Introducing Kotlin FHIR: A new library to bring FHIR to Multiplatform

Build once, deploy everywhere: multiplatform FHIR development on Android, iOS, and Web

by Jing Tang, Google Research

The mission of Google's Open Health Stack team is to accelerate digital health innovation by providing developers everywhere with critical building blocks for next-generation healthcare applications. Expanding its existing components, the team has released Kotlin FHIR (currently in alpha), a new open-source library now available on GitHub. It implements the HL7® FHIR® data model on Kotlin Multiplatform (KMP), enabling developers to build FHIR apps and tools for Android, iOS, and Web simultaneously.

Demo app launched as Android, iOS, and Web applications

Tools to support health data exchange using a modern standard

HL7® FHIR® (Fast Healthcare Interoperability Resources) is a global interoperability standard for healthcare data exchange. It enables healthcare systems to exchange data freely and securely, improving efficiency and transparency while reducing integration costs. Over the years, it has seen rapidly growing adoption, and its use has been mandated by health regulations in an increasing number of countries.

Since March 2023, the Open Health Stack team at Google has introduced a number of tools to support FHIR development. For example, the Android FHIR SDK helps developers to build offline capable FHIR-native apps that can help community health workers carry out data collection tasks in remote communities. With FHIR Data Pipes, developers can build analytics solutions more easily to generate critical insights for large healthcare programmes more easily. Today, apps powered by these tools are used by health workers covering over 75 million people across Sub-Saharan Africa, South and Southeast Asia.

A leap forward to multiplatform development

In low-resource settings, it is imperative to develop apps that can reach as many patients as possible at a low development cost. However, a lack of infrastructure and tooling often hinders this goal. For example, Kotlin Multiplatform (KMP) is a new and exciting technology rapidly gaining traction, but existing FHIR libraries are not suitable for KMP development due to their platform-specific dependencies. Consequently, developing FHIR apps on KMP has not been possible, causing developers to miss out on a significant opportunity to scale their solutions.

Introducing Kotlin FHIR. It is a modern and lightweight implementation of FHIR data models designed for use on KMP with no platform-specific dependencies. With Kotlin FHIR, developers can build FHIR apps once, and deploy them to Android, iOS, Web, and other platforms.

"Any library that helps implementers use FHIR is my favourite, but I'm particularly thrilled to see a new library from the awesome Open Health Stack team.

– Grahame Grieve, Creator of FHIR, Product Director at HL7

Modern, lightweight, and sustainable

Kotlin FHIR uses KotlinPoet to generate the FHIR data model directly from the specification. This ensures that the library is complete and maintainable. The data model classes it generates are minimalist to provide the best usability for developers: it has everything that you need, nothing less and nothing more. It uses modern language features in Kotlin such as sealed interfaces to ensure type-safety and to give developers the best coding experience. It supports all the FHIR versions: R4, R4B and R5, and will be updated when new FHIR versions are released.

The library is currently in alpha, but has received positive feedback from the developer community. To try FHIR multiplatform development using the library, head to the repository.

Beyond data models: more on multiplatform

Our mission is to empower the digital health community, and the Kotlin FHIR library is our latest step in that effort. But handling the FHIR data model on KMP is just the beginning. Rich features provided by the Android FHIR SDK libraries will also be needed on KMP. This is a collaborative effort, and we invite the FHIR community to join us in defining and building the cross-platform tools you need most. To learn more about how you can get involved, head to the Open Health Stack developer site.

Kubernetes 1.34 is available on GKE!

by Benjamin Elder & Pradeep Varadharajan, Google Kubernetes Engine

Kubernetes 1.34 is now available in the Google Kubernetes Engine (GKE) Rapid Channel in just 5 days after OSS release! For more information about the content of Kubernetes 1.34, read the official Kubernetes 1.34 Release Notes and the specific GKE 1.34 Release Notes.

Kubernetes Enhancements in 1.34:

The Kubernetes 1.34 release, themed 'Of Wind & Will', symbolizing the winds that shaped the platform, delivers a fresh gust of enhancements. These updates, shaped by both ambitious goals and the steady effort of contributors, continue to propel Kubernetes forward.

Below are some of the Kubernetes 1.34 features that you can use today in production GKE clusters.

DRA Goes GA

The Kubernetes Dynamic Resource Allocation (DRA) APIs are now GA. This is a huge step in the evolution of Kubernetes to stay the undisputed platform for AI/ML workloads. DRA improves Kubernetes' ability to select, configure, allocate, and share GPUs, TPUs, NICs and other specialized hardware. For more information about using DRA in GKE, see About dynamic resource allocation in GKE. You can use DRA now with self-installed drivers and can expect more improvements in upcoming releases.

