glotel - v0.1.0

glotel/span

Types

SpanContext

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An OpenTelemetry span context

pub type SpanContext

Functions

extract_values

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pub fn extract_values(values: List(#(String, String))) -> Nil

Extract OpenTelemetry attributes like traceparent from request headers.

Examples

pub fn trace_middleware(request: Request, handler: fn() -> Response) -> Response {
  extract_values(request.headers)
}

new

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pub fn new(
  name: String,
  attributes: List(#(String, String)),
  apply: fn(SpanContext) -> a,
) -> a

Creates a new span context, automatically linked to its immediate parent span, if present. Default to a internal span kind.

Examples

fn foo() {
    use span_ctx <- new("foo", [#("attribute", "value")])
}

new_of_kind

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pub fn new_of_kind(
  kind: SpanKind,
  name: String,
  attributes: List(#(String, String)),
  apply: fn(SpanContext) -> a,
) -> a

Same as new, but allows specifying span kind.

Examples

fn server_foo() {
  use span_ctx <- new_of_kind(span_kind.Server, "server_foo", [
    #("attribute", "value"),
  ])
}

set_attribute

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pub fn set_attribute(
  span: SpanContext,
  key: String,
  value: String,
) -> Nil

Sets an additional attribute on a given span.

Examples

fn foo() {
  use span_ctx <- new("foo", [])
  set_attribute(span_ctx, "bar", "baz")
}

set_error

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pub fn set_error(span: SpanContext) -> Nil

Sets error = true on a given span.

Examples

case status_code >= 500 {
  True -> set_error(span_ctx)
  False -> Nil
}

set_error_message

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pub fn set_error_message(
  span: SpanContext,
  message: String,
) -> Nil

Same as set_error, but allows specifying an explicit error message.

Examples

case status_code >= 500 {
  True ->
    set_error_message(
      span_ctx,
      "Request error: " <> int.to_string(status_code),
    )
  False -> Nil
}

try

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pub fn try(
  span: SpanContext,
  result: Result(a, b),
  apply fun: fn(a) -> Result(c, b),
) -> Result(c, b)

Same as standard library result.try(), but automatically calls set_error(span) on an Error.

try_with_message

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pub fn try_with_message(
  span: SpanContext,
  message: String,
  result: Result(a, b),
  apply fun: fn(a) -> Result(c, b),
) -> Result(c, b)

Same as standard library result.try(), but automatically calls set_error_message(span, message) on an Error.

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