How can multiple engineers work on same DB with alembic? - alembic

We have a few engineers all working on the same database.
When one runs alembic revision -m 'name'
We get
FAILED: Multiple heads are present; please specify the head revision on which the new revision should be based, or perform a merge.
Not asking how to solve the direct message, but rather the pattern.
Not really concerned with merge conflicts, more with the ability to work and add items without having to fiddle around a bunch.
How is the person to know which revision to use?
Is there a way to get around this?
We have a similar issue in the context of a production database. If we have multiple pull requests merging to master, then we want to update the production db near when the pull request merges. But the revision identifiers from say a sandbox db won't match. So the whole (revision id concept) just feels confused then?
Is there a whole different approach to using it for production vs development?

Related

Managing github repository while multiple people are making changes to the same file

I have a GitHub repo that has multiple contributors making changes at the same time. I'm having conflicts with merging pull requests because by the time someone wants to submit changes they've made to be reviewed, someone else who had been working on a portion of the code in the same file will end up having an outdated repository on their local device. Whenever they plan to make their pull request with the changes, the repository had already been changed.
What is the proper way to submit changes through the command line before making a pull request to ensure you have the updated repository and the changes on your local device arent removed by re-pulling?
How should I properly be instructing my team to make changes to my repository while avoiding conflicts of files being updated?
What steps should I be taking when reviewing pull requests to make sure I am merging properly?
This is a very common scenario with version control tools like GitHub. There is NO solution to avoid merges completely, being in the same repository but there are a few ways that can help you reduce merges:
If possible, restructure your repo and make it modular for different teams.
See if you can use the concept of a common library and rearrange contents in various smaller repositories.
THE BEST way is to ask all contributors to make small and very frequent changes. This will increase no. of pull requests but it will make review quick for reviewers. And you also need to ensure there is no pipeline being formed for pull request review.
Thanks!

DVCS strategies for mixed-role small team?

