Aerospike迁移--2

emigration_send_start{    ...msg_set_uint32(m, MIG_FIELD_OP, OPERATION_START);    ...    uint64_t start_xmit_ms = 0;    //向目标节点发送消息后，等待emig->ctrl_q队列接收到返回的ACK    //如果在1秒钟内，没收到，则继续向目标节点重发；否则循环等待队列//emig->ctrl_q接收到不同的ACK类型，返回不同结果，外层调用做相应处理    while (true) {        uint64_t now = cf_getms();        if (cf_queue_sz(emig->ctrl_q) == 0 &&             start_xmit_ms + MIGRATE_RETRANSMIT_STARTDONE_MS < now) {            msg_incr_ref(m);            as_fabric_send(emig->dest, m, AS_FABRIC_CHANNEL_CTRL);start_xmit_ms = now;}        if (cf_queue_pop(emig->ctrl_q, &op, MIGRATE_RETRANSMIT_STARTDONE_MS) ==CF_QUEUE_OK) {    switch (op) {            case OPERATION_START_ACK_OK:                as_fabric_msg_put(m);                return EMIG_START_RESULT_OK;            case OPERATION_START_ACK_EAGAIN:                as_fabric_msg_put(m);                return EMIG_START_RESULT_EAGAIN;            case OPERATION_START_ACK_FAIL:                cf_atomic_int_incr(&ns->migrate_tx_partitions_imbalance);                as_fabric_msg_put(m);                return EMIG_START_RESULT_ERROR;            default:                cf_warning(AS_MIGRATE, "unexpected ctrl op %d", op);                break;            }        }    }    ...}

thread:run_fabric_recv->
fabric_connection_process_readable->
fabric_connection_process_msg：
(*g_fabric.msg_cb[m->type])(node, m, g_fabric.msg_udata[m->type]);
m->type；M_TYPE_MIGRATE即该函数是migrate_receive_msg_cb


emig->ctrl_q队列接收ACK是由run_fabric_recv线程处理，即由函数

migrate_receive_msg_cb处理。和迁入消息处理是一个函数。

intmigrate_receive_msg_cb(cf_node src, msg *m, void *udata){uint32_t op;if (msg_get_uint32(m, MIG_FIELD_OP, &op) != 0) {...}switch (op) {//--------------------------------------------// Emigration - handle requests://case OPERATION_MERGE_META:emigration_handle_meta_batch_request(src, m);break;//--------------------------------------------// 迁入Immigration - handle requests://case OPERATION_START:immigration_handle_start_request(src, m);break;case OPERATION_INSERT:immigration_handle_insert_request(src, m);break;case OPERATION_DONE:immigration_handle_done_request(src, m);break;case OPERATION_ALL_DONE:immigration_handle_all_done_request(src, m);break;//--------------------------------------------// 迁出Emigration - handle acknowledgments://case OPERATION_INSERT_ACK:emigration_handle_insert_ack(src, m);break;case OPERATION_START_ACK_OK:case OPERATION_START_ACK_EAGAIN:case OPERATION_START_ACK_FAIL:case OPERATION_DONE_ACK:case OPERATION_ALL_DONE_ACK:emigration_handle_ctrl_ack(src, m, op);break;//--------------------------------------------// Immigration - handle acknowledgments://case OPERATION_MERGE_META_ACK:immigration_handle_meta_batch_ack(src, m);break;default:cf_detail(AS_MIGRATE, "received unexpected message op %u", op);as_fabric_msg_put(m);break;}return 0;}

这里只分析迁出：
emigration_handle_ctrl_ack：
    cf_queue_push(emig->ctrl_q, &op);
    emigration_release(emig);


总结：
1、emigration_send_start函数发送OPERATION_START，目标节点接收到后返回
   OPERATION_START_ACK_OK
2、本节点run_fabric_recv函数接收到ACK，并将ACK类型push到emig->ctrl_q队列中
3、emigration_send_start函数从emig->ctrl_q队列pop出接收到的ACK后，退出，进入下一步
4、emigrate_tree函数发送迁移的记录消息OPERATION_INSERT
5、目标节点插入完成，回应OPERATION_INSERT_ACK。
6、emigrate_tree迁移完成后，进入下一步emigration_send_done
7、emigration_send_done发送OPERATION_DONE进入循环等待emig->ctrl_q接收相应；
   目标节点接收OPERATION_DONE后，发送OPERATION_DONE_ACK，本阶段接收到ACK退出。
   迁移完成。
 这里只是迁移的流程框架，具体细节需要结合代码仔细分析