View source for Configuring the HttpExportService for Connection to XNAT Servers

This article describes how to configure the CTP HttpExportService pipeline stage for efficient export to an XNAT server. The intended audience for this article is CTP administrators.

The HttpExportService configuration element has two child elements intended to invoke special features in coordination with an XNAT server. The Launcher application's Configuration tab allows the administrator to add these children and provides guidance in defining their attributes.

The <b><tt>xnat</tt></b> child element makes authentication of the transfers from the HttpExportService to the XNAT server more efficient. The element has these attributes:

<pre>
    <xnat
        url="https://host:port/data/JSESSION"
        cookieName="JSESSIONID"
        password=""
        username=""/>
</pre>

*<b><tt>url</tt></b> specifies the URL of the XNAT server's authentication service.
*<b><tt>cookieName</tt></b> specifies the cookie name in the set-cookie header returned by the XNAT server after a successful authentication.
*<b><tt>username</tt></b> specifies the username on the XNAT server for authentication.
*<b><tt>password</tt></b> specifies the password on the XNAT server for authentication.

When this element is present, the HttpExportService authenticates on the first transfer, obtains the session cookie, and passes that cookie back to the server on all subsequent transfers. The effect is to reduce the authentication load on the server dramatically and to reduce the number of parallel threads required to handle large transfers.

The <b><tt>compressor</tt></b> child element makes the actual file transfers themselves more efficient. The element has these attributes:

<pre>
    <compressor
        cacheSize="0"
        structure="dir1/dir2/dir3/..."
        defaultString="UNKNOWN"
        whitespaceReplacement="_"/>
</pre>

*<b><tt>cacheSize</tt></b> specifies the maximum number of files to combine into a single zip file for transmission to the XNAT server.
*<b><tt>structure</tt></b> specifies the dynamically constructed structure of the zip file. This attribute is used in the same way as the structure attribute of the DirectoryStorageService.
*<b><tt>defaultString</tt></b> specifies the text to be used when a DICOM element specified in the structure attribute is missing from a file to be transferred.
*<b><tt>whitespaceReplacement</tt></b> specifies the text to be used to replace sequences of whitespace characters in the directory path and filename constructed from the structure attribute.

When this element present and cacheSize is greater than zero, the compressor attempts to group as many files as are available (up to cacheSize) into a single zip file and initiates a single transfer. The compressor never waits for more files if fewer than cacheSize files are available; it just sends all that it has. The XNAT server automatically de-compresses the zip file and stores the content files.