apache/hadoop · error · MetricsException

Unrecognized unit for flush interval: ${flushUnit}. Must be

Error message

Unrecognized unit for flush interval: ${flushUnit}. Must be one of: minute, hour, day

What it means

The optional unit suffix of roll-interval must be one of the recognized minute/hour/day spellings, case-insensitive with abbreviations and plurals: m/min/minute/minutes, h/hr/hour/hours, d/day/days. Any other alphabetic suffix reaches the switch default and throws MetricsException("Unrecognized unit for flush interval: <unit>"). Notably there is deliberately NO second unit — the smallest legal interval is one minute.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/sink/RollingFileSystemSink.java:383

        case "m":
        case "min":
        case "minute":
        case "minutes":
          millis = TimeUnit.MINUTES.toMillis(rollIntervalInt);
          break;
        case "h":
        case "hr":
        case "hour":
        case "hours":
          millis = TimeUnit.HOURS.toMillis(rollIntervalInt);
          break;
        case "d":
        case "day":
        case "days":
          millis = TimeUnit.DAYS.toMillis(rollIntervalInt);
          break;
        default:
          throw new MetricsException("Unrecognized unit for flush interval: "
              + flushUnit + ". Must be one of: minute, hour, day");
        }
      }
    } else {
      throw new MetricsException("Unrecognized flush interval: "
          + rollInterval + ". Must be a number followed by an optional unit."
          + " The unit must be one of: minute, hour, day");
    }

    if (millis < 60000) {
      throw new MetricsException("The flush interval property must be "
          + "at least 1 minute. Value was " + rollInterval);
    }

    return millis;
  }

  /**

View on GitHub (pinned to 2add963021)

Solutions

1. Express the interval using an allowed unit: 30minutes, 2hours, 1day (or abbreviations 30min, 2h, 1d)
2. Sub-minute intervals are impossible — the sink enforces a 1-minute minimum by design
3. Check for accidental characters after the unit (e.g. '1hour,')

Example fix

# before
*.sink.rolling.roll-interval=90seconds  # 'seconds' is not a recognized unit

# after
*.sink.rolling.roll-interval=2minutes

private static final Set<String> UNITS = Set.of("m", "min", "minute", "minutes",
    "h", "hr", "hour", "hours", "d", "day", "days");
Matcher m = Pattern.compile("^\\s*(\\d+)\\s*([A-Za-z]*)\\s*$").matcher(rollInterval);
if (m.matches() && !m.group(2).isEmpty() && !UNITS.contains(m.group(2).toLowerCase())) {
  throw new IllegalArgumentException("Unsupported roll-interval unit: " + m.group(2));
}

try {
  sink.init(subsetConf);
} catch (MetricsException e) {
  // 'Unrecognized unit for flush interval: <unit>' — only minute/hour/day (any case/abbrev/plural) allowed
  LOG.error("Fix roll-interval unit '{}' — allowed: m/min/minute, h/hr/hour, d/day (plural ok)",
      badUnit, e);
}

When it happens

Trigger: roll-interval=30s, 45sec, 1week, 1w, 2fortnights — any suffix letters outside the m/h/d families, including valid units from other systems.

Common situations: Translating durations from Log4j/Logback rolling policies (which accept week) or Prometheus-style '30s'; assuming seconds are supported; trailing stray letters from a paste.

Related errors

• Failed to create ${basePath}[source=${source}, allow-append=
• Unrecognized flush interval: ${rollInterval}. Must be a numb
• The flush interval property must be at least 1 minute. Value
• The ${key} property must be non-negative. Value was ${value}
• The supplied filesystem base path URI is not a valid URI: ${

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/585e6fccae5a65d0. Report an issue: GitHub.