In a DVCS, each developer has an entire repository on their workstation, to which they can commit all their changes. Then they can merge their repo with someone else's, or clone it, or whatever (as I understand it, I'm not a DVCS user).
To me that flags a side-effect, of being more vulnerable to forgetting to backup. In a traditional centralised system, both you as a developer and the people in charge know that if you commit something, it's held on a central server which can have decent backup solutions in place.
But using a DVCS, it seems you only have to push your work to a server when you feel like sharing it. It's all very well you have the repo locally so you can work on your feature branch for a month without bothering anyone, but it means (I think) that checking in your code to the repo is not enough, you have to remember to do regular pushes to a backed-up server.
It also means, doesn't it, that a team lead can't see all those nice SVN commit emails to keep a rough idea what's going on in the code-base?
Is any of this a real issue?
I can understand your concern about devs forgetting backups once their local diff is gone (because they've committed locally) and stops nagging them with copious output. I think the solution can lie in better tools, moar tools! You could set up a cron job on each dev's box that pushes every last reachable object in their repository to the central repo, and labels them in the central (backed-up) repo with namespaced branches. I think "git push" can do this, given the correct refspec. Then, all you aren't doing is affecting the state of your public branches.
But do you really need as aggressive a backup process as before, when the repo existed only in one place? With a DVCS, you need a far higher category of catastrophes to lose all your code. You now need an asteroid or a bomb hitting your office (and all your off-site team members), instead of just a hard disk or RAID controller going bad. Note, I'm not advocating sloppiness; I'm advocating equal risk at lower cost.
I don't think you have an automatism on this. Distributed or centralized VCS can be combined with backup (or not). It's all a question of discipline in the team.
Same for commit-emails. If the team has the discipline to regularly push changes to the right repositories, you can have a working commit-mailinglist too.
Bad habits also can grow in a team with centralized VCS. You have always to fight bad habits.
In most places I imagine that there is probably still a 'central' repository from where builds are made and put to test. If you want your code in the build, it's got to be pushed centrally.
This is also a management issue - tell your team - push regularly (at least daily) so that your code is backed up. If it's not being done, then get out the big stick.
I'd also note, that if you're relying on looking at the commits to see what your staff are doing, you probably have some larger issues that you might look at addressing...
Having a local copy of the repository might encourage poor backup habits, if one were slack. However, your master repository SHOULD be backed up.
The "local copy of the entire repository" has a much more important use than being a backup. It reduces the latency of examining the history of the codebase - say, diffing against the latest version - from being a network round trip to a trip to your local hard drive.
That doesn't sound all that big a deal if your main repository's on your gigabit LAN. If you're a telecommuter, and the repository's a good 600+ ms away over a VPN, it makes a world of difference.
I've never looked into it, but I'm sure both Mercurial and Git support post-commit hooks, allowing you to set up commit mails going to the team lead. Then each developer could set up her repository accordingly, or have an interim repository that permits half-baked features with the commit mails, or whatever.
Edit: Regarding John's comment about a long-running experiment being lost because it wasn't ready to commit to the master repo: work in a separate branch and regularly push your changes to the master. You still get all the benefits of working against a local repository (mainly, for me, very low latency), and still not annoy your colleagues with your half-baked feature... and you can still store your changes off your machine, in a place where your admin can properly back up the repository.
Related
Suppose I have a following situation. Long ago I published some useful code on Github and a lot of people forked it since then. Now I find some really serious error (like a buffer overrun) in my code and fix it and I realize that all forks should better have that fix, otherwise Bad Things™ might happen.
How do I notify owners of all forks that there's this critical change they'd better pull?
An upstream repo doesn't really know about its downstream repo (see "Definition of “downstream” and “upstream”").
And you cannot make a pull request to a fork (that wouldn't scale well anyway).
So the easiest was is to count on the other developers to update their local clone with your latest changes, which will include your latest fixes.
You can update your README.md for all to see, but you cannot really "broadcast" to all the forks (not to mention all the direct clones you have no knowledge about).
Anyway, if they want to contribute back, you will reject any pull request which isn't fast-forward.
That means they will have to rebase their work on top of the latest from "upstream" (your repo), before pushing to their fork and making said pull request.
We've decided on a version control system - using Mercurial clients and Bitbucket for repositories. But it's just occurred to me we have a problem I didn't consider.
We have an internal development LAMP server (Ubuntu) and all the developers work on websites stored on it, which means all developers share a single file source and we are all working from it. It's rare that two different developers will work on the same site at the some time, but it does happen occasionally. This means that two developers can easily overwrite each others work if they are working on the same file at the same time.
