alibaba/nacos · error · UnsupportedOperationException

Condition not supported in Nacos distributed lock

Error message

Condition not supported in Nacos distributed lock

What it means

Thrown unconditionally by NacosLock.newCondition() because Nacos distributed locks cannot back a java.util.concurrent.locks.Condition across multiple processes. The class Javadoc documents this as a hard limitation: Condition is not supported in a distributed lock. Any code path that reaches newCondition() (directly or via frameworks that expect Lock.newCondition()) will hit this UnsupportedOperationException.

Source

Thrown at client/src/main/java/com/alibaba/nacos/client/lock/NacosLock.java:338

                // to prevent the lock from becoming permanently unusable.
                localReentrantCount.set(0);
                watchdog.unregister(key);
                localReentrantCount.remove();
                removed = true;
                LOGGER.error("Failed to unlock, key={}", key, e);
                throw new IllegalStateException("Failed to unlock: " + key, e);
            }
        } finally {
            inUnlock.remove();
            if (!removed && localReentrantCount.get() <= 0) {
                localReentrantCount.remove();
            }
        }
    }
    
    @Override
    public Condition newCondition() {
        throw new UnsupportedOperationException(
            "Condition not supported in Nacos distributed lock");
    }
    
    public String getKey() {
        return key;
    }
    
    public String getLockType() {
        return lockType;
    }
}

View on GitHub (pinned to 9b989acdf1)

Solutions

Do not call newCondition() on a NacosLock; remove all Condition/await/signal usage that targets this lock.
If condition-like coordination is needed across processes, use Nacos config listeners, naming subscription events, or a dedicated coordination primitive instead of Condition.
If using a framework that requires Lock.newCondition(), provide a local in-JVM lock for condition waits and use the NacosLock only for mutual exclusion.

Example fix

// before
NacosLock lock = lockService.getReentrantLock(key);
Condition cond = lock.newCondition(); // throws

// after — use a local lock for condition coordination
ReentrantLock localLock = new ReentrantLock();
Condition cond = localLock.newCondition();
NacosLock distLock = lockService.getReentrantLock(key); // for cross-process mutex only

Defensive patterns

Strategy: validation

Validate before calling

// Do not call newCondition(); use a local in-JVM lock for condition waits
ReentrantLock local = new ReentrantLock();
Condition cond = local.newCondition();

Type guard

public static boolean supportsCondition(Lock lock) { return !(lock instanceof NacosLock); }

Prevention

Do not pass NacosLock to frameworks that require Condition support.
Keep distributed locks for cross-process mutual exclusion only; do condition waits locally.

When it happens

Trigger: Calling nacosLock.newCondition() directly; passing a NacosLock to a library or utility that invokes newCondition() (e.g. some channel/queue implementations); using NacosLock in a JUC abstraction layer that requires Condition support.

Common situations: Porting local ReentrantLock code that used Condition/signal/await to a distributed NacosLock; generic concurrency frameworks that call newCondition() as part of setup; IDE-assisted refactors that keep await/signal calls.

Related errors

AI-assisted analysis of alibaba/nacos@9b989acdf1 (2026-08-14). Data as JSON: /api/errors/a94c87ef75c95cee. Report an issue: GitHub.