英文:
Is there a way to actively get the newest MariaDB GTID without constantly querying the server?
问题
我建立了基于GTID的主从复制。我想获取主服务器或从服务器的最新GTID。我知道可以使用像"show variables like '%gtid%'"这样的方式来获取GTID，但这种方式需要定期查询。是否有任何关于MariaDB服务器可以主动通知的方法，如果我提供一个脚本或一个函数的话，MariaDB服务器可以主动通知最新的GTID？
英文:
I establish the master-slave replication based on GTID. And i want to get the newest GTID of master or slave, I know the way of getting GTID by show variables like '%gtid%', but this way requires constant timed query. Is there any way about mariadb server can active notice if I provide a script or a function.
if I provide a script or a function,Mmariadb server can active notice the newest GTID
答案1
得分: 2
MariaDB和MySQL都不能在没有客户端先前请求的情况下向客户端发送数据。
跟踪GTID（全局事务标识符）受到多个客户端连接器（例如MariaDB Connector/C或MariaDB Connector/Python）的支持，其中GTID将从上一个提交的OK数据包的会话状态信息中获取。
以下是Python中的一个简单示例：
import mariadb
def status_tracker(connection, status):
if 'last_gtid' in status:
print("last_gtid changed: %s" % status['last_gtid'])
conn = mariadb.connect(status_callback=status_tracker, db="test")
cursor = conn.cursor()
# 告诉服务器在会话状态信息中提交last_gtid
cursor.execute("SET @@session.session_track_system_variables='last_gtid'")
cursor.execute("CREATE TEMPORARY TABLE t1 (a int)")
conn.commit()
cursor.execute("CREATE TEMPORARY TABLE t2 (a int)")
conn.commit()
cursor.execute("SET gtid_seq_no=1000")
cursor.execute("CREATE TEMPORARY TABLE t3 (a int)")
conn.commit()
结果/输出：
last_gtid changed: 0-1-40802
last_gtid changed: 0-1-40803
last_gtid changed: 0-1-1000
英文:
Neither MariaDB nor MySQL can send data to clients without a previous request from the client.
Tracking the GTID is supported by several client connectors (like MariaDB Connector/C or MariaDB Connector/Python) where the GTID will be obtainted from the session state information of the OK packet from previous commit.
Here is a simple example in Python:
import mariadb
def status_tracker(connection, status):
if 'last_gtid' in status:
print("last_gtid changed: %s" % status['last_gtid'])
conn= mariadb.connect(status_callback=status_tracker, db="test")
cursor= conn.cursor()
# tell the server to submit last_gtid in session_state_information
cursor.execute("SET @@session.session_track_system_variables='last_gtid'")
cursor.execute("CREATE TEMPORARY TABLE t1 (a int)")
conn.commit()
cursor.execute("CREATE TEMPORARY TABLE t2 (a int)")
conn.commit()
cursor.execute("SET gtid_seq_no=1000")
cursor.execute("CREATE TEMPORARY TABLE t3 (a int)")
conn.commit()
Result/Output:
last_gtid changed: 0-1-40802
last_gtid changed: 0-1-40803
last_gtid changed: 0-1-1000
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