The Prioritized list and Admin access features have been promoted to beta and will be enabled by default, and the kubelet API has been updated to report status on resources allocated through DRA.

KYAML

We've all been there: a stray space or an unquoted string in a YAML file leads to frustrating debugging sessions. The infamous "Norway Bug" is a classic example of how YAML's flexibility can sometimes be a double-edged sword. 1.34 introduces support for KYAML, a safer and less ambiguous subset of YAML, specifically designed for Kubernetes and helps avoid these common pitfalls.

KYAML is fully compatible with existing YAML parsers but enforces stricter rules making your configurations more predictable and less prone to whitespace errors. This is a game-changer for anyone using templating tools like Helm, where managing indentation can be a headache.

To start using KYAML, simply update your client to 1.34+ and set the environment variable KUBECTL_KYAML=true to enable use of -o kyaml. For more details, check out KEP-5925.

Pod-level resource requests and limits

With the promotion of Pod-level resource requests and limits to beta (and on-by-default), you can now define resource requests and limits at the pod level instead of the container level. This simplifies resource allocation, especially for multi-container Pods, by allowing you to set a total resource budget that all containers within the Pod share. When both pod-level and container-level resources are defined, the pod-level settings take precedence, giving you a clear and straightforward way to manage your Pod's resource consumption.

Improved Traffic Distribution for Services

The existing PreferClose setting for traffic distribution in Services has been a source of ambiguity. To provide clearer and more precise control over how traffic is routed, KEP-3015 deprecates PreferClose and introduces two new, more explicit values:

• PreferSameZone is equivalent to the existing PreferClose.
• PreferSameNode prioritizes sending traffic to endpoints on the same node as the client. This is particularly useful for scenarios like node-local DNS caches, where you want to minimize latency by keeping traffic on the same node whenever possible.

This feature is now beta in 1.34, with its feature gate enabled by default.

Ordered Namespace Deletion for Enhanced Security

When a namespace is deleted, the order in which its resources are terminated has, until now, been unpredictable. This can lead to security flaws, , such as a NetworkPolicy being removed before the Pods it was protecting, leaving them temporarily exposed. With this enhancement, Kubernetes introduces a structured deletion process for namespaces, ensuring secure and predictable resource removal by enforcing a deletion order that respects dependencies, removing Pods before other resources.
This feature was introduced in Kubernetes v1.33 and became stable in v1.34.

Graceful Shutdowns Made Easy

Ensuring a graceful shutdown for your applications is crucial for zero-downtime deployments. Kubernetes v1.29 introduced a "Sleep" for containers' PreStop and PostStart lifecycle hooks, offering a simple approach to managing graceful shutdowns. This feature allows a container to wait for the specified duration before it's terminated, giving it time to finish in-flight requests and ensuring a clean handoff during rolling updates.
Note: Specifying a negative or zero sleep duration will result in an immediate return, effectively acting as a no-op (added in v1.32).
This feature graduated to stable in v1.34.

Streaming List Responses

Large Kubernetes clusters can push the API server to its limits when dealing with large LIST responses that can consume gigabytes of memory. Streaming list responses address this by changing how the API server handles these requests.

Instead of buffering the entire list in memory, it streams the response object by object, improving performance and substantially reducing memory pressure on the API server. This feature is now GA and is automatically enabled for JSON and Protobuf responses with no client-side changes.

Resilient Watch Cache Initialization

The watch caching layer in the Kubernetes apiserver maintains an eventually consistent cache of cluster state. However, if it needs to be re-initialized, it can potentially lead to a thundering herd of requests that can overload the entire control plane. The Resilient Watch Cache Initialization feature, now stable, ensures clients and controllers can reliably establish watches.

Previously, when the watch cache was initializing, incoming watch and list requests would hang, consuming resources and potentially starving the API server. With this enhancement, such requests are now intelligently handled: watches and most list requests are rejected with a 429, signaling clients to back off, while simpler get requests are delegated directly to etcd.

In-Place Pod Resize Gets Even Better

In-place pod resize, which allows you to change a Pod's resource allocation without a disruptive restart, remains in Beta, but continues to improve in v1.34. You can now decrease memory limits with a best-effort protection against triggering the OOM killer. Additionally, resizes are now prioritized, and retrying deferred resizes is more responsive to resources being released. A ResizeCompleted event provides a clear signal when a resize completes, and includes a summary of the new resource requirements.

