SCSP INFO
This section provides general information about SCSP INFO that applies to both named and unnamed objects.
INFO is a request to the storage cluster to provide information about a specific object. The INFO message is identical in semantics to the READ request, except that the object (if found) is not returned in the response. If the referenced content is found in the cluster, only the meta information about that object is returned in the form of response headers. The INFO request is formatted as an HTTP request using the HEAD method.
SCSP Method | HTTP Method | RFC 7231 Section |
|---|---|---|
INFO | HEAD |
Note
SCSP allows HEAD requests with mismatched Accept-Encoding headers to receive responses as if the encoding matched that of the object. Swarm relaxed this RFC restriction because a HEAD request returns no body contents, so there is nothing to encode.
INFO for Named Objects
HEAD /mybucket/samplefile.txt HTTP/1.1
Host: cluster.example.com
User-Agent: Swarm Client/0.1INFO for Unnamed Objects
HEAD /06eec5e2c3f1aadcb41ef7fd52adc049 HTTP/1.1
User-Agent: Swarm Client/0.1Error
Error loading excerpt from "WRITE for Unnamed Objects".
INFO for Alias Objects
To INFO an alias object, optionally add the alias=yes query argument to the URI portion of the HTTP request line, as shown below.
HEAD /41A140B5271DC8D22FF8D027176A0821?alias=yes HTTP/1.1
User-Agent: Swarm Client/0.1Error
Error loading excerpt from "WRITE for Unnamed Objects".
Normal Responses to INFO
SeeSCSP Headers for a list of response headers.
The responses described in this section may be returned by the storage cluster in the case where the requested content was found. The content's meta-information can be returned directly by the node that received the request or the request may be redirected to another node in the cluster.
Note
Different Content-Length values in the responses display if ?checkIntegrity is added to HEAD and GET requests for the same object. This occurs because the HEAD response returns the Content-Length of the manifest rather than the object.
The following response indicates the requested object was located, but another node in the cluster services the request for meta-information. Additionally, all future requests of this storage cluster should be made through the new access node until another 301 response is received. There is no message-body, so the content length is always 0. The value of the Location header indicates which node in the cluster should receive the redirect.
301 Moved Permanently
The client is expected to send another INFO request using the exact URI contained in the Location header.
HTTP/1.1 301 Moved Permanently
Date: Wed, 1 Sept 2010 15:59:02 GMT
Server: CAStor Cluster/v8b2
Connection: close
Location: http://node-ip/name-or-uuid?auth=2096EFA659295BBB819D1FECCE77D2EF
Content-Length: 0307 Temporary Redirect
The following response (307) is similar to the 301 response, except the client should continue to use the current node (the one generating this response) for future requests until further notice.
HTTP/1.1 307 Temporary Redirect
Date: Wed, 1 Sept 2010 15:59:02 GMT
Server: CAStor Cluster/5.0.0
Location: http://node-ip/name-or-uuid?auth=2096EFA659295BBB819D1FECCE77D2EF
Content-Length: 0Normal Responses for Named Objects
INFO response for a named object in a domain:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: Digest realm="cluster.example.com/_administrators",
nonce="05d0a60ee1f44361f449496505e05116", opaque="fd9c8e14e20fb7c13408c049b7d222af", `
stale=false, `
qop="auth", `
algorithm=MD5
WWW-Authenticate: Basic realm="cluster.example.com/_administrators"
Content-Length: 51
Content-Type: text/html
Date: Sat, 16 Oct 2010 00:23:24 GMT
Server: CAStor Cluster 5.0.0
Allow: HEAD, GET, PUT, POST, COPY, APPEND, DELETE
HTTP/1.1 200 OK
Castor-System-Alias: ec87e3c7c410cc04fc4c838061898d9c
Castor-System-CID: ffffffffffffffffffffffffffffffff
Castor-System-Cluster: cluster.example.com
Castor-System-Created: Fri, 15 Oct 2010 23:59:40 GMT
Castor-System-Name: cluster.example.com
Castor-System-Owner: admin@CAStor administrator
Castor-System-Version: 1287187180.959
Content-Length: 0
Last-Modified: Fri, 15 Oct 2010 18:35:56
GMT lifepoint: [] reps=16
Etag: "da8bfbb04d089b9c22ae77747f327233"
Date: Sat, 16 Oct 2010 00:23:24 GMT
Server: CAStor Cluster/5.0.0The initial 401 Unauthorized response is a normal initial response to HTTP authentication. An initial 401 on an INFO on a domain is returned because access to a domain always requires administrator credentials.
HTTP/1.1 200 OK
Castor-System-Alias: d36dfca69ba7752f4708b1fa9bf9918b
Castor-System-CID: ec87e3c7c410cc04fc4c838061898d9c
Castor-System-Cluster: cluster.example.com
Castor-System-Created: Fri, 15 Oct 2010 18:36:05 GMT
Castor-System-Name: bucket
Castor-System-Version: 1287167765.255
Content-Length: 0
Content-Type: application/x-www-form-urlencoded
Last-Modified: Fri, 15 Oct 2010 18:36:05 GMT
Etag: "21641b39f4fdc1e86dc67e798a320980"
Date: Fri, 15 Oct 2010 23:54:44 GMT
Server: CAStor Cluster/5.0.0
HTTP/1.1 200 OK
Castor-System-CID: d36dfca69ba7752f4708b1fa9bf9918b
Castor-System-Cluster: cluster.example.com
Castor-System-Created: Fri, 15 Oct 2010 22:09:19 GMT
Castor-System-Name: file.txt
Castor-System-Version: 1287180559.436
Content-Length: 26
Content-Type: application/x-www-form-urlencoded
Last-Modified: Fri, 15 Oct 2010 22:09:19 GMT
Etag: "c744aa90d375aa3e1f228f74b7960e54"
Date: Fri, 15 Oct 2010 23:51:44 GMT
Server: CAStor Cluster/5.0.0The response for a named object is very similar to the response for a bucket except that Castor-System-CID is the identifier of the named object's parent (the bucket).
Normal Responses for Unnamed Objects
The following response indicates that the node that received the request found the requested content and is returning meta-information about the object in the headers of this response.
HTTP/1.1 200 OK
Date: Wed, 1 Sept 2010 15:59:02 GMT
Server: CAStor Cluster/5.0.0
Content-Type: image/jpeg
Content-Length: (length of the content of the Swarm object)
Replica-Count: (number of replicas in cluster)
[ application-meta-information ]Error Responses to INFO
The responses in this section may be returned by the storage cluster when the specified content cannot be found or there is a problem with the INFO request.
The following response indicates a problem with the INFO request, such as missing mandatory headers, invalid message body, or any other violation of HTTP/1.1 by the HEAD request. The reason for the error is included in the status line.
HTTP/1.1 400 Bad Request
Date: Wed, 1 Sept 2010 15:59:02 GMT
Server: CAStor Cluster 5.0.0
Content-Length: 24
Content-Type: text/htmlIndicates the requested object cannot be located in this cluster:
HTTP/1.1 404 Not Found
Date: Wed, 1 Sept 2010 15:59:02 GMT
Server: CAStor Cluster 5.0.0
Content-Length: 56
Content-Type: text/htmlRelated content
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