OPA & Go 1.25: Performance Alert With GOEXPERIMENT=jsonv2
Hey everyone,
I wanted to share something important that I discovered while playing around with Go 1.25 and the new JSON v2 experiment (GOEXPERIMENT=jsonv2). It's not an OPA bug, but it's definitely something that could affect those of us using OPA, so I thought it was worth bringing to your attention.
The Surprise: A Performance Hit
So, here's the deal. I was pretty stoked to try out the new JSON v2 features in Go 1.25. I mean, who doesn't love shiny new things, right? But when I enabled GOEXPERIMENT=jsonv2 with my OPA-related code, I was met with a bit of a surprise – a roughly 20% performance penalty.
geomean 64.06m 77.79m +21.43%
Yeah, you read that right. A 20% slowdown. Ouch!
Now, I know what you might be thinking: "Is OPA the problem?" But after digging a bit, I don't think so. It seems like this might be related to this issue on the Go GitHub repo: https://github.com/golang/go/issues/75026.
Diving Deeper into the Performance Penalty
Let's break down why this performance hit is significant and what it means for OPA users. When we talk about performance in the context of OPA, we're often talking about the speed at which policies can be evaluated. A 20% slowdown can translate to noticeable delays in decision-making, especially in high-throughput environments. This is why it's crucial to understand the potential impact of seemingly low-level changes, like those in the JSON handling library.
The GOEXPERIMENT=jsonv2 flag in Go 1.25 enables a new implementation of the JSON encoding and decoding logic. While the intention behind this experiment is to improve performance and add new features in the long run, it appears that there are some initial performance regressions in certain use cases. The issue linked above (https://github.com/golang/go/issues/75026) provides some insights into the potential causes, which might include changes in memory allocation patterns or the way certain JSON structures are handled.
For OPA users, this is particularly relevant because OPA relies heavily on JSON for both input data and policy definitions. Policies are often written in Rego, a language that works directly with JSON-like data structures. Therefore, any performance bottlenecks in JSON processing can directly impact OPA's evaluation speed.
To give you a clearer picture, imagine a scenario where OPA is used to authorize requests to a web application. Each request comes with a payload, often in JSON format, which OPA needs to parse and use for policy evaluation. If the JSON parsing is 20% slower, the overall request processing time will increase, potentially leading to a less responsive application.
Of course, the actual impact will vary depending on the specific policies, the size of the JSON data, and the overall workload. But the key takeaway here is that the GOEXPERIMENT=jsonv2 flag can introduce a significant performance overhead in certain situations, and OPA users should be aware of this when considering upgrading to Go 1.25.
Why This Matters to OPA Users
OPA, or the Open Policy Agent, is a powerful tool for policy-based control. It's used in a ton of different scenarios, from authorizing access to services to enforcing configurations. Because OPA often deals with JSON data (both as input and within policies), any performance hit in JSON processing can have a ripple effect.
Imagine you're using OPA to authorize requests to your super-cool web app. Each request comes with a JSON payload. If the JSON parsing is slower, that means OPA takes longer to make a decision, which can slow down your app. Nobody wants that, right?
The Current Workaround
For now, I'm sticking with github.com/go-json-experiment/json instead of jumping to encoding/json/v2 in Go 1.25. It's a solid alternative that doesn't seem to have the same performance issues.
Sticking with a Stable JSON Implementation
Given the performance penalty observed with GOEXPERIMENT=jsonv2, the decision to stick with github.com/go-json-experiment/json for now seems like a prudent one. This package provides a stable and well-tested JSON implementation that doesn't exhibit the same performance regressions. It allows OPA users to continue benefiting from the performance they've come to expect, without the overhead introduced by the experimental JSON v2 implementation.
The github.com/go-json-experiment/json package is designed to be a drop-in replacement for the standard encoding/json package in many cases. This means that the transition is relatively straightforward, and most existing code that uses encoding/json can be adapted to use the experimental package with minimal changes. This makes it an attractive option for those who want to avoid the potential performance issues with GOEXPERIMENT=jsonv2 without having to make significant changes to their codebase.
However, it's important to note that github.com/go-json-experiment/json is still an experimental package, and as such, it may have its own set of limitations or potential issues. While it doesn't exhibit the same performance penalty as GOEXPERIMENT=jsonv2 in this particular scenario, it's always a good idea to thoroughly test any changes in your own environment to ensure that they meet your specific requirements.
In the long run, the Go team is likely to address the performance issues with encoding/json/v2, and it may eventually become the preferred JSON implementation. But for now, sticking with a stable alternative like github.com/go-json-experiment/json provides a reliable way to avoid the observed performance penalty.
Raising Awareness
I know I don't have a super-duper OPA-specific benchmark to share (sorry about that!), but I really wanted to get this info out there. It's one of those things that can easily slip under the radar, and nobody wants a surprise performance hit after upgrading their Go version.
Why Sharing Knowledge is Key
This whole experience highlights why it's so important for us to share our findings and experiences within the community. We're all in this together, and by raising awareness about potential issues like this, we can help each other avoid headaches and ensure that our systems run smoothly. Imagine if I had kept this information to myself – other OPA users might have unknowingly enabled GOEXPERIMENT=jsonv2 and experienced the same performance penalty, without understanding the root cause. By sharing this, we can collectively make more informed decisions about our technology choices.
Moreover, this kind of information is valuable not just for OPA users, but also for the broader Go community. The Go team relies on feedback from users to identify and address performance issues and other bugs. By reporting these kinds of observations, we contribute to the overall improvement of the Go language and its ecosystem.
In this case, the performance penalty associated with GOEXPERIMENT=jsonv2 might not be immediately obvious without careful benchmarking and analysis. By sharing my findings, I hope to encourage others to test and report their own experiences, which can help the Go team prioritize and address the issue more effectively. It's a collaborative effort that benefits everyone in the long run.
Call to Action: Test and Share Your Findings
If you're an OPA user and you're planning to upgrade to Go 1.25, I highly recommend testing your code with and without GOEXPERIMENT=jsonv2 enabled. See if you can reproduce the performance penalty I observed, or if your use case is affected differently. And most importantly, share your findings with the community! Let's learn from each other and make sure we're all running the best possible code.
Final Thoughts
So, there you have it. A little heads-up about a potential performance hiccup with GOEXPERIMENT=jsonv2 in Go 1.25. Keep this in mind if you're working with OPA, and happy coding, guys!
I hope this helps you guys out! Let me know if you've seen anything similar, or if you have any other insights to share. We're all in this together, and the more we share, the better off we'll be.
Remember to always benchmark your code and be mindful of potential performance impacts when adopting new technologies or language features.
