The packet-sd exporter in version 0.0.3 creates a temporary file, moves
it to the target location and chmods it there. This creates a race
condition, in which Prometheus can be unable to read the file.
Additionally the outfile was created with too wide permissions (group-
and world-writable).
Both issues are resolved upstream, but not yet released.
This is currently being used as part of the NixOS.org infrastructure [1]
and should probably be included here and not just "downstream" (in the
nixops configs).
[1] 26105e7afa/delft/prometheus/packet-sd.nix
