The HTTPMetadataProvider type is deprecated
As of V3.4, the
HTTPMetadataProvider type is deprecated and will be removed from IdP V4.0. Use a
FileBackedHTTPMetadataProvider loads a metadata file from an HTTP server. The provider periodically reloads the metadata file if necessary.
Use this provider with remote metadata
FileBackedHTTPMetadataProvideris used with remote metadata. See the MetadataManagementBestPractices topic for more information.
FileBackedHTTPMetadataProvider spools the metadata contents to a local backing file, which is used at startup. As of v3.3.0, the backing file is only used at startup. A refresh operation never consults the backing file since the latter can't possibly represent newer metadata than what is already cached in memory.
Schema Names and location
<MetadataProvider> element and the type
FileBackedHTTPMetadataProvider are defined by the
urn:mace:shibboleth:2.0:metadata schema, which can be located at http://shibboleth.net/schema/idp/shibboleth-metadata.xsd.
Any of the Common Attributes, the Reloading Attributes, or the HTTP Attributes may be configured. In addition, a
FileBackedHTTPMetadataProvider has a few attributes of its own, some of which are required:
|URL||required||The URL that the metadata is served from.|
|File specificaton||required||Specifies where the backing file is located. If the remote server is unavailable at startup, the backing file is loaded instead.|
|Boolean||true||Flag indicating whether initialization should first attempt to load metadata from the backup file. If true, foreground initialization will be performed by loading the backing file, and then a refresh from the remote HTTP server will be scheduled to execute in a background thread, after a configured delay. This can improve IdP startup times when the remote HTTP file is large in size.|
|Delay (ISO8601 format)|
Delay duration after which to schedule next HTTP refresh when initialized from the backing file.
|String||required||Identifier for logging, identification for command line reload, etc.|
|String||required||Specifies the exact type of provider to use (from those listed above, or a custom extension type).|
The following attributes are common to all metadata provider types except the
Whether candidate metadata found by the resolver must be valid in order to be returned (where validity is implementation specific, but in SAML cases generally depends on a
|Boolean||true||Whether to fail initialization of the underlying MetadataResolverService (and possibly the IdP as a whole) if the initialization of a metadata provider fails. When false, the IdP may start, and will continue to attempt to reload valid metadata if configured to do so, but operations that require valid metadata will fail until it does.|
|Integer||Defines the order in which metadata providers are searched (see below), can only be specified on top level |
|The following are advanced settings supporting a new low-level feature allowing metadata lookup by keys other than the unique entityID and are rarely of use to a deployer.|
|Bean ID||Identifies the a custom |
|Boolean||true||Flag which determines whether the default |
|Boolean||false||Flag which determines whether predicates used in filtering are connected by a logical 'OR' (true) or by logical 'AND' (false).|
|Bean ID||shibboleth.ParserPool||Identifies a Spring bean for the XML parser used to parse metadata. Generally should not be changed.|
|Bean ID||Identifies a Spring bean containing a Java |
|Duration||PT30S||Lower bound on the next refresh from the time calculated based on the metadata's expiration.|
|Duration||PT4H||Upper bound on the next refresh from the time calculated based on the metadata's expiration.|
|Real Number (strictly between 0.0 and 1.0)||0.75||A factor applied to the initially determined refresh time in order to determine the next refresh time (typically to ensure refresh takes place prior to the metadata's expiration). Attempts to refresh metadata will generally begin around the product of this number and the maximum refresh delay.|
Identifies an optional
Flag indicating whether resolution may be performed solely by applying predicates to the entire metadata collection, when an entityID input criterion is not supplied.
|Duration||PT0S (disabled)||For each attempted metadata refresh (whether or not fresh metadata is obtained), if |
An HTTP metadata provider includes a default implementation of the
org.apache.http.client.HttpClient interface. The attributes in the following subsections control the behavior of the default HTTP client. To override the default client implementation, configure the following attribute:
A reference to an externally defined Spring bean that specifies an
Use of the
httpClientRef attribute precludes the use of any and all of the HTTP attributes in the following subsections.
HTTP Connection Attributes
The following attributes apply to the HTTP connections obtained and managed by an HTTP metadata provider:
|Duration||Depends on the provider type||The maximum amount of time to wait for a connection to be returned from the HTTP client's connection pool manager. Set to |
|Duration||Depends on the provider type||The maximum amount of time to wait to establish a connection with the remote server. Set to |
|Duration||Depends on the provider type|
|Duration||Depends on the provider type||The maximum amount of time to wait between two consecutive packets while reading from the socket connected to the remote server. Set to |
HTTP Security Attributes
The following security-related attributes apply to any HTTP metadata provider:
If true, no TLS certificate checking will take place over an HTTPS connection. This attribute is incompatible with
|Boolean||false||DEPRECATED: Use |
|Bean ID||A reference to an externally defined Spring bean that specifies an |
HTTP Proxy Attributes
The following attributes configure an HTTP proxy for use with an HTTP metadata provider:
The hostname of the HTTP proxy through which connections will be made. This attribute is incompatible with
The port of the HTTP proxy through which connections will be made. This attribute is incompatible with
The username used with the HTTP proxy through which connections will be made. This attribute is incompatible with
The password used with the HTTP proxy through which connections will be made. This attribute is incompatible with
HTTP Caching Attributes
The following attributes configure an HTTP cache on an HTTP metadata provider:
|Depends on the provider type|
The type of low-level HTTP caching to perform. There are three choices:
This attribute is incompatible with
Some metadata providers, most notably the reloading "batch-oriented" providers, implement HTTP caching at a higher layer and tend to work best with
The maximum number of responses written to cache. This attribute is incompatible with
The maximum response body size that may be cached, in bytes. This attribute is incompatible with
Configuring the HTTP Connection Attributes
FileBackedHTTPMetadataProvider, the HTTP Connection Attributes have the following default timeout values:
Since the batch metadata refresh process runs in a background thread, a browser user will not notice such a delay.
