System-load statistics collection

Content Platform S Series Node Help

Version
4.0.0
Audience
anonymous
Part Number
MK-HCPS027-02

When you request system-load information, the S Series Node returns statistics for a variety of processing resources for each server module and for the S Series Node as a whole. On receiving a request for system-load information, the S Series Node uses values stored by both server modules to calculate the statistics to return for the individual server modules and for the S Series Node. The S Series Node returns the calculated statistics in the management API response and also caches the individual server-module values and the calculated statistics in memory.

Each server module updates its system-load values once a minute. As a result, multiple requests made for system-load information within the same one-minute interval return the same statistics.

The S Series Node includes a timestamp in the response to a request for system-load statistics. The timestamp is the earlier of the times when the applicable values were provided by each server module. The older the timestamp is, the less reliable the statistics are.

If a server module has not updated its values for three or more minutes, the values are considered stale. If the values for only one server module are stale, the S Series Node uses the cached values for that server module and the current values for the other server module to calculate the system-load statistics. In this case, the S Series Node does not update the timestamp, so the timestamp returned with the statistics is the time when the server module with the stale values last updated those values. With stale values from one server module, the calculated system-load statistics are not fully reliable.

If the values for both server modules are stale, the S Series Node returns the cached statistics to the client. In this case, the timestamp returned with the statistics is the earlier of the times each server module last updated the applicable values. With stale values from both server modules, the calculated system-load statistics may not accurately reflect the current load on the S Series Node processing resources.

If a server module is unavailable when the S Series Node receives a request for system-load information, the S Series Node uses zero as the default value for each statistic for that server module and uses the current values for the other server module to calculate the system-load statistics. In this case, the S Series Node returns an updated timestamp with the statistics.

After a restart of the S Series Node, until both server modules have finished their startup processing, a request for system-load information returns an HTTP 503 (Service Unavailable) status code.