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NetLogo User Community Models

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WHAT IS IT?

This model is a simulation of sessions and transactions on WebLogic.

HOW IT WORKS

The model starts with cluster-size servers and initial-users sessions and initial-threads on each server. For each iteration tx-volume transactions are simulated using the following algorithm:

* Select the next server (round robin).
* Calculate a random transaction duration between 1 and max-duration.
* If more than 90% of the threads are active, create threads-increase threads (overflow).
* Activate a thread that will live for the transaction duration.
* If no sessions have less than tx-per-user transactions, create a session.
* Add the transaction to a session.

After the transactions are run:

* Threads that have been active for their transaction durations are deactivated.
* Sessions that have no more transactions are deactivated.
* Sessions that have been idle for 1200 seconds are killed.

HOW TO USE IT

Set the initial conditions using the sliders. Press "go" to run the model continually. Press "step" to run one iteration.

World & View:

* Shapes: circles = servers, small triangles = threads, people = sessions
* Colors: red = active, green = idle, orange = thread overflow
* Server Labels: <sessions>:<active>,<idle>|<threads>:<active>,<idle>|<threads-added>

Sliders:

* tx-volume - transaction volume (rate)
* max-duration - maximum transaction duration
* initial-threads - initial threads to create on each server
* initial-users - initial users (sessions) to create on each server
* max-users - maximum users expected across all servers
* cluster-size - number of servers

Buttons:

* setup - Create servers, initial threads, and initial sessions.
* go - Run tx-volume transactions forever.
* step - Run tx-volume transactions for one iteration (tick).

Monitors:

* tx-count - number of transactions run
* ticks - simulated seconds
* tx-per-users - maximum number of transactions that will be run by a user (session)

CREDITS AND REFERENCES

Model created by Thornton Rose (thornton@rosesquared.org)

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