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A Counter instrument that records values of type A. The UpDownCounter is non-monotonic, meaning the aggregated value can both increase and decrease.

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Type Signature

trait UpDownCounter[F[_], A]
Type Parameters:
  • F[_] - the higher-kinded type of a polymorphic effect
  • A - the type of values to record. Must have a MeasurementValue instance. Long and Double are supported out of the box.

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Creating an UpDownCounter

UpDownCounters are created using the Meter API: 
val meter: Meter[IO] = ???

val upDownCounter: IO[UpDownCounter[IO, Long]] =
  meter.upDownCounter[Long]("active.connections")
    .withUnit("connections")
    .withDescription("Number of active connections")
    .create

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Backend Methods

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add

Records a value with a set of attributes.
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value
A
required
The value to add to the counter. Can be positive or negative.
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attributes
immutable.Iterable[Attribute[_]]
required
The set of attributes to associate with the value.
Returns: F[Unit] Example: 
upDownCounter.flatMap { c =>
  c.add(
    5L,
    Attribute(AttributeKey.string("connection.type"), "websocket")
  )
}

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inc

Increments the counter by one.
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attributes
immutable.Iterable[Attribute[_]]
required
The set of attributes to associate with the value.
Returns: F[Unit] Example: 
upDownCounter.flatMap { c =>
  c.inc(Attribute(AttributeKey.string("connection.type"), "websocket"))
}

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dec

Decrements the counter by one.
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attributes
immutable.Iterable[Attribute[_]]
required
The set of attributes to associate with the value.
Returns: F[Unit] Example: 
upDownCounter.flatMap { c =>
  c.dec(Attribute(AttributeKey.string("connection.type"), "websocket"))
}

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Builder Methods

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withUnit

Sets the unit of measure for this counter.
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unit
String
required
The measurement unit. Must be 63 or fewer ASCII characters.
Returns: UpDownCounter.Builder[F, A] Reference: Instrument Unit

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withDescription

Sets the description for this counter.
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description
String
required
The description of the counter.
Returns: UpDownCounter.Builder[F, A] Reference: Instrument Description

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create

Creates an UpDownCounter with the configured unit and description. Returns: F[UpDownCounter[F, A]]

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See Also

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