decision-maker

The decision-maker service resides on the engine module. This service is responsible for the following:

• evaluation of results of the traffic tests (both user-initiated and active probes) and determining which routes are candidates for assertion as the best path to a particular prefix
• management of the CNA system’s in-memory database, which constitutes all of the data the system knows about your network environment; it is kept in memory for speed of access
• management of the hourly snapshots of the systems database, which are stored on the system’s hard disk
• receiving traffic measurement data from the USTAT modules and updating the HRTT values in the database
• generation of data for the show prefix command (on the reporting module, this service uses the most recent database snapshot to generate output for the show prefix command when the last keyword is specified, otherwise data comes from the live database)

The service has a restart routine which you can specify when executing the medic call command.

You cannot partially configure a link and start the decision-maker process. All link configurations must be complete.

A full link configuration consists of the following:

module ustat <slot>
 
   link <link name>
 
      vip <vip address>
 

 
module engine <slot>
 
   link <link name>
 
      provider-as <AS#> <peering address>
 

 
module engine <slot>b
 
   bgp <AS#>
 
      neighbor <peering address> link <link name>
 

Whenever the decision-maker process is restarted, numerous log messages are generated. This is expected behavior; the messages do not indicate a problem.

NOTE: Restarting the decision maker process will clear the internal database in which traffic measurement data is stored. It can take several hours or several days, depending on user traffic to your website and your CNA configuration, to build the database sufficiently for the CNA system to begin choosing winners and asserting routes.