apache/iceberg · error · UnsupportedOperationException

NOOP timer has no unit

Error message

NOOP timer has no unit

What it means

The NOOP Timer has no configured reporting time unit because it never stores measurements. unit() throws UnsupportedOperationException to signal that this timer is a no-op sink and cannot describe its units. Only real timer implementations carry a TimeUnit.

Source

Thrown at api/src/main/java/org/apache/iceberg/metrics/Timer.java:150

      new Timer() {
        @Override
        public Timed start() {
          return Timed.NOOP;
        }

        @Override
        public long count() {
          throw new UnsupportedOperationException("NOOP timer has no count");
        }

        @Override
        public Duration totalDuration() {
          throw new UnsupportedOperationException("NOOP timer has no duration");
        }

        @Override
        public TimeUnit unit() {
          throw new UnsupportedOperationException("NOOP timer has no unit");
        }

        @Override
        public void record(long amount, TimeUnit unit) {}

        @Override
        public void time(Runnable runnable) {}

        @Override
        public <T> T timeCallable(Callable<T> callable) throws Exception {
          return callable.call();
        }

        @Override
        public <T> T time(Supplier<T> supplier) {
          return supplier.get();
        }

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Use a concrete Timer implementation with a defined unit instead of Timer.NOOP when unit information is required.
2. Branch on the NOOP instance and supply a default TimeUnit (e.g. TimeUnit.NANOSECONDS) for reporting purposes.
3. Filter out NOOP timers before iterating timers in report-building code.

Example fix

// before
TimeUnit unit = timer.unit();
// after
TimeUnit unit = (timer == Timer.NOOP) ? TimeUnit.NANOSECONDS : timer.unit();

boolean hasUnit = timer != Timer.NOOP;

if (timer == Timer.NOOP) { return TimeUnit.NANOSECONDS; } return timer.unit();

try { return timer.unit(); } catch (UnsupportedOperationException e) { return TimeUnit.NANOSECONDS; }

When it happens

Trigger: Calling Timer.NOOP.unit(), typically when serializing or reporting metrics and the code asks each timer for its unit regardless of implementation.

Common situations: Metric report/serialization code (e.g. producing commit reports) that queries unit() on every timer in a metrics structure while metrics are disabled; generic metric aggregation utilities.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• NOOP timer has no count
• NOOP timer has no duration
• NOOP counter has no value
• Count is not supported.
• Counter is not supported.

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/2d05fdcf086ebf11. Report an issue: GitHub.