apache/cassandra · error · RuntimeException

CounterCacheKeysToSave must be non-negative.

Error message

CounterCacheKeysToSave must be non-negative.

What it means

CacheService.setCounterCacheKeysToSave sets how many counter-cache entries are saved per cycle and throws an untyped RuntimeException for negative counts before persisting the setting and rescheduling counterCache saving. Reached primarily through the CacheService JMX mbean.

Solutions

1. Pass a non-negative count; 0 is the minimal accepted value.
2. Clamp with Math.max(0, count) at the call site.
3. Fix the source expression producing the negative number.
4. Validate all cache-related JMX arguments before invoking the mbean.

Example fix

// before
mbean.setCounterCacheKeysToSave(delta); // delta may be negative
// after
mbean.setCounterCacheKeysToSave(Math.max(0, delta));

if (count < 0) throw new IllegalArgumentException("CounterCacheKeysToSave must be >= 0");
cacheService.setCounterCacheKeysToSave(count);

When it happens

Trigger: Calling setCounterCacheKeysToSave(count) with count < 0 via JMX or internal code.

Common situations: Runtime tuning with values computed from deltas that can be negative; typos in JMX consoles; porting settings that used -1 as an unlimited sentinel from other systems.

Related errors

• CounterCacheSavePeriodInSeconds must be non-negative.
• KeyCacheKeysToSave must be non-negative.
• KeyCacheSavePeriodInSeconds must be non-negative.
• RowCacheKeysToSave must be non-negative.
• capacity should not be negative.

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/3a50c6dc95c25fed. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/service/CacheService.java:271

    }

    public void setKeyCacheKeysToSave(int count)
    {
        if (count < 0)
            throw new RuntimeException("KeyCacheKeysToSave must be non-negative.");
        DatabaseDescriptor.setKeyCacheKeysToSave(count);
        keyCache.scheduleSaving(getKeyCacheSavePeriodInSeconds(), count);
    }

    public int getCounterCacheKeysToSave()
    {
        return DatabaseDescriptor.getCounterCacheKeysToSave();
    }

    public void setCounterCacheKeysToSave(int count)
    {
        if (count < 0)
            throw new RuntimeException("CounterCacheKeysToSave must be non-negative.");
        DatabaseDescriptor.setCounterCacheKeysToSave(count);
        counterCache.scheduleSaving(getCounterCacheSavePeriodInSeconds(), count);
    }

    public void invalidateKeyCache()
    {
        keyCache.clear();
    }

    public void invalidateKeyCacheForCf(TableMetadata tableMetadata)
    {
        Iterator<KeyCacheKey> keyCacheIterator = keyCache.keyIterator();
        while (keyCacheIterator.hasNext())
        {
            KeyCacheKey key = keyCacheIterator.next();
            if (key.sameTable(tableMetadata))
                keyCacheIterator.remove();
        }

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