So my questions is: what is the best solution to this problem? Bearing in mind we like the convenience of a single internal server so that we can demo sites internally, and it also has a cron job running for backing up the files and databases.
I am guessing each developer would have to run their own LAMP (or WAMP) servers on their individual workstations, commit, and push to bitbucket repository. And of course whenever working on a different site, do a pull and resolve any differences as per usual. This of course takes away the convenience of other team members (non developers) being able to browse to 192.168.0.100 (the LAMP server IP address) and looking at the progress of websites, not to mention that some clients can also access the same server externally (I've set up a port forward and limited to their IP addresses) to see the progress of their websites too.
Any advice will be greatly appreciated.
Thanks in advance.
I think, you have to seriously re-think about used workflow, because LAMP-per-dev is only slightly better than editing sites in-place
I can't see place for Bitbucket in serious corporate development - in-house resources are at least more manageable
I can't see reasons don't use Staging Mercurial-server (pseudo-central) with Staging internal LAMP-server (which you have and use now)
I can imagine at least two possible choices (fast, dirty, draft idea, not ready-to-use solution), both are hook-based
Less manageable, faster for implement
Every developer have in own local repo hook, which after (each?) commit export his tip and copy exported to related site space. Workflow: commit - test results on internal site
Advantages: easy, fast to implement
Disadvantages: Can't prevent (due to distributed nature) overwriting of tested code by code from another developer
Manageable deploy, harder to implement and manage
LAMP-server become also Mercurial-server, which hosts "central" clones of all site-repos, updated by push only from developer local repo. Each repo on this server must get two hooks:
"before-push" checks, is it allowed to push now, or site "locked" by previous developer
"post-push", which export-copy received data and perform also control function for hook 1: based on conditions (subject of discussion) lock/unlock pushes to repo
Workflow: commit - push - test results - tag WC with special (moved) tag - commit tag - push unlocking changeset into repo
Advantages: manageable single-point testing
Disadvantages: possible delays due to push-workflow and blocking of pushes. The need to install, configure, support additional server. Complexity of changegroup and pretxnchangegroup hooks
Final notes and hints for solution 2: I think (not tested), special tag (with -f for movement across changesets) can be used as unlock sign (bookmark will not satisfy condition "move by hand"). I.e - developer commit (and pushes) non-tagged changeset, tag (f.e) "Passed" mark some older changeset. When testing results on Staging server is done, developer tag WC with the above tag, commit tag and pushed to central repo. changegroup hook must detect pushing of .hgtags and (in some-way) allow future data-pushes (control-pushes must be allowed always)
Yes, the better solution is probably to set each developer up with a local server. It may seem inconvenient to you because you're apparently used to sharing a server, but consider:
If you're really interested in using a single server as a demo server, it's probably better that people aren't actively working developing on it at the time. They could break stuff that way! And developers shouldn't have to worry about breaking stuff when they're developing. Developing often means experimenting.
Having each developer running their own server will give them flexibility to, say, work disconnected. You've got a decentralized version control system (mercurial), but your development process is highly centralized. Even if you don't want people to work remotely, realize that when your single server goes down now, everybody goes down.
Any time a developer commits and pushes those commits, you can automate deployment directly to your demo site. That way, you still have a quite up-to-date source on your demo server.
TL;DR: Keep the demo server, but let your devs work on their own servers.
The situation is as follow :
Our company works two main production sites, communicating via WAN. We develop a software internally which uses about 100Gb of disk space on our servers (application data deployed to our customers with a lot of images). In order in improve performance, our network administrators choosed DFS replication (every 6 hours). This means that our users (people from within the company) do not have to wait (sometimes 2-3 hours) to download the needed files, because they are available locally (over LAN).
The problem is that the algorithm used by DFS replication is "Last Writer Wins". So, in case of simultaneous changes (during development/maintenance), the file with the latest date will win. I would like to avoid such data loss.
I am project manager for the overall develop process. What I want to do, is to introduce people to version control systems to tackle the simultaneous modifications problem. I plan to use Mercurial for several reasons, mainly because it is distributed, simple to explain, usable for personal use, free, and (most importantly) has great merging capabilities. However the benefits of the version control system when used locally (LAN) is lost because of the replication process (WAN) which doesn't know how to merge.
Some possible solutions are to :
use only version control over the WAN (hoping that compression will be enough to speed things up)
use only DFS, and track changes manually (error-prone)
find a work-around with both methods
The team is small (about 10 persons). Your help and experience is appreciated.
