When performing software program improvement, a fundamental observe is the versioning and model management of the software program. In lots of fashions of improvement, similar to DevSecOps, model management consists of far more than the supply code but additionally the infrastructure configuration, take a look at suites, documentation and lots of extra artifacts. A number of DevSecOps maturity fashions think about model management a fundamental observe. This consists of the OWASP DevSecOps Maturity Mannequin in addition to the SEI Platform Impartial Mannequin.
The dominant instrument for performing model management of supply code and different human readable recordsdata is git. That is the instrument that backs widespread supply code administration platforms, similar to GitLab and GitHub. At its most simple use, git is superb at incorporating modifications and permitting motion to totally different variations or revisions of a undertaking being tracked. Nevertheless, one draw back is the mechanism git makes use of to call the variations. Git variations or commit IDs are a SHA-1 hash. This downside will not be distinctive to git. Many instruments used for supply management remedy the issue of find out how to uniquely establish a set of modifications from another in the same manner. In mercurial, one other supply code administration instrument a changeset is recognized by a 160-bit identifier.
This implies to discuss with a model in git, one might need to specify an ID similar to 521747298a3790fde1710f3aa2d03b55020575aa (or the shorter however no much less descriptive 52174729). This isn’t a great way for builders or customers to discuss with variations of software program. Git understands this and so has tags that enable task of human readable names to those variations. That is an additional step after making a commit message and ideally relies on the modifications launched within the commit. That is duplication of effort and a step that might be missed. This results in the central query: How can we automate the task of variations (by way of tags)? This weblog publish explores my work on extending the traditional commit paradigm to allow automated semantic versioning with git tags to streamline the event and deployment of software program merchandise. This automation is meant to avoid wasting improvement time and forestall points with handbook versioning.
I’ve just lately been engaged on a undertaking the place one template repository was reused in about 100 different repository pipelines. It was essential to check and ensure nothing was going to interrupt earlier than pushing out modifications on the default department, which many of the different tasks pointed to. Nevertheless, with supporting so many customers of the templates there was inevitably one repository that may break or use the script in a non-conventional manner. In a number of instances, we wanted to revert modifications on the department to allow all repositories to move their Steady Integration (CI) checks once more. In some instances, failing the CI pipeline would hamper improvement for the customers as a result of it was a requirement to move the script checks of their CI pipelines earlier than constructing and different phases. Consequently, some customers would create a long-lived department within the template repository I helped preserve. These long-lived branches are separate variations that don’t get the entire similar updates as the primary line of improvement. These branches are created in order that customers didn’t get all of the modifications rolled out on the default department instantly. Lengthy-lived branches can change into stale once they don’t obtain updates which were made to the primary line of improvement. These long-lived, stale branches made it troublesome to wash up the repository with out additionally presumably breaking CI pipelines. This grew to become an issue as a result of when reverting the repository to a earlier state, I usually needed to level to a reference, similar to HEAD~3, or the hash of the earlier commit earlier than the breaking change was built-in into the default department. This problem was exacerbated by the truth that the repository was not utilizing git tags to indicate new variations.
Whereas there are some arguments for utilizing the most recent and biggest model of a brand new software program library or module (sometimes called “reside at head,”) this methodology of working was not working for this undertaking and consumer base. We wanted higher model management within the repository with a approach to sign to customers if a change can be breaking earlier than they up to date.
Standard Commits
To get a deal with on understanding the modifications to the repository, the builders selected adopting and imposing typical commits. The standard commits specification provides guidelines for creating an specific commit historical past on high of commit messages. Additionally, by breaking apart a title and physique, the influence of a commit may be extra simply deduced from the message (assuming the creator understood the change implications). The usual additionally ties to semantic versioning (extra on that in a minute). Lastly, by imposing size necessities, the crew hoped to keep away from commit messages, similar to mounted stuff, Working now, and the automated Up to date .gitlab-ci.yml.
For typical commits the next construction is imposed:
<sort> [optional scope]: <description>
[optional body]
[optional footer(s)]
The place <sort> is one in every of repair, feat, BREAKING CHANGE or others. For this undertaking we selected barely totally different phrases. The next regex defines the commit message necessities within the undertaking that impressed this weblog publish:
^(characteristic|bugfix|refactor|construct|main)/ [a-z ]{20,}(rn?|n)(rn?|n)[a-zA-Z].{20,}$
An instance of a traditional commit message is:
characteristic: Add a brand new publish about git commits
The publish explains find out how to use typical commits to routinely model a repository
The principle motivation behind imposing typical commits was to wash up the undertaking’s git historical past. Having the ability to perceive the modifications {that a} new model brings in by way of commits alone can velocity up code evaluations and assist when debugging points or figuring out when a bug was launched. It’s a good observe to commit early and infrequently, although the stability between committing each failed experiment with the code and never cluttering the historical past has led to many totally different git methods. Whereas the undertaking inspiring this weblog publish makes no suggestions on how usually to commit, it does implement at the very least a 20-character title and 20-character physique for the commit message. This adherence to traditional commits by the crew was foundational to the remainder of the work finished within the undertaking and described on this weblog publish. With out the flexibility to find out what modified and the influence of the change instantly within the git historical past, it might have difficult the trouble and probably pushed in direction of a much less transportable answer. Imposing a 20-character minimal could seem arbitrary and a burden for some smaller modifications. Nevertheless, imposing this minimal is a approach to get to informative commit messages which have actual that means for a human that’s reviewing them. As famous above this restrict can pressure builders to rework a commit message from ci working to Up to date variable X within the ci file to repair construct failures with GCC.
