Difference between revisions of "Storage Manager"

Revision as of 16:11, 9 July 2012

Role

Library for access and storage of unstructured bytestreams, or files, can be provided through a standards-based, POSIX-like API which supports the organisation and operations normally associated with local file systems whilst offering scalable and fault-tolerant remote storage.

The library acts a facade to the service and allows clients to download, upload, remove, add, and list files. Files have owners and owners may define access rights to files, allowing private, public, or group-based access.

Access Mode

There are 3 ways to access remote files

Private

Accessible only to the owner of the file

Public

accessible to all users of the community

Shared

Accessible to all users of the same group that owner

These types of access will be specified when instantiating the client. If the client is instantiated for example,with the access mode private, all the operations do with this client instance will be in access mode private.

Operations

The StorageManger library implements many operation on remote files, the methods LFile and RFile refer to, respectively, Local File (if needed) and Remote File. In the call's signature, they are preceded by a method that identify a operation, see examples below:

put(boolean replace)

put a local file in a remote directory. If replace is true then the remote file, if exist, will be replaced.

If the remote directory does not exist it will be automatically

Example: put(true).LFile(“localPath”).RFile(“remotePath”)

get()

downloads a file from a remote path to a local directory

Example: get().LFile(“localPath”).RFile(“remotePath”);

remove()

removes a remote file

Example: remove().RFile(“remotePath”);

removeDir()

removes a remote directory. The directory must be empty.

Example removeDir().RDir(“remoteDirPath”);

showDir()

shows the content of a directory

Example showDir.RFile(“remoteDirPath”);

lock()

locks a remote file to prevent multiple access. Return a id string for unlock the file. Remember that every lock have been a TTL associated (Default: 180000 ms).

Example lock().RFile(“remotePath”);

unlock(String lockKey)

if the file is locked, unlocks the remote file.

Example unlock(“key”).RFile(“remotePath”);

getTTL()

return the TimeToLive associated to a remote file if the file is currently locked

Example getTTL().RFile("remoteDirPath");

setTTL(int milliseconds)

reset the TimeToLive to a remote file that is currently locked. This operation is consented max 5 times for any file.

Example setTTL(180000).RFile("remoteDirPath");

getUrl()

return the url of a file stored in the repository

Example: getUrl().RFile(“remotePath”);

Sample Usage

The following code explains how to instatiate a client for do remote operation on the storage repository:

GCUBEScope scope = GCUBEScope.getScope("/gcube");
 // The Access type can be private | shared | public
IClient client=new StorageClient("ServiceClass", "ServiceName", "owner", AccessType.SHARED, scope).getClient();

The following code explains how to upload a new file in the storage repository:

String id=client.put(true).LFile("/home/rcirillo/FilePerTest/pippo.jpg").RFile("/img/pippo.jpg");

The following code explains how to download a file from the storage repository:

client.get().LFile("/home/rcirillo/FilePerTest/pippo.jpg").RFile("/img/pippo.jpg");

or alternatively, download the file by Id

client.get().LFile("/home/rcirillo/FilePerTest/pippo.jpg").RFileById(id);

The following code explains how to show the contents of a remote directory on the storage repository:

List<StorageObject> list=client.showDir().RDir("img");

The following code explains how to lock a file on the storage repository:

String id=client.lock().RFile("/img/pluto.jpg");

The following code explains how to unlock a file on the storage repository:

client.unlock(id).RFile("/img/pluto.jpg");

The following code explains how to remove a file on the storage repository:

client.remove().RFile("/img/pluto.jpg");

or alternatively, remove a file by Id

client.remove()..RFileById(id);

The following code explains how to remove a dir on the storage repository:

client.removeDir().RDir("/img");

Deployment

To release the library at a particular gcube scope you need to create only a generic resource that specifies the address of the server used for storing data. This is an example of generic resource used. The attribute "ip" of tag "service" specifies the ip of the server used for storing data.

<Resource version="0.4.x">
 
   <ID>99afe260-1f49-11e1-92b4-e7131d88e32e</ID>
 
   <Type>GenericResource</Type>
 
   <Scopes>
 
      <Scope>/gcube/devsec/devVRE</Scope>
 
   </Scopes>
 
   <Profile>
       <SecondaryType>StorageManager</SecondaryType>       <Name>MongoDBServer</Name>       <Description>Server MongoDB for StorageManager</Description>
 
      <Body>
 
         <server_list>
 
            <server ip="xxx.xx.xxx.xxx" port="" />
 
         </server_list>
 
      </Body>
 
   </Profile>
 
</Resource>

Example

Scenario 1

In this example a GCUBE service s1 (identify by: ServiceClass: sc, ServiceName: sn), running in the GCUBEScope /gcube upload the file: /home/xxx/FilePerTest/test.jpg in shared mode and another instance of the same service, s2 (identify by: ServiceClass: sc2, ServiceName: sn2) running in the same scope but on another node, download it.

The following code show the file uploading operation:

GCUBEScope scope = GCUBEScope.getScope("/gcube");
 // The Access type can be private | shared | public
IClient client=new StorageClient("sc", "sn", "s1", AccessType.SHARED, scope).getClient();
String id=client.put(true).LFile("/home/xxx/FilePerTest/test.jpg").RFile("/img/test.jpg");

The following code show the file downloading operation:

GCUBEScope scope = GCUBEScope.getScope("/gcube");
 // The Access type can be private | shared | public
IClient client=new StorageClient("sc2", "sn2", "s2", AccessType.SHARED, scope).getClient();
String id=client.get().LFile("/home/yyy/FilePerTest/test.jpg").RFile("/img/test.jpg");

The file is downloaded in the local directory: /home/yyy/FilePerTest/ where s2 is running and the file name is test.jpg

Scenario 2

In this example a GCUBE service s1 (identify by: ServiceClass: sc, ServiceName: sn), running in the GCUBEScope /gcube uploads the file: /home/xxx/FilePerTest/test2.jpg in shared mode, retrieve the url of the file uploaded by the method getUrl and passes it to another service s2 that is in running on another node. The s2 service retrieves the inputStream of the file that the service s1 had uploaded by the url:

IClient client=new StorageClient("sc", "sn", "s1", AccessType.SHARED, scope).getClient(); 
String id=client.put(true).LFile("/home/xxx/FilePerTest/test.jpg").RFile("/img/test1.jpg"); 
String url=client.getUrl().RFile("/img/test1.jpg"); 

The s2 service retrieve the inputStream of the file by the url stored in the "url" variable:

Handler.activateProtocol();
URL smsHome = new URL("smp://img/test1.jpg5ezvFfBOLqbElsh5xYVgBTxt8lwt4fl");
URLConnection uc = null;
uc = ( URLConnection ) smsHome.openConnection();
InputStream is=uc.getInputStream();