Re: GCoS2019--pgBackRest port to Windows (2019)

Hello Youssef,

On 4/1/19 5:16 PM, Youssef Khedher wrote:
> Hello,
> 
> I’m Youssef Khedher, 19 years old student from Tunisia.
> 
> I’m a computer science student in Tunisia, and also an online student 
> for Harvard CS50 Program.
> 
> I’m interested in the ” pgBackRest port to Windows (2019)”.

Excellent!

 > To be frank with you, I’m not an expert in C

You'll need to be able to understand and modify many areas of the C code 
in order to be successful in this project.  I would encourage you to 
review the code and make sure you are able to follow what it's doing in 
general before submitting an application:

https://github.com/pgbackrest/pgbackrest/tree/master/src

I don't think you'll be writing a bunch of new code, but anything is 
possible when porting software.

> In order to achieve the project goal, all I need from you MR. Stephen 
> Frost or MR. David Steele is some help to understand perfectly the task 
> and to help me enter to world of software development.

For this project it's important to have knowledge about how Windows 
differs from Unix, e.g. the way child processes are spawned.  In the 
core code we only use fork() with an immediate exec(), so this should be 
straightforward enough to port:

https://github.com/pgbackrest/pgbackrest/blob/master/src/command/archive/get/get.c#L235

We also use fork() quite a bit in our testing and I was thinking the 
HARNESS_FORK*() macros could be enhanced to use threads instead on Windows:

https://github.com/pgbackrest/pgbackrest/blob/master/test/src/common/harnessFork.h

If not, then the tests will need to be adjusted to accommodate whatever 
testing method is developed.

pgBackRest uses SSH to communicate with remote processes:

https://github.com/pgbackrest/pgbackrest/blob/master/src/protocol/helper.c#L288

Eventually we would like to move away from requiring SSH, but for this 
port I think the best idea would be to get pgBackRest working with some 
open source SSH solution such as OpenSSH (which is easily installed on 
recent versions of Windows, but not sure about older versions).  If 
there is time at the end we might look at alternate solutions.

There may be other minor areas in the code that need be adjusted or 
#ifdef'd to work with Windows.  We've tried to keep this to a minimum by 
enforcing C99 and Posix standards, but there will be some differences. 
The config code that enforces Unix path structure is an obvious area 
that will need to be updated:

https://github.com/pgbackrest/pgbackrest/blob/master/src/config/parse.c#L1034

Note that we want to port to native Windows without the presence of 
Cygwin (or similar) in production.  My preference would be to use 
something like Strawberry Perl for testing, and then as few dependencies 
as possible for the production distribution.

A CI testing platform for Windows will need to be selected -- mostly 
likely AppVeyor.

The documentation will also need to be updated for Windows.

You should delve into the areas mentioned above and propose possible 
solutions when writing your proposal.  Feel free to ask questions.

Porting code from one platform to another can be quite complicated, but 
we believe this project can be accomplished over the summer by a skilled 
and motivated student.

If you are interested in proceeding, you should create an issue here:

https://github.com/pgbackrest/pgbackrest/issues

We do our development on Github and issues are the way we discuss 
projects, enhancements, and bugs.

Good luck!
-- 
-David
david@pgmasters.net