Atlassian adds bigger Bitbucket build sizes and retires the old runtime on Sept 17

What Atlassian launched

Atlassian has released a new engine for Bitbucket Pipelines, its tool for automatically building and testing software every time a developer changes code. This kind of automation is called CI/CD. The engine that runs these jobs is called the runtime. As atlassian.com reported, the new runtime is available now, following an earlier preview.

The most visible change is two new build sizes, called 4x and 8x. They give each build far more computing power than before, and they are the first step in a wider rework of how Pipelines names and measures its build sizes.

A note on the headline: it promises builds up to 8x faster. The announcement itself describes up to 8x more CPU and memory. More power can shorten build times, but the source does not give speed measurements, so treat the speed claim as a ceiling rather than a guarantee.

The new sizes in numbers

The two new sizes are specific. A 4x build gets 8 CPU cores and 16GB of memory. An 8x build gets 16 CPU cores and 32GB of memory. CPU cores are the processing units that do the work, and memory is the workspace a job can hold in use at once.

Builds using these sizes also get dedicated compute resources, meaning the capacity is assigned only to your builds. Atlassian says CPU and memory will now scale in line with the size number, so the ratio stays standard as sizes go up.

There is a catch on cost and access. The new sizes work only for builds running under a paid Bitbucket Cloud plan, either Standard or Premium. The source does not give a price for the larger sizes.

Why the runtime matters beyond size

Atlassian describes the new runtime as the base for future features. It names ARM builds and multi-arch builds in the cloud. ARM is a family of processor chips, and multi-arch means building software that runs on more than one chip type. These are future plans, not part of today's launch.

Any step that uses the 4x or 8x size is placed on the new runtime automatically. Steps at the existing 1x and 2x sizes stay on the legacy runtime until September, when they will move too.

The deadline: September 17th, 2024

On September 17th, 2024, Atlassian will retire the legacy Pipelines runtime. Atlassian stresses that the 1x and 2x sizes are not going away. They are simply being moved to the new runtime, and no changes are needed in your Pipelines configuration.

The exception is IP allowlisting. Some companies protect their internal networks by letting in traffic only from a list of approved IP addresses, which work like street addresses for computers. If your setup does this for Pipelines, you must update the list to the new address ranges, which are published in the Pipelines documentation, before September 17th. If you skip this, your builds may be blocked from reaching internal systems.

Testing and possible surprises

Atlassian admits the new platform has some underlying changes that, in extremely rare cases, could cause unexpected behavior. The risk is higher if your builds depend on specifics of the current environment, such as a particular Linux kernel version or a certain number of CPU cores visible to the build container.

Its advice is to run full end-to-end tests on the new runtime before making it your default. It also suggests trying your existing 1x and 2x builds on the 4x size before September 17th, even if you never plan to use the larger sizes, to catch any incompatibilities early. If none of this sounds like your setup, Atlassian says you should not need to worry.

For reassurance, the company says it has run its own internal CI/CD on the new runtime for an extensive period and completed millions of builds with no major incompatibility.