maximum expiry time interval that can be requested by clients - content-store specific setting.

Its value cannot exceed the system-wide configuration (system.directAccessUrl.maxExpiryTimeInSec) - it can only be equal or lower (otherwise DAUs for the specific content store will be disabled).

If it’s not set, the default system-wide setting is used (system.directAccessUrl.maxExpiryTimeInSec).

Note: Callers within the platform (i.e. Java interfaces) can either request a specific expiry time or rely on the default value.

Note: When multiple S3 buckets are used for storage in Alfresco, each S3 Content Store can be configured with either the default (common) S3 Connector-specific properties (i.e. connector.s3.directAccessUrl.enabled etc.), or new separate properties can be defined for each and every store (i.e. connector.s3store1.directAccessUrl.enabled, connector.s3store2.directAccessUrl.enabled, etc.).

Configuration priorities

For DAUs to be usable on the service-layer, the feature must be enabled both system-wide and on the content-store(s). For the feature to be usable through REST (outside the JVM) the rest-api configuration must also be enabled.

The system.directAccessUrl.enabled property is the main switch for this feature. If this is set to false, then all DAUs are disabled.

The next configuration that controls specific DAUs is the one for the content store. The connector.s3.directAccessUrl.enabled property controls whether DAUs are enabled for that specific store.

Whether or not a client can request a DAU by using a REST endpoint is controlled by the restApi.directAccessUrl.enabled property. If the REST endpoint is disabled, but the feature is enabled system-wide and on the content-store, then the DAUs will only be usable by Java clients (i.e. only service-level requests will be possible).

APIs

REST endpoints

The following endpoints can be used to send requests to obtain DAUs in Content Services:

  • POST /nodes/{nodeId}/request-direct-access-url
  • POST /nodes/{nodeId}/renditions/{renditionId}/request-direct-access-url
  • POST /nodes/{nodeId}/versions/{versionId}/request-direct-access-url
  • POST /deleted-nodes/{nodeId}/request-direct-access-url
  • POST /deleted-nodes/{nodeId}/renditions/{renditionId}/request-direct-access-url

Optionally, the POST body can specify an attachment flag. A value of true indicates that a download link is required; false indicates an embedded link is required. This defaults to true if it’s not specified.

The endpoints return the following response:

{
  "entry": {
    "contentUrl": "<url>"
    "attachment":"<boolean>"
    "expiresAt": "<date-time>"
    }
}

The length of time for which a direct access URL is valid defaults to 30 seconds if not configured otherwise in alfresco-global.properties.

Method: POST

Response:

Link to the resource wrapped in a JSON Object which also contains an attachment flag and the DAU expiration date.

Error codes:

If there’s no DAU provider installed in Alfresco (such as the S3 Connector), or DAUs aren’t enabled, then a 501 HTTP status code is returned.

Parameters:

  • attachment is an optional flag which controls the download method (attachment URL vs. embedded URL). Defaults to true when not specified, which means the value of the Content-Disposition response header will be attachment.
  • The filename part of the Content-Disposition header will be set in the service layer logic, and can’t be controlled by the DAU client.

Discovery API

The Discovery API provides status information about the DAUs feature (enabled/disabled) via a new field:

  • RepositoryInfo > StatusInfo > isDirectAccessUrlEnabled

For example:

"status": {
        "isReadOnly": false,
        "isAuditEnabled": true,
        "isQuickShareEnabled": true,
        "isThumbnailGenerationEnabled": true,
        "isDirectAccessUrlEnabled": true
      },

This field is true only when all of the following conditions are met:

  • DAUs are enabled system-wide.
  • DAUs are enabled on the REST API.
  • If there’s at least one ContentStore that’s configured and has DAUs enabled.

S3 Connector

The AWS Java S3 SDK is used to generate the pre-signed DAUs with the configured duration (see the configuration settings for the repository and Content Store expiry times). The pre-signed request generates a download for the remote content.

Known limitations:

DAU generation on AWS S3 depends on the security credentials used - see Sharing an object with a presigned URL for more details.

See the project documentation for a detailed view of the main flows and other parts of the implementation.

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