How to design HTTP API to push massive data?

I need to provide an HTTP API for clients to push massive data, in the shape of a set of records. My first idea was to provide a set of three calls, like:

• "BeginPushData" (no parameters, returns an Id),
• "PushSomeData" (parameters: id, subset of data, no return value)
• "EndPushData" (parameter: id)

The first call should be used to initialize some temporary data structure and give the user an identifier, so that subsequent calls can refer to it and data from multiple users don't mess up. The second call should be invoked as many times as needed, until all data is sent to the server. Finally, invoking the last call, the client confirms that all data has been pushed, so the server can process all the temporary data just stored.

In general, it's considered a good practice to conform to REST principles, but this strategy of uploading large data clearly violates the REST principle of being stateless. For this reason, I'm looking for some better alternative way of doing the job. References to well-known patterns would be appreciated!