Eddie contains in-built real-time load monitoring
routines to track the usage of each Back End Server (shown in black) on
your site. This information is passed to a set of designated Front End
Servers (shown in blue) which perform Admission Control.
The Eddie Front End
Servers maintain a table of active sessions, tracking users who are
currently interacting with the site. As a client request comes in, a
check is made to see if this user has visited the site recently, say
in the last ten minutes. If they have, the request is immediately
passed to the appropriate server. If they have not, the Front End asks
Are there sufficient resources to serve this customer
properly right now?
If there are sufficient resources, the customer is immediately
accepted, and the Front End decides to which Back End Server to pass
the client request.
If there are not sufficient resources, the Front
End queues the request and returns a page to the client asking them to
be patient and informing them that their request will be processed as
soon as the next server becomes available (much like waiting in queue
for an airline booking operator over the telephone). When the
resources to process the request become available, the request is
passed to a server.
Eddie dynamically adjusts the rate at which new
customers are accepted to match resource availability. In this way
Eddie can provide rapid response time for every transaction the
customer initiates during a session with the site.