Clash Royale CLAN TAG#URR8PPP

Redisson openning too many connections to add data to Redis queue

Redis: 4.9.103
Redisson:3.7.5


I have a Spring boot application that uses Redisson to access Redis.

I have been struggling with connection leak issue that is ultimately causing the application to fail with the following "Unable to get connection" error

[ERROR] – Servlet.service() for servlet [dispatcherServlet] in context with path threw exception [Request processing failed; nested exception is org.redisson.client.RedisTimeoutException: Unable to get connection! Node source: NodeSource [slot=null, addr=null, redisClient=null, redirect=null, entry=org.redisson.connection.SingleEntry@30bc754c], command: (RPUSH), command params: [PQ5, PooledUnsafeDirectByteBuf(ridx: 0, widx: 72, cap: 256)] after 3 retry attempts] with root cause
org.redisson.client.RedisTimeoutException: Unable to get connection! Node source: NodeSource [slot=null, addr=null, redisClient=null, redirect=null, entry=org.redisson.connection.SingleEntry@30bc754c], command: (RPUSH), command params: [PQ5, PooledUnsafeDirectByteBuf(ridx: 0, widx: 72, cap: 256)] after 3 retry attempts
at org.redisson.command.CommandAsyncService$8.run(CommandAsyncService.java:532) ~[redisson-3.6.5.jar!/:?]
at io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:668) ~[netty-common-4.1.24.Final.jar!/:4.1.24.Final]
at io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:743) ~[netty-common-4.1.24.Final.jar!/:4.1.24.Final]
at io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:471) ~[netty-common-4.1.24.Final.jar!/:4.1.24.Final]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_121]


The primary activity of the application is to get data from the customer and post it on a blocking queue.

To test what exactly is happening to the connection count when data is added to the queue, I tested the following test program.

public static void main(String args)
RedissonClient redisson = Redisson.create();
RBlockingQueue<String> pq = redisson.getBlockingQueue("PQString");
for (int i = 0; i < 1_000; i++)
pq.add("x");
try
Thread.sleep(100);
catch (InterruptedException e)

redisson.shutdown();



Before starting this program, Redis connections are 3

->watch -n 0.5 'lsof -i tcp:6379 | wc -l'

Every 0.5s: lsof -i tcp:6379 | wc -l
3


When the program runs, my connection count jumps to 69 .

Every 0.5s: lsof -i tcp:6379 | wc -l
69


I was not expecting the connections to go above 67 (64 default connections + 3 to begin with). I am trying to find out who is using additional 2 connections and is that the reason why in the actual application, connections increase rapidly as in the actual application, I have many such queues where data is being added. There I see, connections keep on increasing before they run out.

My Redisson configuration in the actual application is as follows:

Config config = new Config();
config.useSingleServer()
.setIdleConnectionTimeout(20_000)
.setPingTimeout(1000)
.setConnectTimeout(20_000)
.setTimeout(30_000)
.setRetryAttempts(3)
.setRetryInterval(1500)
.setReconnectionTimeout(3000)
.setFailedAttempts(3)
.setAddress("http://SERVER:PORT")
.setConnectionMinimumIdleSize(10)
.setConnectionPoolSize(64)
.setSubscriptionsPerConnection(5);


Why does queue add method adds up these many connections. What am I missing that is causing connections to leak?

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