fix(analytics): keep polling alive when fetch throws a Throwable (SDK-86)

[tylerjroach]

Summary

ScheduledExecutorService#scheduleAtFixedRate permanently cancels future executions if the runnable throws an uncaught Throwable. fetchDefinitions() only catches Exception, so an Error (OutOfMemoryError, StackOverflowError, LinkageError, etc.) escaping would silently kill flag-definitions polling for the JVM's lifetime — and the thread factory has no UncaughtExceptionHandler to even surface it.

Wrap the scheduled runnable in a defensive try { fetchDefinitions(); } catch (Throwable t) { logger.log(SEVERE, ...) }. fetchDefinitions() keeps its Exception handling unchanged; the wrapper exists purely to swallow + log JVM-level escapes so the schedule keeps firing.

Context

Linear: SDK-86. Practical scope is narrow (JVM-level errors only) but the defense is one-line.

Test plan

• Full test suite passes (173 tests, was 172, +1 new)
• New testPollingSurvivesThrowableFromFetch arms an Error to escape the second httpGet call, then asserts the polling task continues to fire (callCount >= 3 after 2.5s with a 1s interval). Before the fix the scheduler would have cancelled the task on the Error and callCount would have stopped at 2.

[linear-code]

SDK-86

[greptile-apps]

Confidence Score: 5/5

Safe to merge — the change is a one-line catch-clause broadening with a targeted new test that directly validates the fix.

The change is minimal and well-scoped: broadening the catch inside fetchDefinitions() prevents the scheduler from ever seeing an uncaught Throwable. The new test exercises the exact failure mode (Error escaping httpGet) and confirms polling continues. No data-path or correctness regressions introduced.

No files require special attention.

Important Files Changed

Filename	Overview
src/main/java/com/mixpanel/mixpanelapi/featureflags/provider/LocalFlagsProvider.java	Broadens catch clause in fetchDefinitions() from Exception to Throwable, preventing ScheduledExecutorService from cancelling the polling task on JVM-level errors.
src/test/java/com/mixpanel/mixpanelapi/featureflags/provider/LocalFlagsProviderTest.java	Adds testPollingSurvivesThrowableFromFetch: arms an Error on the second httpGet call, then asserts callCount >= 3 after 2.5s to verify the polling task continues despite the thrown Error.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant SE as ScheduledExecutorService
    participant FD as fetchDefinitions()
    participant API as Mixpanel API

    loop Every pollingIntervalSeconds
        SE->>FD: run()
        FD->>API: httpGet(url)
        alt Success
            API-->>FD: JSON response
            FD->>FD: parseDefinitions()
            FD->>FD: flagDefinitions.set(...)
        else Exception (IOException, JSONException, etc.)
            FD->>FD: catch Exception log WARNING
        else Error (OOM, StackOverflow, etc.) NEW
            FD->>FD: catch Throwable log WARNING
        end
        FD-->>SE: return (no uncaught Throwable)
        Note over SE: Task stays scheduled
    end

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sequenceDiagram
    participant SE as ScheduledExecutorService
    participant FD as fetchDefinitions()
    participant API as Mixpanel API

    loop Every pollingIntervalSeconds
        SE->>FD: run()
        FD->>API: httpGet(url)
        alt Success
            API-->>FD: JSON response
            FD->>FD: parseDefinitions()
            FD->>FD: flagDefinitions.set(...)
        else Exception (IOException, JSONException, etc.)
            FD->>FD: catch Exception log WARNING
        else Error (OOM, StackOverflow, etc.) NEW
            FD->>FD: catch Throwable log WARNING
        end
        FD-->>SE: return (no uncaught Throwable)
        Note over SE: Task stays scheduled
    end

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_{Reviews (2): Last reviewed commit: "refactor: simplify Throwable catch to fe..." | Re-trigger Greptile}

[ketanmixpanel]

Using catch (Throwable t) instead of catch (Exception e) here will achieve same?

[ketanmixpanel]

@copilot can you check if this comment is valid?

[Copilot]

Yes, that's correct and simpler. Changed catch (Exception e) to catch (Throwable t) directly in fetchDefinitions() and removed the wrapper lambda — same protection, less indirection. Commit: refactor: simplify Throwable catch to fetchDefinitions directly.