private boolean maybeDrainPendingCall(Call call, long now) {
            try {
                Node node = call.nodeProvider.provide();
                if (node != null) {
                    log.trace("Assigned {} to node {}", call, node);
                    call.curNode = node;
                    getOrCreateListValue(callsToSend, node).add(call);
                    return true;
                } else {
                    log.trace("Unable to assign {} to a node.", call);
                    return false;
                }
            } catch (Throwable t) {
                // Handle authentication errors while choosing nodes.
                log.debug("Unable to choose node for {}", call, t);
                call.fail(now, t);
                return true;
            }
        }
Check whether a pending call can be assigned a node. Return true if the pending call was either
transferred to the callsToSend collection or if the call was failed. Return false if it
should remain pending.
clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java