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Feature Proposal: Deprecate RCS Directories Feature

Motivation

Bugs:Item4863

Description and Documentation

We have - on "paper" - a feature where you can configure TWiki to save the RCS files (the files that ends by ,v) in sub directories.

We also know it is broken.

We do not know how long it has been broken (someone should find out)

In the Bugs:Item4863 and at the GeorgetownReleaseMeeting2008x03x03 all developers agreed that we should remove the feature again.

It was introduced to help on performance when you get too many files in same web. But it is only a factor 2 it gives then you have the problem again and we are not sure it really helps anyway.

In TWiki 5.0 we have plans to change the way TWiki gets its data anyway so fixing this seems a waste.

UNLESS some customers already use it AND NEED IT. (Customers are polled via blog entry)

For an upgrader to 5.0 all you need to do is to copy the ,v files back in the same directories where you find the .txt files.

There may be additional work on attachments. We should in that case provide the needed shell command to aid an upgrader.

But since the feature is broken and noone has reported it until recently there may not be manay that actually use it.

Impact

WhatDoesItAffect: Install

Implementation

Remove the bits of code and remove the doc that says you can do this. In the first step we can just remove the configure setting from the spec file.

This is a serious non-compatible step which CAN have impact so the agreement per release meeting is that I raise the proposal, raise a blog post, we include this in the news letter and we pull back the proposal if we get negative reactions. This also means that I raise concern against my own proposal to stop the 14 day clock

-- Contributors: KennethLavrsen - 04 Mar 2008

Discussion

The tradeoff here is between the effort required to remove the code, versus the effort required to get it working. Removing the code has three risks:

  1. Someone is using it, and throws a wobbly when it disappears.
  2. The project loses an obvious opportunity for a performance hike.
  3. Removing the code silently breaks something else.
To get it working requires:
  1. The RcsTests to be extended to re-run all the tests with the relevant configure setting enabled
  2. The code to be fixed (which I suspect is trivial)
If there is a genuine performance advantage, then we have to ask the question why isn't this the default for new installs? It can still be made the default, because as you point out an upgrade is a simply matter of moving existing ,v files to a new structure. But it's only worth doing if there is a significant performance advantage; something which AFAICT no-one has tried to determine.

-- CrawfordCurrie - 05 Mar 2008

Thanks Kenneth for raising this in the proper way. The customer gets time to provide feedback so that we can make an informed decision.

FWIW, on performance, ColasNahaboo posted an interesting link on file system performance: http://ygingras.net/b/2007/12/too-many-files%3A-reiser-fs-vs-hashed-paths

-- PeterThoeny - 05 Mar 2008

The performance advantage of separating txt and ,v will start to kick in at a number of topics twiki isn't able to deal with in a single web anyway, for other reasons. If you do have such large webs, you'd better don't use a filesystem based storage like rcs.

-- MichaelDaum - 05 Mar 2008

I'm pretty sure it has never worked. And it has been reported before.

In mid 2003 I set up a brand new twiki installation with rcsdirs. I reported a problem in the Support web, and was then informed that it does not work and cannot be made to work.

See RevisionRevertsTo1 and NoRcsIncrementalPastFirstOne

-- SueBlake - 11 Mar 2008

its not just that there are problems with the data dir files - in the pub dir, TWiki fails to work out the correct location of the ,v files, not only when uploading, but also for web creation, and does not fall back to looking in the non-RCS dir just in case.

Then to make matters worse, if you do have some RCS dirs, and then decide to stop using them, you have to go through all the pub dirs and move the ,v files... its a mess :/

I doubt that many plugins do the right thing either - sadly, this feature is just asking for trouble - so the sooner it goes, the safer the world will be.

-- SvenDowideit - 18 Mar 2008

... and template webs being shipped with one or the other RCS style.

-- MichaelDaum - 18 Mar 2008

I think we have a clear conclusion.

This feature will not be attempted repaired. Instead it will be removed.

I will take on that task.

As also discussed at release meetings, the feature can be removed because it never worked so it cannot harm anyone to remove it.

-- KennethLavrsen - 07 Apr 2008

Good analysis, decision and action.

-- PeterThoeny - 09 Apr 2008

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Topic revision: r10 - 2008-04-09 - PeterThoeny
 
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