apache/pulsar · warning · RestException

Subscription has active connected consumers

Error message

Subscription has active connected consumers

What it means

HTTP 412 PRECONDITION_FAILED returned when deleting a subscription whose cursor still has active connected consumers. The per-partition delete throws PreconditionFailedException (broker refuses to remove a subscription in use) and the aggregated handler converts it to 'Subscription has active connected consumers'.

Source

Thrown at pulsar-broker/src/main/java/org/apache/pulsar/broker/admin/impl/PersistentTopicsBase.java:1721

                        try {
                            adminClient = pulsar().getAdminClient();
                        } catch (PulsarServerException e) {
                            return CompletableFuture.failedFuture(e);
                        }
                        for (int i = 0; i < partitionMetadata.partitions; i++) {
                            TopicName topicNamePartition = topicName.getPartition(i);
                            futures.add(adminClient.topics()
                                    .deleteSubscriptionAsync(topicNamePartition.toString(), subName, force));
                        }

                        return FutureUtil.waitForAll(futures).handle((result, exception) -> {
                            if (exception != null) {
                                Throwable t = exception.getCause();
                                if (t instanceof NotFoundException) {
                                    throw new RestException(Status.NOT_FOUND,
                                            "Subscription not found");
                                } else if (t instanceof PreconditionFailedException) {
                                    throw new RestException(Status.PRECONDITION_FAILED,
                                            "Subscription has active connected consumers");
                                } else {
                                    throw new RestException(t);
                                }
                            }
                            return null;
                        });
                    }
                    return internalDeleteSubscriptionForNonPartitionedTopicAsync(subName, authoritative, force);
                });
            }
        });
    }

    // Note: this method expects the caller to check authorization
    private CompletableFuture<Void> internalDeleteSubscriptionForNonPartitionedTopicAsync(String subName,
                                                                                          boolean authoritative,
                                                                                          boolean force) {

View on GitHub (pinned to 820761864e)

Solutions

1. Disconnect all consumers of the subscription, then retry the delete.
2. Use force delete (`DELETE .../subscription/{sub}?force=true` or `pulsar-admin topics unsubscribe --force`) after confirming the consumers should be evicted.
3. Identify connected consumers with `pulsar-admin topics stats <topic>` (look at the subscription's consumers list) and shut them down first.
4. Schedule subscription cleanup during maintenance windows when consumers are stopped.

Example fix

// before
curl -X DELETE .../persistent/t/ns/topic/subscription/old-sub   // 412
// after
curl -X DELETE .../persistent/t/ns/topic/subscription/old-sub?force=true

TopicStats stats = admin.topics().getStats(topic);
boolean hasConsumers = stats.getSubscriptions().getOrDefault(subName,
        new SubscriptionStats()).consumers.stream().findAny().isPresent();
if (!hasConsumers) {
    admin.topics().deleteSubscription(topic, subName);
}

try {
    admin.topics().deleteSubscription(topic, subName);
} catch (PulsarAdminException.PreconditionFailedException e) {
    // consumers still connected: disconnect then retry, or use force=true
}

When it happens

Trigger: DELETE .../subscription/{subName} (or force=false unsubscribe) while consumers are connected on that subscription; also via `pulsar-admin topics unsubscribe` with connected readers/consumers using shared/exclusive subscriptions.

Common situations: Ops tries to clean up a subscription during business hours with live consumers; shared-subscription consumers reconnecting between check and delete; consumers stuck due to network issues but still registered; batch jobs deleting stale subscriptions without checking consumer count first.

Related errors

• Subscription not found
• getSubNotFoundErrorMessage(topicName.toString(), subName)
• cluster data is required
• Cannot delete non empty namespace
• Namespace does not exist

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/4a1950137eee3b39. Report an issue: GitHub.