I've done a lot of reading, and have been trialing GIT, GIT Tortoise, Tortoise SVN and PlasticSCM, to find the right source control for our small team (5-10 users).
Some background on our team: 6 copy writers/editors (2 remote), 2 developers, 2 graphic designers. We are not always working on projects together, sometimes up to 5 of us might be working on a given project. I'm unconcerned about the developers with DVCS, my concern is mainly around the other roles who are (in the nicest way) limited in their technical capability. Some of our copy writers update multiple source files (HTML, PDFs and adding concept graphics) to live, unversioned build directories (backed up as build.23.06.11.new.new.final.zip!). The copy and GD team will not have time, or to be brutally honest, the inclination to merge/resolve conflicts, or probably even remember to switch branches.
A few SO questions have shed light on what what seems to be a fairly consistent approach - main trunk (no junk in the trunk!) with teams having their own branches, and having release branches etc.
Every time I've re-read the links...
https://stackoverflow.com/questions/3854583/version-control-system-for-small-in-house-team
Getting started with Version Control
http://svn-ref.assembla.com/subversion-how-tos.html
...and google in general, I still end up asking myself the same questions:
Is it a Bad Idea to create role-specific branches for "trouble points" (copy team), where they can push to the repo, then our developers will merge their work into the actual project branch?
Should I still try to enforce a task-per-branch for everyone else?
Should I do task-per-branch for everyone but let the copy team create very broad tasks?
Is there usually a team/group/person who is considered an "admin" role for a repo who does crucial merges?
(is there an alternative suggested workflow where copy writers don't touch source?)
Unfortunately, the copy teams play a vital role in updating files which in turn affect layouts and all sorts of things, on a continual basis during dev. Its not like I can keep them in a bubble until the end of a project and chuck their work in.
... the good news is that hopefully, after a number of years, I'm ready to force everyone to move to version control! We've also settled on PlasticSCM for its intuitive GUI and Windows integration.
The best answer to this question would try to answer the 4 points above - tackle point 5 if you like - explain weak points if possible, and provide advice, gotchyas, etc.
cheers!
So basically you want to know how to get team-member of different skill-levels to use SCM and play nice with each other.
Buy-in from your team is priority #1. If you can't make them learn it, then you're left with providing a path of least resistance. So you really need to be flexible. There might be a wrong-way and a right-way to use the tool, but if the users won't accept the right-way, then the wrong-way is better than them not using it at all. How you achieve this balance is going to be different for every team.
Is it a Bad Idea to create role-specific branches for "trouble points" (copy team), where they can push to the repo, then our developers will merge their work into the actual project branch?
No, maybe its not optimal, but if this makes it easy for the Copy Team, then thats what you're left with. You could probably go even further and setup each user with their own branch. Then they never have to worry about merging other peoples changes.
Should I still try to enforce a task-per-branch for everyone else?
Each dev should have a unique "local" branch, that is not tracking an upstream branch. For example, use something generic like mydev. This makes it easy for them to switch between their local code and the current upstream branch.
You don't necessarily need to force everyone to create a local branch for every task, cause in the end, you're going to want them just to rebase their working branch onto the upstream one, and commit so it just becomes a fast-forward (i.e. linear commit).
Now for tasks that multiple devs are working on, or it is a feature that involves groups of smaller commits, then yes it does make sense to force them to create a new specific task branch. When they merge they can make sure to force a merge-commit, then it is clear that a set of commits are grouped together and all were part of a specific task. The merge commit will display like merged branch feature-X.
Should I do task-per-branch for everyone but let the copy team create very broad tasks?
It's really up to how much buy-in you can get from the Copy Team. I think if they really get confused with the DVCS tools, then you have to scale back until you can find something that does not cause too much of an impact.
One solution, is to have one of your devs help integrate the Copy Teams changes into another branch that everyone else will look at. That will help offload the learning-curve of the tool onto someone outside of the Copy Team.
Is there usually a team/group/person who is considered an "admin" role for a repo who does crucial merges?
Yes, this makes sense. However the great thing about SCM, is that everyone will be able to go back and do a code review on a merge. So if a merge breaks the code, you can either append the corrections after the merge, or remove the merge, and do it over.
(is there an alternative suggested workflow where copy writers don't touch source?)
Well, one possible technique is the Integration Manager model. The developers commit changes to their own share repos, but its up to the integration manger, to merge in the changes to the blessed repository.
I'm sure there are other methods that might work for your users, but this question is slightly ambiguous.

Mercurial: Indicating that a branch has passed testing?

I am working on establishing a workflow at my company if we were to migrate to DVCS (most likely Mercurial). One of the things I would like to do is to have a repository for QA. The idea being that each developer works on a branch and when they are done the branch is pushed to QA. From there the test team can do their testing and report back any bugs. Once the branch is fully tested and acceptable it will be pushed to a staging repository where the merge back to the mainline will happen before pushing to the central repository.
This can work quite easily if everyone just communicates the status of their work in some way, but I know this doesn't always happen as you would want it to. What I am worried about is branches in the QA repo waiting around but nobody knows if it is waiting to be tested, currently being tested, waiting for fixes, waiting to be pushed to the staging area etc. So what I am looking for are ideas of how a status can be added to a branch? What would also be good would be to do it in a way that we could use hooks to also notify people of changes in the status.
Any ideas would be appreciated.
Unfortunately I think you need a different system to keep track of this part of your workflow.
A repository consists of things that aren't supposed to change all willy nilly, yet the current Q&A status will by necessity change orthogonal to the contents of the repository.
Let me rephrase that. You have 10 changesets in the Q&A repository, ready to be tested. Exactly what each tester focuses on, the status of each test, etc. will change, even though those 10 changesets stay the same.
I would definitely try to use a bugtracking system where you can integrate the repository history in some way, even if it is just by linking an issue in the system to its changeset.
I notice your comment about not getting support for buying Kiln, but there are other systems you should be able to integrate that would give you something similar.
I would very much resist trying to press Mercurial into service of something it wasn't built to support, trying to use tags for this would fail miserably, and bookmarks would give you problems, as you've already noted.
So again, try to find a separate system for keeping track of Q&A status.
One simple method might be to keep a metadata file in your repo's root folder, named .teststatus or somesuch, that looks like:
# branch-name, last passed revision
default, 0123456789ab
stable, 0123456789ac
bobs-dev-branch, 0123456789ad
marys-dev-branch, none
Using tags or bookmarks would feel like a sort of abuse, here. You couldn't use the same tag across branches (e.g. passed would have to be stable-passed), and tags are generally not moving. Bookmarks, on the other hand, are intended to move, but you still have the branch-namespacing issues.
Joel Spolsky, one of the founders of this site, produces a program called FogBugz that is integrated with Mercurial and makes it easy to keep track of everyone's status.
I'm not completely sure how your workflow works, but here are a few ideas:
Tags.
Use named branches and close the branch when tested.Typing hg branches will show you which branches are still pending.
You could probably use an incoming hook for the automatic notification of new changesets being added to the QA repo.
Why would a developer push something to a QA repository if it wasn't ready to be QA'd? I think the act of pushing changesets to a QA designated repository should be the signal that the feature is ready to be tested.
Feature branches by cloning is my favorite approach.

