Sessions allow identifying and storing information about users across multiple requests or page visits to a website. The Java Servlets API provides sessions through the HttpSession interface. Sessions are implemented using attributes to store data, listeners to handle events, and cookies or URL parameters to propagate the session ID. Application servers provide high availability of sessions through features like replication and failover.

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6. a presentation
from 2001

7. J2EE Servlet Sessions
_ javax.servlet.http.HttpSession
_ A way to identify a user across more than one page
request or visit to a Web site and to store information
about that user.
_ Application servers implement high availability features
• Replication, failover

8. J2EE Servlet Sessions API
_ Attributes
• set/getAttribute
_ Listeners
• Adding/removing attributes
• Creation/Expiry of sessions
• Failover of sessions
_ Propagated via cookie (JSESSIONID) or via URL or via
FORM parameters
jsession
attribute value
attribute value
attribute value
Set-Cookie:
JSESSIONID=eVMwvIslqWWdilsxbs!738403096!-1321526768;
path=/; secure; HttpOnly

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New Gen Old Gen Meta

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Since beginning of sessions - slow

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key{sharding_part}
twemproxy

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key{sharding_part}

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• Filter
• HttpServletRequestWrapper.getSession()
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Web App
Filter

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expire
session1 instant
session2 instant
session3 instant

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expire
session1 instant
session2 instant
session3 instant

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DEPENDENCIES!

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Session Filter
Web App
Filter
Filter

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Agent
Container
Web App
Filter

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java -javagent:$SESSION_PATH/session-agent.jar
-jar ../start.jar
--lib=$SESSION_PATH/session-replacement-shaded.jar
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