Setting Max Idle connections with Redis in Spring Boot - spring-boot

Question

I have a Simple Spring Boot 1.5.x REST API application with Redis Caching. I haven't added any custom configuratators and Spring boot automatically gets configured with Jedis. Redis properties are as follows,
spring.cache.type = redis
spring.redis.host = localhost
spring.redis.port = 6379
spring.redis.pool.max-active = 10000
spring.redis.pool.max-idle = 9000
spring.redis.pool.min-idle = 9000
Spring Boot Application Class
#SpringBootApplication
#EnableCaching
public class DemoApplication {
public static void main(String[] args) {
pringApplication.run(DemoApplication.class, args);
}
}
Usage
#RestController
public class UserController {
#Autowired
private UserService userService;
#RequestMapping(value = "/api/users/{id}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
#Cacheable(value = "UserDto", key = "#id")
public UserDto getUser(#PathVariable("id") Integer id){
User u = userService.getUser(id);
UserDto dto = new UserDto(u.getId(), u.getFirstName(), u.getLastName());
return dto;
}
}
If I load an API Endpoint with JMeter and monitor the number of connections maintained to Redis with a netstat continuously I can see the following output.
Netstat command :
while [ true ] ; do sudo netstat -anp | grep EST|grep "127.0.0.1:6379 ESTABLISHED"|wc -l; done
The Output
9000
9000
9006
9016
9031
9019
9000
9015
9005
9027
9046
9011
9005
9013
9011
9054
9010
9094
9061
9091
9036
9010
9004
9003
8935
8826
8387
7910
7122
6631
6524
6420
6300
6190
5776
5482
5475
5293
5187
5118
5081
5020
4992
4817
3996
3485
3582
6504
8964
9031
9136
9000
9025
9035
9000
9000
As you can clearly see the number of connections is getting decreased at the middle and then again rises to 9000 which does not seem like the desirable result.
Additionally I can see the following DEBUG logs.
2018-06-11 14:20:18.010 DEBUG 4151 --- [io-8080-exec-44] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.012 DEBUG 4151 --- [io-8080-exec-19] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.015 DEBUG 4151 --- [io-8080-exec-19] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.015 DEBUG 4151 --- [io-8080-exec-34] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.015 DEBUG 4151 --- [io-8080-exec-34] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.015 DEBUG 4151 --- [io-8080-exec-41] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.015 DEBUG 4151 --- [io-8080-exec-41] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.015 DEBUG 4151 --- [io-8080-exec-49] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.016 DEBUG 4151 --- [io-8080-exec-49] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.016 DEBUG 4151 --- [io-8080-exec-29] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.016 DEBUG 4151 --- [io-8080-exec-29] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.016 DEBUG 4151 --- [nio-8080-exec-3] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.016 DEBUG 4151 --- [nio-8080-exec-3] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.016 DEBUG 4151 --- [io-8080-exec-51] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.016 DEBUG 4151 --- [io-8080-exec-51] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
2018-06-11 14:20:18.017 DEBUG 4151 --- [io-8080-exec-45] o.s.d.redis.core.RedisConnectionUtils : Closing Redis Connection
2018-06-11 14:20:18.017 DEBUG 4151 --- [io-8080-exec-45] o.s.d.redis.core.RedisConnectionUtils : Opening RedisConnection
Based on the code in GitHub this happens due to continuous calling of doGetConnection and releaseConnection methods.
Is this desirable? If so what is the explanation for seeing a connection count less than 9000?
If this is not accurate what are the things I can try?