5.9.12 Measurement servers

The current section only deals with active and discovery capable measurement servers.

Every measurement server has a main process which starts and restarts the child processes. The child processes terminate themselves after RESTART_COLLECTOR_AFTER days, afterwards the main process automatically restarts them. The child processes are:

·       Automatic rediscovery process: it has two purposes. It reads the configuration from the database periodically and stores it in a local file for the other processes. It also rediscovers the equipments and updates the configuration in the database if there was some change. The process does this with the default measurement cycle and rediscovers every equipment during IF_CHECK_CIKLUS cycles. The possible configuration changes applied by the process depends on the measurement type but in neither case does it automatically create new measurements:

o   SNMP: it checks the interface description, index and speed. It also checks the name and the index of the non-interface measurements if the measurement type has a description field and it also deletes those interfaces and measurements according to the COLLECTOR_DELETE_MEASUREMENT which cannot be found in the equipment anymore. The default setting is that the application deletes these measurements.

o   Non SNMP: it checks the name, the index and the optional additional parameters of the measurements if the measurement type has a description field and it also deletes those interfaces measurements according to the COLLECTOR_DELETE_MEASUREMENT which cannot be found in the equipment anymore. The default setting is that the application deletes these measurements.

·       For every measurement interval there is a child process which reads the configuration from the local file, does the measuring and writes the result into SQLLDR files for the data loader component

Normally a measurement server cannot handle more than 370 000 measurements. If there is a need to measure more measurement then either new measurement servers need to be created for the same server group or NETvisor professional services is required. If the system has that many or more measurements for a server group and that server group has more than one member, then it is strongly recommended to use the start_stop_pvsr command line program to start the collector servers: either with the start parameter and no server id specified (starting every module) or with the start_group parameter. If we start the collector servers one-by-one with the start parameter and the server id (even if we give ALL server ids in one command to the program) then the system will eventually start, but very slowly and with an increased server load. This slow starting applies also if the start_host parameter is used.

The SNMP measurement server has an two additional specialitis. It checks the interface traffic counters received from the equipments against the interface speeds. Unless the value of the DISABLE_IFSPEED_CHECKING is 2, it disregards the received value if it is smaller than the previous one and the calculated interface traffic from the two values is greater than 150% of the interface speed. The other speciality is the DNS name => IP address conversation. If the address field of the equipment contains a name and not the IP address then PVSR uses asynchronous DNS queries to determine the IP address. It does so when it refreshes the equipments needed to collect data for, meaning that if the translation is not successful then the measurements will also not be successful at least until the next refresh cycle.