Outreachy 2017 MayAugust

Introduction

QEMU is participating in Outreachy 2017 May-August. This page contains our ideas list and information for applicants and mentors.

How to apply

1. Read the Outreachy website first
2. Choose a project idea from the list below. You should have the necessary technical skills for the idea you have chosen.
3. Contact the mentor for your project idea to introduce yourself and discuss how you want to tackle the project.
4. Choose a small task from the BiteSizedTasks page and submit a patch contribution. See Contribute/SubmitAPatch for guidelines on patch submission.

Find Us

• IRC: #qemu-outreachy on irc.oftc.net

For general questions about QEMU in Outreachy, please contact the following people:

• Stefan Hajnoczi (stefanha on IRC)

Project Ideas

This is the listing of suggested project ideas.

Disk Backup Tool

Summary: Write a tool that performs both full and incremental disk backups

QEMU has added command primitives that can be combined to perform both full and incremental disk backups while the virtual machine is running. A full backup copies the entire contents of the disk. An incremental backup copies only regions that have been modified. Orchestrating a multi-disk backup to local or remote storage is non-trivial and there is no example code showing how to do it from start to finish.

It would be helpful to have a "reference implementation" that performs backups using QEMU's QMP commands. Backup software and management stack developers wishing to add QEMU backup support could look at this tool's code as an example. Users who run QEMU directly could us this tool as their backup software.

You need to be able to read C since that's what most of QEMU is written in. This project will expose you to backup and data recovery, as well as developing command-line tools in Python.

See the links to familiarize yourself with disk image files, backups, and snapshots.

Links:

• Backups (and snapshots) with QEMU, KVM Forum 2016 (PDF)
• Incremental Backups, KVM Forum 2015 presentation (PDF)
• Features/IncrementalBackup

Details:

• Skill level: intermediate
• Language: Python
• Mentors: John Snow <jsnow@redhat.com> (jsnow on IRC), Stefan Hajnoczi <stefanha@redhat.com> (stefanha on IRC)

Moving I/O throttling and write notifiers into block filter drivers

Summary: Refactor the block layer so that I/O throttling and write notifiers are implemented as block filter drivers instead of being hardcoded into the core code

QEMU's block layer handles I/O to disk image files and now supports flexible configuration through a "BlockDriverState graph". Block drivers can be inserted or removed from the graph to modify how I/O requests are processed.

Block drivers implement read and write functions (among other things). Typically they access a file or network storage but some block drivers perform other jobs like data encryption. These block drivers are called "filter" drivers because they process I/O requests but ultimately forward requests to the file format and protocol drivers in the leaf nodes of the graph.

I/O throttling (rate-limiting the guest's disk I/O) and write notifiers (used to implement backup) are currently hardcoded into the block layer's core code. The goal of this project is to extract this functionality into filter drivers that are inserted into the graph only when a feature is needed. This makes the block layer more modular and reuses the block driver abstraction that is already present.

This project will expose you to QEMU's block layer. It requires refactoring existing code for which there is already some test coverage to aid you.

Links:

• I/O throttling code
• Write notifier code
• Implementing New Block Drivers: A QEMU Developer Primer, KVM Forum 2013 (video)

Details:

• Skill level: intermediate
• Language: C
• Mentor: Kevin Wolf <kwolf@redhat.com> (kwolf on IRC), Stefan Hajnoczi <stefanha@redhat.com> (stefanha on IRC), Alberto Garcia (berto on IRC)

Project idea template

=== TITLE ===
 
 '''Summary:''' Short description of the project
 
 Detailed description of the project.
 
 '''Links:'''
 * Wiki links to relevant material
 * External links to mailing lists or web sites
 
 '''Details:'''
 * Skill level: beginner or intermediate or advanced
 * Language: C
 * Mentor: Email address and IRC nick
 * Suggested by: Person who suggested the idea

Information for mentors

Mentors are responsible for keeping in touch with their candidate and assessing the candidate's progress.

The mentor typically gives advice, reviews the candidate's code, and has regular communication with the candidate to ensure progress is being made.

Being a mentor is a significant time commitment, plan for 5 hours per week. Make sure you can make this commitment because backing out during the summer will affect the candidate's experience.

The mentor chooses their candidate by reviewing candidate application forms, giving out bite-sized tasks so applicants can submit a patch upstream, and conducting IRC interviews with candidates. Depending on the number of candidates, this can be time-consuming in itself. Choosing the right candidate is critical so that both the mentor and the candidate can have a successful experience.