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@@ -142,17 +142,20 @@ Accepted metric types vary based on the field type:
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[%collapsible%open]
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====
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// tag::time-series-metric-counter[]
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-`counter`:: A number that only increases or resets to `0` (zero). For
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+`counter`:: A cumulative metric that only monotonically increases or resets to `0` (zero). For
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example, a count of errors or completed tasks.
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// end::time-series-metric-counter[]
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+
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-Only numeric and `aggregate_metric_double` fields support the `counter` metric
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-type.
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+A counter field has additional semantic meaning, because it represents a cumulative counter. This works well with
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+the `rate` aggregation, since a rate can be derived from a cumulative monotonically increasing counter. However a number
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+of aggregations (for example `sum`) compute results that don't make sense for a counter field, because of its cumulative nature.
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++
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+Only numeric and `aggregate_metric_double` fields support the `counter` metric type.
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-NOTE: Counter fields do come with a limitation in aggregations. Only the following aggregations are supported with the `counter` field: `rate`, `histogram`, `range`, `min`, `max`, `top_metrics` and `variable_width_histogram`.
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+NOTE: Due to the cumulative nature of counter fields, only the following aggregations are allowed with the `counter` field: `rate`, `histogram`, `range`, `min`, `max`, `top_metrics` and `variable_width_histogram`.
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// tag::time-series-metric-gauge[]
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-`gauge`:: A number that can increase or decrease. For example, a temperature or
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+`gauge`:: A metric that represents a single numeric that can arbitrarily increase or decrease. For example, a temperature or
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available disk space.
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// end::time-series-metric-gauge[]
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+
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Martijn van Groningen