MutatingAdmissionPolicy Gets to Beta

MutatingAdmissionPolicy, working as a declarative, in-process alternative to mutating admission webhooks, goes to Beta in Kubernetes 1.34.

Mutating admission policies use the Common Expression Language (CEL) to declare mutations to resources. Mutations can be defined either with an apply configuration that is merged using the server side apply merge strategy, or a JSON patch. This feature is highly configurable, enabling policy authors to define policies that can be parameterized and scoped to resources as needed by cluster administrators.

Acknowledgements

As always, we want to thank all the Googlers that provide their time, passion, talent and leadership to keep making Kubernetes the best container orchestration platform. We would like to mention especially Googlers who helped drive some of the open source features mentioned in this blog: Tim Allclair, Natasha Sarkar, Jordan Liggitt, Marek Siarkowicz, Wojciech Tyczyński, Tim Hockin, Benjamin Elder, Antonio Ojea, Gaurav Ghildiyal, Rob Scott, John Belamaric, Morten Torkildsen, Yu Liao, Cici Huang, Joe Betz, and Dixita (Dixi) Narang.

And thank the many Googlers who helped bring 1.34 to GKE!

This Week in Open Source #9

This Week in Open Source for 09/05/2025

A look around the world of open source
by Daryl Ducharme, amanda casari & Shane Glass, Google Open Source

Upcoming Events

• September 5-7: NixCon 2025 is happening in Switzerland. It is the annual conference for the Nix and NixOS community where Nix enthusiasts learn, share, and connect with others.
• September 9: Kubernetes Community Day 2025 SF Bay Area event, the ultimate gathering for cloud native enthusiasts! This full-day event, sponsored by the Cloud Native Computing Foundation (CNCF), is packed with insightful cloud native talks and unparalleled opportunities for community networking.
• September 11 - 14: ASF Community over Code is happening in Minneapolis, Minnesota. It is for ASF members, committers, and open source developers from around the world, focusing on Search, Big Data, Internet of Things, Community, Geospatial, Financial Tech, and many other topics. Google Open Source's own Stephanie Taylor will be giving a talk on cultivating contributors through mentorship.
• September 12 - 16: PyCon AU 2025 is happening in Narrm/Melbourne. It is the national conference for the Python programming community, bringing together professional, student and enthusiast developers, sysadmins and operations folk, students, educators, scientists, statisticians, and many others besides, all with a love for working with Python.
• September 23 - 27: Nerderarla 2025 is happening in Buenos Aires. It is a 100% free, world-class event in Latin America with high-quality content in science and technology.
• September 29 - 30: Git Merge 2025 celebrates 20 years of Git in Sunnyvale, California.
• October 2 - 3: Monktoberfest is happening in Portland, Maine. The only conference focused on how craft, technology and social come together. It's one of the most unique events in the industry.

Open Source Reads and Links

• [Blog Post] Gemini CLI comes to Zed - Built to be extensible, the Gemini CLI is showing itself as a boon to developers and contributors are giving it many new features. Open source itself, it is a perfect fit for the open source code editor Zed.
• [Article] Why Morgan Stanley open sourced its app development tool - Compliance and security are huge issues in the financial sector. Even though open source has historically been a hard sell in that sector, Morgan Stanley saw the value in opening up their Common Architecture Language Model (CALM) and a desire for industry-wide standards helped it gain traction.
• [Blog Post] What the EU's Cyber Resilience Act Means for Open Source - During the Open Source Summits in both North America and Europe, there were many discussions about what needs to happen amongst open source maintainers and enterprises with regards to the CRA.
• [Blog Post] The Cyber Resilience Act: A Five Alarm Fire - On paper, the CRA makes sense. The world of software, after all, cannot be built indefinitely on a foundation that includes Munroe's "project thanklessly maintained by a single developer from Nebraska since 2003" as a load bearing component. Change was and is necessary, as are new incentives – and penalties.The question isn't, therefore, whether or not something like the CRA is necessary and inevitable. The question is whether or not the CRA as it is written today is the appropriate tool for the job. And after multiple briefings on the subject, it seems safe to say that the jury is still very much out on that subject.
• [Blog Post] How much energy does Google's AI use? We did the math. - Concerned about the energy use of AI? The open access technical paper titled Measuring the environmental impact of delivering AI at Google Scale is available.

What exciting open source events and news are you hearing about? Let us know on our @GoogleOSS X account.

