What would happen to the agent if the Foglight Server goes down? (4289432)

What will happen to the agent (in terms of resources and space and impact) when the Foglight Management Server (FMS) goes down?

Is it possible to change the buffer caches used by the agent to avoid data loss when the FMS needs to be stopped for any reason?

See KB 4217414 "FglAM configuration to store more messages in case of FMS communication loss"

Since the agents are separate from the FMS and communicate via the Foglight Agent Manager (FglAM) as long as the FMS is down the agent will continue to collect data as if nothing was wrong with the FMS. The data will be buffered in cache, as the buffer fills the data will be discarded and the newly collected data will start to buffer. Once the FMS is available again the buffered data will be send to the FMS to be posted.

The flgam.config.xml (fglamhome/state/default/config) can be configured to govern the size (amount) of data buffered on the client where the FglAM is installed. In order for any change to this file to take place the FglAM will need to be restarted.

There are a few options documented in the fglam.config.xml

FglAM accumulates messages that are destined to be sent either upstream or downstream in queues between connections. This prevents messages from getting lost in the event of a disconnection. The 'MaxQueueSize' setting specifies the maximum number of messages that will be stored in the queue. If the queue overflows the newest messages will be discarded. Zero means no messages will be queued in memory, -1 means that the queues will be allowed to grow indefinitely. 'MaxDiskSpace' indicates how much disk space (in kB) that can be used to store messages. If zero then messages will never be written to disk, -1 means no limit. 'MaxBatchSize' is the number of messages that will be sent from the queue when a connection has successfully been made. -1 means every available message will be included in each batch. Changing these settings is only recommended when instructed to do so by Quest support. Most FglAM clients will use the default settings.