Good github structure when dealing with many small projects that have a common code base?

I'm working for a web development company and we're thinking about using GitHub for version control. We work with several different .NET-based CMS-platforms and of course with a lot of different customers.
We have a standard code base for each CMS which we start from when building a new site. We of course would like to maintain that and make it possible to merge some changes from a developed site (when the standard code base has been improved in some way).
We often need to make small changes to a published site at a later date and would like to be able to do this with minimal effort (i.e. the customer gladly pays for us to fix his problem in 2 hours, but doesn't want to pay for a 2 hour set up first).
How should we set this up to be able to work in an efficient fashion? I'm not very used to distributed version control (I've worked with CVS, Subversion and Clear Case before), but from my imagination we could:
Set up one repository for each customer, start with a copy of the standard code base and go from there. Lots of repositories of course.
Set up one repository for each CMS and then branch off one branch for each customer. This is probably (?) the best way, but what happens when we have 100 customers (=branches) in the same repository? It also doesn't feel entirely nice that we create a lot of branches that we don't really have any intention of ever merging back to the main branch.
I don't know, perhaps lots of branches is only a problem in my imagination or perhaps there are better ways to do this that I haven't thought about. I would be interested in any experince in similar problems.
Thank you for your time and help.
With Git, several repos make sense for submodules purpose (sharing common component, see nature of Git submodules, in the third part of the answer)
But in your case, one repo with a branch per customer can work, provided you are using the branches to:
isolate some client-specific changes (and long-lived branch with no merging back to master are ok),
while rebasing those same branches on top of master (which contains the common code, with common evolutions needed by all the branches).

