The time has comeWanted to send this out to developers just before I branch for a release.
To branch on some,
And so it will
Be the head is still.
A branching poem
Wrote this for an branching thought:
Full or partial releases
Working in the web app world, I frequently get asked, often by managers who aren't thinking about the product and SOX compliance, if it is OK to plop just a jsp file or a jar instead of rebuilding the entire war each time.
My answer is always "No!". There are a number of reasons why, but most simply is that doing so defeats the basic tenets of release engineering: reproducability, traceability, accountability.
As a simple example that recently occurred in my own job, we were starting to upgrade a pair of server that had not been touched in nearly three years. We started in on the first of the pair however we soon found that the code needed to be reverted. When we redeployed the backup of the war file, the code was exhibiting incorrect behavior, especially compared to its twin. Turns out that soon after the deployment three years earlier, a developer also deployed a single JSP file into the exploded war directory. Three years go by, developer has moved on, managers have forgotten everything, two different release engineers moved on. The developer was playing around with a production system, didn't document what happened and didn't re-release the product to correct the situation. As a result, the product could have been in jeopardy if we had not been more tentative and worked on only one server at a time (another topic of discussion: a lot of developers want me to deploy to all the servers at once). By only working on one, we could compare the old war with the changed war on its twin.
This anecdote illustrates one major issue with partial deployments. There was no accountability for the product: none of the manager, developer or the release engineer at the time of the first release held themselves accountable. There was not tracability: no documentation was kept, no build records, no labeling - just a file plopped down into a directory. No reproducability: the environment could not be reproduced without looking at the twin server. If that twin production server hadn't existed, then there would have been nothing to revert to.
Full deployments from a single, release distribution build lead to all of these tenets. Anything less breaks release engineering practices.
My answer is always "No!". There are a number of reasons why, but most simply is that doing so defeats the basic tenets of release engineering: reproducability, traceability, accountability.
As a simple example that recently occurred in my own job, we were starting to upgrade a pair of server that had not been touched in nearly three years. We started in on the first of the pair however we soon found that the code needed to be reverted. When we redeployed the backup of the war file, the code was exhibiting incorrect behavior, especially compared to its twin. Turns out that soon after the deployment three years earlier, a developer also deployed a single JSP file into the exploded war directory. Three years go by, developer has moved on, managers have forgotten everything, two different release engineers moved on. The developer was playing around with a production system, didn't document what happened and didn't re-release the product to correct the situation. As a result, the product could have been in jeopardy if we had not been more tentative and worked on only one server at a time (another topic of discussion: a lot of developers want me to deploy to all the servers at once). By only working on one, we could compare the old war with the changed war on its twin.
This anecdote illustrates one major issue with partial deployments. There was no accountability for the product: none of the manager, developer or the release engineer at the time of the first release held themselves accountable. There was not tracability: no documentation was kept, no build records, no labeling - just a file plopped down into a directory. No reproducability: the environment could not be reproduced without looking at the twin server. If that twin production server hadn't existed, then there would have been nothing to revert to.
Full deployments from a single, release distribution build lead to all of these tenets. Anything less breaks release engineering practices.
Significant builds in continuous integration
With agile methodologies, it is very common to have continuous integration builds. In those methodolog, there are two types of builds: successful and unsuccessful. Unsuccessful builds are builds where either the code could not compile, unit tests fail or regression tests (if part of the build system) fail. Successful builds are ones where the build completes successfully.
Considering how often continuous integration builds are executed, with cascading, downstream builds of other products, even large disks could fill up quickly. Many limit the number of builds preserved or the number of days preserved. Here I suggest a different approach.
There are two types of successful builds. A significant successful build is one where a change occur to initiate this build or an upstream (assumed to be successful) build. An insignificant successful build is one where no change has occurred to initiate this build.
Insignificant builds could be deleted on the next successful build. Significant builds should be kept for some period determined by the SCM.
An example of an insignificant build within the system is builds activated hourly or when changes are detected in version control. It is easily conceivable, especially overnight, that the hourly builds would become insignificant compared to the version-control based builds.
When what would the purpose of having insignificant builds? There may be other tasks outside of the build that are triggered by the build, for example, regression tests on a remote system, load tests run at night. Each of these could be triggered by a specific build, but generating the same build objects (for example, publishing them to the same object repository).
Significant and insignificant successful builds have their place within the build framework. Identification of each and more importantly, getting the build systems to identify each, and managing these would become the next stage.
Considering how often continuous integration builds are executed, with cascading, downstream builds of other products, even large disks could fill up quickly. Many limit the number of builds preserved or the number of days preserved. Here I suggest a different approach.
There are two types of successful builds. A significant successful build is one where a change occur to initiate this build or an upstream (assumed to be successful) build. An insignificant successful build is one where no change has occurred to initiate this build.
Insignificant builds could be deleted on the next successful build. Significant builds should be kept for some period determined by the SCM.
An example of an insignificant build within the system is builds activated hourly or when changes are detected in version control. It is easily conceivable, especially overnight, that the hourly builds would become insignificant compared to the version-control based builds.
When what would the purpose of having insignificant builds? There may be other tasks outside of the build that are triggered by the build, for example, regression tests on a remote system, load tests run at night. Each of these could be triggered by a specific build, but generating the same build objects (for example, publishing them to the same object repository).
Significant and insignificant successful builds have their place within the build framework. Identification of each and more importantly, getting the build systems to identify each, and managing these would become the next stage.
Subscribe to:
Posts (Atom)