Semantic Versioning
As famous, typical commits tie themselves to the notion of semantic versioning, which semver.org defines as “a easy algorithm and necessities that dictate how model numbers are assigned and incremented.” The usual denotes a model quantity consisting of MAJOR.MINOR.PATCH the place MAJOR is any change that’s incompatible, MINOR is a backward appropriate change with new options, and PATCH is a backward appropriate bug repair. Whereas there are different versioning methods and a few famous points with semantic versioning, that is the conference that the crew selected to make use of. Having variations denoted on this manner through git tags permits customers to see the influence of the change and replace to a brand new model when prepared. Conversely a crew may proceed to reside at head till they run into a difficulty after which extra simply see what variations had been accessible to roll again to.
COTS Options
This problem of routinely updating to a brand new semantic model when a merge request is accepted will not be a brand new concept. There are instruments and automations that present the identical performance however are usually focused at a particular CI system, similar to GitHub Actions, or a particular language, similar to Python. For instance, the autosemver python bundle is ready to extract info from git commits to generate a model. The autosemver functionality, nonetheless, depends on being arrange in a setup.py file. Moreover, this undertaking will not be extensively used within the Python neighborhood. Equally, there’s a semantic-release instrument, however this requires Node.js within the construct setting, which is much less frequent in some tasks and industries. There are additionally open-source GitHub actions that allow automated semantic versioning, which is nice if the undertaking is hosted on that platform. After evaluating these choices although, it didn’t appear essential to introduce Node.js as a dependency. The undertaking was not hosted on GitHub, and the undertaking was not Python-based. As a result of these limitations, I made a decision to implement my very own minimal viable product (MVP) for this performance.
Different Implementations
Having determined in opposition to off-the-shelf options to the issue of versioning the repo, subsequent I turned to a couple weblog posts on the topic. First a publish by Three Dots Labs helped me establish an answer that was oriented towards GitLab, just like my undertaking. That publish, nonetheless, left it as much as the reader find out how to decide the following tag model. Marc Rooding expanded the Three Dots Labs publish along with his personal weblog publish. Right here he suggests utilizing merge request labels and pulling these from the API to determine the model to bump the repository to. This method had three drawbacks that I recognized. First, it appeared like a further handbook step so as to add the proper tags to the merge request. Second, it depends on the API to get tags from the merge request. Lastly, this might not work if a hotfix was dedicated on to the default department. Whereas this final level must be disallowed by coverage, the pipeline ought to nonetheless be strong ought to it occur. Given the probability of error on this case of commits on to most important, it’s much more essential that tags are generated for rollback and monitoring. Given these elements, I made a decision to decide on utilizing the traditional commit sorts from the git historical past to find out the model replace wanted.
Implementation
This template repository referenced within the introduction makes use of GitLab because the CI/CD system. Consequently, I wrote a pipeline job to extract the git historical past for the default department after being merged. The pipeline job assumes that both (1) there’s a single commit, (2) the commits had been squashed and that every correctly formatted commit message is contained within the squash commit, or (3) a merge commit is generated in the identical manner (containing all department commits). Which means the setup proposed right here can work with squash-and-merge or rebase-and-fast-forward methods. It additionally handles commits on to the default department, if anybody would do this. In every case, the idea is that the commit–whether merger, squash, or regular–still matches the sample for typical commits and is written appropriately with the proper typical commit sort (main, characteristic, and so forth.). The final commit is saved in a variable LAST_COMMIT in addition to the final tag within the repo LAST_TAG.
A fast apart on merging methods. The answer proposed on this weblog publish assumes that the repository makes use of a squash-and-merge technique for integrating modifications. There are a number of defensible arguments for each a linear historical past with all intermediate commits represented or for a cleaner historical past with solely a single commit per model. With a full, linear historical past one can see the event of every characteristic and all trials and errors a developer had alongside the best way. Nevertheless, one draw back is that not each model of the repository represents a working model of the code. With a squash-and-merge technique, when a merge is carried out, all commits in that merge are condensed right into a single commit. This implies that there’s a one-to-one relationship with commits on the primary department and branches merged into it. This permits reverting to anyone commit and having a model of the software program that handed by way of no matter assessment course of is in place for modifications going into the trunk or most important department of the repository. The proper technique must be decided for every undertaking. Many instruments that wrap round git, similar to GitLab, make the method for both technique easy with settings and configuration choices.
