[TAJO-367] Separate the locality information from Fragment

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Component/s: QueryMaster, Storage, Worker
• Assignee: Unassigned
• Reporter: Jihoon Son
• Created: 03/Dec/13 05:06
• Updated: 13/Jul/16 12:36
• Resolved: 13/Jul/16 12:36

Description

Fragment is designed to represent a portion of the abstracted input source.
However, since It is currently used for the task scheduling and the task allocation, it includes the locality information as well as the abstraction of the input data.
The locality information is used only in the task scheduling, and thus the locality information should be separated from Fragment.

The locality information is used in the task scheduling to assign tasks to workers closes to the data regardless of the kind of the storage layer.
To consider input data and their locality in the task scheduler, we need to design a new class including a Fragment and the locality information such as FragmentWithHost.

In this issue, following works should be resolved.

• Removing the host information from FileFragment
• Creating a new class FragmentWithHost that contains an instance of the Fragment interface and the locality information consisting of hosts and disk ids
• Refactoring SubQuery, StorageManager and TaskScheduler to use FragmentWithHost

Issue Links

• requires: TAJO-337 Tajo Generic Storage Support