Spring 数据 Neo4J - 无法在配置的最长时间内从池中获取连接

Question

We have a Reactive REST API using Spring Data Neo4j (SpringBoot v2.7.5) deployed to Kube.netes. When running a stress test to determine the breaking point, once the volume of requests that the service can handle has been breached, the service does not auto-recover, even after the load has dropped to a level at which the service can handle.

After the service has fallen over the Neo4J health indicator shows: “org.neo4j.driver.exceptions.ClientException: Unable to acquire connection from the pool within configured maximum time of 60000ms”

With respect to connection/configuration settings we are using defaults configured by SDN.

Observations: Up until the point at which the service breaks only a small number of connections are utilised, at the point at which it breaks the connections in use jumps up to the max pool size and the above mentioned error is observed. No matter how much time passes (even well beyond the max connection lifetime) the service is unable to acquire a connection from the pool. Upon manually shutting down and restarting the service/pod the service returns to a healthy state.

As an interim solution we now check the Neo4J health indicator, if the mentioned error is present the liveness state is set to down which triggers Kube.netes to restart the service automatically. However, I'm wondering if there is an underlying issue with the connections in the pool not getting 'cleaned up'?

Answer 1

You can take a look at this discussion https://github.com/spring-projects/spring-data-neo4j/issues/2632

I had the same issue. The problem is that either Spring Framework or Neo4j reactive transaction manager doesn't close connections in a complex reactive flow eg when there are a lot of inner calls/mappings and somewhere inside an exception is thrown.

So as a workaround you can add @Transactional in such places to avoid multiple transactions to be created.