# Purge Queue (/sdks/java/how-to/management/purge-queue)



## Overview [#overview]

Purging a queue is a management-plane operation for wiping a channel's backlog without receiving and discarding messages one at a time. It's the tool you'd reach for when a bad producer floods a channel, when you need a clean slate between test runs, or when you're resetting a queue during a maintenance window — all without deleting and recreating the channel itself. Done properly, it's a single server-side call that tells the broker to acknowledge and drop every pending message on a channel, returning an affected-message count so you can confirm how much backlog was cleared.

> **Not implemented in the Java SDK.** `QueuesClient.purgeQueue()` always throws `NotImplementedException` in the current SDK version (3.x). The KubeMQ server supports the underlying `AckAllQueueMessages` gRPC call, but the Java SDK does not yet expose it as a stable API. Track progress in the [SDK feature matrix](https://github.com/kubemq-io/kubemq-java/blob/main/clients/feature-matrix.md).

As a workaround, you can drain a queue by receiving all waiting messages with `receiveQueueMessages` using `autoAckMessages(true)`, or by using the KubeMQ dashboard/CLI to purge channels in the meantime.

**Gotchas:** a client-side drain-and-ack loop is not atomic like a real purge — messages can be redelivered to other consumers mid-drain, and it competes with production traffic instead of running as a single server-side operation. It also won't reach messages already delivered to and held by another active consumer.

## Prerequisites [#prerequisites]

* KubeMQ server running on `localhost:50000`
* Java SDK installed (see [Getting Started](/sdks/java))

## Steps [#steps]

1. Build a `QueuesPollRequest` for the target channel with `autoAckMessages(true)` so every fetched message is acknowledged immediately — no separate `ack()`/`reject()` call needed.
2. Call `client.receiveQueueMessages(request)` in a loop until a poll returns zero messages, to drain a backlog larger than a single `pollMaxMessages` batch.
3. Track the running total from each response's message count to confirm how many messages were cleared.

```java title="DrainQueueExample.java"
QueuesClient client = QueuesClient.builder().address("localhost:50000").clientId("java-drain-client").build();

int totalDrained = 0;
while (true) {
    QueuesPollResponse response = client.receiveQueueMessages(QueuesPollRequest.builder()
            .channel("orders")
            .pollMaxMessages(100)
            .pollWaitTimeoutInSeconds(1)
            .autoAckMessages(true)
            .build());
    if (response.getMessages().isEmpty()) break;
    totalDrained += response.getMessages().size();
}
System.out.println("Drained " + totalDrained + " messages.");
```

## Related [#related]

* [Java SDK Reference](/sdks/java/reference)
* [Create Channel](/sdks/java/how-to/management/create-channel)
* [Delete Channel](/sdks/java/how-to/management/delete-channel)