ArithmeticError in Harvest.Collector.Metric.Harvester.merge_metric/2 since 1.22.4

[Tom Taylor]

Since upgrading to 1.22.4 our reporting has halted, as every attempt to call NewRelic.Harvest.Collector.Metric.Harvester.merge_metric/2 causes an ArithmeticError on line 155, causing the GenServer to crash.

The full stack trace is:

ArithmeticError: bad argument in arithmetic expression
  Module "erlang", in :erlang.*/2
  File "lib/new_relic/harvest/collector/metric/harvester.ex", line 155, in NewRelic.Harvest.Collector.Metric.Harvester.merge_metric/2
  File "lib/enum.ex", line 2181, in Enum."-reduce/3-lists^foldl/2-0-"/3
  File "lib/new_relic/harvest/collector/metric/harvester.ex", line 46, in NewRelic.Harvest.Collector.Metric.Harvester.handle_cast/2
  File "gen_server.erl", line 680, in :gen_server.try_dispatch/4
  File "gen_server.erl", line 756, in :gen_server.handle_msg/6
  File "proc_lib.erl", line 226, in :proc_lib.init_p_do_apply/3

Arg 0 is nil and arg 1 is 1000.

We've since reverted, and everything is working again. If it's useful, we could try and spin up New Relic locally and try and debug it further.

[Tom Taylor]

We've worked out this is because os_mon is disabled, so some of the CPU metric parameters are nil. NewRelic.Harvest.Collector.Metric.Harvester is being called with:

{:report, %NewRelic.Metric{call_count: 1, max_call_time: nil, min_call_time: nil, name: :"CPU/User Time", scope: "", sum_of_squares: 0, total_call_time: nil, total_exclusive_time: 0}}

[Vince Foley]

Oh right, must be because of #289

We need that cpu_utilization measurement to report the standard CPU metric.

Since you are asking for this, are you OK with not getting CPU metrics in this situation?