If it were me, I'd have a "central" repository at each location, with the developers from each site working on a different branch. One of those should probably be chosen as the "main" branch (ideally the one that will be making the most changes), although in practice it won't really matter much.
Each team's repo should be synchronized regularly (e.g., daily, on your 6 hour schedule, or even more often) with the repo from the other location, to reflect changes made in that branch. Then they would be merged to the site's branch (ideally this would be done automatically as part of the same update, but the exact details of how that merge will happen may vary, depending on your VCS of choice and your branching model).
Remember: "sync early, sync often"
I'm currently signed up with a third party service that hosts my mercurial repositories as a central hub to push my changes to as a sort of backup.
Now, I'm looking at a system to backup my laptop and am concidering Mozy. I'm a loan developer, and work on a laptop and am usualy connected to my internet via wifi with my laptop only really being on when I'm working, so feel something like Mozy is my best option.
My question is, if I'm the only developer, could I get away with just using local mercurial repos and using Mozy to backup everything up? Rather than pushing to an external repo?
Many thanks
Matt
Disclaimer: My experience is with git rather than hg, but as I understand it the concepts apply equally to both systems.
An advantage of backing up to a remote repo is that if your local repo becomes corrupted (perhaps due to a problem with the underlying filesystem), that corruption does not get transferred over to the backup, unless the files in your working tree themselves are corrupted.
For example, it's possible for some of the objects in the repository, perhaps those which are rarely accessed because you don't change them, to become corrupted. It could be months before you use one of those files again, and so months before you notice (though I think doing a garbage collect run, eg git gc, will detect corruption).
So if you are backing up by pushing commits, you're creating an independent version of those objects, and using checksums (ie the commit hash) to verify the transfer of any new files. Whereas if you are backing up to a backup provider, you're duplicating the actual objects in the repo, in whatever state they are in, and duplicating any changes to those files, including corruption of them.
Usually backup providers will give you rollback (spideroak seems to be particularly good for this) but you'll still have to sift through a lot of versions to figure out when the corruption happened; also with some providers, the rollback period is limited (especially for free accounts).
We've got two developers on the same closed (ugh, stupid gov) network, Another developer a couple minutes drive down the road, and a fourth developer half-way across the country. E-Mail, ftp, and removal media are all possible methods of transfer for the people not on the same network.
I am one of the two closed network developers, consider us the "master" location.
What is the best Mercurial setup/pattern for group? What is the best way to trasmit changes to/from the remote developers? As I am in charge, I figured that I would have to keep at least one master repo with another local repo in which I can develop. Each other person should just need a clone of the master. Is this right? I guess this also makes me responsible for the merging?
As you can see, I'm still trying to wrap my head around distributed version control. I don't think there is any other way to do this with the connectivity situation.
Patches are a simple and versatile solution.
For moving around larger groups of changes (especially binary changes and merges), Mercurial offers binary bundles. A bundle is basically the binary stuff that is sent on the network when you do hg push, but here it is captured in a file.
Let's imagine I have gotten a clone somehow (by flash drive, DVD, etc.). Call it upstream. I then make a second clone, call it devel. I do all my development in devel and make lots of commits, merges, etc. Since Mercurial is distributed I can do all this offline.
To see which changesets are missing in upstream I do
% hg outgoing ../upstream
When I have something to send, I can use
% hg bundle changes.hg ../upstream
to get a binary compressed file which contain the changesets including all their meta data. I can then burn this file on a CD and send it by mail...
The recipient of the bundle can do
% hg incoming changes.hg
to see the changeset list and
% hg pull changes.hg
to unpack and add the changesets to his repository. He will then most likely have to merge -- this is exactly as if he had pulled directly from your repository over HTTP or SSH.
Note, the upstream repository is only used as a convenient way to remember which changesets are already found in the upstream repository. You can also just jot down the changeset ID and use hg bundle --base when bundling to specify the base (common) changeset. See hg help bundle or look in the wiki.
The users outside the network can make patches, and/or use email to send the updates to the main repo or someone, like yourself to merge them. The other internal people can have local copies, like yourself and do merges --but if you are having these out of network patches, it might be better that one person deal with them so nobody gets confused, but that's something you'd have to consider yourself.
Syncing the other way, you'd create a patch, and them email or get a flash drive to the remote developers to patch their system. You're going to need some good communication in the team man, I am thankful I'm not in your shoes.
Those are my only suggestions --well, the obvious, get them a VPN connection! I'd love to hear how it goes, what plans stabilize into a weekly groove, et cetera.
Correct. The only way anything makes it onto the closed network is via flash drive.