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mysql cannot connect to mysql-server in post-processing , if the host is not localhost in the .mylogin.cnf

Description

During the post-processing step in wsrep_sst_common , the script will connect mysql-server to check replication status via the $upgrade_socket.

slave_status=$($mysql_client_path \ --defaults-file=/dev/stdin \ --socket=$upgrade_socket \ --unbuffered --batch --silent --skip-column-names \ -e "SHOW SLAVE STATUS;" \ 2> ${mysql_upgrade_dir_path}/show_slave_status.out <<EOF [client] user=${sst_user} password="${sst_password}" EOF

Because the mysql-server is started with --skip-networking, the mysql can only connect to mysql-server with socket.

If we set the host to 127.0.0.1 in the .mylogin.cnf , the post-processing step will be failed.

shell> mysql_config_editor set --login-path=mysql --host=127.0.0.1 --user=msandbox --password

The error log can be found below

2024-11-07T04:12:33.970763Z 0 [Note] [MY-000000] [WSREP-SST] Waiting for server instance to start..... This may take some time 2024-11-07T04:12:35.112298Z 0 [Note] [MY-000000] [WSREP-SST] (debug) MySQL server(1922514) started 2024-11-07T04:12:35.112345Z 0 [Note] [MY-000000] [WSREP-SST] (debug) Checking run_reset_slave: check 2024-11-07T04:12:35.112354Z 0 [Note] [MY-000000] [WSREP-SST] (debug) Checking slave status 2024-11-07T04:12:35.112379Z 0 [Note] [MY-000000] [WSREP-SST] (debug) Checking slave status command: /home/opt/percona_xtradb_cluster/8.0.36/bin/mysql 2024-11-07T04:12:35.126841Z 0 [ERROR] [MY-000000] [WSREP-SST] ******************* FATAL ERROR ********************** 2024-11-07T04:12:35.126890Z 0 [ERROR] [MY-000000] [WSREP-SST] Failed to execute mysql 'SHOW SLAVE STATUS'. Check the parameters and retry 2024-11-07T04:12:35.126899Z 0 [ERROR] [MY-000000] [WSREP-SST] Line 896 errcode:1 2024-11-07T04:12:35.127607Z 0 [ERROR] [MY-000000] [WSREP-SST] ------------ show slave status log (START) ------------ ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1:3306' (111) 2024-11-07T04:12:35.127654Z 0 [ERROR] [MY-000000] [WSREP-SST] ------------ show slave status log (END) ------------

Because I add some codes for debugging, the Line 896 should be different

Before setting the host, the mysql will use the unix socket

shell> mysql \ --defaults-file=/dev/stdin \ --socket=/tmp/mysql_test.sock \ --unbuffered --batch --silent --skip-column-names \ -e "\s" <<EOF EOF ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql_test.sock' (2)

After we set the host, the mysql will use TCP/IP

shell> mysql_config_editor set --login-path=mysql --host=127.0.0.1 --user=msandbox --password Enter password:
shell> mysql \ --defaults-file=/dev/stdin \ --socket=/tmp/mysql_test.sock \ --unbuffered --batch --silent --skip-column-names \ -e "\s" <<EOF EOF ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1:3306' (111)

 

reproduce

  • stop a pxc node

  • setting host to 127.0.0.1 in the .mylogin.cnf

mysql_config_editor set --login-path=mysql --host=127.0.0.1 --user=msandbox --password

  • remove all files in the datadir of the node to invoke SST

  • start the node

suggestion

Changing the environment MYSQL_TEST_LOGIN_FILE=/dev/stdin can avoid this issue, for example

shell> mysql \ --defaults-file=/dev/stdin \ --socket=/tmp/mysql_test.sock \ --unbuffered --batch --silent --skip-column-names \ -e "\s" <<EOF EOF ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1:3306' (111) shell> MYSQL_TEST_LOGIN_FILE=/dev/stdin mysql \ --defaults-file=/dev/stdin \ --socket=/tmp/mysql_test.sock \ --unbuffered --batch --silent --skip-column-names \ -e "\s" <<EOF EOF ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql_test.sock' (2)

Environment

None

AFFECTED CS IDs

CS0050666

Activity

Kamil Holubicki December 10, 2024 at 9:34 AM

I think the issue is not only on the joiner side, however, in real-life scenario, only joiner is affected slightly smiling face

If the donor’s port is not the default one (let’s say 4000) and there is .mylogin.cnf file present with only host parameter (no port), the donor will fail as well, because during the SST process, the SST script queries the server for keyring_component status.

On the Joiner side, the script connects to short-living SST instance that has networking disabled (as per ticket description). At the beginning, it pings the instance using mysqladmin, to detect if the instance is up and ready, then executes a few queries. If .mylogin.cnf file is present, both mysqladmin and mysql client are affected.

Done

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Created November 7, 2024 at 4:29 AM
Updated January 23, 2025 at 4:50 PM
Resolved December 17, 2024 at 11:51 AM

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