Constructing Red Hat Enterprise Linux v. 3
Just as the sun never sets on kernel development, our near-and-dear partners and customers don't sit still either. One of the few constants in this dynamic environment is that throughout the course of the release development, there is a steady influx of must-have crisis feature additions. We endeavor to make it a trade-off and kick out a lower priority feature in order to keep the workload sane. In the end, however, it never seems to work out to such a sweet balance. The ability of the team to persevere through all these demands is remarkable.
As productive as the Red Hat developers are, some late-breaking features always have to be deferred to a later release or update. These situations cause no end of trauma for our partner managers who have to be the bearers of bad news. It's improbable that our partners ever heard the saying “don't shoot the messenger”. There was one incident when we were two hours from shipping the release and a delivery arrived on the loading dock. It was a new computer platform we needed in order to be able to develop and test support for it. The partner was incredulous that we were unable to accommodate.
Several different levels of testing are performed throughout the development process. It all begins with the developers performing unit testing. This consists of manual, hands-on testing as well as development of automated testing programs. The set of automated tests constantly is being augmented as new problems are addressed. These automated test programs then are incorporated into a test grid that is managed by the QA department. In addition to the internally written unit tests, our test grid includes a wide range of regression tests. Examples include POSIX, LSB conformance, LTP, crashme, gcc suite and diabolical tests provided by our partners. Stress tests also are performed for a range of system functions using such tests as cerberus, lmbench, bonnie, spec and other micro-benchmarks, to name a few. These automated tests are run nightly in order to detect regressions quickly. This is critical in order to isolate the offending code. In contrast, if we waited to perform monthly base-level testing, it would be much more difficult to identify the culprit.
On top of the nightly tests, more time-consuming test scenarios are run less frequently. Examples include installation testing using a wide range of configuration options across the many different languages we support. Hands-on testing rounds out the internal QA coverage. Doing justice to the staggering range of testing done by the hardworking QA team here substantially exceeds the scope of a single article.
After the kernels have passed internal units tests and QA scrutiny, we make them available to our development partners. This vastly broadens the coverage to include external QA and development teams in other companies. Our partners focus testing on their hardware platforms as well as the typical server capabilities their enterprise customers demand.
The last layer of testing includes external beta testers. These beta testers include high-profile customers, as well as the many people in the Linux community who respond to our open invitation to help with testing.
The combination of all these different testing activities yields an extremely stable and well-tested product. It also points out the huge value of the open-source model. It is the combination of testing resources from many different companies and dedicated individuals that scales well beyond the resources a single company could bring to bear to tackle an infinite testing matrix.
Figure 3, composed by Nick Carr, summarizes the development model from requirements gathering, development and testing, culminating in production.
In the end, the Red Hat Enterprise Linux v. 3 distribution did ship on schedule in mid-October 2003. Having worked for many years for a major IHV on a large-scale operating system engineering team, I have been exposed to both the proprietary operating system development model and the open-source development model. The successful outcome of the Enterprise Linux v. 3 release clearly demonstrates the power of cooperative open-source development. The quantity of features, rapid development time and caliber of participants, both internal and external, is remarkable and stands as a strong testament to the Linux community.
When the release shipped, we all were proud to have contributed to such a tremendous accomplishment. But the time window to rejoice was short indeed. As soon as Enterprise Linux v. 3 finished, it seemed we already were late with the development of Enterprise Linux v. 4. This reminds me of the quote, “Congratulations for winning this battle, that earns you the privilege to come back and fight another day.” Gotta go, more battles to fight.
Tim Burke is the director of Server Development at Red Hat. This team is responsible for the kernel and the set of core applications included in Red Hat Enterprise Linux. Prior to becoming a manager, Tim earned an honest living developing Linux highly available cluster solutions and UNIX kernel technology.
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