My problem is probably quite similar to this question since I'm also getting the error:
2018-08-15T15:25:55.463Z INFO [monitoring] log/log.go:124 Non-zero metrics in the last 30s {"monitoring": {"metrics": {"beat":{"cpu":{"system":{"ticks":60,"time":{"ms":4}},"total":{"ticks":100,"time":{"ms":4},"value":100},"user":{"ticks":40}},"info":{"ephemeral_id":"28e49603-c421-4d2a-9a4d-c472b31f49b2","uptime":{"ms":360018}},"memstats":{"gc_next":4194304,"memory_alloc":1885672,"memory_total":4989872}},"filebeat":{"harvester":{"open_files":0,"running":0}},"libbeat":{"config":{"module":{"running":0}},"pipeline":{"clients":1,"events":{"active":0}}},"registrar":{"states":{"current":0}},"system":{"load":{"1":0.13,"15":0.11,"5":0.18,"norm":{"1":0.0217,"15":0.0183,"5":0.03}}}}}}
When running the filebeat command in verbose mode, my container terminal looks like this:
2018-08-15T16:28:41.991Z DEBUG [input] input/input.go:124 Run input
2018-08-15T16:28:41.992Z DEBUG [input] log/input.go:147 Start next scan
2018-08-15T16:28:41.992Z DEBUG [input] log/input.go:168 input states cleaned up. Before: 0, After: 0, Pending: 0
2018-08-15T16:28:51.992Z DEBUG [input] input/input.go:124 Run input
2018-08-15T16:28:51.992Z DEBUG [input] log/input.go:147 Start next scan
2018-08-15T16:28:51.992Z DEBUG [input] log/input.go:168 input states cleaned up. Before: 0, After: 0, Pending: 0
2018-08-15T16:29:01.993Z DEBUG [input] input/input.go:124 Run input
2018-08-15T16:29:01.993Z DEBUG [input] log/input.go:147 Start next scan
2018-08-15T16:29:01.993Z DEBUG [input] log/input.go:168 input states cleaned up. Before: 0, After: 0, Pending: 0
2018-08-15T16:29:11.880Z INFO [monitoring] log/log.go:124 Non-zero metrics in the last 30s {"monitoring": {"metrics": {"beat":{"cpu":{"system":{"ticks":230,"time":{"ms":4}},"total":{"ticks":510,"time":{"ms":8},"value":510},"user":{"ticks":280,"time":{"ms":4}}},"info":{"ephemeral_id":"21e234ab-cfd6-42a5-8084-93980e8895c2","uptime":{"ms":2190022}},"memstats":{"gc_next":4194304,"memory_alloc":1373432,"memory_total":15936832}},"filebeat":{"harvester":{"open_files":0,"running":0}},"libbeat":{"config":{"module":{"running":0}},"pipeline":{"clients":1,"events":{"active":0}}},"registrar":{"states":{"current":0}},"system":{"load":{"1":0,"15":0.04,"5":0.01,"norm":{"1":0,"15":0.0067,"5":0.0017}}}}}}
2018-08-15T16:29:11.993Z DEBUG [input] input/input.go:124 Run input
2018-08-15T16:29:11.993Z DEBUG [input] log/input.go:147 Start next scan
2018-08-15T16:29:11.993Z DEBUG [input] log/input.go:168 input states cleaned up. Before: 0, After: 0, Pending: 0
2018-08-15T16:29:21.993Z DEBUG [input] input/input.go:124 Run input
2018-08-15T16:29:21.994Z DEBUG [input] log/input.go:147 Start next scan
2018-08-15T16:29:21.994Z DEBUG [input] log/input.go:168 input states cleaned up. Before: 0, After: 0, Pending: 0
2018-08-15T16:29:31.994Z DEBUG [input] input/input.go:124 Run input
2018-08-15T16:29:31.994Z DEBUG [input] log/input.go:147 Start next scan
2018-08-15T16:29:31.994Z DEBUG [input] log/input.go:168 input states cleaned up. Before: 0, After: 0, Pending: 0
2018-08-15T16:29:41.879Z INFO [monitoring] log/log.go:124 Non-zero metrics in the last 30s {"monitoring": {"metrics": {"beat":{"cpu":{"system":{"ticks":240,"time":{"ms":4}},"total":{"ticks":520,"time":{"ms":8},"value":520},"user":{"ticks":280,"time":{"ms":4}}},"info":{"ephemeral_id":"21e234ab-cfd6-42a5-8084-93980e8895c2","uptime":{"ms":2220022}},"memstats":{"gc_next":4194304,"memory_alloc":1558872,"memory_total":16122272}},"filebeat":{"harvester":{"open_files":0,"running":0}},"libbeat":{"config":{"module":{"running":0}},"pipeline":{"clients":1,"events":{"active":0}}},"registrar":{"states":{"current":0}},"system":{"load":{"1":0,"15":0.04,"5":0.01,"norm":{"1":0,"15":0.0067,"5":0.0017}}}}}}