Metricbeat option to ignore NFS auto-mount

[brandonmensing]

With drop_event.when.regexp.mount_point set, metricbeat does not send stats for those filtered out file systems, but it still touches them keeping mount points active. Eventually systems started to have thousands of mount points causing input/output errors for new workers. Need a setting like ignore_nfs_automount. Metricbeat will NOT touch nfs automounts at all, so the mount point timeout can kick in.

[andrewkroh]

It looks like we already have the filesystem types internally from when we query /etc/mtab to get a list of filesystems. So if we introduce a new filter option like filesystem.ignore_types: [nfs], we can apply that filter before continuing to stat the filesystems. This should keep Metricbeat from ever touching any of the NFS mounts.

The same filter would also need to be applied to the fsstat metricset.

[andrewkroh]

Branches with the feature:

• 5.6 - Add filesystem.ignore_types to ignore filesystem types #4823 (it likely was merged in time for v5.6.0)
• 6.0 - Cherry-pick #4823 to 6.0: Add filesystem.ignore_types to ignore filesystem types #4918 (will be in v6.0.0-beta2)
• master - Cherry-pick #4823 to master: Add filesystem.ignore_types to ignore filesystem types #4906 (will be v6.1.0)