This is the counterpart to get_distributed_trace_ctx/0. It is used to "extract" trace context information from http headers. This context information is stored in a string so it can be passed around by other means as well.

Examples:

iex> O11y.attach_distributed_trace_ctx([traceparent: "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01"])
iex> O11y.attach_distributed_trace_ctx("00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01")
iex> O11y.attach_distributed_trace_ctx(nil)

@spec end_span(OpenTelemetry.span_ctx() | :undefined) ::
  OpenTelemetry.span_ctx() | :undefined

Ends the current span and marks the given parent span as current.

Examples:

iex> span = O11y.start_span("checkout")
iex> O11y.end_span(span)

This function is typically used to "inject" trace context information into http headers such that the trace can be continued in another service. However, it can also be used to link span in cases where OpenTelemetry.Ctx.attach/1 will not work (such as when the parent span has already ended or been removed from the dictionary).

Examples:

iex> res = Tracer.with_span "some_span", do: O11y.get_distributed_trace_ctx()
iex> [{"traceparent", _}] = res

Records an exception and sets the status of the current span to error.

Examples:

iex> O11y.record_exception(%RuntimeError{message: "something went wrong"})
%RuntimeError{message: "something went wrong"}

Produces a span like:

{:span, 28221055821181380594370570739471883760, 5895012157721301439, [],
  :undefined, "checkout", :internal, -576460751313205167, -576460751311430083,
  {:attributes, 128, :infinity, 0, %{}},
  {:events, 128, 128, :infinity, 0,
  [
    {:event, -576460751311694042, "exception",
     {:attributes, 128, :infinity, 0,
      %{
        "exception.message": "something went wrong",
        "exception.stacktrace": "...",
        "exception.type": "Elixir.RuntimeError"
      }}}
  ]}, {:links, 128, 128, :infinity, 0, []}, {:status, :error, ""}, 1, false,
  :undefined}

Sets the given attribute on the current span. If the value is not a valid OTLP type, it will be converted to a string with inspect.

This method does not support structs to maps, regardless of whether the struct implements the O11y.SpanAttributes protocol. You need to use set_attributes/1 for that.

Examples:

iex> O11y.set_attribute("key", "value")
:ok

# Produces span attributes like:
{:attributes, 128, :infinity, 0, %{key: "value"}}

iex> O11y.set_attribute("key", "value", namespace: "cool_app")
:ok

# Produces span attributes like:
{:attributes, 128, :infinity, 0, %{"cool_app.key" => "value"}}

Namespace can also be set globally via configuration like:

config :open_telemetry_decorator, :attribute_namespace, "app"

Adds the given attributes as a list, map, or struct to the current span. If the value is a maps or struct, it will be converted to a list of key-value pairs. If the struct derives the O11y.SpanAttributes protocol, it will honor the except and only options.

Examples:

iex> O11y.set_attributes(%{id: 123, name: "Alice"})
%{id: 123, name: "Alice"}

# Produces span attributes like:
{:attributes, 128, :infinity, 0, %{id: 123, name: "Alice"}}

iex> O11y.set_attributes(%{name: "Steve", age: 47}, prefix: "user")
%{name: "Steve", age: 47}

# Produces span attributes like:
{:attributes, 128, :infinity, 0, %{"user.age" => 47, "user.name" => "Steve"}}

iex> O11y.set_attributes(%{name: "Steve", age: 47}, namespace: "app")
%{name: "Steve", age: 47}

# Produces span attributes like:
{:attributes, 128, :infinity, 0, %{"app.age" => 47, "app.name" => "Steve"}}

Namespace can also be set globally via configuration like:

config :open_telemetry_decorator, :attribute_namespace, "app"

Sets the status of the current span to error

Sets the status of the current span to error, and sets an error message.

Examples:

iex> O11y.set_error("something went wrong")
"something went wrong"

iex> O11y.set_error(%RuntimeError{message: "something went wrong"})
%RuntimeError{message: "something went wrong"}

iex> O11y.set_error(%Jason.DecodeError{position: 0, token: nil, data: ""})
%Jason.DecodeError{position: 0, token: nil, data: ""}

@spec start_span(String.t(), Keyword.t()) :: OpenTelemetry.span_ctx() | :undefined

Starts a new span and makes it the current active span of the current process.

This is a little tricky because it actually returns the parent span, not the new span. However, this is because we want to be able to end the span and set the current span back to the parent which is not the default behavior. The API end_span function doesn't take a span to end anyway (though it seems like it should) so you sort of use this as I would expect the actual API to work and get similar behavior to with_span

Examples:

iex> Tracer.with_span "checkout" do
iex>  parent = O11y.start_span("calculate_tax")
iex>  # gnarly_calculations()
iex>  O11y.end_span(parent)
iex> end