java - Why R2DBC connection pool allocating MAX connections when not needed by the application - Stack Overflow

admin管理员组

文章数量:1122833

I have a Reactive JAVA Spring Boot application with R2DBC mysql with following configuration:

spring.r2dbc.pool.enabled=true
spring.r2dbc.pool.initial-size=0
spring.r2dbc.pool.max-size=20
spring.r2dbc.pool.max-acquire-time=30s
spring.r2dbc.pool.max-idle-time=1m

My Application has two workflow:

A. Generate data for processing - Uses 1 thread

• This consumes message from SQS and use it to prepare data.

• processMessage method is a reactive method which is processing message and generate data in reactive flow. Used .block as I have used Session Acknowledgement Mode as CLIENT_ACKNOWLEDGE

  myConsumerService.processMessage(message).block();

B. Process data - Uses 10 threads

• A single thread is processing these 3 operations one after another.

• Every MySQL operation is completed within two digit milliseconds.

• Used following code to get records from for MySQL Operations:

   public class MyRepository {
  
       private final R2dbcEntityTemplate template;
  
       public MyRepository(R2dbcEntityTemplate template) {
           this.template = template;
       }
  
       public Mono<MyEntity> getEntityById(Long id) {
           return template.select(MyEntity.class)
               .matching(Query.query(Criteria.where("id").is(id))).one();
       }
  }
  

I have used DEBUG logging mode for R2DBC(logging.level.io.r2dbc.pool=DEBUG) and it shows connection is acquired just before MySQL operation and released immediately after the MySQL operation.

Expected result : Application suppose to use maximum of 11 connections so allocated connections by the R2DBC connection should be 11.

Actual result : Logs shows 20 connections are allocated by the R2DBC connection pool.

Here is the log which I have observed : ConnectionPoolStats : Allocated : 20, Acquired : 1, Idle : 0, Pending : 9

For reference I have used following code to get ConnectionPoolStats:

 PoolMetrics metrics = connectionPool.getMetrics().orElse(null);

 if (metrics != null) {
     String connectionPoolStats = String.format("Allocated : %d, Acquired : %d, Idle : %d, Pending : %d",
             metrics.allocatedSize(), metrics.acquiredSize(),
             metrics.idleSize(), metrics.pendingAcquireSize());
     logger.info("ConnectionPoolStats : {}",  connectionPoolStats);
 } else {
     System.out.println("Connection Pool Metrics are not available.");
 }

Questions :

1. Why all the connections shows as allocation as application doesn't required at any point of time?
2. Is any probability where I lead to any unusual connection state?

本文标签： javaWhy R2DBC connection pool allocating MAX connections when not needed by the applicationStack Overflow