Alexey Serbin created KUDU-3566:
-----------------------------------
Summary: Incorrect semantics of Prometheus-style histogram-type
metrics
Key: KUDU-3566
URL: https://issues.apache.org/jira/browse/KUDU-3566
Project: Kudu
Issue Type: Bug
Components: master, tserver
Affects Versions: 1.17.0
Reporter: Alexey Serbin
Original KUDU-3375 implementation incorrectly exposes [summary-type Prometheus
metrics|https://prometheus.io/docs/concepts/metric_types/#summary] as
[histogram-type
ones|https://prometheus.io/docs/concepts/metric_types/#histogram] for data
collected by corresponding HDR histograms. For example, below are snippets
from {{/metric}} and {{/metrics_prometheus}} for statistics on ListMasters RPC.
JSON-style:
{noformat}
{
"name": "handler_latency_kudu_master_MasterService_ListMasters",
"total_count": 26,
"min": 152,
"mean": 301.2692307692308,
"percentile_75": 324,
"percentile_95": 468,
"percentile_99": 844,
"percentile_99_9": 844,
"percentile_99_99": 844,
"max": 844,
"total_sum": 7833
}
{noformat}
Prometheus-style counterpart:
{noformat}
# HELP kudu_master_handler_latency_kudu_master_MasterService_ListMasters
Microseconds spent handling kudu.master.MasterService.ListMasters RPC requests
# TYPE kudu_master_handler_latency_kudu_master_MasterService_ListMasters
histogram
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_bucket{unit_type="microseconds",
le="0.75"} 324
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_bucket{unit_type="microseconds",
le="0.95"} 468
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_bucket{unit_type="microseconds",
le="0.99"} 844
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_bucket{unit_type="microseconds",
le="0.999"} 844
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_bucket{unit_type="microseconds",
le="0.9999"} 844
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_bucket{unit_type="microseconds",
le="+Inf"} 26
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_sum{unit_type="microseconds"}
7833
kudu_master_handler_latency_kudu_master_MasterService_ListMasters_count{unit_type="microseconds"}
26
{noformat}
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