@Test
    public void testConnectionTimeoutAfterThrottling() {
        awaitReady(client, node);
        short requestVersion = PRODUCE.latestVersion();
        int timeoutMs = 1000;
        ProduceRequest.Builder builder = new ProduceRequest.Builder(
            requestVersion,
            requestVersion,
            new ProduceRequestData()
                .setAcks((short) 1)
                .setTimeoutMs(timeoutMs));
        TestCallbackHandler handler = new TestCallbackHandler();
        ClientRequest r1 = client.newClientRequest(node.idString(), builder, time.milliseconds(), true,
                defaultRequestTimeoutMs, handler);

        client.send(r1, time.milliseconds());
        client.poll(0, time.milliseconds());

        // Throttle long enough to ensure other inFlight requests timeout.
        ProduceResponse pr = new ProduceResponse(new ProduceResponseData().setThrottleTimeMs(timeoutMs));
        ByteBuffer buffer = RequestTestUtils.serializeResponseWithHeader(pr, requestVersion, r1.correlationId());
        selector.delayedReceive(new DelayedReceive(node.idString(), new NetworkReceive(node.idString(), buffer)));
        ClientRequest r2 = client.newClientRequest(node.idString(), builder, time.milliseconds(), true,
                defaultRequestTimeoutMs, handler);
        client.send(r2, time.milliseconds());
        time.sleep(timeoutMs);
        client.poll(0, time.milliseconds());

        assertEquals(1, client.inFlightRequestCount(node.idString()));
        assertFalse(client.connectionFailed(node), "Connection should not have failed due to the extra time spent throttling.");
    }
This is a helper method that will execute two produce calls. The first call is expected to work and the
second produce call is intentionally made to emulate a request timeout. In the case that a timeout occurs
during a request, we want to ensure that we {@link Metadata#requestUpdate() request a metadata update} so that
on a subsequent invocation of {@link NetworkClient#poll(long, long) poll}, the metadata request will be sent.

<p/>

The {@link MetadataUpdater} has a specific method to handle
{@link NetworkClient.DefaultMetadataUpdater#handleServerDisconnect(long, String, Optional) server disconnects}
which is where we {@link Metadata#requestUpdate() request a metadata update}. This test helper method ensures
that is invoked by checking {@link Metadata#updateRequested()} after the simulated timeout.

@param requestTimeoutMs Timeout in ms
clients/src/test/java/org/apache/kafka/clients/NetworkClientTest.java