[FIXED] Error while deploying the Spring Boot app using Redis server in Tomcat server

Issue

I have a web application based on Spring boot (2.1.9.RELEASE) and using Redis server (Redis-x64-3.2.100 running as service) for Session attributes storage

The deployment in Eclipse as Spring Boot App goes well, the application can connect to Redis server and we can store/retrieve Session attributes

But when I wanted to deploy in Tomcat (version 9), I faced a problem linked to redis api in springframework :

Caused by: java.lang.LinkageError: loader constraint violation:
when resolving method "io.reactivex.Flowable.fromPublisher(Lorg/reactivestreams/Publisher;)Lio/reactivex/Flowable;"
the class loader (instance of org/apache/catalina/loader/ParallelWebappClassLoader) of the current class,
org/springframework/core/ReactiveAdapterRegistry$RxJava2Registrar, and the class loader (instance of java/net/URLClassLoader)
for the method's defining class, io/reactivex/Flowable, have different Class objects for the type org/reactivestreams/Publisher used in the signature

Given that I have set all required configuration in Tomcat server, in context.xml:

<ResourceLink name="bean/redisson"
              global="bean/redisson"
      type="org.redisson.api.RedissonClient" />

<Manager className="org.redisson.tomcat.JndiRedissonSessionManager"
     readMode="REDIS"
     jndiName="bean/redisson" />
<!-- Uncomment this to disable session persistence across Tomcat restarts -->
<!--
<Manager pathname="" />
-->
<Manager className="org.redisson.tomcat.RedissonSessionManager"
  configPath="${catalina.base}/conf/redisson.yaml" 
  readMode="REDIS" updateMode="DEFAULT" broadcastSessionEvents="false"/>

Change in server.xml:

<Resource name="bean/redisson"
      auth="Container"
          factory="org.redisson.JndiRedissonFactory"
          configPath="${catalina.base}/conf/redisson.yaml"
      closeMethod="shutdown"/>

The redisson.yaml contains:

singleServerConfig:
  idleConnectionTimeout: 10000
  connectTimeout: 10000
  timeout: 3000
  retryAttempts: 3
  retryInterval: 1500
  password: null
  subscriptionsPerConnection: 5
  clientName: null
  address: "redis://127.0.0.1:6379"
  subscriptionConnectionMinimumIdleSize: 1
  subscriptionConnectionPoolSize: 50
  connectionMinimumIdleSize: 24
  connectionPoolSize: 64
  database: 0
  dnsMonitoringInterval: 5000
threads: 16
nettyThreads: 32
codec: !<org.redisson.codec.FstCodec> {}
transportMode: "NIO"

And I put redisson-all-3.11.6.jar and redisson-tomcat-9-3.11.6.jar in Tomcat lib folder

Is the problem about redis vs Tomcat compatibility ? Did I miss something ? Thanks for your help in advance.

Solution

After a long examination of the issue, discovered that there are conflicts between Redis libraries and Tomcat server internal libraries

At the end, I decided to switch the session storage to JDBC and discard completely Redis :

In application.properties file

• Set the app property spring.session.store-type=jdbc
• Set the app property spring.session.jdbc.table-name=SPRING_SESSION
• Set the app property spring.jpa.hibernate.ddl-auto=none (create schema directly from an sql script)

In schema.sql file

Add two tables managing the session:

CREATE TABLE IF NOT EXISTS SPRING_SESSION (
    PRIMARY_ID CHAR(36) NOT NULL,
    SESSION_ID CHAR(36) NOT NULL,
    CREATION_TIME BIGINT NOT NULL,
    LAST_ACCESS_TIME BIGINT NOT NULL,
    MAX_INACTIVE_INTERVAL INT NOT NULL,
    EXPIRY_TIME BIGINT NOT NULL,
    PRINCIPAL_NAME VARCHAR(100),
    CONSTRAINT SPRING_SESSION_PK PRIMARY KEY (PRIMARY_ID)
);
CREATE UNIQUE INDEX IF NOT EXISTS SPRING_SESSION_IX1 ON MATFRONT.SPRING_SESSION (SESSION_ID);
CREATE INDEX IF NOT EXISTS SPRING_SESSION_IX2 ON MATFRONT.SPRING_SESSION (EXPIRY_TIME);
CREATE INDEX IF NOT EXISTS SPRING_SESSION_IX3 ON MATFRONT.SPRING_SESSION (PRINCIPAL_NAME);

CREATE TABLE IF NOT EXISTS SPRING_SESSION_ATTRIBUTES (
    SESSION_PRIMARY_ID CHAR(36) NOT NULL,
    ATTRIBUTE_NAME VARCHAR(200) NOT NULL,
    ATTRIBUTE_BYTES BLOB NOT NULL,
    CONSTRAINT SPRING_SESSION_ATTRIBUTES_PK PRIMARY KEY (SESSION_PRIMARY_ID, ATTRIBUTE_NAME),
    CONSTRAINT SPRING_SESSION_ATTRIBUTES_FK FOREIGN KEY (SESSION_PRIMARY_ID) REFERENCES MATFRONT.SPRING_SESSION(PRIMARY_ID) ON DELETE CASCADE
);

Thanks to that, I got rid of an additional entire server used only for storing session data

Answered By - Shessuky