apache/seatunnel · error · IllegalArgumentException

Already an MDCExecutor

Error message

Already an MDCExecutor

What it means

MDCTracer.tracing(context, Executor) rejects a delegate that is already an MDCExecutor with IllegalArgumentException. Double-wrapping an Executor would propagate MDC context through two layers and restore state out of order.

Source

Thrown at seatunnel-api/src/main/java/org/apache/seatunnel/api/tracing/MDCTracer.java:96

    public static <V> MDCCallable<V> tracing(MDCContext context, Callable<V> delegate) {
        if (delegate instanceof MDCCallable) {
            throw new IllegalArgumentException("Already an MDCCallable");
        }
        return new MDCCallable<>(context, delegate);
    }

    public static MDCExecutor tracing(Executor delegate) {
        return tracing(MDCContext.current(), delegate);
    }

    public static MDCExecutor tracing(Long jobId, Executor delegate) {
        return tracing(MDCContext.of(jobId), delegate);
    }

    public static MDCExecutor tracing(MDCContext context, Executor delegate) {
        if (delegate instanceof MDCExecutor) {
            throw new IllegalArgumentException("Already an MDCExecutor");
        }
        return new MDCExecutor(context, delegate);
    }

    public static MDCExecutorService tracing(ExecutorService delegate) {
        return tracing(MDCContext.current(), delegate);
    }

    public static MDCExecutorService tracing(Long jobId, ExecutorService delegate) {
        return tracing(MDCContext.of(jobId), delegate);
    }

    public static MDCExecutorService tracing(MDCContext context, ExecutorService delegate) {
        if (delegate instanceof MDCExecutor) {
            throw new IllegalArgumentException("Already an MDCExecutor");
        }
        return new MDCExecutorService(context, delegate);
    }

View on GitHub (pinned to cf67b549a7)

Solutions

1. Reuse the existing MDCExecutor instead of wrapping again
2. Keep a single wrapping point (executor factory) and never re-trace returned executors
3. Guard with `if (executor instanceof MDCExecutor) use it else tracing(...)`

Example fix

// before
MDCExecutor e = MDCTracer.tracing(jobId, MDCTracer.tracing(jobId, pool));
// after
MDCExecutor e = MDCTracer.tracing(jobId, pool);

Executor safeWrap(Long jobId, Executor e) {
    return e instanceof MDCExecutor ? e : MDCTracer.tracing(jobId, e);
}

boolean isWrapped(Executor e) {
    return e instanceof MDCExecutor;
}

try {
    return MDCTracer.tracing(jobId, executor);
} catch (IllegalArgumentException e) {
    return (MDCExecutor) executor;
}

When it happens

Trigger: Calling tracing(jobId, executor) or tracing(context, executor) where executor is already an MDCExecutor (possibly from wrapping an ExecutorService, since MDCExecutorService subclasses MDCExecutor).

Common situations: An application already returns MDC-wrapped executors from a factory and calling code wraps again; wrapping an MDCExecutorService obtained from tracing(ExecutorService).

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Already an MDCRunnable
• Already an MDCCallable
• Already an MDCConsumer
• Already an MDCFunction
• Already an MDCPredicate

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/d11e5728365360cc. Report an issue: GitHub.