mongodb connection not getting closed in Spring-boot - spring

Question

My SpringConfig.xml says:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mongo="http://www.springframework.org/schema/data/mongo"
xsi:schemaLocation="http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/data/mongo
http://www.springframework.org/schema/data/mongo/spring-mongo-1.10.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<mongo:mongo-client id="mongo" host="127.0.0.1" port="27017" >
<mongo:client-options
connections-per-host="8"
threads-allowed-to-block-for-connection-multiplier="4"
connect-timeout="1000"
max-wait-time="1500"
socket-keep-alive="true"
socket-timeout="1500"
/>
</mongo:mongo-client>
<mongo:db-factory dbname="test" mongo-ref="mongo" />
<bean id="mappingContext"
class="org.springframework.data.mongodb.core.mapping.MongoMappingContext" />
<bean id="defaultMongoTypeMapper"
class="org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper">
<constructor-arg name="typeKey"><null/></constructor-arg>
</bean>
<bean id="mappingMongoConverter"
class="org.springframework.data.mongodb.core.convert.MappingMongoConverter">
<constructor-arg name="mongoDbFactory" ref="mongoDbFactory" />
<constructor-arg name="mappingContext" ref="mappingContext" />
<property name="typeMapper" ref="defaultMongoTypeMapper" />
</bean>
<bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate">
<constructor-arg name="mongoDbFactory" ref="mongoDbFactory" />
<constructor-arg name="mongoConverter" ref="mappingMongoConverter" />
</bean>
</beans>
I am calling this only once in constructor of my service:
ApplicationContext ctx;
public DoctorService() {
ctx = new GenericXmlApplicationContext("SpringConfig.xml");
}
And then using ctx like:
MongoOperations mongoOperation = (MongoOperations) ctx.getBean("mongoTemplate");
Query searchUserQuery = new Query(Criteria.where("_id").is( new ObjectId(userId)));
Keys k = new Keys();
Doctor doctor = mongoOperation.findOne(searchUserQuery, Doctor.class);
k.setSessionId(doctor.getSessionid());
k.setToken(doctor.getToken());
List<Keys> keys = new ArrayList<Keys>();
keys.add(k);
return keys;
However, the connection is not getting closed, even after the timeout period.
Any idea?
Thanks

Answer 1

There is a max 100 sized connection pool for each mongo template (as default), and these are reused again & again for speed, so the connections will not be closed, that is connections-per-host="8" in your mongo client options. So you will have at most 8 connections, and they will stay as long as your app stays. To have auto
EDIT: To kill connections, you can use the following property to have them commit suicide with a timer maxConnectionIdleTime: 1000, so any idle connection that has a idle time > 1000ms will be killed, this does work, I've tested & the change of connection pool size can be seen below;
Spike after server restart is my load test, and it did not reach its full connection pool limit, and after peaking, the connections were killed. Though it must be said that the connection creation is indeed really costly, my response time increased more than hundredfold, so not the best solution not having a connection pool, though it would be better to have a somewhat long maxConnectionIdleTime so only after a long inactivity you'd start killing connections, and also having a minConnectionsPerHost value, so you'd always have a decent amount of connection pool ready, if needed you'd increase it, then kill the excess when server is less active, rinse and repeat!