Grails reconnect to mysql when having communications link failure - mysql

Question

I have an error that has plagued for quite some time and still no solution
Whenever I receive :
2018-07-16 11:21:27,815 [Thread-4] WARN spi.SqlExceptionHelper - SQL
Error: 0, SQLState: 08S01 2018-07-16 11:21:27,815 [Thread-4] ERROR
spi.SqlExceptionHelper - Communications link failure
The last packet successfully received from the server was 197,301
milliseconds ago. The last packet sent successfully to the server was
197,301 milliseconds ago.
The application never seems to reconnect. Even though this is my datasource configuration (it's an external configuration):
dataSource.dbCreate=none
dataSource.driverClassName=com.mysql.jdbc.Driver
dataSource.url=jdbc:mysql://****/*****?autoReconnect=true&failOverReadOnly=false&maxReconnects=10
dataSource.username=***
dataSource.password=******
dataSource.properties.maxActive = 50
dataSource.properties.maxIdle = 25
dataSource.properties.minIdle = 1
dataSource.properties.initialSize = 1
dataSource.properties.numTestsPerEvictionRun = 3
dataSource.properties.maxWait = 10000
dataSource.properties.testOnBorrow = true
dataSource.properties.testWhileIdle = true
dataSource.properties.testOnReturn = true
dataSource.properties.validationQuery = "select now()"
dataSource.properties.minEvictableIdleTimeMillis = 300000
dataSource.properties.timeBetweenEvictionRunsMillis = 300000
I saw several questions on this issue, but nothing that actually solved it for me.
NOTE : I just want to emphasis that this occurs rarely, so i'm not trying to solve the issue of link connection failure, I just want that when it happens to reconnect after retry so the system won't hang (another C process handles this adequately so I suspect the issue is with Hibernate or Grails)
These are my mysql config
[client]
port=3306
socket=/data/db/mysql/mysql.sock
[mysqld]
port=3306
datadir=/data/db/mysql
socket=/data/db/mysql/mysql.sock
log-bin=/data/db/mysql/mysql-bin
binlog_format=row
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
server-id=1
max_connections=250
[mysqld_safe]
log-bin=/data/db/mysql/mysql-bin
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
server-id=1
max_connections=250
Some other info
| wait_timeout | 28800
| tx_isolation | REPEATABLE-READ
| thread_handling | one-thread-per-connection
| Table_locks_immediate | 15090998 |
| Table_locks_waited | 7453 |
| table_definition_cache | 256
| table_lock_wait_timeout | 50
| table_open_cache | 64
| table_type | MyISAM
|Bytes_received | 2844964922 |
| Bytes_sent | 5623597485 |
| Com_select | 15003437 |
| Com_set_option | 35905 |
| Handler_commit | 10842183 |
| Handler_delete | 76 |
| Handler_discover | 0 |
| Handler_prepare | 410224 |
| Handler_read_first | 90118 |
| Handler_read_key | 47411397 |
| Handler_read_next | 6354573941 |
| Handler_read_prev | 2900331388 |
| Handler_read_rnd | 449 |
| Handler_read_rnd_next | 2183682054024 |
| Handler_rollback | 44 | |

Answer 1

This may cause because of initial datasource pool size and your mysql timeout config.
I use following configuration:
dataSource {
pooled = true
jmxExport = true
dbCreate = 'validate'
driverClassName = 'com.mysql.jdbc.Driver'
dialect = 'org.hibernate.dialect.MySQL5InnoDBDialect'
properties {
jmxEnabled = true
maxActive = 50
maxIdle = 25
minIdle = 5
initialSize = 5
minEvictableIdleTimeMillis = 60000
timeBetweenEvictionRunsMillis = 5000
maxWait = 10000
maxAge = 10 * 60000
numTestsPerEvictionRun = 3
testOnBorrow = true
testWhileIdle = true
testOnReturn = false
ignoreExceptionOnPreLoad = true
validationQuery = "SELECT 1"
validationQueryTimeout = 3
jdbcInterceptors = "ConnectionState;StatementCache(max=200)"
defaultTransactionIsolation = java.sql.Connection.TRANSACTION_READ_COMMITTED
abandonWhenPercentageFull = 100
removeAbandonedTimeout = 120
removeAbandoned = true
logAbandoned = false
dbProperties {
autoReconnect = true
jdbcCompliantTruncation = false
zeroDateTimeBehavior = 'convertToNull'
}
}
}
along with:
dataSource {
url = "jdbc:mysql://localhost:3306/dbname?useSSL=false&useUnicode=yes&characterEncoding=UTF-8&autoReconnect=true"
username = "user"
password = "xxxxx"
logSql = true
}

Answer 2

Does the application work fine on another database?
Kindly check your mysql settings and share what is in the following lines:
sudo nano /etc/mysql/my.cnf
wait_timeout = 28800
interactive_timeout = 28800
I am thinking this might not be a grails issue.