[MESOS-3112] Fetcher should perform cache eviction based on cache file usage patterns.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.24.0
• Component/s: fetcher
• Labels: mesosphere performance
• Target Version/s: 0.24.0
• Epic Link: Fetcher Cache
• Sprint: Mesosphere Sprint 15
• Story Points: 8
• Assignee: Jan Schlicht
• Reporter: Bernd Mathiske
• Shepherd: Bernd Mathiske
• Created: 21/Jul/15 11:19
• Updated: 26/Nov/18 12:21
• Resolved: 26/Nov/18 12:21

Description

Currently, the fetcher uses a trivial strategy to select eviction victims: it picks the first cache file it finds in linear iteration. This means that potentially a file that has just been used gets evicted the next moment. This performance loss can be avoided by even the simplest enhancement of the selection procedure.

Proposed approach: determine an effective yet relatively uncomplex and quick algorithm and implement it in `FetcherProcess::Cache::selectVictims(const Bytes& requiredSpace)`. Suggestion: approximate MRU-retention somehow.

Unit-test what actually happens!