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Many novices are not very clear about the comparison of several session synchronization solutions in the cluster. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can get something.

Session security and synchronization is the biggest problem in the cluster. Here are several session synchronization schemes I have collected, hoping to find out their adaptive scenarios by analyzing their respective advantages and disadvantages.

1. Client cookie encryption

This is the way I used to use, simple and efficient. A better way is to use the cookie mechanism to implement a session, and use this session in the application.

Problem: there can't be too much data in session, and it's best to have only one user id.

2. Session replication of application server

It is possible that most application servers provide session replication to implement clustering, and tomcat,jboss,was provides this feature.

Question:

Performance declines sharply as servers increase, and it is easy to cause broadcast storms

Session data needs to be serialized, affecting performance.

3. Use a database to save session

Use a database to save session, even if the server is down, session is still there.

Question:

The program needs to be customized

It is expensive to read and write to the database for each request (using an in-memory database can improve performance, and data will be lost due to downtime. Available in-memory databases with BerkeleyDB,Mysql memory tables)

Database is a single point, of course, you can do database ha to solve this problem.

4. Use shared storage to save session

Similar to the database, even if the server is down, session is still there. Use either nfs or windows file sharing, or a dedicated shared storage device.

Question:

The program needs to be customized

Frequent serialization and deserialization of data, whether there is an impact on performance

Shared storage is a single point, which can be solved through raid.

5. Use memcached to save session

This approach is similar to a database, but because it is accessed in memory, the performance is naturally much better than the database.

Question:

The program needs to be customized, which increases the workload.

The data stored in memcached needs to be serialized, so it is inefficient.

As soon as the memcached server dies, all session is lost. Can memchached be a HA? I don't know. It's not on the website.

6. Use terracotta to save session

Similar to memcached, but the data does not need to be serialized, and it is Find-Grained Changes, so the performance is better. The configuration is completely transparent to the original application, and the original program hardly needs to be modified. And terracotta itself supports HA.

Question: what is the performance of terracotta's HA for data replication?

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