Cause:java.sql.SQLException:Could not retrieve transation read-only status server

Background

Recently in the deployment of a complete set of projects, the deployment process encountered a lot of problems, in order to summarize some such as the title of this error!

• Environment Description:
  using a distributed database , using the mysql!

### Cause: java.sql.SQLException: Could not retrieve transation read-only status server
; SQL []; Could not retrieve transation read-only status server; nested exception is java.sql.SQLException: Could not retrieve transation read-only status server, dubbo version: 2.5.3, current host: 127.0.0.1
org.springframework.dao.TransientDataAccessResourceException: 
### Error querying database.  Cause: java.sql.SQLException: Could not retrieve transation read-only status server

Troubleshoot problems

Because the code of the project has not changed, the current set of code has been run on the production, the cause of the error is not encountered in the previous production.

1, error, online search related information

By finding information on the Internet,
There are two ways to say it:
1), modify the isolation level of the database, andREPEATABLE-READmodify it toREAD-COMMITED.
2), database and application database driver (MySQL driver version inconsistent)

2. View database Information

mysql> SHOW VARIABLES LIKE ‘%iso%‘;
+-----------------------+-----------------+
| Variable_name         | Value           |
+-----------------------+-----------------+
| transaction_isolation | REPEATABLE-READ |
| tx_isolation          | REPEATABLE-READ |
+-----------------------+-----------------+
mysql> select version();
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    662239
Current database: shop

+-----------------------------------+
| VERSION()                         |
+-----------------------------------+
| 5.7.21-dbproxy-4.0-20180412155855 |
+-----------------------------------+

The discovery database configuration is indeedREPEATABLE-READ, because I cannot arbitrarily change this database, the database isolation level this business has the close relationship, then first solves from the version whether matches, has asked the related colleague:

q : Hello, 5.7.21-dbproxy-4.0-20180412155855 This version of the MySQL driver is required, the minimum MySQL driver is supported how much?
answer : 5.1.27~5.1.35

Check out the MySQL driver configuration for the current project, and discover that it is 5.1.24, version below the required version.

3. Upgrade MySQL Driver

Upgrade the MySQL version to 5.1.30, redeploy, find or error, and then upgrade to 5.1.32, after deployment, found no error. The problem is solved!

Summarize

There may be a number of ways to solve a problem, choose the most appropriate method, such as the above problem, there are two possible solutions, one is to modify the MySQL isolation level, a modification of the application of the MySQL driver version, the impact on the business is smaller, that must be Modify the MySQL driver version .

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Cause:java.sql.SQLException:Could not retrieve transation read-only status server