Configuring the HTTP Caching Attributes
By default, a
FileBackedHTTPMetadataProvider does not cache metadata (
httpCaching="none"). Unless you've read the code or otherwise know what you're doing, do not override this setting.
Regardless of the value of the
httpCaching attribute, a
FileBackedHTTPMetadataProvider always issues HTTP conditional GET requests. For this reason, a custom HTTP client is seldom needed.
HTTP conditional GET is independent of caching strategy
Out of the box, a
FileBackedHTTPMetadataProvider caches the response headers it needs to subsequently perform HTTP conditional GET but this caching-like behavior is not true HTTP caching. In particular, a
FileBackedHTTPMetadataProvider does not cache the full HTTP response by default.
Any of the following child elements may be specified (in order).
|0 or more||A metadata filter applied to candidate metadata as it flows through the metadata pipeline|
|0 or 1||A custom |
The former is common to all metadata providers while the latter is common to all HTTP metadata providers. The
FileBackedHTTPMetadataProvider type has no child elements of its own.
A typical use of
FileBackedHTTPMetadataProvider is to load (and periodically reload) a metadata aggregate from a remote source via HTTP:
Note that the metadata is loaded (and reloaded) out-of-band and therefore will not interfere with any SAML protocol exchange.
Frequently Asked Questions
See also Troubleshooting.
What triggers the metadata refresh process?
FileBackedHTTPMetadataProvider loads (and reloads) metadata in the background, independent of normal IdP operation. The frequency of metadata refresh is influenced by the Reloading Attributes. In particular, the
maxRefreshDelay attributes strongly influence the frequency of metadata refresh. Any
validUntil attributes in the metadata itself also influence the process.
What if the metadata resource is large?
Large metadata files consume a significant amount of memory, especially during the reload process (when the IdP must have both the old and the new metadata at hand). Precise memory requirements depend on overall IdP load and other deployment-specific factors but large metadata files (such as those distributed by some federations) may require a system configured with 2GB of memory or more. Ask your federation operator for specific recommendations.
Although metadata refresh can put significant load on the system, all refresh operations are performed in the background, independent of normal IdP operation. Assuming there are no resource limiting factors (such as inadequate memory), end users will not notice the effects of metadata refresh.
What can I do to minimize the impact of metadata refresh?
There are at least two things you can do to help minimize the impact of the metadata refresh process: 1) install and configure adequate memory on your system, and 2) customize the frequency of metadata refresh for optimal performance. In any case, the
FileBackedHTTPMetadataProvider implementation has two features that positively affect metadata refresh: background processing and HTTP conditional GET. Neither of these features is configurable, however, so there is nothing further you need to do beyond the two items mentioned above.
What is HTTP conditional GET?
A conforming server will respond to an HTTP conditional GET request (RFC 7232) with a 304 (Not Modified) status code if the target resource has not changed since the last time it was requested. Note that a 304 response does not include a response body, which is more efficient than the corresponding 200 response (especially for large metadata files). More importantly, due to the manner in which the
FileBackedHTTPMetadataProvider is implemented, the IdP can safely ignore a 304 response, which precludes the need to redundantly process the metadata. For large signed metadata files, the savings can be quite significant.
How do I customize the frequency of metadata refresh?
To influence the frequency of metadata refresh, configure the following attributes on a
refreshDelayFactor. Optimal values for these attributes depend on 1) whether or not the server supports HTTP conditional GET, 2) the life cycle of metadata published on the server, and possibly other factors. Ask the metadata publisher for recommended best practices with respect to published metadata.
What is the backing file used for?
The backing file is only used at startup. If the remote server is unavailable at startup, the backing file is loaded instead and all the configured filters are run on the backing file. If a single filter fails, the backing file is not loaded. For example, if the provider contains a SignatureValidationFilter but the signature on the backing file can not be verified, the entire load operation fails.
What happens if the provider is unable to load the backing file?
FileBackedHTTPMetadataProvider is unable to load the backing file at startup, and the
failFastInitialization attribute on the provider is set to true (default: true), the metadata initialization process will halt. Additionally, if the service property
idp.service.metadata.failFast is set to true (default: false), the IdP as a whole will fail to initialize.
Does the provider support HTTP caching?
Yes, it does so internally, though not across restarts of the system (it will not have a cache tag at startup but will maintain one in memory after the initial request for metadata and do conditional GETs until the next restart).