Kill slow queries in REST API Java Spring Boot - mysql

Question

We're designing an API Rest with the following technologies :
spring-boot 1.5.7
spring-data-jpa
MySQL 5.5.59
It's a Java REST API designs with spring-boot and connected to a MySQL database via a mysql-connector. Most of the queries in repositories are written in the JPA Query way.
To compile it we use maven and we deploy it in fatjar running in a tomcat sever.
The fact is several tables and resources within can be very large for one user. So when a GET request is made with high offset, we can deal with slow queries.
We tried several solutions like :
set tomcat parameters for the mysql connection
use hikari but no available parameters to kill slow queries
deploy the rest api in a glassfish5 server but the spring data jpa queries throw an execption (could not extract result set), so it's a problem.
Moreover, a lot of people gonna say me "use pagination and check the offset in the request". The fact is that we're using that but the class PageRequest have a tricky behaviour. Indeed, the resource the API give you back with this class has the shape below :
{
"content": {},
"links": [
{
"href": "string",
"rel": "string",
"templated": true
}
],
"page": {
"number": 0,
"size": 0,
"totalElements": 0,
"totalPages": 0
}
}
As you can see you have an object page with a field totalElements. This is the problem if you have a lot of entries in a table for one user. Because spring data gonna do a "SELECT COUNT(*)" to have this totalElements information. Pagination is not the solution cause we arleady have thid.
So what we're asking you are the best practices and maybe the solution to handle and kill slow queries in a Restful API designs with spring-boot.
Thanks !

Answer 1

Regarding the pagination have a look at this answer: Way to disable count query from PageRequest for getting total pages?
Basically return a List and not a Page. This of course will not give you the total so you will need to handle the situation differently. It might require one extra query for next page that will return an empty list but you will save the count on each page.
If you however still need the total for some reason you will have to do the count.
Regarding your comment "slow queries caused by your database": it is not the database that generates the slow queries. Slow queries are generate by you and your code. There might be solutions to your problems other than killing the running queries but you would need to provide more information about your database: structure, number of records, exact queries issues, what indexes are in place, etc. Maybe you could introduce caching?
If you still insist on killing the query you could run in inside a CompletableFuture and await for completion with timeout: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html

Answer 2

After a lot of research, I found a solution to my problem simply by reading focusely the tomcat datasource documentation. I found the jdbc interceptors I have set in my application.yml as below :
jdbc-interceptors: QueryTimeoutInterceptor(queryTimeout=20);SlowQueryReport(threshold=20000,logFailed=true)
So this do what I want, e.g that throws an exception if my query exceed 20 secs and kill it !
Thanks anyway for your help !