redisson: RedisTimeoutException: Unable to get connection

Expected behavior

Should work without any exception.

Actual behavior

Getting the following exception intermittently:

WARN  - org.redisson.client.RedisTimeoutException: Unable to get connection! Node source: NodeSource [slot=null, addr=null, redisClient=null, redirect=null, entry=MasterSlaveEntry [masterEntry=[freeSubscribeConnectionsAmount=1, freeSubscribeConnectionsCounter=50, freeConnectionsAmount=32, freeConnectionsCounter=128, freezed=false, freezeReason=null, client=[addr=redis://my.server.2.1.com:6379], nodeType=MASTER, firstFail=0]]], command: (INCR), command params: [mycommand:params] after 3 retry attempts org.redisson.client.RedisTimeoutException: Unable to get connection! Node source: NodeSource [slot=null, addr=null, redisClient=null, redirect=null, entry=MasterSlaveEntry [masterEntry=[freeSubscribeConnectionsAmount=1, freeSubscribeConnectionsCounter=50, freeConnectionsAmount=32, freeConnectionsCounter=128, freezed=false, freezeReason=null, client=[addr=redis://my.server.2.1.com:6379], nodeType=MASTER, firstFail=0]]], command: (INCR), command params: [mycommand:params] after 3 retry attempts
	at org.redisson.command.CommandAsyncService$10.run(CommandAsyncService.java:703) ~[redisson-2.14.1.jar:?]
	at io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:670) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
	at io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:745) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
	at io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:473) ~[netty-common-4.1.31.Final.jar:4.1.31.Final]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]

Steps to reproduce or test case

I have no idea when this occurs.

Redis version

4.0.11

Redisson version

2.14.1

Redisson configuration

ReplicatedServers. Please let me know if any specific setting is required.

What are the possible reasons for this exception? How to fix this?

Well, we don’t have too much load on the servers.