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208 Already Reported

syndicated from planet-php.net on August 28, 2018

208 Already Reported is, like 207 Multi-Status a HTTP status code specific to WebDAV. It’s even more obscure, because it’s defined in a rarely used extension of WebDAV.



The extension adds ‘Binding’ extensions to WebDAV. WebDAV is a bit like a filesystem over HTTP, and the Binding extensions add support for a feature similar to Hard links to this filesystem.



When a client asks information about resources (files/directories), due to the bindings it becomes possible that a response lists the same file/directory twice, because 2 things can link to the same underlying resource. This means that duplicated data is sent over the wire, which is wasteful.



Another issue is that a Directory (or Collection in WebDAV terminology) might contain a resource that loops back on itself. If a recursive query is used, this can cause an infinite loop.



The 208 Already Reported allows a client to tell the server that the same resource (with the same binding) was mentioned earlier. This solves both those problems.



The 208 status never appears as a true HTTP response code in the status line, and only appears in bodies.



Example from the specification:



HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset="utf-8"
Content-Length: 1241

<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
  <D:response>
    <D:href>http://www.example.com/Coll/</D:href>
    <D:propstat>
      <D:prop>
        <D:displayname>Loop Demo</D:displayname>
        <D:resource-id>
          <D:href>urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8</D:href>
        </D:resource-id>
      </D:prop>
      <D:status>HTTP/1.1 200 OK</D:status>
    </D:propstat>
  </D:response>
  <D:response>
    <D:href>http://www.example.com/Coll/Foo</D:href>
    <D:propstat>
      <D:prop>
        <D:displayname>Bird Inventory</D:displayname>
        <D:resource-id>
          <D:href>urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf9</D:href>
        </D:resource-id>
      </D:prop>
      <D:status>HTTP/1.1 200 OK</D:status>
    </D:propstat>
  </D:response>
  <D:response>
    <D:href>http://www.example.com/Coll/Bar</D:href>
    <D:propstat>
      <D:prop>
        <D:displayname>Loop Demo</D:displayname>
        <D:resource-id>
          <D:href>urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8</D:href>
        </D:resource-id>
      </D:prop>
      <D:status>HTTP/1.1 208 Already Reported</D:status>
    </D:propstat>
  </D:response>
</D:multistatus>


I don’t think it makes sense to use 208 Already Reported for a true HTTP response. I would not recommend using it.



References