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3.3. Connect & Response timeouts
The HTTP request has two steps: contact the server, and then retrieve the file. A timeout can be specified for
each step, i.e. how long to wait for a connection, how long to wait for a response. A good value for both is 3
seconds.
3.4. Re-try Count
This specifies the number of retry attempts the check will make before it determines that the server is not
functioning. A value of 1 or less disables retries.
4. Adaptive Parameters
4.1. Adaptive Interval
This is the interval, in seconds, at which the balancer checks the load on the servers. A low value means the
balancer is very sensitive to load, but this comes at a cost of extra load on the balancer itself. 7 seconds is a
good starting value. This value must not be less than the HTTP checking interval (see below).
4.2. Adaptive URL
The Adaptive method retrieves load information from the servers via an HTTP inquiry. This URL specifies the
file where the load information of the servers is stored. The standard location is "/load". It is the servers’ job
to provide the current load data in this file in ASCII format. In doing so, the following must be considered:
An ASCII file containing a value in the range of 0 to 100 in the first line (where
0=idle and 100=overloaded). The file is set to "/load" by default.
The file must be accessible via HTTP
The URL must be the same for all servers that are to be supported by the adaptive method
Note: This feature is not only of interest for HTTP based Virtual Services, but for all Services. HTTP is merely
used as the transport method for extracting the application specific load information from the Real Server.
4.3. Port
The port number of the HTTP daemon on the servers. The default value is 80.
4.4. Min Control Variable Value
This value specifies a threshold below which the balancer will switch to static weight-based scheduling, i.e.
normal Weighted Round Robin. The value is a percentage of the maximum load (0-50 max.). The default is 5.
4.5. Min Weight Adjustment Value
This value specifies the minimum weight that can be assigned to this server, as a percentage of the initial
static weight it was given. For example, if the server was given 50 to start with and this adjustment value is
10, then the weight will never be set to below 10. A value of 5 is recommended.
4.6. Real Server Availability
This section displays the current online status of real servers, and enables a real server to be disconnected or
shut down cleanly. Each real server has a corresponding button, and pressing this button will take an online
server offline, and vice-versa.
