private void onSuccessfulResponse(
        final long currentTimeMs,
        final FindCoordinatorResponseData.Coordinator coordinator
    ) {
        // use MAX_VALUE - node.id as the coordinator id to allow separate connections
        // for the coordinator in the underlying network client layer
        int coordinatorConnectionId = Integer.MAX_VALUE - coordinator.nodeId();
        this.coordinator = new Node(
                coordinatorConnectionId,
                coordinator.host(),
                coordinator.port());
        log.info("Discovered group coordinator {}", coordinator);
        coordinatorRequestState.onSuccessfulAttempt(currentTimeMs);
    }
Mark the current coordinator null.

@param cause         why the coordinator is marked unknown.
@param currentTimeMs the current time in ms.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/CoordinatorRequestManager.java