Version control best practices

I just made the move to version control the other day, and after a bad experience with Subversion, I switched to Mercurial, and so far am happy with it.
Although I understand and appreciate the idea of version control, I don't really have any practical experience with it.
Right now, I am using it for a couple websites I am working on, and a couple questions have come to mind:
When/how often should I commit? After any major change, whether it works or not? When I'm done for the night? Only when it reaches it's next stable iteration? After any bugfixes?
Would I branch off when I wanted to, say, change the layout of a menu, then merge back in?
Should I branch? What is the difference (for just me, a lone developer) between branching, then merging back in, and cloning the repository and pulling it back in?
Any other advice for a version control newbie?
So far, everyone has given me good advice, but very team-oriented. I would like to clarify:
At the moment, I am just using VC on some websites I do on the side. Not quite full-out freelance work, but for the purposes of VC, I am the only one that really touches the website code.
Also, since I am using PHP on the sites, there is no compiling to be done.
Does this change your answers significantly?
Most of the questions you're asking about depends mostly on who you are working with. If you're a lone developer it shouldn't matter a lot, since you can do whatever you'd like. But if you're in a team where you have to share your code then you should discuss with your team members what the code of conduct should be since sharing changes between one another can become tricky at times.
The discussion regarding code of conduct doesn't need to be lengthy, it can be very brief; as long everyone is on the same page on how to use the repository that is shared between the programmers in the team. If you want to use the more advanced features in Mercurial, such as cherry picking or patch queues, then try using them so that it won't impact your team members in a negative way, such as rebasing on a public repository.
Remember version control has to be easy to use for everyone in the team, or else it won't be used.
When/how often should I commit? After any major change, whether it works or not? When I'm done for the night? Only when it reaches it's next stable iteration? After any bugfixes?
While working with a team there are several approaches, but the common rule is to commit early and often. The main reason on why you should commit often is to make merge conflicts easier to handle.
A merge conflict is simply put whenever merging a file that has been changed by at least two people doesn't work because they've been editing on the same lines. If you're holding on to a commit that involves a very large change with several lines of changes across several files, it will become very difficult to manage for the receiver to manage the conflicts that may occur. The merge conflict becomes even more difficult to handle if the said set of changes are held on for too long.
There are some exceptions to the rule of committing often and one is whenever you have a breaking change. although if you have the ability to commit locally (which you are doing in Mercurial and git inherently) you could commit breaking changes. As long as you fix whatever broke, you should push it upstream to the shared repository when you've fixed your own breaking change.
Would I branch off when I wanted to, say, change the layout of a menu, then merge back in?
Should I branch?
There are many branching strategies to choose from (there is the Streamed Lines paper from 1998 that has an exhaustive pattern list of branching strategies) and when you're making them for yourself it should be open game for yourself. However when working in teams, you'd better discuss openly with the team if you need to branch or not. Whenever you have the urge to branch though you should ask yourself the following questions:
Will my future changes be breaking the work of others?
Will my team have a direct negative impact from the changes I'll be doing until I'm done?
Is my code throwaway code?
If the answer is yes in any of the questions above you should probably branch publically, or keep it for yourself (since you can do that in Mercurial in several ways). You should first discuss with your team on how to execute the whole endavour to see if there is any other way of doing it and if you're going to merge your changes back in, sometimes there are factors at play where there is no need to branch (this is mostly related to how modular the code is).
When you decide to branch be prepared to handle a merge conflict. It is sane to assume the one who created the branch and made the commits to be able to merge it back into the "main branch". At these times it would be great if everyone in the team made relevant commit comments.
As a side note: You do write good commit comments, right? RIGHT!? A good commit comment usually tells why that particular change was made or what feature the committer was working on instead of a nondescript "I made a commit" kind of comment. This makes it easier for the one who is handling the big merge conflict to figure out what line changes can be overwritten and which ones to keep while going through the revision history.
Compile times, or build times rather, sometimes play into the branch discussion you may have. If your project has a slow build time then it might be a good idea to use a staging strategy in your branches. This strategy takes into account that all developers should integrate to a "main line" and changes that are approved are elevated (or "promoted") to the next stage, such as testing or release lines. It is classically illustrated with tag names for open source software like this:
main -o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-o-> ...
\ \ \
test o-----------o--------------o---------> ...
1.0 RC1 \ 1.0 RC2 2.0 RC1
release o----------------------> ...
1.0
The point with this is that testers can work without being interrupted by the programmers and that there is a known baseline for those who are in release management. In distributed version control, the different lines could be cloned repositories and it may look a bit different since repositories share the versioning graph. The principle however is the same.
Regarding web development, there are virtually no build times. But branching in stages (or by tagging your release revisions) it becomes easier to roll-back if you want to check a difficult-to-track-down bug.
