Distributed Media Storage/Internship report/Final UML design

Component model

Component model

Logical model

Logical model

Controller

Logical model: Controller

Replication

Logical model: Replication

HTTP Service

Logical model: HTTP Service

Index

Logical model: Index

Node Web

Logical model: Node Web

Object Store

Logical model: Object Store

Object

Logical model: Object

Configuration

Logical model: Configuration

Monitoring

Logical model: Monitoring

Dynamic model

Replication

Dynamic model: Replication

Dynamic model: Object replication

Request flow: retrieve

Dynamic model: Retrieve flow in the SQL controller model

Dynamic model: Retrieve flow (continued)

Request create

Dynamic model: Request create

Control flow

The HTTP component of a node can return a variety of HTTP response code to indicate the success or failure of the operation. These HTTP control codes are to be interpreted by either the client library or another node, acting as a client. The codes can be interpreted and acted on differently, depending on the context and state.

• OK
• CREATED

These should be returned when the system successfully answered the GET request (in case of OK), or has successfully added the object to the system in response to a PUT/POST request (in case of CREATED).

• NOT_FOUND

In case of a recursive (client library -> node) request, this should be interpreted as a definite "object does not exist in the system" message. In case of a non-recursive (node -> node) request, this means that the node node in question does not have the object, but it may or may not exist elsewhere in the distributed system.

• GATEWAY_TIMEOUT

The answering node in question could not contact any of the nodes that (should) have the requested object.

• SERVICE_UNAVAILABLE

The node encountered some unspecified problem that does not allow it to offer the requested service. This may or may not imply a global problem.

• CONFLICT

The object offered in a PUT/POST request already exists in the system.

Abstract error situations

• Index not found
• Index lookup failure
• Storage not found
• Storage conflict
• Storage retrieval failure
• Storage write failure
• Forward gateway timeout

• No available nodes

• Operation completed