[Meta] Ensuring Stateless Services for Worker Mode (FrankenPHP/Swoole) - Audit results

[KevinMartinsDev]

Description

With the rise of persistent memory runtimes like FrankenPHP, ensuring that services are strictly stateless has become a priority. While FPM hides state-related issues by killing the process after each request, Worker mode exposes them, leading to memory leaks or data contamination between requests.

While auditing a project for FrankenPHP compatibility using Igor-PHP (a static analysis tool I'm developing), the tool identified several state-related issues within the API Platform core (vendor folder). After verifying these findings on the main branch, I've confirmed that several core services are not yet fully stateless or lack memory reset mechanisms.

Identified Patterns & Examples

1. Static State Persistence

Properties using the static scope persist across the entire process lifetime. In Worker mode, these are overwritten on every request but stay in memory, which is inefficient and bypasses service-oriented architecture benefits.

• Example: EntrypointAction
• Current code: private static ?ResourceNameCollection $resourceNameCollection = null;
• Risk: Unnecessary global state persistence.

2. Unbounded Memory Growth (Missing ResetInterface)

Several singleton services maintain internal caches (as arrays) that grow with each unique input. Without a mechanism to clear them, these services cause slow memory leaks in long-running processes.

• Examples: ResourceClassResolver, YamlPropertyExtractor.
• Impact: RAM usage will grow linearly over time until the worker is restarted.

3. State Contamination

Some services mutate internal properties during a request cycle. If an error or a specific edge case occurs, the property might keep its value for the next request, leading to unpredictable behavior.

• Example: ErrorListener (mutation of $this->controller).
• Impact: Request B might inherit the "error state" or decision logic of Request A.

Proven track record

I have already applied a similar audit to the Symfony core, leading to improvements regarding state management in worker mode (see symfony/symfony#63964). My goal is to bring the same level of robustness to API Platform.

Proposed Solution

I suggest a series of PRs to:

1. Refactor static properties into instance properties (since services are already singletons).
2. Implement ResetInterface on services holding internal caches so Symfony can automatically clear them between requests.
3. Ensure methods are stateless by moving temporary state into local variables or method arguments.

I've already started working on these fixes. I'm aware of related issues like #7868, but this audit focuses specifically on service state and memory stability.

Are you open to receiving PRs for these improvements on the main branch?

[KevinMartinsDev]

I've just submitted 4 Pull Requests addressing the most critical state issues (static properties, state contamination, and primary memory leaks).

I have identified a few other services (mostly metadata extractors and IRI converters) that could also benefit from ResetInterface to ensure 100% memory stability in long-running processes. I'll wait for your initial feedback on the current PRs before submitting the remaining fixes.