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A gauge is a metric that represents a single numerical value that can arbitrarily go up and down. Gauges are typically used for measured values like temperatures or current memory usage, but also “counts” that can go up and down, like the number of concurrent requests.

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create_gauge

Creates a new Gauge metric. 
pub fn create_gauge(
  registry registry: String,
  name name: String,
  help help: String,
  labels labels: List(String),
) -> Result(Nil, String)
​
registry
String
required
The name of the registry to create the gauge in (typically “default”).
​
name
String
required
The name of the gauge metric.
​
help
String
required
A description of what the gauge measures.
​
labels
List(String)
required
A list of label names for this metric. The order matters and must match when setting values.

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Returns

  • Ok(Nil) if the gauge was created successfully
  • Error(String) with an error message if creation failed (e.g., “Metric already exists”)

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Example

create_gauge(
  registry: "default",
  name: "cache_size",
  help: "Number of items in the cache",
  labels: [ "cache_name" ],
)

​
set_gauge

Sets the value of the Gauge. 
pub fn set_gauge(
  registry registry: String,
  name name: String,
  labels labels: List(String),
  value value: Int,
) -> Result(Nil, String)
​
registry
String
required
The name of the registry where the gauge exists.
​
name
String
required
The name of the gauge metric to set.
​
labels
List(String)
required
A list of label values for this observation. Must match the number and order of labels defined when creating the gauge.
​
value
Int
required
The value to set the gauge to. Can be any integer value.

​
Returns

  • Ok(Nil) if the gauge was set successfully
  • Error(String) with an error message if the operation failed (e.g., “Unknown metric” or “Invalid metric arity (labels mismatch)“)

​
Example

set_gauge(
  registry: "default",
  name: "cache_size",
  labels: [ "image_cache" ],
  value: 123,
)

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