However, a whole other thing comes into play and that is the time it takes to deploy the site. Version control tools in my experience are really bad at asset management. Handling art assets that are in total up to several GB usually is a huge pain in the butt to handle in Subversion (more so in Mercurial). Assets may require you to handle them in another way that is less time consuming, such as putting them in a shared space that are synched and backed up in a traditional manner (art assets are usually not worked on concurrently as with source code files).
What is the difference (for just me, a lone developer) between branching, then merging back in, and cloning the repository and pulling it back in?
The concepts of branching and keeping remote repositories are closer now than with centralized version control tools. You could almost consider them being the same thing. In Mercurial (and in git) you can "branch" either by:
Cloning a repository
Creating a named branch
Creating a named branch means that you're making a new path in the versioning graph for the repository you're creating it on. Creating a cloned repository means you're copying the source repository into a new location, and making a new path in the cloned repository's versioning graph. They are both two different implementations of branching as a general concept in version control.
In practice, the only difference between both methods that you should care about is in usage. You clone a repository to have a copy of the source code and have a place to store your own changes in and you create named branches whenever you want to do small experiments for yourself.
Since browsing through branches is a bit quirky for those who accustomed to a straight line of commits, advanced users know how to manipulate their versions so the version history is "clean" with e.g. cherry picking or rebase. At the moment git docs actually explain rebase rather well.
These are the practices that I follow
Each commit should make sense: one bug fix (or a set of bugs related to each other), one (small) new feature, etc. The idea is that if you need to rollback, your rollbacks fall on well defined "boundaries"
Every commit should have a good message explaining what you are committing. Really get into this habit, you will thank yourself later. Doesn't have to be verbose, a few sentences can do. If you are using a bug tracking system, associating a bug number with your commit is also extremely helpful
Now that I use git and branching is so incredibly fast and cheap, I tend to make a new branch for each new feature I'm about to implement. I'd never even consider doing this for many other VCSes. So branching depends on the system you are using, your codebase, your team, etc, there are no hard rules there.
I prefer to always use the command line and get to know my VCS's commands directly. The disconnect that a GUI based frontend can cause can be a pain, and even damaging. Controlling your source code is very important, it's worth getting in there and doing it directly. But that's just my preference.
Back up your VCS. I back up my local repository with Time Machine, and then I push out to a remote repository on my server, and that server is backed up as well. VCS alone is not really a "backup", it can go down too just like anything else.
When/how often should I commit?
You'll probably get lots of contradictory answers on this one. My view is that you should commit changes when they are working, and each commit (or checkin) should contain exactly one "edit". An "edit" is an atomic set of changes that go together to fix a bug or implement a new feature.
There is a theory that you should check in code every few hours even if it's not working, but in that case you will need to be working on your own branch - you don't want to be checking in broken code to your main line, or onto a shared branch.
The advantage of checking in every night is that you have backups (assuming that your repository is on a different machine).
As for branching:
you should have main line that contains always working code.
you should have a current development branch that contains the latest code. When you are happy with this (and it's passed all it's tests) you should merge it back into the main line.
you might want a branch that contains the last released version. This can be used for testing/debugging bugs and releasing patches (in extremis).
update before each commit
provide commit comments
commit as soon as you have something finished
don't commit anything that makes the code in the repository not compiling or buggy
update every morning
sometimes verbally communicate with colleages if there is something important to update
commit code relevant to exactly one thing (i.e. fixing a bug, implementing a feature)
don't worry to make very small commits, as long as they conform to the previous rule
Btw, what's the bad experience with Subversion?
I commit when I am finished a piece of work and only if it is working. It's bad practise to commit to somewhere where other people use the code.
Branching is something that people will argue about. Some people say never branch and just have switches to get something working or not. Do what you feel more comfortable but don't branch just because you can. I use branching and Branch when i am working on a major bit of work where if I commit broken code by accident its not going to affect everyone else.
Q: When/how often should I commit? After any major change, whether it works or not? When I'm done for the night? Only when it reaches it's next stable iteration? After any bugfixes?
A: Whenever you are feeling comfortable, I am commiting as soon as a unit of work is finished and working (which does not mean that the complete task has to be finished). But you should not commit something that does not compile (might inhibit other people in the team,if any). Also, you should not commit incomplete stuff to the trunk if there is any possibility that you have to implement a quick fix or small change before completing it.
Q: Would I branch off when I wanted to, say, change the layout of a menu, then merge back in?
A: Only if there is a possibility that you have to implement a quick fix or small change before completing your task.
The nice thing about branching is that all commits you are doing in the branch will still be available for future reference (if necessary). Also it is much simpler and faster than cloning the repo, I think ;-)
I agree with others on commit times.
Regarding branching, I generally branch only when working on something that breaks what others are doing or when a patch needs to be rolled to production in a file that already has changes that should not go to production. If you're only one developer, then the first scenario doesn't really apply.
I use tags to manage releases - the "production" tag is always associated with the current prod code, and each release is tagged with "release-YYYYMMDD". This allows you to roll back if necessary.