MySQL and Wicket: perform multiple queries parallel - mysql

Question

I have Wicket (8.6) application which access a MySQL (5.7) database. The mysql connection is established as follows in the spring-context.xml:
<bean id="dataSource" class="com.zaxxer.hikari.HikariDataSource"
destroy-method="close">
<property name="dataSourceClassName" value="com.mysql.cj.jdbc.MysqlDataSource" />
<property name="maximumPoolSize" value="5" />
<property name="maxLifetime" value="90000" />
<property name="idleTimeout" value="90000" />
<property name="connectionTimeout" value="90000" />
<property name="dataSourceProperties">
<props>
<prop key="url">jdbc:mysql://${db.url}/${db.name}?useGmtMillisForDatetimes=true&serverTimezone=UTC&useUnicode=true&characterEncoding=utf8</prop>
<prop key="user">${db.username}</prop>
<prop key="password">${db.password}</prop>
<prop key="prepStmtCacheSize">250</prop>
<prop key="prepStmtCacheSqlLimit">2048</prop>
<prop key="cachePrepStmts">true</prop>
<prop key="useServerPrepStmts">true</prop>
</props>
</property>
</bean>
I have the problem that I need to perform a very long SQL query which can easily take several minutes depending on the selected time range. I have expirienced that while the query is executed that the whole wicket application slows down to the point, that no other query is executed anymore. BTW: the long query is just a reading query. So it should not lock a table.
I would appreciate if anybody could help me to improve the connection between wicket and the mysql so that I can still run multiple queries while the long query is executed. I am not very familiar with the configuration of MySQL
Here are some settings from the my.cnf file:
skip-external-locking
innodb_file_per_table = 1
innodb_file_format = Barracuda
internal_tmp_disk_storage_engine=MyISAM
max_allowed_packet = 16M
thread_stack = 192K
thread_cache_size = 8
query_cache_limit = 1M
query_cache_size = 16M

Answer 1

The problem you experience is that you keep the HTTP connection during the long period of SQL Select operation.
Wicket allows at most one request to a Page instance. I.e. once you click the button/link Get data it will make an HTTP request to a particular page instance (identified by the page id parameter in the url, ?123&...) and until the SQL operation returns the user cannot make another request to the same page instance. The user can make requests to other page instances or create new ones though!
How to solve the problem ?
Change your button/link #onClick() callback method to make an asynchronous request to MySQL, i.e. in a new thread. This way the HTTP processing thread can continue and return an empty response.
Store the DB result in some temporary place, e.g. in-memory, in temporary DB table, ...
Show the data once it is available
An easy way is to use AbstractAjaxTimerBehavior to poll every few seconds for the DB result. Once the result is ready just render it by updating the model of some invisible Wicket Component, like DataTable, and show it via AjaxRequestTarget#add(table)
Use Wicket Native WebSocket to send the DB result as soon as possible. This way there is no need to store the result temporarily. You can even stream it