This Week in Open Source #8

This Week in Open Source for 08/15/2025

A look around the world of open source
by Daryl Ducharme & amanda casari, Google Open Source

Upcoming Events

• August 14-16: Open Source Festival 2025 (OSCAFest'25) is happening in Lagos, Nigeria. It uses community to help integrate the act of open source contribution to African developers whilst strongly advocating the movement of free and open source software.
• August 25-27: Open Source Summit Europe (OSSEU) is happening in Amsterdam, Netherlands. It is the premier event for the open source community to collaborate, share information, solve problems, and gain knowledge, furthering open source innovation and ensuring a sustainable open source ecosystem. Many Googlers will be there giving talks along with so many others.
• September 5-7: NixCon 2025 is happening in Switzerland. It is the annual conference for the Nix and NixOS community where Nix enthusiasts learn, share, and connect with others.
• September 9: Kubernetes Community Day 2025 SF Bay Area event, the ultimate gathering for cloud native enthusiasts! This full-day event, sponsored by the Cloud Native Computing Foundation (CNCF), is packed with insightful cloud native talks and unparalleled opportunities for community networking.
• September 12 - 16: PyCon AU 2025 is happening in Narrm/Melbourne. It is the national conference for the Python programming community, bringing together professional, student and enthusiast developers, sysadmins and operations folk, students, educators, scientists, statisticians, and many others besides, all with a love for working with Python.

Open Source Reads and Links

• [Article] Google Brings the A2A Protocol to More of Its Cloud - Last month, Google transferred the A2A protocol to the Linux Foundation and we are still continuing to improve it. Be it updating the spec, integrating it into Cloud Run and GKE we are still happy to see excitement about the future of this protocol.
• [Book] OSPO Book - Open Source Programs Offices are an important part of connecting open source communities to your company (if we do say so ourselves). If you are an open source enthusiast who thinks they can start one in their company, here is a good guide from CNCF. There's also a github repo for it.
• [Analysis] The RedMonk Programming Language Rankings: January 2025 - Redmonk's regular analysis of programming languages. Trends are remaining mostly steady across languages, which is an interesting trend of itself!
• [Blog] One Event at a Time: Funding Your Community the Realistic Way - Great writeup, from a PSF Board member, advising event organizers in the Python community on developing responsible and sustainable funding plans for their community events.
• Python Software Foundation News: The PSF has paused our Grants Program - The PSF is temporarily pausing their Grants Program after reaching their 2025 grant budget cap earlier than expected. While they know how important this program is to many in the community, this is a necessary step to protect both the future of the program and the short- and long-term sustainability of the PSF. (If this moves you immediately to donate to the PSF, we welcome your contributions via our donations page).

What exciting open source events and news are you hearing about? Let us know on our @GoogleOSS X account.

Google Summer of Code 2025: Contributor Statistics

The Numbers Are In: A Deep Dive into GSoC 2025 Stats

Google Summer of Code (GSoC) is an online global program that introduces students and beginner developers to open source software development. For our 21st year of the program we welcomed 1280 Contributors from 68 countries who are coding for 185 Mentoring Organizations.

With the coding period starting June 2nd, GSoC contributors are focused on their 2025 projects alongside their Mentors and the thriving open source communities they are working with. We are excited to share some statistics about the accepted contributors in this year's program.

Accepted GSoC Contributors

• 92.32% are participating in their first GSoC
• 43.04% had not contributed to open source before GSoC 2025
• 89.02% are enrolled in an academic program

Projects

• 53.68% of projects were large (~350 hours), 41.54% medium (~175 hours), 4% (~90 hour) projects
• Currently, 77.9% of projects are the standard 12 weeks in length, with 18.3% extending their projects between 14-22 weeks.

Proposals

We got a whopping 15,240 applicants submitting proposals (an increase of 130% of our previous high - a new record!) from 130 countries. These folks submitted 23,559 proposals, a 159% increase over last year!

96.55% applied to GSoC for the first time in 2025

Registrations

We had a record 98,698 people registering from 172 countries for the 2025 program, an increase of 124.4% over the previous high.

Mentors

This summer, 185 open-source organizations are participating in GSoC. Their projects are supported by over 2,100 mentors from 75 countries. These dedicated volunteers guide new contributors, helping them hone their skills.

Many of these mentors are highly experienced. Almost two-thirds have mentored GSoC contributors for four or more years.

A big thank you for being part of this wonderful community and for helping to spread the word about GSoC, which offers an invaluable opportunity for all the individuals beginning their journey in Open Source. We'll keep you updated with future entries about GSoC 2025, stay tuned!

–by Stephanie Taylor, Mary Radomile & Lucila Ortiz, Google Open Source Team