With all the traditional commit messages because the final merge to most important captured, these commit messages had been handed off to the next_version.py Python script. The logic is fairly easy. For inputs there’s the present model quantity and the final commit message. The script merely appears to be like for the presence of “main” or “characteristic” because the commit sort within the message. It really works on the premise that if any commit within the department’s historical past is typed as “main” the script is completed and outputs the following main model. If not discovered, the script searches for “minor” and if not discovered the merge is assumed to be a patch model. On this manner the repo is at all times up to date by at the very least a patch model.
The logic within the Python script may be very easy as a result of it was already a dependency within the construct setting, and it was clear sufficient what the script was doing. The identical might be rewritten in Bash (e.g., the semver instrument), in one other scripting language, or as a pipeline of *nix instruments.
This code defines a GitLab pipeline with a single stage (launch) that has a single job in that stage (tag-release). Guidelines are specified that the job solely runs if the commit reference identify is similar because the default department (often most important). The script portion of the job provides curl and Python to the picture. Subsequent it will get the final commit through the git log command and shops it within the LAST_COMMIT variable. It does the identical with the final tag. The pipeline then makes use of the next_version.py script to generate the following tag model and eventually pushes a tag with the brand new model utilizing curl to the GitLab API.
```
phases:
- launch
tag-release:
guidelines:
- if: $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH
stage: launch
script:
- apk add curl git python3
- LAST_COMMIT=$(git log -1 --pretty=%B) # Final commit message
- LAST_TAG=$(git describe --tags --abbrev=0) # Final tag within the repo
- NEXT_TAG=$(python3 next_version.py ${LAST_TAG} ${LAST_COMMIT})
- echo Pushing new model tag ${NEXT_TAG}
- curl -k --request POST --header "PRIVATE-TOKEN:${TAG_TOKEN}" --url "${CI_API_V4_URL}/tasks/${CI_PROJECT_ID}/repository/tags?tag_name=${NEXT_TAG}&ref=most important"
```
The next Python script takes in two arguments, the final tag within the repo and the final commit message. The script then finds the kind of commit through the if/elseif/else statements to increment the final tag to the suitable subsequent tag and prints out the following tag to be consumed by the pipeline.
```
import sys
last_tag = sys.argv[1]
last_commit = sys.argv[2]
next_tag = ""
brokenup_tag = last_tag.break up(".")
if "main/" in last_commit:
major_version = int(brokenup_tag[0])
next_tag = str(major_version+1)+".0.0"
elif "characteristic/" in last_commit:
feature_version = int(brokenup_tag[1])
next_tag = brokenup_tag[0]+"."+str(feature_version+1)+".0"
else:
patch_version = int(brokenup_tag[2])
next_tag = brokenup_tag[0]+"."+brokenup_tag[1]+"."+str(patch_version+1)
print(next_tag)
```
Lastly, the final step is to push the brand new model to the git repository. As talked about, this undertaking was hosted in GitLab, which gives an API for git tags within the repo. The NEXT_TAG variable was generated by the Python script, after which we used curl to POST a brand new tag to the repository’s /tags endpoint. Encoded within the URL is the ref to make the tag from. On this case it’s most important however might be adjusted. The one gotcha right here is, as said beforehand, that the job runs solely on the default pipeline after the merge takes place. This ensures the final commit (HEAD) on the default department (most important) is tagged. Within the above GitLab job, the TAG_TOKEN is a CI variable whose worth is a deploy token. This token must have the suitable permissions arrange to have the ability to write to the repository.
Subsequent Steps
Semantic versioning’s most important motivation is to keep away from a state of affairs the place a bit of software program is in both a state of model lock (the shortcoming to improve a bundle with out having to launch new variations of each dependent bundle) or model promiscuity (assuming compatibility with extra future variations than is affordable). Semantic versioning additionally helps to sign to customers and keep away from working into points the place an API name is modified or eliminated, and software program won’t interoperate. Monitoring variations informs customers and different software program that one thing has modified. This model quantity, whereas useful, doesn’t let a consumer know what has modified. The subsequent step, constructing on each discrete variations and standard commits, is the flexibility to condense these modifications right into a changelog giving builders and customers, “a curated, chronologically ordered listing of notable modifications for every model of a undertaking.” This helps builders and customers know what has modified, along with the influence.
Having a approach to sign to customers when a library or different piece of software program has modified is essential. Even so, it isn’t essential to have versioning be a handbook course of for builders. There are merchandise and free, open supply options to this problem, however they could not at all times be match for any explicit improvement setting. In terms of security-critical software program, similar to encryption or authentication, it’s a good suggestion to not roll your individual. Nevertheless, for steady integration (CI) jobs generally industrial off-the shelf (COTS) options are extreme and convey important dependencies with them. On this instance, with a 6-line BASH script and a 15-line Python script, one can implement auto-semantic versioning in a pipeline job that (within the deployment examined) runs in ~10 seconds. This instance additionally exhibits how the method may be minimally tied to a particular construct or CI system and never depending on a particular language or runtime (even when Python was used out of comfort).
