Bots/Crawlers session management at Tomcat Valves

Tomcat Valves are nothing but filters at the container level.

Conventional servlet filters are at request specific whereas Tomcat Valves will act as filters for the whole container instead of a specific requests.

OOTB Implementation CrawlerSessionManagerValve : 

1. It identifies whether the request comes from Bots/Crawlers or from legitimate users.

2. If the request is from bots :

• Store the session ID in a Map and use the same session ID for all the requests from the same Bot/Crawler.
• Key: request.getHost() + request.getContext() + clientIp
• Value:  Session ID

 3. This way we can reduce the number of sessions created by Bots. Otherwise, a huge number of requests from Bots will create too many session objects which are not desirable. 

Overriding OOTB Tomcat Valves or Create Custom Tomcat Valve :

Please refer to this link: https://stackoverflow.com/questions/6573325/implementing-tomcat-custom-valve